ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-01-93 16:43 From: Robert Taylor To: Richard Quick Subj: 10KVA TESLA COIL ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Wanted to pass along some reference material that may be of interest. In addition to the _Tesla, Man Out of Time_ book, Barnes & Noble also has _The Inventions, Researches, and Writings of Nikola Tesla_ (edited by Thomas Martin--ISBN 0-88029-812-X)--I picked this one up form them for about $15 w/in the last 6-9 months--think they still show it in their catalog. The book is made up of transcripts of lectures & demonstrations given by Tesla, & several chapters are devoted to the coil & what he saw as its practical applications. Included are a lot of technical details of his construction methods, as well as schematics. Unfortunately, there is nothing included as to the math that he used in design. While looking at this thread, I noticed that someone made mention as to a variety of spark gap designs. Some of this is covered- -including magnetic & compressed air quenching. I did some fooling around with these designs a few years ago, but never got it to your level of development. Did not know the details of the oil-immersion cap at the time so I built a humongous Lleyden Jar cap for the tank circuit (after having blown up a ceramic high freq xmitter cap, not a pretty sight). However, did discover that a good power supply is a plain ol' 15 KV neon sign transformer (found some used ones at local sign shops). My biggest problem was working out the inductance--never could get the primary & secondary to sync properly--but it made one heckuva broad-band spark gap transmitter. Still interested in Tesla & his work. Quite a mind there. (1:123/70) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-03-93 20:42 From: Richard Quick To: Robert Taylor Subj: 10KVA TESLA COIL ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ RT> Wanted to pass along some reference material that may be of RT> interest. In addition to the _Tesla, Man Out of Time_ book, RT> Barnes & Noble also has _The Inventions, Researches, and RT> Writings of Nikola Tesla_ (edited by Thomas Martin--ISBN RT> 0-88029-812-X)--I picked this one up from them for about $15 RT> w/in the last 6-9 months--think they still show it in RT> their catalog. The book is made up of transcripts of RT> lectures & demonstrations given by Tesla, & several chapters RT> are devoted to the coil & what he saw as its practical RT> applications. Included are a lot of technical details of RT> his construction methods, as well as schematics. RT> Unfortunately, there is nothing included as to the math that RT> he used in design. Math? Tesla did not use math. Seriously. Oh, he used some equations to give ballpark figures. But the numbers he was working with were for the most part taken from machines he had already constructed and were operating. Most of the math was not figured out until years and years later. The mathematical treatise on extra coil work was not derived until the 1980's, Sloans work on resonators (mathmatical treatise) was not published until the 1930's. Tesla invented and built, he left the math for others to clean up later. RT> While looking at this thread, I noticed that someone made RT> mention as to a variety of spark gap designs. Some of this RT> is covered--including magnetic & compressed air quenching. The book is OK, but read it for generalities and direction only, outside of the schematics (which are his more primitive circuits) it should not be followed closely. We are in the age of plastics, and Tesla was in the age of wood, and rubber (carbon rich and a poor RF insulator). Some of the experiments are interesting, but I have performed many better ones that do not require $300.00 (modern prices) custom made tubes. RT> I did some fooling around with these designs a few years RT> ago, but never got it to your level of development. Did not RT> know the details of the oil-immersion cap at the time so I RT> built a humongous Lleyden Jar cap for the tank circuit RT> (after having blown up a ceramic high freq transmitter RT> cap--not a pretty sight). Good capacitance is a must! I too have built many, many, homemade capacitors and leyden jars. Blew every one! Your not coiling unless your blowing capacitors! Then when you get things worked out to where the capacitors stop blowing, you start blowing transformers. By this time though your usually running well over a kilowatt and are getting (or have seen) some decent spark. Then you start working with power controllers, and HEAVY RF choking, next thing you know your in the big leagues. The best capacitors for beginners are salt water types. Bottles are filled with salt water, and placed in a salt water filled pan. The pan is lined with alum. foil, and a long bolt or some other conductor is placed in the bottle. The salt water in the pan is one plate, the salt water in the bottle is another plate, and the glass bottle is the dielectric. Oil can be poured over the water to reduce corona loss. Tesla used salt water caps on the Colorado Springs machine, and I have a friend running 5-8 KVA with plastic bucket salt water caps. RT> However, did discover that a good power supply is a plain RT> ol' 15 KV neon sign transformer (found some used ones at RT> local sign shops). I recommend beginners start with 9000 volt neons, then move up to 12,000 volt units before jumping into the 15s. The 15KV neons put too much stress on the capacitors (unless you are using glass leyden jars, or salt water caps with thick bottles). RT> My biggest problem was working out the inductance--never RT> could get the primary & secondary to sync properly--but it RT> made one heckuva broad-band spark gap transmitter. You just needed to learn the ins and outs of tuning. It takes a little practice. A lot of balancing is required to get optimum performance. Coupling, spark gap quenching, terminal capacitance, as well as the primary/secondary inductance all come into play. Sounds like you made a good start, to bad you did not take it any further. Thinking about picking it up again? With modern materials, a little time and effort, and modern designs, you would be surprised what you can achieve with coils. RT> Still interested in Tesla & his work. Quite a mind there. Me too, and I agree. Tesla was a man very far ahead of his time and technology. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-04-93 19:17 From: Richard Quick To: Robert Taylor Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ BTW, I have read the book you mentioned in the post received here yesterday. I bought it from Barnes & Nobel last month and have read it cover to cover twice. The books I mentioned earlier, (example _NICKOLA TESLA ON HIS WORK WITH ALTERNATING CURRENTS AND THEIR APPLICATION TO WIRELESS TELEGRAPHY, TELEPHONY, AND TRANSMISSION OF POWER_ ISBN 0-9632652- 0-2, from 21st Century Books, P.O. Box 2001, Breckenridge, Colo. 80424) is a much more informative work. Tesla did not go public with much after he saw the tide of his fortunes turning. He kept his more advanced work very close to his chest. Even his basic experimental circuits used in developing the Magnifier were not published until the 1970's, the math not worked out until late in the 1980's, and the systems actually re-tested (with the exception of Golka's primitive efforts) until the last two years! Right now work on the Magnifier is at the point where any serious hobbyist can make a mark. The book above is a candid interview with Tesla's attorneys in 1916 (after Wardenclyff), he talks, submits photographs, sketches, and schematics; all of which is recorded by stenographer. All documents submitted by Tesla are reproduced. This book really cuts to the core. We see that Tesla used red herrings, even from the start, to disguise the true nature of his work. An example is his submission of photos and patent wrappers of an alternator. The alternator was patented (#447,920 March 10, 1891) as the power supply in a "Method of Operating Arc Lamps". Yet Tesla goes on to produce schematics showing it as the signal generator for the first radio, AND shows how the circuit evolved in a matter of months into a powerful lumped tuned circuit transmitter. He submits schematics of his experimental tank circuit used in the New York lab prior to leaving for Colorado Springs, complete with three phase synchronous gaps (never published or patented). We see photos taken from Wardenclyff powerplant showing huge four phase high frequency alternators, and text describing the operation and performance. The Colorado Springs notes are another example of Tesla revelations. Tesla never intended those notes be published, and we see circuits in there that are meaningless, until you add perhaps a little note from the book mentioned top. We see the circuit that Tesla used to create ball lightning in the lab (Colorado Springs Notes pp 115,162), advancements made on the three phase gap (but not showing the gaps, just the improvement). Then we add information gleaned from the Corums' book _VACUUM TUBE TESLA COILS_ (ISBN 0-924758-00-7) and we begin to see that his later claims of particle beam weapons, worldwide power transmission, robotics, etc. are not based on some "crackpot's fantasy" (as Guy Daugherty would have some believe). He completed all of the basic research, had an operational worldwide transmitter (Wardenclyff, look at the powerplant photos) though nobody had receivers yet. He had operational remote control robots (ISBN 0-9632652-0-2, pp 157 {photo}, patent 613,809 11/8/1898!). I guess what I am trying to say is that his lectures, published explanations, even to some extent his patents are misleading, and deliberately so. You have to dig into sources that Tesla did not intend to become public, then you have to build and test these systems, then you are on the road to his later secrets. But they all seem to reach back to his 1/4 wave coil systems and the lectures, for the roots. The problem is that the work he presented in the lectures is now obsolete, both from a design and engineering point of view. With exception of some of the experiments, skip on to the material I have documented. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-05-93 01:25 From: Richard Quick To: David Tiefenbrunn Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Well Dave, I talked with the architect again today. Things are firming up for a real lab. The building so far is looking like this: 50' x 60' with 8' masonry walls and 8' sheet metal walls on top. This gives a total wall height of 16 feet, with a slope up to the center of the roof for a 20' peak. The half masonry, half sheet metal wall was a compromise for security, cost, and you'll never guess what else... My testing shows an all metal walled building will induct, and large currents will cruise through the structure. So masonry for the first 8' feet seems a good compromise. For electrical service I'm getting 480 volt 3 phase, 400 amps, and 110/220 single phase 200 amps. The building will have 4" x 15' galvanized pipe driven into the ground before the slab is poured as an RF ground, and I plan to extend it later. Thought I would drop you a line and let you know, as I was pretty excited to see some drawings. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-03-93 13:43 From: Dave Halliday To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ RQ>Dave, RQ>I got your package in the mail today, and your tape went back >out. It is after the pickup time on Saturday, but you should >have the tape by midweek. RQ>Let me know when you get it, and what you think. I am sorry I >had to cut a lot of material out, but two hours just doesn't >seem to be enough time to give you the tour, show you some m >techniques, and show all of the systems. I cut back on a lot >of smaller test and prototype stuff to let you focus on the >big coil. GREAT! I will look forward to viewing it! Also, emphasis on the big coil is perfect. 301-794-6496 (1:109/546) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-05-93 02:22 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ If you are interested in making a high voltage, high current, power supply, I can tell you how to do it for free.... First call the local neon shop(s) and tell them that your working with Tesla coils. Ask them to hold all of their failed xfrmrs so you can pick them up. Make sure you talk to the boss or foreman, and tell them that you want dead units. I have never had a shop turn me down for free cores. They are happy to get rid of them. There are two types of failed neon xfrmrs: warranty units, and old junk. The local shop must return units that fail within the two year warranty period back to the distributor for credit. Old junk (older than two years) you can pick up for free right from the local shop, but I also scavenge from the distributor. Ask where the failed warranty units go. If you can locate the distributor who sells wholesale, and handles failed warranty units, you have found a gold mine of high voltage xfrmrs. The distributor removes the PLATE from the xfrmr for return to the manufacturer, and throws the unit away. The manufacturer credits the distributor for the plate, as the shipping is too expensive. The cores go to the dumpster. After locating your source of failed units, be selective. Try to bring home the high current units. Ratings commonly used are 9 kv, 12 kv, & 15 kv, with common current ratings of 30 & 60 ma. Once in awhile you will come across a 120 ma unit. I grab all of the high current units (60 ma+) I can get in these voltages. First test your units. Use wire with a 15 kv rating or better. This wire can be obtained where you pick up the transformers. If you ask they will usually cut you off a few feet for free. I prefer using the solid polyethylene core from RG-213 coax, as it will withstand the voltage with gobs of extra safety margin. Draw an arc from the HV bushing to the case, one at a time. About 50% of the "failed" units I pick up are just fine and need nothing other than a clean up. There is nothing wrong with them. Often shops get these units from signs they have dismantled, and they just toss them into the junk pile with the rest. The other 50% are bad. Either one, or both, of the HV windings have broken down. These units can frequently be repaired. Remove all hardware, and insulators if possible. Take a hammer and a chisel and remove the cases by splitting them down the corners. Break off any stubborn insulators, but try to preserve the lead wire. You are left with a block of tar. Set the unit outside when it is very cold, and let it freeze solid overnite; or place in a freezer or deep freeze until frozen solid. The next morning, short the high voltage lead wires with a clip lead, and connect 110 volts across the primary. Since the cores on these transformers are shunted, they may be shorted without harm or blowing fuses. Let the unit cook for 15-30 minutes. Disconnect your leads, and with the chisel and hammer, chip a groove around the block. You want to score a groove lengthwise that will allow the block to cleave in two. Then starting from one end of the block, chip until you hit the core, then do the same with the other end. Pry and chip the tar away from the core until the xfrmr is free. The core may then be disassembled, and the windings removed and examined. Kerosene and a stiff brush will clean up the windings and core of any remaining tar. The "cold-cook" method is fast, clean, and works very well. Since the tar is frozen it chips away cleanly. The "cooking" softens up the tar around the core allowing it to release. The only other ways I know to free the cores are long soaks in solvent such as kero or gas, (the nasty waste does make a good crack filler), or melting out the tar with external heat from a fire or oven. Most units fail when the high voltage breaks down the tar insul- ation. The resulting carbon track shorts the winding. Simply removing the tar brings them back to life. Other times the coils break down internally. In this case I discard the winding after disassembling the core, and replace it with a good winding from another unit of the same model with the same type failure. While the core is apart, you can beef up the current output by removing a few of the shunting plates between windings. Never take out more than 2 or 3 of these plates per side, as the additional power output will burn out the secondaries. Generally I get about 70-75 ma out of 60 ma units after I have finished. (Continued in next post) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-05-93 04:13 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ (cont.) Rebuilt units need a little protection from the high voltage secondary outputs. The first thing I do is solder on a new lead wire to the high voltage windings. The HV secondaries are wound with very fine magnet wire, in the 30 ma units the wire is not much thicker than a coarse hair. Once a good solder connection is made, bed the connection and the first 1/2 inch or so of lead wire to the top of the HV winding with hot glue or clear epoxy. The lead wire need not be anything special, any thin insulated stranded wire may be used. Heavy wire increases the chances of a failed connection due to mechanical stress. When setting the unit up to fire you simply have to route it on insulators. The windings themselves are wedged against the core to prevent vibration. I have seen wood, bakelite, and plastic wedges used commercially. What I like to do is to soften up some 30 mil polyethylene plastic sheet in boiling water, and heat the core in a warm oven. I wrap dry softened plastic around the core and gently force the windings down on it. Once cooled, the windings have some insulation from the core, and they will not vibrate. The base wire from the HV windings must be grounded to the core. Use the original grounding point if possible, if not you may split the core apart slightly with a thin blade and insert the wire into the gap before you clamp the core back up. If required you may splice on a small piece of wire for added length. Neon sign transformers that have been rebuilt may be fired dry. The tar used to pot the cores for neon use does not really insulate well against the RF and kickback from the Tesla Tank. The units last longer when they are freed of the tar potting. The only other choice is to sink rebuilt units in mineral or xfrmr oil which is a very good RF insulator. I choose to fire them "dry"; it works, and there is no mess. Neons may be run in parallel to deliver the current required to fire medium sized coils, and I have run up to 4000 watts with banked neon power supplies. The general practice is to run these banks off of 240 volt feeds controlled through a variac. Neons with matched outputs are run in pairs in these banks. The primaries are paired up in series, and the secondaries are all paralleled to the HV buss. Phasing is important here, and each transformer must be checked as it is added to the bank to ensure it is in phase with the other units. If an xfrmr draws an arc from a lead wire brought to the HV buss, the primary or secondary connections must be reversed. Neons typically have an efficiency of about 50%, in that they draw twice as much power as they put out. This problem can be resolved with the use of power factor correction (pfc) capaci- tance across the line. The pfc capacitors used are the same as for alternating current motors. The voltage rating should be at least twice the line current used, and I like a 4x voltage margin for long life. The formula used to determine ballpark pfc is as follows: 9 10^ C = Corrected kVA ------ 2 2(pi)fe^ This should read C = Corrected kVA times (10 to the ninth power) over, (2 pi times f times e squared) C = required capacitance in microfarads f = frequency of applied voltage e = applied voltage CORRECTED KVA is determined by dividing the volt*amps (watts) output of the neon sign xfrmr by 1000 Using a pair of rebuilt 12 kv, 60 ma neons, with 2 shunting plates removed from the core next to each HV winding, and power factor correction capacitance, you can get a nice 1.5 KVA Tesla power supply with over 90% efficiency. Total cost: $5.00 for the pfc capacitors, and a few hours of time. I have unpotted dozens of neon transformers from many different manufacturers. I have tried to make this as informative as possible, and have checked it over for mistakes. If I have erred, or was not clear on something, please let me know. Use common sense, and don't expect the first attempt to work out. On my first attempt I managed to destroy a HV winding during the unpotting, as I did not know where the windings were located on the core. But once you see one core unpotted, with minor differences, you have seen them all. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-01-93 10:21 From: Guy Daugherty To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ RQ>But if everybody thinks I'm wacky, should I stop posting? I RQ>don't want to waste people's time. I just thought you all were RQ>interested. I'd guess that the ones of us who are doing similar research are completely engrossed with your findings and research- I think it's interesting, though I fail to see the utility of what the devil it is you're up to, as opposed to my productive reduction of lifespan, i.e., posting smartass remarks in a few conferences and running up the phone bill for dozens of sysops across the globe. I'm curious what your end goal is, if you believe that even if you can prove Tesla's principles and concepts to have the validity his proponents trumpet, how could your break into the lockup current utility companies have over the conversion and distribution of electrical energy. I have similar feelings about the use of dinosaur ooze for internal-combustion engine fuel --hydrogen would solve the pollution, supply limitation and toxicity problems-- but I have no fantasy of it coming to pass in my lifetime. I say keep posting. We're interested. Plus, it narrows down the amount of territory we'll have to look for you in when something goes horriblly awry. (209)472-0843 (1:208/216) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-07-93 02:03 From: Richard Quick To: Guy Daugherty Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ GD> I'm curious what your end goal is, if you believe that even GD> if you can prove Tesla's principles and concepts to have the GD> validity his proponents trumpet, how could your break into GD> the lockup current utility companies have over the GD> conversion and distribution of electrical energy. We may never see this one, even if commercial feasibility is proven. But you are taking a bit of a narrow view, that is all. My personal goal is not only to prove Tesla's principals and concepts (which I believe has already done as far as his patents are concerned), but also for the pure search of knowledge. Practical applications, something I think may be possible to achieve, would be perhaps a true "high efficiency" laser. If we have one, then someone will figure out how to employ it for profit, maybe in fusion. Me, I am looking to spend money with this, not make it. You must be misunderstanding the breakthrough that the Magnifier circuit represents. Just because Tesla saw one commercial application for the circuit in a transmitter does not mean that this is the only single use, or the only use Tesla saw. This is definitely not the case. The circuit is a very, very, very efficient RF power supply. It can be set up to provide RF current, or voltage (or both) depending on the intended app- lication. As a power supply for large tuned resonate loads there is nothing equal. In effect the circuit is narrow band RF signal generator capable of enormous powers. It is relatively cheap and easy to build, and the design and components are easily modified. The Magnifier was not recognized as a high efficiency, narrow band signal generator until the mid 1980's; 90 years after Tesla had industrial scale operational units, and a full ten years after Tesla's Colorado Springs Notes went into print for the first time. The photos published at the time (early 1900s) only show, and the only thing people remember, are the sparks. Yet in the opening pages of the Notes, Tesla clearly stated his intended goals for the machine, he does not mention sparks. In an era with no o'scopes, multimeters, RF detectors, or stabilized RF generators (other than his); Tesla proceeded to design, construct, and test, a narrow band RF signal generator driving a tuned 1/4 wave resonate load to a voltage of 9.5 Megavolts with RMS currents of 1100 amps. Figure it out Guy, that's 10.45 Billion watts. He did this with an input power of 250 kVA, and so named the circuit "The Magnifier". The only way he could judge the performance of the system was to tune for spark occasionally. The reason the system was so large was because physical size was the only way to contain the energy in the system without break- down. He had to keep his charge density low or he lost energy. He did not have plastic film type pulse discharge capacitors, poly- ethylene core coax, PVC jacketed wire, or any of the dozens of other modern materials I use daily. When Tesla perfected the circuit, the only 1/4 wave resonator in existence was the resonate coil. We now have coaxial, tapped helix coaxial, and pure cavity geometries. Tesla never mentioned coherent radiation, and now we have lasers and masers. The Kapitza fusion experiment and the maser are examples of modern applications of resonate loads. Both are cavity type 1/4 wave resonators driven by signal generators. In my recent research I ran across an article, "Cavity-Coupling Investigation for the Phermex 50 MHz RF Accelerator", by E.W. Pogue and F.R. Buskirk, IEEE Trans. on Nuclear Science, Vol. NS- 32, No. 5, October, 1985, pp 2852-2853. The boys at Phermex seemed really excited to discover an increase of performance in the accelerator when run off parallel drivers. Yet Tesla shows the SAME IDENTICAL CIRCUIT, and at least three variations, with notes relative to the performance and character- istics of each in The Colorado Springs Notes in 1899! See Colorado Springs Notes, pp 153-156, mid August 1899. The circuit is precisely identical, the only differences being the frequency of operation and the geometries of the resonator. Tesla BTW was running powers an order of MAGNITUDE greater the Phermex team. The magnifier is a very efficient signal generator, NOT a transmitter unless you CHOOSE to set it up as one. The entire purpose behind the magnifier circuit, it's only true function, is to drive resonators, not to transmit power. So lets forget the sparks for a moment, and lets forget global transmission of power. Why not hook the system to a tuned 1/4 wave resonator designed as a laser tube? A system 1/10th the power of Tesla's Colorado Springs oscillator would deliver a billion watts. With modern materials the size could be reduced greatly because we can insulate with plastics. In real dollars the cost is cheaper than Tesla's because we can tap the industrial surplus markets; transformers he paid thousands for then, I can buy surplus for a few hundred. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-03-93 22:00 From: Bob Stephenson To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ GD> Well I have a Jacob's ladder on an old theater marquis GD> neon transformer. Really makes the kitty stop and pay GD> attention. Worries people who see it, too. My inner Beavis GD> loves it. ^^^^^^^^^^^^^^^ Oh man, I love it....Thank you! Bob (1:2604/109) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 05 Nov 93 02:22:00 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ If you are interested in making a high voltage, high current, power supply, I can tell you how to do it for free.... First call the local neon shop(s) and tell them that your working with Tesla coils. Ask them to hold all of their failed xfrmrs so you can pick them up. Make sure you talk to the boss or foreman, and tell them that you want dead units. I have never had a shop turn me down for free cores. They are happy to get rid of them. There are two types of failed neon xfrmrs: warranty units, and old junk. The local shop must return units that fail within the two year warranty period back to the distributor for credit. Old junk (older than two years) you can pick up for free right from the local shop, but I also scavenge from the distributor. Ask where the failed warranty units go. If you can locate the distributor who sells wholesale, and handles failed warranty units, you have found a gold mine of high voltage xfrmrs. The distributor removes the PLATE from the xfrmr for return to the manufacturer, and throws the unit away. The manufacturer credits the distributor for the plate, as the shipping is too expensive. The cores go to the dumpster. After locating your source of failed units, be selective. Try to bring home the high current units. Ratings commonly used are 9 kv, 12 kv, & 15 kv, with common current ratings of 30 & 60 ma. Once in awhile you will come across a 120 ma unit. I grab all of the high current units (60 ma+) I can get in these voltages. First test your units. Use wire with a 15 kv rating or better. This wire can be obtained where you pick up the transformers. If you ask they will usually cut you off a few feet for free. I prefer using the solid polyethylene core from RG-213 coax, as it will withstand the voltage with gobs of extra safety margin. Draw an arc from the HV bushing to the case, one at a time. About 50% of the "failed" units I pick up are just fine and need nothing other than a clean up. There is nothing wrong with them. Often shops get these units from signs they have dismantled, and they just toss them into the junk pile with the rest. The other 50% are bad. Either one, or both, of the HV windings have broken down. These units can frequently be repaired. Remove all hardware, and insulators if possible. Take a hammer and a chisel and remove the cases by splitting them down the corners. Break off any stubborn insulators, but try to preserve the lead wire. You are left with a block of tar. Set the unit outside when it is very cold, and let it freeze solid overnite; or place it in the freezer section of the fridge. The next morning, short the high voltage lead wires with a clip lead, and connect 110 volts across the primary. Since the cores on these transformers are shunted, they may be shorted without harm or blowing fuses. Let the unit cook for 15-30 minutes. Disconnect your leads, and with the chisel and hammer, chip a groove around the block. You want to score a groove lengthwise that will allow the block to cleave in two. Then starting from one end of the block, chip until you hit the core, then do the same with the other end. Pry and chip the tar away from the core until the xfrmr is free. The core may then be disassembled, and the windings removed and examined. Kerosene and a stiff brush will clean up the windings and core of any remaining tar. The "cold-cook" method is fast, clean, and works very well. Since the tar is frozen it chips away cleanly. The "cooking" softens up the tar around the core allowing it to release. The only other ways I know to free the cores are long soaks in solvent such as kero or gas, (the nasty waste does make a good crack filler), or melting out the tar with external heat from a fire or oven. Most units fail when the high voltage breaks down the tar insul- ation. The resulting carbon track shorts the winding. Simply removing the tar brings them back to life. Other times the coils break down internally. In this case I discard the winding after disassembling the core, and replace it with a good winding from another unit of the same model with the same type failure. While the core is apart, you can beef up the current output by removing a few of the shunting plates between windings. Never take out more than 2 or 3 of these plates per side, as the additional power output will burn out the secondaries. Generally I get about 70-75 ma out of 60 ma units after I have finished. (Continued in next post) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 05 Nov 93 04:13:56 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ (cont.) Rebuilt units need a little protection from the high voltage secondary outputs. The first thing I do is solder on a new lead wire to the high voltage windings. The HV secondaries are wound with very fine magnet wire, in the 30 ma units the wire is not much thicker than a coarse hair. Once a good solder connection is made, bed the connection and the first 1/2 inch or so of lead wire to the top of the HV winding with hot glue or clear epoxy. The lead wire need not be anything special, any thin insulated stranded wire may be used. Heavy wire increases the chances of a failed connection due to mechanical stress. When setting the unit up to fire you simply have to route it on insulators. The windings themselves are wedged against the core to prevent vibration. I have seen wood, bakelite, and plastic wedges used commercially. What I like to do is to soften up some 30 mil polyethylene plastic sheet in boiling water, and heat the core in a warm oven. I wrap dry softened plastic around the core and gently force the windings down on it. Once cooled, the windings have some insulation from the core, and they will not vibrate. The base wire from the HV windings must be grounded to the core. Use the original grounding point if possible, if not you may split the core apart slightly with a thin blade and insert the wire into the gap before you clamp the core back up. If required you may splice on a small piece of wire for added length. Neon sign transformers that have been rebuilt may be fired dry. The tar used to pot the cores for neon use does not really insulate well against the RF and kickback from the Tesla Tank. The units last longer when they are freed of the tar potting. The only other choice is to sink rebuilt units in mineral or xfrmr oil which is a very good RF insulator. I choose to fire them "dry"; it works, and there is no mess. Neons may be run in parallel to deliver the current required to fire medium sized coils, and I have run up to 4000 watts with banked neon power supplies. The general practice is to run these banks off of 240 volt feeds controlled through a variac. Neons with matched outputs are run in pairs in these banks. The primaries are paired up in series, and the secondaries are all paralleled to the HV buss. Phasing is important here, and each transformer must be checked as it is added to the bank to ensure it is in phase with the other units. If an xfrmr draws an arc from a lead wire brought to the HV buss, the primary or secondary connections must be reversed. Neons typically have an efficiency of about 50%, in that they draw twice as much power as they put out. This problem can be resolved with the use of power factor correction (pfc) capaci- tance across the line. The pfc capacitors used are the same as for alternating current motors. The voltage rating should be at least twice the line current used, and I like a 4x voltage margin for long life. The formula used to determine ballpark pfc is as follows: 9 10^ C = Corrected kVA ------ 2 2(pi)fe^ This should read C = Corrected kVA times (10 to the ninth power) over, (2 pi times f times e squared) C = required capacitance in microfarads f = frequency of applied voltage e = applied voltage CORRECTED KVA is determined by dividing the volt*amps (watts) output of the neon sign xfrmr by 1000 Using a pair of rebuilt 12 kv, 60 ma neons, with 2 shunting plates removed from the core next to each HV winding, and power factor correction capacitance, you can get a nice 1.5 KVA Tesla power supply with over 90% efficiency. Total cost: $5.00 for the pfc capacitors, and a few hours of time. I have unpotted dozens of neon transformers from many different manufacturers. I have tried to make this as informative as possible, and have checked it over for mistakes. If I have erred, or was not clear on something, please let me know. Use common sense, and don't expect the first attempt to work out. On my first attempt I managed to destroy a HV winding during the unpotting, as I did not know where the windings were located on the core. But once you see one core unpotted, with minor differences, you have seen them all. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-04-93 22:11 From: David Tiefenbrunn To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ On 10-30-93 Richard Quick wrote to Guy Daughterty... RQ> But if everybody thinks I'm wacky, should I stop posting? I RQ> don't want to waste people's time. I just thought you all RQ> were interested. I'm interested. On another un-usual experimental topic, have you ever seen / read about / or heard of a rail gun? Dave (1:320/5967) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-06-93 19:22 From: Richard Quick To: David Tiefenbrunn Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ DT> I'm interested. On another un-usual experimental topic, DT> have you ever seen / read about / or heard of a rail gun? Sure, two different types. Steve Hanson runs a particle accelerator rail gun in his basement. It is small, but it cooks! He has extensive vacuum equipment, and the basic setup looks like this: Two copper rods form the rails. They are set up in parallel bar fashion with the bases mounted in an insulator block. At the base of the rods, near the insulator, he wraps a tungsten filament removed from a common light bulb. He places a glass cylinder, like an elongated bell jar, with a target mounted in the closed end, over the rails. The jar is sealed at the base and pumped down to a hard vacuum. Two high current lead wires are connected to the rails. They are epoxies into the insulator base so as to be air tight. He takes a HVDC power supply and charges a massive capacitor bank. He throws the switch, and BANG! the tungsten is vaporized. The plasma is highly conductive, and maintains a current flow between the rails. The high current produces electro-magnetic force which propels the plasma under high acceleration down the rails and into the target. A regular microscope shows the plasma impact damage on plate glass targets. It really sinks the tungsten into the material. Steve publishes a journal in which he covers his work. You may write to him at: 35 Windsor Drive, Amherst, NH. 03031. The other type of rail gun uses a monorail system. A "bullet" of conductive material is loaded onto a single nonconducting rail surrounded by heavy coils. The coils are energized by a timed capacitive discharge. A special rotary gap with varied spaced electrodes may be used, but recent work points to computers to control to pulses. Timing is most critical. The heavy current flow through a coil induces a current in any conductive material, in this case the projectile. The circulating currents in the projectile produce a magnetic field, which repels it from the coil. As it passes the next coil down the rail, the second coil is pulsed and so on. Since the current and voltage from the capacitive discharge is high, the forces imparted to the projectile are great. I believe the speed of sound has been broken by projectiles from small "hobby" guns. I have not had contact with a working monorail gun. I have seen several photos. Information Unlimited, P.O. Box 716, Amherst, NH. 03031, tel: 603-673-4730 (9-5) may have additional information on monorail guns of this type. Then there is this guy in California with a multi-gigawatt Taser gun.... The commonality of these systems is capacitive discharge, and power supplies. You must have HV pulse discharging capacitors and a high current, high voltage, power supply to experiment in these areas. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-07-93 16:14 From: Richard Quick To: Dave Halliday Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ- DH> Hi Richard - again, thanks for the fantastic video! Loaned DH> it to my dad this morning - he used to teach physics ( still DH> writes textbooks ) and is a Tesla fan too... DH> Anyway, I was wondering how you went about getting your pole DH> pig - line xfrmr - and how much it set you back... I called DH> our local City Light and they cannot sell them because of DH> the EPA regulations. They actually ship them to some company DH> overseas for salvage... I will try some of the smaller PUD's DH> and see if they are not so "Politically Correct" Well you can try the utilities, I did, with no luck:-( Unless you are willing to climb the fence into their transfer yard and climb back out, in the dark, with a 200+ lb. pole pig under your arm, you will not get one there :-) I bought mine from: Larry J. Rebman The Transformer Bank, Inc. University Technology Center 1313 Fifth St. SE Minneapolis, MN 55415 Tel: (612) 379-3958, Fax: (612) 379-5962 The transformers they sell are brand new GE surplus, certified PCB free. GE manufactures at their plant in Hanover, North Carolina. Unsold units sit in the yard, and on GE's balance sheet, for 5 years and depreciate. Once GE has depreciated them to zero, The Transformer Bank buys them for 50 cents a pound. The Transformer Bank enters all of the plate information from these surplus pigs into their database in Minneapolis. They will fax you the plate specs on any surplus pig in the Hanover yard. Once you have chosen the xfrmr you want by comparing a few plate specs, call them for a price, then send them a certified check. The retail cost is a little over $1.00 a pound, so figure a 230 pound, 10 KVA xfrmr, will run about $250.00. The Transformer Bank has a shipping contract with Consolidated Freightways. The units are shipped directly from the Hanover yard. The contractual rate is about 50% the normal retail rate, and the Transformer Bank passes the entire savings on to the customer. Figure about $50.00 shipping per 250 pounds. My pole pig ran $303.00, including shipping, and was delivered to me ten days from the date I dropped the certified check in the mail to Minneapolis. It arrived still strapped on the original pallet, and it had no dings, dents or chips. The pallet was heavily weathered as one would expect, but once the pig was cleaned up, it looked (and is) brand new. The unit came with certification papers that match the serial number on the plate, showing it to be PCB free. Copies of the certification are on file with GE, so disposal or transfer of the pig will not be a problem. In shopping for a pig, you should be looking for a unit with two high voltage bushings, no taps, 120/240 primary, and a secondary voltage of 14,400 volts or higher. Remember! I am accustomed to running pigs backwards! You will always see me refer to inputs and outputs in reverse of utility practice when I talk about pigs. Thus my "primary" is the actual secondary, and v.v.. The kVA rating on pigs are of course for continuous duty. They will run 24-7 at the plate rating and not warm appreciably. You may run them at twice the rated kVA output for 5 min or so without any problem. 10 kVA seems to be a nice size for high powered Tesla work. The 15 kVA pigs have a substantially larger core, and require more energy to energize. Since the cores on these are shell wound, you will not encounter appreciable core saturation. These units must be run with a heavy current limiter or they will pull the entire neighborhood into your experiment. You should be able to energize them without dimming the lights. Due the heavy current limiting required, your input and output voltage will be lower than your line. My 10 kVA pig has a rated output of 23,890 volts, but with current limiting, the calculated output is closer to 20,000 volts. Both resistive and inductive current limiting may be used. The inductive delay (about 1 sec.) in the current limiter and variacs make control pretty jumpy, so it is best to use at least some resistive ballast to smooth things out, especially if you are not accustomed to these powers. The smoothest coils use all resistive ballast, but things get pretty hot. The best combination seems to be 6 or more paralleled oven elements placed in series with an inductor. I opted for pure inductance because I hate to waste energy as heat, but I feel the tug on my variacs through the control wheel, and Gary has seen some arcing in the variac brushes when the current limiter finally lets loose. When I add some resistive ballast these problems are eliminated. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-10-93 12:15 From: Richard Quick To: Dave Halliday Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ -=> SEZ Dave Halliday to Richard Quick 'bout Tesla Video <=- RQ> sections of my preliminary Magnifier work, which I encourage RQ> others to follow up on. If you and your friends decide to RQ> take on DH> That was at the beginning - fascinating because I was DH> completely un-aware that the other coil was involved - I DH> just thought it was part of the background because I could DH> not see any arcs coming from it. DH> Very interesting that so much of the energy from it could be DH> so closely coupled to the second coil... This will be a fun DH> winter project!!! The "extra coil" is completely uncoupled from the driver system. Current from the driver is being fed into the base of the free standing "extra" coil by transmission line. While you are not able to see in the video... The transmission line glows with corona from the heavy current. DH> I was talking with one of the people and they agreed to DH> start on a smaller coil - I was thinking in the order of 4" DH> diameter and about 3' long. The aspect ratio (height to width ratio) is important. The planned coil has an aspect ratio of 9:1 (36" long, 4" diam.) this should be reduced to no more than 5:1 on a 4" diam. coil. 6" coils work best with 4:1 aspect ratio, anything larger 3:1. DH> The vacuum gap looked easy enough to build. This gap underwent about two weeks of prototyping not shown in the video, but once it was working, it worked great. It has trouble at power levels over 5 kVA. After an evening on the big coil at 8 to 10 kVA I had some pitting and melting of the electrode faces. This was reduced as I cut back on the number of electrodes, increased the size (both length and diam.) of the electrodes, and allowed for a larger gap between electrodes. DH> file about building a capacitor also looks pretty DH> straightforward. I guess the main deal there is just to be DH> patient and very careful. I have a vacuum pump so getting DH> all the air bubbles out of it should be pretty DH> straightforward. These homemade capacitors are high Q, reliable, and relatively easy to build. Pumping them down will really help. > please feel free to fire of any questions to me. As > you can tell, I have some little experience with all of these > systems, and may be able to help. DH> Questions???? Hoooo boy - stand back! DH> You talk a bit about the kind of plastic to use for form for DH> the secondary coil. There is PVC and ABS available readily. DH> You mention that PVC is better but you also say not to use DH> Schedule 40 - both kinds of pipe are rated as being Schedule DH> 40... PVC is the worst plastic for use in secondary coils. It is "lossy" (high RF dissipation factor) and has a low dielectric strength. But it is commonly used because, as you mentioned, it is available. Coil forms, regardless of material, should be as thin as possible. Schedule 40 is thick, and is rated for pressure use. Try to locate the thinner "drain" pipe or "flume duct" PVC or other thin wall plastic. If PVC is used, it MUST be dry (baked is preferred) and well sealed with a low loss sealant like poly- urethane or two part epoxy. DH> How about plexiglass... Acrylic and plexiglas is pretty good. Dielectric strength could be better, but the RF dissipation factor is much lower than PVC. I have a couple of small acrylic secondaries and I have been pleased with them. Plexi in large diam. tubes gets expensive. DH> What determines a certain plastic being good? Should I look DH> up the dielectric constants and select for a high number? A combination of dielectric strength, and the RF dissipation factor. PVC fails this test, and requires drying and sealing to make it suitable. Teflon is the best; good dielectric strength, and the lowest RF dissipation factor; then comes polyethylene, polystyrene, and polypropylene, all of which are good. The same standards are also used to judge capacitor dielectrics and for general insulation in Tesla work, and the plastics rate in the same order. You asked about power supplies: The pole pig info is on it's way. See my two part post on obtaining neons for free, and rebuilding them for high output, high efficiency, Tesla power supplies. Remember Tesla power supplies must be protected with extensive RF choking, and safety gaps. This is especially important with neons, which are much more delicate than pole pigs or potential xfrmrs. I also use bypass capacitors. For bypass capacitance across the power supply HV terminals you WANT a dielectric with a high RF dissipation factor. Barium titanate capacitors with a DC rating are ideal for this use. Use a 4x voltage safety factor. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-10-93 22:16 From: Richard Quick To: Dave Halliday Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ >< DB> How did you go about winding your coil? What are the specs? The first step in winding a coil is to select a coil form. The coil form should be a low loss material (we are talking RF losses) like polyethylene, polystyrene, or polypropylene: but the most common material is PVC plastic drain pipe (thinnest wall is best) which is high loss. I used a section of PVC thin wall flume duct. Ratios of coil height to width are important. Small coils work best with aspect ratios (height to width) around 5:1 - 4:1, larger coils (over 8" diam.) have aspect ratios around 3:1. Now we are talking about the actual winding length here, so allow an extra inch or so of coil form on each end. Determine the length required and cut the ends square. The form must be sanded smooth of surface imperfections, dried thoroughly, and if PVC is used, it must be sealed. A good sealer is polyurethane, another is two part epoxy paint. By sealing the surface of the PVC before you wind on wire you can negate the excessive losses in PVC plastic coil forms. If necessary the coil form may be sanded again after the sealer had dried. The coil should be wound with good quality magnet wire. I use double Formvar enamel coated magnet wire. Magnet wire gives you maximum inductance. A coil should have over 900 turns, but not too much over 1000 turns. There is a little leeway here. Select a gauge of wire which will allow the aspect ratio and number of turns to fall within this range. I dug that up as it pretty much explains things, and you may have missed the post. DH> What determines a certain plastics being good? As I omitted in the other message, the dielectric constant is not the factor to go by when choosing a coil form. It is really preferable to use a plastic with the lowest dielectric constant. The reason for this is you want the distributed capacity of the coil to be as low as possible. Capacitance in a coil stores energy, and we want the throughput to be as rapid as possible. The distributed capacitance in a coil retards the current peak that follows the VSWR (resonate rise). Coils have enough problems with distributed capacity from the length of wire, the closeness of turns, and the number of windings. No need to make things worse by choosing a plastic with a high dielectric constant. What is most important in choosing a coil form material is the dissipation factor. The dissipation factor of all commercial plastics has been calculated, and somewhere in this mess I have those figures. If my memory serves me correctly, the standard RF dissipation factors are based on a frequency of 1 MHz, close enough to judge if the plastic is suitable for coil work. The next important factor to look at is the dielectric strength. This should take second place to dissipation factors if your goal is to build the most efficient coil possible. Proper con- struction, more than anything, prevents electrical breakdown. Even if the dissipation factor is very low (good efficiency) it is best to use the thinnest wall coil form possible. Turns of wire, coats of sealer, and hard plastic end caps will stiffen the coil some. Low density polyethylene forms (such as wastebaskets) give coils with very high "Q" factors (a measure of efficiency) but are difficult to work with, as this plastic is VERY flexible. As far as the electrical strength of a coil wound on a very thin walled plastic tube, it should not break down internally if THE WIRE IS NEVER ALLOWED INSIDE THE COIL FORM. Do not drill holes or introduce the wire into the side of the coil. A hole anywhere on the coil sidewall will cause a failure regardless of the di- electric strength of the coil form plastic. My coils are capped top and bottom with plexiglass plates that are approximately the same thickness as the coil form wall. I use two-part epoxy cement and I seal them airtight. It is OK to drill one small hole in the bottom plexiglas plate to equalize air pressure, but I do not. The air terminal capacitance is connected by lead wire (I just use the magnet wire and avoid splicing) from the top of the coil. The lead wire is "air wound" up to the terminal, with the turns about the same diameter as the coil, or a little smaller. You will see me doing this in the video when I set up for a low power test in the garage. The terminal capacitance must have a diameter greater than the coil form, or spark will break out; either from the top of coil, or from the air wound turns connecting the coil to the terminal. The other construction secret not covered in the video is the ground connection. Once the coil is wound and sealed I take the base wire and pull it up out of the sealant until it is free all the way to the beginning of the first turn. I clip off the excess wire, leaving about a 2" tail. I lay the tail on a metal block, and using a small ballpeen hammer, flatten it out as best I can. A strip of copper sheet about 3/4" by 2" is then cut from stock and bent slightly to match the curvature of the coil form. Solder the flattened tail to the back of the copper strip. Position the strip on the coil form just below the bottom turn of wire, and scribe a rectangle through the sealant all the way to the coil form plastic. Remove the sealer from the scribed area, then score and clean the bared plastic. I then use epoxy to bed the copper strip. This forms a high current grounding plate without drilling. Ground wire or strap (preferred) can be held in firm connection to the plate with tape or a large rubber band. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-11-93 17:08 From: Richard Quick To: Robert Taylor Subj: Re: 10KVA TESLA COIL ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ -=> SEZ Robert Taylor to George Powell <=- > using neon xformers.. GP> Do you have any probs with the xformers heating up after a GP> while? RT> To be honest--has been a while since I've had my xformers to RT> play with. But as I remember, the Jacob's Ladder hook-up RT> didn't cause any unusual overheat. You might check the size RT> of your initiating gap at the bottom of the ladder. If it's RT> too close--it will put extra strain on the xformer. Nope, it will not make any difference. The gap at the bottom of the rails can be closed and the xfrmr will not be subject to any extra strain. If the rails are properly set, the gap will be pretty close. RT> One thought--if your xformer is in a small case, the RT> overheat may be natural. Even in a big case the heating is normal. A bigger case means it takes longer for the heat to get to the point where you feel it. RT> The ones that I used were fairly big monsters that weighed RT> in at about 20 lbs. If yours is in a case about 5" high by RT> about 10" long--then yours may be prone to overheating. It's not "overheating", it's normal heating. Unless the tar is melting, or output is diminished, there is no problem. RT> However, if you have any questions as to your coil's RT> integrity try using a VOM or continuity tester on both the RT> secondary & primary & the case to make sure that there are RT> no obvious shorts. A serious overheat can really test your RT> fire insurance. Doubtful, the secondaries can be shorted without any harm, and no overheating will result. Shorts through the tar potting form carbon tracks which are high in resistance and may not be detectable with a VOM. And since these xfrmrs are magnetic leakage shunted in the core, a short in a HV winding will basicly cut the secondary out of the field flux generated by the primary. The best way to test these suckers is to grab some HV rated wire and draw an arc from each HV bushing to the case. If the arc sputters, is weak, nonexistent, or intermittent then the core should be unpotted and the winding replaced or restored. As I mentioned in another post, about half the time unpotting alone will cure a carbon track short. RT> You might also want to hook your VOM up on the primary side RT> & monitor your current draw (should be some specs on the RT> case as to 120 VAC draw). If you see way-out draws or if RT> the draw starts up w/time--then you may have a problem w/ RT> the windings. If you go by this then every unit tested will show a problem unless they were power factor corrected at the factory. The plate specs give the OUTPUT wattage, output voltage, and output current in miliamps. If you measure the input power vs. the output specs you will find 50% of your input energy missing. The unit gets hot.... You will lead Mr. Powell to believe there is a problem in the core when that may not be the case. Due to the design of the core this is completely normal. Fully one half of the input power is converted to heat eventually, as energy is bypassed through the core shunts to limit the output. Unless the xfrmr is getting hot enough to melt the potting, or the output is markedly diminished, there is no problem. If tar is melting, then the most common problem is a shorted primary winding. I have unpotted dozens of these transformers, and my experience covers every major manufacturer. I have seen nearly every problem that can cause failure, as I only rebuild failed units. I have experimented with the effects of altering the core shunts for greater output, and I have experimented with power factor correcting in these units. I have done testing to measure the efficiencies, and have developed procedures to improve these efficiencies. In other words I know these cores backwards and forwards. Mr. Powell may not have much experience with magnetic leakage controlled xfrmrs. He is most likely interpreting the normal heat production as a problem. A normal step up xfrmr weighing 10 lbs, with a throughput under a kilowatt, would not get warm. The normal step up xfrmr is not shunted, and wastes very little energy. Yet the neon gets quite warm with throughputs of only a third of a kilowatt. The neon is a different breed, and produces as much heat as output. I hope I have set the record straight. If you doubt my analysis, please unpott a neon core, and look at the physical placement of the shunts. You will wonder how any magnetic flux at all can get to the secondary windings. The shunts are positioned so as to place a direct magnetic bypass that completely surrounds the primary. It is in effect, a built in magnetic short circuit. The field flux passed through these shunts is wasted energy, and the wasted energy heats the iron core. If you have a 360 watt neon core, no power factor correction, and no core modifications, you will get about 360 watts of heat if you put a Jacob' Ladder or Tesla coil on it. 360 watts of heat will bring the core temp up quickly and it will stay quite warm to the touch. Yet everything is working fine, except for your efficiencies. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-12-93 14:56 From: Richard Quick To: Dave Halliday Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ -=> SEZ Dave Halliday to Richard Quick <=- DH> Hi Richard - again, thanks for the fantastic video! RQ> Larry J. Rebman > The Transformer Bank, Inc. > University Technology Center > 1313 Fifth St. SE > Minneapolis, MN 55415 RQ> Tel: (612) 379-3958, Fax: (612) 379-5962 DH> GREAT!!!!! >The retail cost is a little over $1.00 a pound, so figure a 230 >pound, 10 KVA xfrmr, will run about $250.00. RQ>The Transformer Bank has a shipping contract with RQ>Consolidated Frieghtways RQ>My pole pig ran $303.00, including shipping, and was >delivered to me ten days from the date I dropped the >certified check in the mail. Your shipping rate may be higher since you are all the way cross country, and your delivery time will most likely take longer. Still, where else are you going to go? RQ>The unit came with certification papers that match the serial >number on the plate, showing it to be PCB free. DH> This is exactly the info I have been looking for! Having been there I pretty much know the score. I looked for over a year for a supplier for these units, while the utilities educated me on the EPA requirements. Do not accept a pig, even a free one, if it does not have PCB certification papers. Some pigs I have seen will carry a PCB free cert. number on the plate, and that too is OK. You can then write the manufacturer and they will mail the papers if you provide them with the number. It is not the PCBs that bother me. The problem occurs if you want to sell or dispose of the unit. With current regulations, and lack of certification, you have a legal hot potato that can cause you problems. I have not seen the letter of the law, but the utilities have informed me the legal implications are rather severe, and place serious liabilities on the owners of pigs containing PCB. There are a few transfer yards that have clean room holding facilities. They are expensive to own, maintain, and operate, but they are licensed to drain the old oil, rinse the cores, and scrap them. Cores can be purchased for a few bucks ($5-$20). The problem is that the cores are old, frequently damaged, or contaminated with water (from sitting in the rain) and won't hold up unless they are dried, repaired, and resubmerged in xfrmr oil. Better off to pay a little more and buy a surplus new unit. Another type of xfrmr excellent for coil work is the potential type xfrmr. These are potted in plastic, not tar, and are not shunted like neons. They carry the HV ratings required, and/or can be placed in series (two 7500 volt units for a total of 15KV). Since the cores are NOT shell wound, they will saturate, and so they are safer and require little or no current limiting. These xfrmrs may be obtained from utilities without the problem of EPA regs. The normal ratings on potential xfrmrs runs from about 1-3 KVA, and so are ideal for the middle area between neons and pole pigs. The surplus cost on these runs from $25.00 - $50.00 each, but they will be used, not new, surplus. These xfrmrs are used to step down a kilowatt or two for cooling fans, and for line voltage sensors in substations; so they are not manufactured in the quantities that pigs are. They are much harder to find in the surplus market, but definitely worth grabbing if you come across one. If you developed any contacts at the local utilities while searching for a pig, you might call them back and ask them about potential transformers. DH> I also got your postings on neon sign transformers yesterday DH> - the idea of getting the reject units from a sign company DH> is obvious - should have thought of that one... DH> ( sound of head hitting desk ) Yeah, neons are not built very solid. The secondaries are el'cheapo, as the thinnest wire possible is used. The failure rate is pretty high even in their rated service. Since the copper content is low, they are not commonly recycled, and the cores pile up quickly. The higher the output current rating, the better they are built. Once the tar potting is removed, they last much longer in Tesla use. Tar is a very poor RF insulator. To a Tesla discharge, the tar looks more like an impedance! Pick up dead units for nothing, remove the tar, modify the core slightly, and use pfc capacitance; then they will serve cheaply and effi- ciently. You must use heavy RF choking, safety gaps, and bypass capacitors if you want more than a few hours of heavy duty service from a bank of neons. As far as RF choking is concerned, the HV filter board I designed and built in the video is the best I have ever used. I have not had a single xfrmr failure since I built it. Bypass capacitors on neon power supplies must be center tap grounded, so I switch to using a different capacitor setup. As the secondaries on neons are center tap ground, so must the bypass capacitors. I use two stacks of caps; each stack has a connection to a HV bushing, and to the system ground. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-13-93 13:26 From: Richard Quick To: Brian Mcmurry Subj: Re: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ BM> On Sun 7-Nov-1993 4:14p, Richard Quick wrote: RQ> These units must be run with a heavy current limiter or they RQ> will pull the entire neighborhood into your experiment. You RQ> should be able to energize them without dimming the lights. BM> I've been following all the Tesla threads and wonder what BM> your monthly electric bill runs. :) BM> BTW, keep it coming. Thanks, another vote of confidence. Much appreciated. Well it's not as bad as it sounds. Tesla had one god: EFFICIENCY! If you follow his work, you will find that efficiency is what makes his systems beautiful, they don't waste much. At one time I hooked a standard electric company wattmeter up to the 240 V 100 A single phase supply circuit that I am using at this time. Over a period of a month or so I used about $20.00 worth of electricity to actually fire coils. There are other circuits that I tap to provide utilities to the coils. Some of my spark gaps use compressed air to quench, others use 240 volt vacuum motors, yet another uses muffin fans, I also run a rotary gap motor in combination with a static gap on all my bigger stuff for better efficiency and performance. These utilities might use 25% of the energy I put into the coil, so add another $5.00. I would feel comfortable saying $25-$30 a month. Even when I run a big coil at 8-10 KVA I don't leave it running all night. Five or six runs of between 3-8 minutes each is enough to satisfy me, give me the data I need to improve, and get some good video. I don't fire every night. It is much more fun to have company over and have a friend video tape the coils in action. The big stuff has to be fired outdoors since I don't have the ceiling height or floor space to fire anything bigger than an 8" coil indoors. Outdoor firing is weather and neighbor dependant. I have had some bad luck firing coils in windy conditions, and the neighbors have threaten to get their torches and burn me out if I fire too late at night (spark gaps sound like unmuffled chainsaws at this power level). The pole pigs used in heavy work are over 95% efficient, but current limiting, depending on type, can waste 50% of your input energy in the form of heat. In every area of my work I have pushed the edges of my efficiencies, just as Tesla would have. I use efficient step up power supplies to drive the oscillators, with efficient: current limiters, tank circuits, capacitors, spark gaps, etc.. With neons power factor correction helps a lot. The goal in 1/4 wave coils is to turn every watt possible into discharge, and waste as little as possible between the wall and the discharge terminal. I am very good at it, and I believe I am holding record spark lengths for input powers. If I do not hold records, then I am very very close, but I have not seen any system outperform mine up to 10KVA. And there is still room to do better with my 1/4 wave coils. To give you an idea, my power processing efficiencies range from 460 to 1100 watts (power drawn from the wall), per foot of spark generated on my large coil. These figures are not linear, as I am not using a synchronous rotary spark gap. The average strike from the coil will reach anywhere from nine to eleven feet at 5-8 KVA. But have seen more than a few 15' strikes at powers under 10 KVA. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 13 Nov 93 19:17:00 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Tesla "Q" Factors Since some people are saving these posts to disk, and at least one other person (Dave Halliday) is going to embark on some coil building. I thought I would take a moment and discuss some Tesla theory that directly relates to coil efficiencies. The subject is the "Q" factor. Q is literally the "Quality" factor. There is no real way to calculate Q in a subassembly, assembly, connection, or component in a Tesla coil. But Q exists. Q in a secondary coil can be calc- ulated from the physical coil data after it is wound, but with most coil parts it is more like a "god". Some people dedicate their lives in search of god, coilers dedicate their lives in search of higher Qs. The Q factor of any Tesla component is a combination of material, design, and construction. A coiler never reaches near theoretical Q factors. We don't wind our coils out of high temperature super- conductors and fire them submerged in liquid nitrogen. Indeed people hardly ever submerge their coils in oil like in good old days. Oil submersion is probably the single greatest thing you can do to raise the overall Q factor in any Tesla coil system. In the old days they almost had to submerge the coils in oil to regain Q that was lost in the use of "classic" materials such as wood or cardboard coil forms, rubber or tar insulators, silk or cotton covered wire. These "classic" construction materials are inherently low Q and result in designs and construction techni- ques that are also low Q. Builders tolerated oil leaking wooden boxes and greasy cabinets in many cases to get a good spark. We live in an age of high Q materials and construction techni- ques. I have mentioned some of the most commonly used materials in several posts, but I will list a few again. Teflon, polyethy- lene, polystyrene, polypropylene, acrylics, epoxy, hot glue, enamel and polyurethane sealers. As well as the all time classic high Q corona suppressant, mineral oil. Modern coils had to be redesigned in order to take advantage of these new materials. These modern designs differ in many ways from a coil using "classic" low Q materials. Secondary coils can be close wound with magnet wire rather than space wound with insulated wire. Primary coils can be tighter, placing higher inductance into a smaller area. Coupling can be increased dramatically, even in 1/4 wave systems, by using corona sup- pressing sealers and toroid discharge terminals. The coils get smaller, more powerful, and more efficient. Building high Q systems means we can live without things like oil submersion, and still get better spark. With these higher Q systems it is more economical to put additional capacitance and heavier power supplies on line to increase spark than it is to struggle getting the system Q closer to ultimate theoretical. Theoretical Q can go to infinity. So when you are designing, hunting materials, and building; always keep an eye on the Q factor. Attention paid to many little areas adds up to substantially higher overall system Q. A solid ground, tight clean connections, close wound and sealed secondary, primary coil of high Q material wound on a high Q plastic form, well aligned gaps that quench, plastic film HV pulse discharging capacitance, and toroid dischargers are some of the major factors in the overall system Q. Experiments in a variety of Tesla systems shows that the overall Q of the system is limited by the lowest Q component used. The old expression "The chain is as strong as its' weakest link" applies. One area that is frequently neglected by Tesla coilers is the Q of the system RF ground and the ground path. Since coil systems are built from the "ground" up, this is the first thing a good coiler will look at when he goes to set up and fire a coil. I know a guy in New York who fires at about the same power levels as I do. My coil systems are much higher Q and I get much better spark using less energy with a smaller coil. When I took a close look at his coil setup, I noticed he was grounding his coil system to the neutral wire in the breaker box. Walking outside, I traced the ground path to a single 3' copper plated rod driven in by the utility company to ground the supply xfrmr to the building. This is completely inadequate for high powered Tesla work, and is quite unsafe. I also noticed that this guy had a newly constructed all wood power control cabinet. Now there is nothing wrong with that as long as it is well wired with ground strap, which it wasn't. But out back I could see a nice metal control cabinet that had been recently gutted. When I inquired, he stated he had to switch to an ungrounded, wooden, control cabinet because he was drawing sparks to fingers when he touched the controls... The paced distance from the base of his secondary to the 3' copper clad ground rod was slightly over 75'. Most of the distance was traversed with #10 wire. No wonder when he grounded the cabinet and touched to controls he drew spark, his ground path had a high RF impedance, and was backing up like a clogged toilet. I tactfully offered some advice, which was refused. Obviously he had spent a lot of effort compounding his mistakes, and had no desire to let someone else point them out. Don't make the same mistake. Be efficient and safe. Ground properly from the very start. Think Q! ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-13-93 00:42 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Looking over my last post, I can anticipate a few questions. I described a very poor grounding system. What then makes a good RF ground? Well a small coil can fire off a radiating counterpoise (insul- ated metal plate) a few feet square. But when you overload a counterpoise, you get a really wicked corona display, and the coil will produce no additional spark. Having set up various experiments to study this effect, including tracing the ground current, and using a current transformer to measure the RMS amps coming from the base of a Tesla secondary, I can tell you this. There is no such thing as a RF "system" ground that is too heavy. Not in Tesla coils! This is another thing that Tesla went on and on about. But my follow up experiments in this area, which have been quite extensive, show that he knew what he was talking about. I got extremely lucky in that we have a hydraulic car lift in our back driveway. There is a 5' steel cylinder that is 14" in diam.. In addition to the giant piston, there are buried oil and air tanks with all of the associated plumbing. The lift controls are sunk right where the house foundation drains, and it is in the lowest spot in rear of the house. There are no electrical connections made to this lift, air being supplied when needed by a hose. This is my Tesla ground. A good Tesla RF ground is usually developed, not happened upon. It will require some digging and post driving. It needs to be kept moist. Drive deep with copper pipe, or copper clad rod, and keep adding to it. Metal culverts, metal sewer drain pipe should be connected if available. Spread out! Do not drive rod or pipe close together. Four or five 8' rods driven in a long row, 8' apart will work. A ground that you are absolutely sure will ground a bolt of natural lightning, will be heavy enough to ground most coils. DON'T CHINCH! People have asked me if I get complaints about RFI. The answer is no. The reason is that I isolate my coil (system) ground from the copper water pipe and from the utility ground (which in my house are the same). Here is a basic list of things that you DO NOT CONNECT to the system RF ground: WATER PIPE, GAS PIPE, UTILITY GROUND, ANYTHING THAT STICKS UP IN THE AIR (fences, gutters, downspouts) TELEPHONE GROUNDS, & CABLE GROUNDS. Most anything else is fair game, but use common sense. You build or find a heavy ground and you ground your coil system to it. The connections made to this RF ground are as follows: SECONDARY COIL, SAFETY GAP, STEP UP XFRMR CORE, BYPASS CAPACITORS (if using a center tap grnd xfrmr), SPARK GAP MOTOR HOUSINGS, SPARK SHIELDS, AND ANY OBJECT SUBJECT TO BE STRUCK WITH DISCHARGE I don't usually use my caps lock, but this is important. This technique prevents RFI complaints, and will save valuable electronic equipment in your area from destruction. It may save you from the last shock of your life. You ground your variac housing to your neutral wire. All other coil controls, relay housings, control xfrmr cores, line RFI filters (run backwards) are grounded to the variac housing. Strap is taken from the variac housing to a well grounded water pipe. This protects the coil operator and the control circuits from kickback that may come down the line from the step up xfrmr. Two 60 cycle cables are run from the variac, through reversed line filters, out to the step up xfrmr. No ground connection is made anywhere between the 60 cycle cabinet ground and the RF system ground. Hot wires only are given to the primary of the step up xfrmr, as well as any gap motors or other utility for the coil tank circuit. This is called the "two ground system" and it is highly recom- mended. The idea of the two ground system is to send all of the RF to a dedicated ground, and prevent bleedover into your house wiring, control cabinet and/or water pipe. It also protects the operator with two low potential grounds from the lethal possi- bilities of a coil misfire or similar "incident". People have told me I am crazy for messing with all of this HV. I take NO CHANCES with my ground. The ground strap is literally the "bottom line" in coil safety or any other HV apparatus. If an accident occurs; a core shorts out, a capacitor blows, or the secondary decides to dump a 10' spark back to the tank circuit; I know my safety gap - RF ground will handle the load. My 60 cycle cabinet ground is my backup. With tank circuit energies in the megawatt range you can't afford to have a weak point. Keep the physical distance between the base of the secondary coil and the system RF ground as short as possible. I try never to go further than 20 feet for low power stuff, and 15' or less for the high powered work. Use the heaviest strap possible. I run two heavy straps; one from the base of the secondary directly to system ground, the second snakes around and grounds everything else. This is a high Q Tesla grounding system. It gives the best coil performance, the most safety for the coil operator, and guess what? People in my house, and the neighbors next door, can watch TV or listen to the radio, with no snow or static! Even during high power operation! I never get spark from my coil controls. All of the RF currents that are not expended in spark are directly, positively, grounded through a high Q ground path to a high Q ground that is electrically isolated from all other equipment. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-13-93 15:17 From: Dave Halliday To: Richard Quick Subj: Tesla coils ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Hi Richard - I have had time to go through and read the stuff you posted - thanks again for the time you are spending here - this info will be not only a great help but also a great motivator. I had thought about getting back into Tesla coils for some time and it took seeing what some one else out there was doing it to get me started DH> Very interesting that so much of the energy from it could be DH> so closely coupled to the second coil... This will be a fun DH> winter project!!! The "extra coil" is completely uncoupled from the driver system. Current from the driver is being fed into the base of the free standing "extra" coil by transmission line. While you are not able to see in the video... The transmission line glows with corona from the heavy current. I figured that it was not part of the primary / secondary circuit but got it's power through the wire off of the Tesla secondary. Amazing stuff and definitely the next thing to try after building the first coil. DH> I was talking with one of the people and they agreed to DH> start on a smaller coil - I was thinking in the order of 4" DH> diameter and about 3' long. The aspect ratio (height to width ratio) is important. The planned coil has an aspect ratio of 9:1 (36" long, 4" diam.) this should be reduced to no more than 5:1 on a 4" diam. coil. 6" coils work best with 4:1 aspect ratio, anything larger 3:1. ******(cut from another part of a post)******* The coil should be wound with good quality magnet wire. I use double Formvar enamel coated magnet wire. Magnet wire gives you maximum inductance. A coil should have over 900 turns, but not too much over 1000 turns. There is a little leeway here. Select a gauge of wire which will allow the aspect ratio and number of turns to fall within this range. ********************************************** OK - I made an "editorial decision" today to go for a 6" diameter form and make it 24" long. I just was out running errands and got 1,500' of 22 gauge Heavy Formvar insulated magnet wire so with a diameter of 0.0253, this works out to 948 turns - right in the ballpark that you suggested in another part of this post. I think the other people were thinking in the realm of the normal misconception of Tesla coils as being long and skinny but I guess that would make them longer than 1/4 wave... We'll see what happens! Vacuum Spark Gap...the video, but once it was working, it worked great. It has trouble at power levels over 5 kVA. After an evening on the big coil at 8 to 10 kVA I had some pitting and melting of the electrode faces. This was reduced as I cut back on the number of electrodes, increased the size (both length and diam.) of the electrodes, and allowed for a larger gap between electrodes. OK - I wonder if it would be feasible to make it with continuously variable gap size - something with threaded plastic rods... I think that since we are starting with neon sign x-formers, we can just use the standard 6" PVC gap you showed - aren't going to be running too much power through it These homemade capacitors are high Q, reliable, and relatively easy to build. Pumping them down will really help. As I said - I do printing as well as the electronics and computers and every piece of equipment here ( almost ) has some kind of vacuum pump associated with it. These are all rotary-vane types so not really high Torr but should be OK for "potting" the caps in oil. DH> You mention that PVC is better but you also say not to use DH> Schedule 40 - both kinds of pipe are rated as being Schedule PVC is the worst plastic for use in secondary coils. It is "lossy" (high RF dissipation factor) and has a low dielectric strength. But it is commonly used because, as you mentioned, it is available. Coil forms, regardless of material, should be as thin as possible. Schedule 40 is thick, and is rated for pressure use. Try to locate the thinner "drain" pipe or "flume duct" PVC or other thin wall plastic. If PVC is used, it MUST be dry (baked is preferred) and well sealed with a low loss sealant like poly- urethane or two part epoxy. OK - there is some pretty thin wall stuff in our local "Home Center" store - I was worried about mechanical strength though - I can deflect... (Continued to next message) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-13-93 15:17 From: Dave Halliday To: Richard Quick Subj: Tesla coils ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ (Continued from previous message) this pipe with just moderate pressure - I will have to stop into the Cadillac Plastics store and see what they have in their cut-off's bin... Also, I have a small South Bend lathe and could probably get Schedule 40 and then turn off a bunch of it until it got too thin... Baking it and then sealing it is a good idea - I will probably use the slow speed on the lathe to wind the coil so I could also turn it slowly while I was applying the sealer - keep it drip- free... A combination of dielectric strength, and the RF dissipation factor. PVC fails this test, and requires drying and sealing to make it suitable. Teflon is the best; good dielectric strength, and the lowest RF dissipation factor; then comes polyethylene, polystyrene, and polypropylene, all of which are good. The same When I was getting the wire, I made the mistake of pricing Teflon insulated wire. That would be a coil that shocks people twice. You spent ??HOW?? much... You asked about power supplies: The pole pig info is on it's way. See my two part post on obtaining neons for free, and rebuilding them for high output, high efficiency, Tesla power supplies. I got both sets of info - the guy you recommended was out hunting but will be back on this Monday - they knew about Tesla coils though and recognized your name... Remember Tesla power supplies must be protected with extensive RF choking, and safety gaps. This is especially important with neons, which are much more delicate than pole pigs or potential xfrmrs. I also use bypass capacitors. For bypass capacitance across the power supply HV terminals you WANT a dielectric with a high RF dissipation factor. Barium titanate capacitors with a DC rating are ideal for this use. Use a 4x voltage safety factor. Got it - the insulation of the neon is only meant to handle 15 KV, not whatever the coil is putting out... I have a bunch of largish ferrite toroids so I'll use them and a spark gap. The other construction secret not covered in the video is the ground connection. Once the coil is wound and sealed I take the base wire and pull it up out of the sealant until it is free all the way to the beginning of the first turn. I clip off the excess wire, leaving about a 2" tail. I lay the tail on a metal block, Great idea - high current, low impedance and quick connection. Anyway, this message is kind of chopped up, I saved your posts and then just went in with Q Edit and edited and added replies but you should follow who is talking... Again - thanks for your time and info - I'll have to send you copies of the pictures once we start building this puppy! 301-794-6496 (1:109/546) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 15 Nov 93 22:51:20 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Spark Gap Technology I recently explained the definition of "Q", and the requirements and functions of high Q grounding systems in Tesla coils. Another area that needs attention is spark gap technologies. Spark gaps are the "brain" of the Tesla Coil. They are high the voltage switches that allow the tank circuit capacitance to charge and discharge. As performance of the spark gap switch is improved, peak powers in the tank circuit grow without requiring additional input power. When a good coiler sets up and fires a system, the first thing he looks at is his ground. The second thing he looks at is his spark gap system. Before I cover the main points on spark gaps, I want to talk for a moment about their more modern replacements, the vacuum tube, and the solid state transistor (FET etc.). Both modern day replacements can be made to function in Tesla type oscillators in several modes. A single resonating coil may be base fed RF current from solid state and tube drivers, or primary coils may be driven with amplifier circuits. Class C amplifiers are preferred. Both of these modes work well within the power handling abilities of the switch (tube or solid state device), but when it comes to handling raw power, nothing delivers the megawatts like the old fashion spark gap. The spark gap gives the biggest bang for the buck. No discussion of spark gaps is complete without at least a rough definition of "quenching". This term is commonly thrown around when talking about spark gaps. When I began coiling, I saw the term frequently, but never could find a good definition. Quenching refers, more than anything else, to the art of extin- guishing an established arc in the gap. The term points to the fact that it is much easier to start a gap firing than it is to put one out. In Tesla coils, putting out the arc is imperative to good tank circuit performance. A cold, non-firing, spark gap is "clean". It contains no plasma, or hot ions. On applying voltage to the gap, a tension is esta- blished, and electromagnetic lines of force form. The physical shape of the electrodes determines to a large degree the shape of the field, or lines of force, and the resultant breakdown voltage of the gap at any given distance. In other words, electrodes of different shapes will break down at different voltages, even with identical distances between them. Once the voltage punctures the air (or other dielectric gas) the gap resistance drops. The breakdown ionizes the gas between electrodes, and the arc begins to ablate and ionize the metal electrodes themselves. This mixture of ions forms a highly cond- uctive plasma between the gap electrodes. Without this highly conductive channel through the gap, efficient tank circuit oscillation would be impossible. But the plasma also shorts the gap out. A gap choked with hot ions does not want to open and allow the capacitors to recharge for the next pulse. The gap is gets "dirty" with hot ionized gases, and must be quenched. Quenching typically relies on one or more techniques. The most common method used is expending the arc out over a series of gaps. Gaps of this type are know as "series static gaps". "Static" in this use refers to the fact that the gap is not actively quenched. The plasma is formed in several locations, and the voltage at each gap is lowered as more electrodes are placed in series. Heat, hot ions, and voltage are distributed. As the tank circuit loses energy to the secondary coil, the voltage and current in the tank circuit, and likewise across the series of gaps, drops to the point where the arc is no longer self sustaining. The arc breaks, and the capacitors are allowed to recharge for the next pulse. The second type of quenching technique involves using an air blast. A high speed air stream is introduced into one or more gaps. The air stream does not alter the magnetic lines of force that cause a dielectric breakdown in the gap, so gap distance remains unchanged. But once an arc is established, the air stream removes hot ions from between electrodes and physically disrupts the established arc. The gap is swept clean of hot ions, the arc breaks, and the capacitors are allowed to recharge. A third type of quenching used is the magnetically quenched gap. A strong magnetic field is placed between the electrodes. Since this field alters the field formed by the high voltage prior to breakdown of the dielectric in the gap, it may affect the break- down voltage of a given set of electrodes. Once the gap breaks down however, the field shape changes. The high current flowing through the gap generates a field shape associated with the current. By placing a strong magnetic field in right angles to the current flow, the arc is disrupted. This disruption tears at the magnetic lines of force formed by the high current channel flowing through the gap. The arc is twisted, and broken, without having to remove ions. Another type of spark gap called the "quench gap" is used on coils designed for CW output. This gap was discussed in a previous post and will not be covered here. The next stage employed in spark gap technologies is placing a rotary gap in the circuit. The rotary gap is a mechanical spark gap usually consisting of revolving disk with electrodes mounted on the rim. The rotor is spun and the electrodes move in relation to a set of stationary electrodes nearby. As a moving electrode comes near a stationary electrode, the gap fires. As is moves away the arc is stretched and broken. The rotary gap offers the sophisticated coiler the opportunity to control the pulse in the tank circuit. A properly designed rotary gap can control the break rate (bps) and the dwell time. (continued in next post) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 15 Nov 93 22:57:11 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ (cont.) Rotary gaps are run in two modes, synchronous and asynchronous. A synchronous gap runs at a fixed speed and is constructed so that the gap fires in direct relation to the 60 cycle waveform of the line feed to the capacitors. The point in the waveform where the gaps are closest can be changed by rotating the synchronous motor housing or by altering the disk position on the motor shaft. By carefully matching the output of the supply transformer to the value of capacitance in the tank circuit, then running a properly set up synchronous gap, it is possible to have the gap fire only at the voltage peaks of the 60 cycle input current. This technique allows the tank circuit to fire only on the maximum voltage peaks and delivers the pulse from a fully charged capacitor each time the gap fires. If properly engineered, synchronous spark gap systems will deliver the largest EMFs to the secondary coil. They are however, the most finicky, and difficult to engineer of any spark gap, and require sophisticated test equipment to set up. Asynchronous gaps are more common. They work quite well and are much easier to run. Fixed or variable speed motors may be used, though variable speed gaps give the builder the most experimental leeway. Break rates need to be in excess of 400 bps, and I have found that breaks rates around 450-480 bps give the best discharge. Since the gap is firing more often than the 60 cycle waveform switches polarity, more power can be fed into the tank circuit, as the capacitors can be charged and discharged more rapidly. Though this system will increase the amount of spark from the secondary, sparks are generally not as long as with synchronous gaps. At higher powers (over 5 kVA) even a rotary gap will not deliver the quench times required for excellent performance unless it is very large. If the arc in the spark gap hangs too long (NOT quenched), it leaves the tank circuit electrically closed. With the gap still firing energy will backflow from the secondary into the primary and create continued oscillation in the tank circuit. The secondary is then supplying energy to maintain the arc in the spark gap. As power levels build, so does the pressure on the spark gap. Engineering more sophisticated gap systems is the only solution in large 1/4 wave coils and Magnifiers. The easiest solution at 5 kVA is to add a static gap in series with the rotary. By messing with the gap settings it is not difficult to develop a gap system that fires smoothly and quenches well. As power levels increase though static gaps will be overwhelmed. More sophisticated gaps are required to replace the static series gaps. Magnetic or airblast gaps must be used in conjunction with the rotary gap to remove the strain on the rotary and get the quench times back down. Somewhere in here I need to cover the Q of spark gaps. Not all spark gaps have the same Q. I have found that using large series static gaps with lots of electrodes; the Q of the gap system decreases as the quench time decreases! Try to avoid static gap designs with more than 6 - 8 electrodes in series. As my power levels went up, and my spark gap Qs went down, I experimented with options to regain performance. I found that by running static gaps in a combination of series/parallel gave me good quench times and I regained some lost Q from the arc having to make so many series jumps. The idea was to split the arc down into two or three equal paths, reducing the current traveling each set of series gaps. In this fashion I was able to achieve excellent quench times with a small rotary running around 5 kVA. The lesson learned was too many gaps in series kills the Q of a spark gap. By adding gaps in parallel, and reducing the number of gaps in series, some Q was regained while power levels increased. This is a valuable hint in spark gap designs. Another factor that should be brought into this discussion is the effects of cooling the electrodes. To start with, I have never run even a simple static gap without some airflow. My first few really good static gaps were constructed inside of PVC pipe sections with a 5" muffin fan on top. The fan did not supply sufficient air to disrupt the arc, but did assist in removing hot ions, and cooling the electrodes down. This allows for longer run times. As my work progressed I realized that reducing the electrode temperature, while not actually quenching the gap, reduces the amount of metal ions introduced into the arc, and makes the gap easier to quench with an airblast or magnets. I am going to cut this off here. I feel I have covered most of the basics, and thrown a few ideas out into the cyberspace. I would be more than happy to expand on spark gap technologies at any time should somebody have any specific questions, comments, problems, or corrections. Remember, armchair debate is no substitute for actually going out an experimenting with a few live systems, and I am always hoping someone will tell me a better way to do it! One final safety note. Spark gaps are loud, and emit a lot of hard UV radiation. Wear hearing protection as required, and never stare at an operating spark gap without welding goggles. To examine the arc on large coils, a sun observation filter on a small telescope will tell you if your gaps are quenching. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 16 Nov 93 20:33:44 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Well, lets see; I covered basic spark gaps yesterday, next on the list would have to be pulse capacitance. I posted a two part message last month sometime detailing construction of a rolled type pulse discharge capacitor. Since the detail of this partic- ular unit was pretty well covered, I will focus on other homemade types; the flat stacked plate type capacitor, a little on the salt water cap, and a little on capacitor theory as it applies to Tesla coils. I have seen several types of homemade stacked plate capacitors. The two types differ as to the orientation of the plate stacks. Some are stacked vertically, others are stacked horizontally. Before I go into construction details I should cover some of the advantages of flat stacked plate caps for use in Tesla coils and other high voltage applications. Flat plate caps have no inductance. Rolled caps contain two or more plates which are tightly rolled up. Rolled plates exhibit some properties of coils, they contain a certain degree of self inductance. This limits the size of the rolled cap in Tesla applications. As plates grow in size, the self inductance grows, and the caps exhibit self-resonance that will interfere destruct- ively with the oscillation of the Tesla tank circuit. The rolled cap that I posted about previously, is about as large as you can get in a single unit without having self-resonance drop below 1 megahertz. Flat plate caps are better adapted for pulse applications. Rolled caps have to discharge a long plate. The further away the free end of the plate is from the high current terminal, the longer it takes for the cap to discharge. In essence this distance is also an extension of the tank circuit wiring, as the plate gets longer losses increase. Again the rolled capacitor I posted previously is pushing the design limits of efficiency in this area. As the rolled cap gets larger, efficiency of pulsing drops off. Flat plate caps can be constructed to handle higher voltages. Rolled caps have efficiency limits in individual units as to the breakdown voltage. A single dielectric is used per plate. If dielectrics are made thicker, efficiency drops off, if made thinner efficiency increases, but they break down. Using standard materials, the rolled cap I posted about is at the edge of this design limit as well. Flat plate caps can be built for larger capacitance. The rolled cap, because of the design constraints listed above, won't give you much additional capacitance without increases in losses, problems with self-resonance, and lowering of the capacitor Q. The rolled cap that I posted is a good unit. I have built nearly 20 of these caps, and I use them a lot. But do not look to expand much on this design. It has passed through several improvements and I really think it is pushing the design limits in all of the important areas. Next we need to look at the flat plate cap, as there is much to be done yet, but first look at the dielectric. The best Tesla capacitor dielectric is low density polyethylene plastic. Whether you build rolled, stacked plate, or salt water caps you should look hard at this plastic before settling on anything else. It has an extraordinarily low RF dissipation factor for the cost. The actual "in use" dielectric constant on homemade caps using this plastic is right around 2. This is a little lower than the book value, but homemade applications of this dielectric rarely have the close plate bonding that are achieved commercially with clean room vacuum presses. This dielectric melts at 100 deg. C. But because of the very low dissipation factor the plastic is subject to very little in- ductive heating. There is little loss, therefore little heating. When using this plastic however, it is imperative to cover in mineral oil to distribute any heat that is formed, suppress corona and displace air. Plastic caps not covered in oil are guaranteed to fail in seconds. Plates, dielectric, and oil MUST BE CLEAN!... BTW The cheapest and most common plate material is aluminum. In the rolled cap, aluminum flashing is available precut in a perfect plate width, and there are other widths available. Flat plate caps can use flashing, but it is frequently more cost effective to use foil. Now that we have established a few basics, lets talk plate cap design. The first type of flat stacked plate requires the cap be pumped down to a pretty hard vacuum to remove air. This is the horizontal stacked plate capacitor. Typically these are built in a Tupperware type storage box. Plastic, plate, plastic, plate etc. are stacked one atop the other to build up the value. The breakdown voltage is directly related to the dielectric thick- ness used. 60 mil poly sheet is recommended and will have a breakdown voltage in the Tesla tank circuit between 11-17 kv rms input voltage depending on the quality of material, and the cleanliness of the construction. Once the box is filled, and all parallel plate connections are made, high current busses are brought through the lid of the container and sealed airtight with hot glue. Then the lid is snapped on, and it too is sealed with a bead of hot glue around the edges. The next part is important: A single hole is made in the lid for the vacuum connection. A fitting is hot glued into the hole and a hose is attached to the vacuum pump. The cap is pumped down, then the hose is clamped off and disconnected with- out allowing air back into the cap. Submerge the hose in a bucket of clean mineral oil and release the clamp. This allows the oil to backfill the capacitor, and displaces the air that was removed. Once backfilled to normal pressure, I pump them down a second time, and repeat the procedure to make sure that all trapped air between the plates is removed. Air bubbles will form corona hot spots that will cause dielectric failure. The vertical stacked plate capacitor is much like the cap I just covered. But the vertical cap does not require pumpdown. A tank is used to hold the vertically stacked plates and dielectrics. The unit I examined was built in a glass fish tank that employed no metal in construction. Foam padding was laid in the bottom of the tank, and wedged in around the sides of the vertical capacitor stack to cushion it and wedge it in place. The foam padding also reduced the mineral oil required to cover the stack. The reason these caps do not require pumpdown is that eventually the oil will displace the air trapped in the unit. A break in period of low voltage operation assists the removal of trapped air, as the pulsing of the cap vibrates the plates and agitates the air bubbles. The disadvantage of the unit I examined was the glass fish tank. I have seen plastic waste cans that could be cut down for use as a tank in this construction. (continued next post) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 16 Nov 93 21:48:37 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ (cont from previous post) Higher Qs, higher voltage, and additional capacitance in stacked plate capacitors can be easily obtained. The trick is to use thinner dielectric. Now the dielectric strength of polyethylene is given as 1000 volts per mil, but this is not the case in Tesla coils. The standard breakdown voltages of a dielectric are calculated using DC voltage. When you run AC across the dielectric, the breakdown voltage must be divided by two. Then you must figure that the peak voltage from a AC sine wave is higher than the rms voltage most people go by. You meter won't see it, but your dielectric will. Then you have resonate rise in the Tesla tank circuit. To give you an idea of resonate rise in a tank, think about the tidal forces that can be created with timed pushes in a bathtub. It don't take much energy to push water over the side. The same principal operates in the tank circuit in a coil, especially with a synchronous gap system. The current pulsing back and forth from capacitor plate to capacitor plate causes a voltage rise that appears on the dielectric in the capacitors. The standard 60 mil poly is supposed to hold up to 60,000 volts per the book. I have blown holes through 60 mil poly with a 12 kv neon sign xfrmr in a Tesla tank circuit and my gap wide open. My pinky finger fit inside the hole. One of the neatest homemade stack plate caps I have seen was built by Bill Richards of T.C.B.O.R., the cost was pretty low, the materials came from his laundry room, the grocery store, and the drugstore. The only thing required was 56 hours of time in arranging the plates according to Bill. But he did end up with .03 uf 15 kv pulse capacitor in a five gallon bucket. It was quite a performer on his coil at 3600 watts! He shopped around for one gallon ziplock freezer bags with a 3 mil thickness. With a sharp scissors he cut the ziplocks off of the tops of the bags. Then he cut aluminum foil squares that fit inside the bag leaving a 1/2" of space around all four sides of the plate. So the plate had dielectric borders 1/2" on all sides. When two bags were stacked on top of one another, there were two layers of dielectric, for a total of 6 mils. Being practical, Bill figured correctly that the stacked bags would hold up to at least 1000 volts rms input in the Tesla tank. He built up stacks that had a value of about .45 uf each, with each stack rated at 1000 volts. Then he wired stacks in series. By squeezing fifteen stacks vertically into a bucket, and covering the whole thing in about three gallons of mineral oil, he got the required capacitance at the required voltage. Since the electrical forces are so well distributed among hundreds of dielectrics, he had plenty of breakdown safety margin. He gave the unit a couple of days to rest after construction, topping it up with oil as required, and gave her the works at 15 kv on a big coil. The heavy buss wiring never even got warm, and even though it bubbled out enough air to displace a few more pints of oil, it did not break down. It turns out that this is a homemade version of commercial pulse discharging capacitors. Stacked capacitor sections of very high value are placed in series until the proper voltage requirement is met. The cap has a very high Q because all of the plates are very close together, with a minimum of connections and bussing required. They deliver a very sharp pulse discharge. Bill's cap was pretty cramped in the bucket. Because of the square shape of the bags, a rectangular tank would have made things easier to fit and wire. But he ran his buss bars through the side of the bucket (sealed with hot glue) and by snapping on the lid, he could pick it up by the handle and move it around with ease. The novice coiler should think about the capacitor requirements and experiment some before beginning large scale homemade caps. Shop for materials; frequently a wholesaler can be found where bulk products (like mineral oil in 5 gallon pails) can be purchased for a fraction of the retail cost. But just because you don't have some big bang pulse caps on line does not mean that you should wait to begin firing a small coil. Nearly every beginner gets hir feet wet in salt water capacitors. Tesla used salt water tanks in Colorado Springs. A tribute to the genius of the man was his ability to develop his huge peak powers using low Q saltwater/glass caps. I do not recommend glass as a dielectric for coiling work. The dielectric constant is much better than plastic, but the RF dissipation factor is so great that they can rupture from dielectric heating (even in salt water the trapped water under the bottles does not circulate) and they always give a spindly, violet colored spark. Polyethylene again is the material of choice, and bottles and buckets can be assembled in a couple of hours that will fire small stuff. I mentioned he before that I have a friend who is firing 5 kVA coils, and still using banks of salt water caps to keep his investment down. As with any homemade capacitor, the salt water must be covered in oil to suppress surface corona. But the quality of oil need not be high, and the capacitors need not be exceptionally clean. A saturated solution of rock salt is all that is needed for the plates. I think I have accomplished what I intended to say on this subject. As always, I am happy to respond on any unclear areas, the need for additional information, or to note corrections. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-16-93 10:49 From: Richard Quick To: Dave Halliday Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ DH> Thanks for the clarification re: the Schedule 40 pipe - I DH> had always looked at it as being heavier so therefore DH> "better" - never thought of the actual material as being a DH> liability. What about ABS - is there any difference with DH> that? I don't have any experience with ABS plastic secondaries. I have seen some, but had nothing that I could compare to. Look up the RF dissipation factor and that should give you some idea. Off the top of my head, I would GUESS that ABS would work better than PVC; not because I think ABS is any better, but because I know PVC just couldn't be much worse. If I were using ABS I would dry and seal the plastic like PVC. DH> Anyway, we will probably do a couple capacitors in the next DH> week or so. Like I said, I have an OK vacuum pump ( I do DH> graphic arts and printing ) and can pump it out so that DH> should improve things. Good luck on the rolled caps, and look for some different capacitor designs in the next few days. DH> Anyway, many many thanks for your time and help! No problem, glad to be of assistance. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Msg#: 3004 Date: 11-18-93 15:22 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Primary coils In order to move towards a complete presentation we need to talk primary coils. This will take me one step closer to coverage of of the major components in the basic 1/4 wave oscillator. The primary coil is a low resistance, heavy coil, through which the currents produced by the pulse capacitance travel. In discussing primaries we need to cover the "skin effect". Both high voltage and high frequency currents exhibit a property called skin effect. Skin effect describes a situation where the current does not penetrate the conductor, but instead flows on the surface of the conductor. This effect is very pronounced in Tesla tank circuits where both high voltage and high frequency are components of the capacitor pulse. Studies of the Tesla tank circuit current show that the RF current ringing through the tank has very little penetration of the tank circuit conductors. This should be reflected in the choice of the conductors used to wire the tank circuit, and to wind the primary coil. I have had very good luck with conductors that offer a lot of surface area, as opposed to a large solid cross section. The preferred material for winding primary coils is thin wall soft copper water pipe or refrigerator tubing, wide sheet copper strap, or heavy braided copper ground strap. These materials offer a low RF impedance, high Q, and large radiating surface areas. For wiring the Tesla tank circuit, such areas as buss connectors to capacitors, tap leads, and spark gap connectors, any of the materials above may be used, but I prefer heavy DC transmission wire. The DC transmission wire (like battery cable or welding cable) offers flexibility and this material is available with a high grade insulation which helps prevent breakdown. The cables and connections should be carefully examined for areas where Q can be gained. Sharp edges or points should be removed to prevent corona losses, connections should be tight to reduce impedance, and sharp turns should be eliminated to reduce "off axis" inductance. The tank circuit wiring should be as short and straight as possible. The primary coil itself should be wound on a high Q insulator. For a coil form or coil supports, high density poly, plexiglas, lexan, acrylic, or other high Q hard plastic is ideal. The primary coil should be large. I have seen lots of holdovers from the classic age of coil building who insist on 2-3 turn primaries and HUGE capacitors to achieve the proper frequency of operation in the tank circuit. This is wrong. A tank circuit with a small capacitor, and a large primary inductance, will reach down to the same frequencies of operation. A tank circuit of this design will use less power, and therefore require a smaller step up xfrmr. The capacitor will be smaller, which further reduces the cost of the system. A large primary coil offers a much greater surface area for radiation and distributed energy transfer to the secondary. It couples better with a properly designed secondary. Due to these design advantages, an equal or greater amount of power is actually delivered to the secondary, despite the much smaller capacitance and input power. Using a large primary will allow you to reduce the value of your capacitor and your input power by 50% or more (frequently much more) without a reduction in output. Primaries designed to be operated with 9-15 turns will obtain power processing energies that are at least 50% greater than 2-3 turn primaries, provided that the secondaries are constructed to take advantage of the design. Secondary coils with the aspect ratios and numbers of turns that I have recommended here before, work best with large primaries tapped at 9-15 turns. So to give some advice to my friend Dave Halliday, who is building a 6" secondary coil sometime in the near future, plan on winding a primary coil from a conductor material that I have listed above, and use a conductor length of around 75 feet. Your primary should end up about as wide as, or wider, than your secondary is tall. This way the secondary will nest in the large primary. The field flux from the primary will couple the entire length of the secondary winding for a distributed, high efficiency, energy transfer. More energy can be forced into the secondary, with lower input power, and reduced chance of breakdown and loss. Primary coils take several forms depending on the type secondary used with them. Modern secondaries, with high inductance and low aspect ratios, need primaries that are flat pancakes, or "saucer" (rising upwards as the turns move out) shaped spirals. Because this design is so efficient in energy transfers, critical coupling coefficients are achieved without using the old fashion vertical helix type primary coil. When designing primary coils, it is generally a good idea to test a particular coil shape before committing to a time consuming and expensive permanent coil. This is especially true for those who have not had much experience with primary coils of different shapes and sizes. Some cheap low Q wire can be picked up and used to make a temporary primary coil for testing. I set the secondary up on an insulated platform equipped with a good ground, then wind the test primary. To achieve the desired shape I use tire tubes (to build up "saucers") plastic wedges, tape, etc. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-18-93 11:45 From: Richard Quick To: Mark Lawton Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ML> Sounds just like my stuff! Change the Vespas to dirt bikes ML> and you've got it. I haven't built a coil in a few years, ML> but I'd like to send you a blank VHS to get a copy of your ML> work. Write me back with details on where to send the tape ML> and the dough. Richard T. Quick II 10028 Manchester Rd. Suite 253 Glendale, MO 63122 Send a two hour blank VHS high quality tape. $10.00 and a self addressed postage pre-paid mailer. The tape will be return mailed the morning after I get your package. I have sent out three in the last three weeks, so don't worry about me getting rich off this. BTW I will trade video even, tape for tape, for coil, rail gun, high powered laser, and other high voltage stuff. My tapes are one off masters, recorded on SP for highest quality, and a full two hours long. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-19-93 14:38 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Toroid Discharge Terminals Another feature of the "classic" Tesla coil design is the sphere or ball discharge terminal. Tesla clearly was using spheres while he was developing the Colorado Springs oscillator, but during his work there he made the discovery of toroids. Photographs of the Colorado Springs machine clearly shows a brass toroid as part of the antenna mast to prevent corona leakage and premature breakout from the top of the extra coil. As we examine photos of the Wardenclyff machine he built on Long Island, it is clear that the entire tower was constructed to carry the giant toroid terminal. I do not have verifiable inform- ation as to the exact size of this terminal, but it is easily over 50' in diameter. Probably closer to 75-100'. Toroids perform several functions as discharge terminals on Tesla coils. They provide a large top capacitance. This top capacitance helps "cancel" the high inductance in the secondary coil, and increase throughput in the system. They break down at much higher voltages than other shapes. The donut shaped field distributes the charge density. Higher voltages must reached before electrical breakdown occurs. To the coiler this means longer, higher voltage spark. For those of you that have my video, you can see a 30% increase in spark lengths with no change to input power, the only thing I did was add a larger toroid and retune the system. Toroids sever the coupling. This may be a controversial statement on my part. But from what I have seen, appears to be true. A sphere discharge terminal does not want to separate from the field flux interactions between the primary and secondary. The primary field flux wants to couple the sphere discharger into the system as if it were another turn of the secondary. The spark from the discharger will frequently follow these lines of force, and seek to strike back to the primary. The spark discharge bends back down, and aligns itself with the magnetic lines of force. While this may be useful if you wish to visualize the size and shape of the field, it does nothing to increase your spark lengths. A large toroid on the other hand will establish a field identity that interacts destructively with the primary/secondary field interaction. Since this destructive interaction occurs above the top turns of the secondary is does not affect the coil performance or ability to process energy. It does however allow the spark to leave the system unaffected by the primary/secondary lines of force. This has the effect of allowing a clean getaway for the discharge and promotes those long strikes to the ground or other more distant objects. Toriods also have the beneficial effect of lowering the frequency of the secondary coil dramatically. By loading a large toriod on a relatively small coil, a very low secondary frequency is reached. Low frequency in Tesla systems means long spark. This way a small coil can give big coil performance. Because of this ability of the toriod to drop the frequency of the secondary to such low frequencies, it is important to have a very large primary available that can be tapped out to over 10-12 turns in order to regain the system tune. Larger capacitors may be added, but my experience shows that no additional power or capacitance is required to get big increases in spark production. Clearly the toriod is the ultimate in high Q dischargers and radiators in Tesla systems. Now go out and buy one. I can hear Dave Halliday now..... "You Paid _HOW MUCH?_"!!! Yup, spun aluminum toroids are available commercially, and they run hundreds, even thousands of dollars each. My 20" wide by 5" high commercial toriod ran me over 350 clams. My ten inch secondary needs a toroid at least twice as big to achieve optimum performance, and as commercial toroids get larger, the price increases exponentially. I priced a 40" toroid for my coil at $2000.00 not including shipping, and they gave me a six month delivery time... So I built one for $35.00, and it works GREAT! I will never spend another penny on commercial spun aluminum toroids. Here are the brief instructions: I buy the 4" or 6" diam. polypropylene flexible black plastic drain piping. This is made out of ridged plastic, so it does not have a smooth surface, but it easy to bend to form circles of varying diameters. I cut the flange off with a sharp knife, match the ends, and tape them together with wide plastic tape. Once a large ring is formed, I cover the entire surface with wide plastic tape to smooth out the ridges in the material. The goal is to have an even, smooth, surface. The tape choice helps with this con- struction, Mylar and other tapes have no stretch, and are difficult to work with as they wrinkle. I shopped several stores before I found a stretchy material similar to electrical tape. Tape is applied in overlapping strips, or bands, around the drain pipe 4" or 6" cross section. Some surface irregularities are OK. Once the ring is smoothed with a layer of plastic tape, I retape the entire ring with aluminum plumbers tape. This tape comes in two standard widths, I bought a large roll of each. Apply strips of plumbers tape over the prepared surface, make sure the entire surface is covered, and press out any wrinkles with a fingernail or tool. You should now have an aluminized ring. Cut out a circle of thin masonite, wood paneling, or thin plastic so that it will friction fit in the center of the aluminized ring. Place some blocks up under this panel, set the ring in place, and tape the edges all around on both sides with aluminum tape to hold it in place. Spray adhesive and heavy duty foil are used to cover both sides if the center plate. Roll out all wrinkles with a socket or a wood dowel. Works great, about 1/100th the cost. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-19-93 16:49 From: Richard Quick To: Dave Halliday Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ >recently gutted. When I inquired, he stated he had to switch to >an ungrounded, wooden, control cabinet because he was drawing >sparks to fingers when he touched the controls... DH> I also recall stories about ham radio shacks having this DH> problem. DH> Used to work for the public aquarium in Boston and we had DH> grounding problems like you wouldn't believe - I was DH> responsible for all of the non-living exhibits ( PA and AV DH> stuff ) and the ground at every single outlet was at a DH> different potential than any other outlet. I once found 50 DH> volts difference between two located 20' apart... A guide DH> was setting up a temporary exhibit and used both outlets for DH> their equipment. They got a bit of a rude awakening that DH> day A few months back when our local sysop first added this conference, there was an thread on grounds and grounding that you just would not believe (well maybe you would), anyway, the misunderstandings and misconceptions about grounds and grounding, and the bizzare things that happen when equipment and systems are not properly grounded... I have threatened to write a book on the subject and post it chapter by chapter! Tesla was the first person to apply ground to a tuned circuit. His studies of grounds, and grounding practices was extremely extensive, but unfortunately little was documented or survived. By reading the Colorado Springs Notes it is quite clear that Tesla struggled to get a good ground on site for his system and cited the local geology (sand & rock) as the source of his problem. He eventually had to run water 24 hours a day over his ground. He used a two ground system in his CS lab, and documents the resistance, and electrical distance between the two. The system ground was a 3' square copper plate dropped in the bottom of a 12' hole with a couple of wheelbarrows of coke dumped on top. The hole was backfilled and watered as I mentioned. His control, or line frequency, ground was the water pipe. Tesla was capable of producing serious ground currents from the machine. Some of the effects were reported many miles away; sparks coming off the shoes of horses which caused the animals to spook, clouds of insects covered in St.Elmos fire, in addition to the locals getting sparks from their water taps. When he went on to Wardenclyff, he spent half of the tower construction cost on the well with 18" copper plated steel pipe driven into bedrock 50' below the water table. He did not intend to mess around. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-19-93 17:04 From: Richard Quick To: David Tiefenbrunn Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ DT> I have sent you a video tape. I hope the DT> offer is still good. I included a few DT> minutes of the first run of the 45KW generator. DT> The new lab sounds great. DT> Of course, you will probably get the tape before DT> this message. :) Yeah I did! And you will probably get the tape back before you get this message. It went out yesterday. Yes the offer is still good, and so is the tape. You will really enjoy watching it. New lab so far is looking good. Expensive, contractor wants $32.50 per square foot. Read my letter in with the tape about the generator video. I am still kicking myself (I recorded over it before I read your letter) BTW I will trade tapes happily if anyone has goodies I would be interested in. Video tape is an excellent way to archive our little projects; not only are they useful as a personal reference, but they are amazingly effective teaching tools. Nothing explains something like a coil project as well as the designer/operator pointing to, and talking about, the operational working equipment. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-20-93 00:42 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Tesla Coil Builders Association I posted this address a few months back, but many people dropped in recently so I will post it back up again. The organization is called TCBA for short and is run by one, Harry Goldman, retired high school science teacher. He publishes a quarterly news letter called _NEWS_ The news letter has articles submitted by members on a regular basis, new coil designs, sparks gaps (my first submission was published here), spark photos, articles on "classic" coils gleaned from age old science magazines, questions and answers sections, as well as a "trading post" buy and sell section for new and used HV caps, xfrmrs, coils, coil forms, etc., and a list of the best commercial parts suppliers. Subscriptions and membership is $24.00 U.S., $30 CAN., and includes a framable certificate. Harry has been publishing the NEWS since 1982 and all back issues are available as well a comprehensive index of all articles in those back issues. If you are interested write to: Harry Goldman TCBA 3 Amy Lane Queensbury, NY 12804 Tel: (518) 792-1003 Tell him I sent you!!! ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-17-93 23:52 From: Dave Halliday To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ RQ>never stare at an operating spark gap without welding goggles. >To examine the arc on large coils, a sun observation filter >on a small telescope will tell you if your gaps are quenching. RQ>... And if all else fails... Put another megavolt through it I got your whole post on Spark Gaps - Once again - Thanks! I had an experience with hard UV light - purchased a small Lincoln Wire Welder and proceeded to ignore the instructions about covering all parts of the body - I was thinking about metal splatters but I never thought about the UV light - wearing sandals at the time and got a bad sunburn on my feet... Status report: Got the wire for the secondary as well as the basic design. I got the 50' of AL flashing for the capacitor as well as all of the PVC pipe and already had the nuts and bolts... Also, found a *wonderful* three terminal plus ground RF filter for 240 volt @ 60 Hz rated at 60 amps! $20 - couldn't resist! I will be able to keep the rest of the electronics in my house ( as well as the neighbors houses ) somewhat happy :) Still looking for a source of the form for the secondary - will be checking prices at local plastics stores when I go to get the 60 mil. Polyethylene sheet - if not, I will use thin-wall PVC but the stuff I saw at a local Home Depot was poorly out of round... Maybe some plexiglass disks glued inside to maintain shape. The local Boeing Aircraft Co. has an interesting "surplus" store that is a little toooo well known but might have something there. Have a bunch of 3/8" refrigeration tubing that I can use for the primary - also into home brewing and this stuff comes in handy... Still need to get the step-up transformer - already have a 12kV 30mA neon but the "potential" transformers you mentioned that were used in power substations sound very good too - will check locally. Pole pig will probably be somewhat later although the demonstration you did on your video - using it - were pretty impressive - the simple Jacob's Ladder was way beyond what a 15kV neon can do - had a really nice sound to it! Anyway - work progresses - I will be busy during this "holiday" season, also the people that were interested in working with me are still very very much interested - showed the primary person your video and their jaw dropped p.s. - an idea for the gap - you could have a rotary system that also had a valving plate ( circular plate with holes drilled into it ) where the output of the valves could be forced over the spark gaps - pulsed air quenching of a rotary gap - I have a small metal lathe and this might be something to do... As always - Dave 301-794-6496 (1:109/546) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-22-93 03:18 From: Richard Quick To: Dave Halliday Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ DH> Status report: DH> Got the wire for the secondary as well as the basic design. OK, I got some soft figures for you. Given the specs of the planned coil you gave me here's what your looking at: Bare secondary frequency around ~260 kHz Secondary top loaded with 18" diam, 4" cross section toriod will resonate around ~180 kHz Using the rolled capacitor as per my specs you should get .02 uf capacitance, so to tune this secondary in on the tank circuit, your tank will have to be: Saucer shaped spiral wound primary. Angle of inclination from first turn to last turn will be right around 30 degrees slope; this should give pretty close to critical coupling with this secondary. Diameter of the first turn (inside diameter) will need to be ~9" giving you 1-1/2" space between the coils. With the toroid discharge terminal on the secondary coil, the tank should tune in when the primary is tapped right around 9 turns. These numbers are going to off a little, but I tuned a guys coil once over the telephone when he was six states away. I was throwing stuff off the top of my head and set the coil up in my mind from his verbal description. He claimed I had the coil in it's best tune the first time he turned it on, said every time he altered anything the spark decreased. It COULD have been dumb luck... But I checked the numbers you gave me against my programs and my documented systems in this size. You'll need at least 9 turns on a saucer primary to get that coil to fire with that cap. DH> I got the 50' of AL flashing for the capacitor as well as DH> all of the PVC pipe and already had the nuts and bolts... Your looking good here. DH> Also, found a *wonderful* three terminal plus ground RF DH> filter for 240 volt @ 60 Hz rated at 60 amps! $20 - DH> couldn't resist! I would have picked it up too. This is looking good, be sure to run the filter backwards. If your using only one filter, place it between in the supply line before the variac. Ground the case to your 60 cycle neutral. DH> Still looking for a source of the form for the secondary - DH> the stuff I saw at a local Home Depot was poorly out of DH> round... DH> Maybe some plexiglass disks glued inside to maintain shape. I would avoid using baffles inside the coil form, they tend to reduce the Q of the coil. Find a different supplier for some rounder pipe before you go this route. DH> Have a bunch of 3/8" refrigeration tubing that I can use for DH> the primary - Just fine for this sized primary coil, make sure it is long enough, though you can braze in a splice for added length. DH> Still need to get the step-up transformer - already have a DH> 12kV 30mA neon but the "potential" transformers you DH> mentioned that were used in power substations sound very DH> good too - will check locally. If you use 12 kv neons you will need about 120 ma total to drive this coil to good spark. That's four 12,30s. DH> Pole pig will probably be somewhat later although the DH> demonstration you did on your video - using it - were DH> pretty impressive - the simple Jacobs Ladder was way beyond DH> what a 15kV neon can do - had a really nice sound to it! I should hope so!!! I run the Jacob's Ladder between 5-7 kVA with a rail voltage of 20,000 volts. DH> Anyway - work progresses - I will be busy during this DH> "holiday" season, also the people that were interested in DH> working with me are still very very much interested - showed DH> the primary person your video and their jaw dropped His was not the first, and won't be the last!!! You should have seen the look on MY face while I was running it! I was 20' away and under cover and the sparks looked like they were going to wipe my nose for me. DH> p.s. - an idea for the gap - you could have a rotary system DH> that also had a valving plate ( circular plate with holes DH> drilled into it ) where the output of the valves could be DH> forced over the spark gaps - pulsed air quenching of a DH> rotary gap - I have a small metal lathe and this might be DH> something to do... I think I understand the idea, may be a good one. I can give you specs for basic systems that will give excellent performance. But for ideas like this, I encourage people to develop as far as profitable. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-22-93 18:53 From: Richard Quick To: All Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Tuning The Tesla Tank Circuit Once a Tesla coil is set up and ready to fire, certain steps should be taken before power is applied. Don't expect to throw the works on a newly built or newly re-arranged system. If you do you may have to go back to the drawing board. The coil must be brought into tune, and up to power gradually. The use of a variac autotransformer is highly recommended for controlling power on a system, even if the coil is eventually to be used in on/off applications. Never throw full power to a coil until you are sure the system is in proper tune. Set the tank circuit up first. Double check all of your connections. Run your grounds and double check those, never take a solid connection for granted. Set the secondary into the primary and ground it. Use a small discharge terminal at first if available. The smaller terminal will break down and produce spark at a lower voltage than a larger terminal, and new setups are not the place to stress the secondary. CLOSE YOUR SPARK GAPS DOWN! This is the numero uno step in bringing a coil into tune, don't run a lot of gap. I set up a static test with the power supply and no capacitors. Close down the safety gap until it has reached the point where the transformer will jump the gap 50% of the time when full voltage is applied in the test. Measure this gap distance and record it. When tuning a coil you will reduce this safety gap distance by 50% to provide kickback protection. It is a good idea to run a static test on the main system spark gap and close it down by 75% But on some gap systems this may not be practical, as series gaps behave much differently that a single gap. These differences are caused by the opposing lines of force in the single gap used for the safety. Apply a bit of power until the tank circuit fires. If no spark breakout is seen from the discharge terminal don't worry. Use a florescent bulb as an indicator. As the coil is closer to tune, the farther and brighter the bulb will glow. Turn off the coil and move the tap connection on the primary coil a half turn and check the bulb brightness, then move it a full turn in the opposite direction and note the brightness of the bulb again. This way you can determine the direction the tap needs to be moved to locate the tune spot. Open the main and safety gaps up in steps. Apply the same voltage input (low power) and check for discharge. Once spark has begun to break out of the discharge terminal use it as a visual indicator of tune as long as full power is not applied. With full power into a system the spark frequently gets so wild and distracting you cannot judge accurately. I have found that recording the tuning on video, and watching the tape provides a way to look at the system objectively. A system in proper tune should not break down the safety gap. The safety gap set at the full static test setting should not be too active. Once the coil is in good tune the safety gap electrodes may be opened to the point where the gap only fires perhaps once every three or four seconds weakly. Tuning is an art, and it takes a little practice. I recently came across some information that will be quite helpful for the novice (and even an expert on high powered systems) obtain better tuning. Use an arc meter. The arc meter is made by suspending a series of gaps on monofilament fishing line. One end of the arc meter is connected to the toroid, the other end of the meter is strung across the room and grounded. By placing a series of air gaps on an insulated line, the arc strength and voltage may be accurately gaged with the eye. Discharge will follow the gap path (it looks like a ray gun firing) and gaps may be counted as a reference. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-21-93 22:40 From: David Tiefenbrunn To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ On 11-18-93 Richard Quick wrote to Dave Tiefenbrunn... RQ> Got your tape out this morning. Let me know that you got it RQ> and Tape received 11-20-93. As was the post quoted herein. RQ> what you think of the spark. I was checking the tape for a RQ> minute as it was recording... Even I forget sometimes how RQ> awesome a 10" secondary looks with a proper discharger and RQ> 10 KVA pumped cleanly through it. I think you will agree, RQ> get back with me. *Quite* awesome... Previously the largest Tesla coil I had seen was in a science museum in Boston, MA. It's spark was maybe 1/2 of the >small< coil in your video. I *used* to think it was a big one. At what power level does it become dangerous to draw spark with the pole? The one I built when I was in college (over 10 years ago) had 230W input, but I didn't have all the details of how to optimize / tune it. It still threw sparks a few inches long. It also had a nasty static charge that would build up while it was running, and while I drew sparks (with a rod) the static charge would pop and I'd get a jolt. Your coils never displayed that particular problem in the video, just nice clean HV RF. I'm going to show a few friends your tape. One of them has a small (by your standards) coil. His coil's primary is wound like a regular coil, not flat like yours (or for that matter, the others I've seen. I will have to check with him to find out why. I think he is using flat glass / foil caps. With a little luck & timing maybe I can get video of it when we do the generator tape deal. (see other post) I have been saving all of the "how to" stuff for future reference. (203)345-7635 (1:320/5967) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-23-93 15:21 From: Richard Quick To: David Tiefenbrunn Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ DT> Tape received 11-20-93. As was the post quoted herein. RQ> what you think of the spark. I was checking the tape for a RQ> minute as it was recording... Even I forget sometimes how RQ> awesome a 10" secondary looks with a proper discharger and RQ> 10 KVA pumped cleanly through it. I think you will agree, DT> *Quite* awesome... Previously the largest Tesla coil DT> I had seen was in a science museum in Boston, MA. DT> It's spark was maybe 1/2 of the >small< coil in your DT> video. I *used* to think it was a big one. Yup, we have one in our science museum too. Small system putting out about 2' of spark. I decided I could do a little better if I put my mind to it. DT> At what power level does it become dangerous to DT> draw spark with the pole? This is a very good question. Very good. I routinely pull spark off of my coils with a key, pipe, or other conductor. It is not the power level of the spark that makes a difference, it is the quality of insulation you are standing on and the distance you place yourself from ground. I have had sparks coming off of my shoes over a foot long while in direct contact with voltages of at least a million volts. I can light 40 watt bulbs from the CURRENT heating the filament, and my body in series with the circuit. Power arcs leaving the body and hitting the ground are very dangerous, especially for those who are more shock sensitive than myself. I do not experience "shocks" in these instances, but do feel the RF burns. I have also had a few RF burns from change, keys, etc. on my person, as well as having lost all the magnetic strips on my bank and credit cards. My brother lost a nice digital watch once. But, if you know what you are doing, and the system is well set up in proper tune, it is OK to take up to 5 kVA output through a conductor to your person. But this is not recommended for amateurs. There IS a danger with certain tank circuits. I never ground the tank circuit or the primary coil, nor do I connect the secondary anywhere to the tank circuit or the primary. Coils with the primary and secondary connected, or both grounded to system ground can be LETHAL!!!! This allows an open pathway for deadly 60 cycle from the step up xformer to appear in the spark discharge. I avoid this problem by never using these circuits. My tank circuits and primary coils float ungrounded. Remember tank circuits are always deadly. A person with a conductor in hir hand and approaching a Tesla coil had better know the circuit, and have a cool head. Accidental contact with a primary coil or tank circuit has thought provoking possibilities. Like I stated in my original post when offering video: I cannot be responsible for people attempting to reproduce any of the experiments that I perform on the tape. I know what I am doing. DT> The one I built when I was in college (over 10 years DT> ago) had 230W input, but I didn't have all the details DT> of how to optimize / tune it. You do now! DT> It still threw sparks a few inches long. It also had a DT> nasty static charge that would build up while it was DT> running, and while I drew sparks (with a rod) the static DT> charge would pop and I'd get a jolt. Your coils never DT> displayed that particular problem in the video, just nice DT> clean HV RF. Yup, they do run clean. Very little RFI, high output, and efficient. Even my little temporary test setups perform better than most peoples end product. Having seen a lot of coils, and talking with people that build them, I feel qualified to post to "ALL". Nobody here has said any different. I know the circuits and systems to the point where I literally dream about them sometimes. I have set up and fired systems in my dreams several times, and I find the data I get from there is as valid as anything I do while awake. DT> I'm going to show a few friends your tape. Please do. All I ask is that you do not make copies without my permission. DT> One of them has a small (by your standards) coil. His DT> coil's primary is wound like a regular coil, not flat like DT> yours (or for that matter, the others I've seen. I will have DT> to check with him to find out why. Most likely his plan or design hails back to the "classic" era of coil building where a vertical helix primary (all primary turns equally spaced from the secondary) was common. This type primary is used to couple energy into systems using the "classic" style, space wound or low inductance secondary coil. The design I promote has been completely modernized and takes full advantage of modern high Q construction materials. The very high inductance secondary is so much more efficient that you have to reduce the aspect ratio of the primary coil or it will force a breakdown of the secondary from overloading. Then I use toroids to balance the secondary right to the load limit. The result of this work on my 10" coil has yielded sparks to the strike rail protecting the primary that are as fat as my leg, and up to 15' full current strikes. The spark is fully five times the length of the secondary winding which is only 32" high. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-21-93 23:01 From: Dave Halliday To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ RQ> Primary coils RQ>In order to move towards a complete presentation we need to RQ>talk primary coils. This will take me one step closer to RQ>coverage of the major components in the basic 1/4 wave RQ>oscillator. Once again - THANKS! Also, just had a bit of a "conceptual" breakthrough - was trying to see why 1/4 wave was best and then saw that this is 1/4 wave reflected over a ground plane... Makes a lot of sense ( arcs too ) Again, this has been saved, will be printed tomorrow. TTYL - Dave ð:-) ::Status report:: Got some PVC pipe - flimsy stuff but I will use wooden braces to hold it circular while I wind it. Actually, will probably cut out some plexi circles and glue them in... Got a bunch from some old signs Still have yet to get to the plastics store to get the material for the capacitors but looking at this week - also probably "have" to make a run to one of our distributors located near the Boeing surplus store - check for Teflon wire as well as "exotic" 6" tubes... Question - there are some very cheap cutting boards available made out of a high-density polyethylene plastic - was thinking of using them for the "breadboard" for the transformer protection stuff as well as the base of the coil - do you have any feedback on the Q of this material Thank you for your post on Primary coils - haven't read it completely but I got the idea that the diameter was critical - will check and get large tubing if that is true... 301-794-6496 (1:109/546) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-25-93 11:59 From: Richard Quick To: Dave Halliday Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ DH> Once again - THANKS! No problem DH> Also, just had a bit of a "conceptual" breakthrough - was DH> trying to see why 1/4 wave was best and then saw that this DH> is 1/4 wave reflected over a ground plane... DH> Makes a lot of sense ( arcs too ) Yeah, It took me a few minutes of looking at sine, then a 1/4 wave antenna before I realized what was going on and was able to conceptualize in my mind. Only then did Tesla's repeated use of the terms "fundamental note" and "harmonic" make sense. The length of wire vibrates electrically and is more or less the perfect analogy of a musical string. When the length of wire is wound to form a coil, it is simply compressed into a smaller volume where it can be efficiently excited. Now you can force that length of wire to accept SOME energy at any frequency, but the wire has a natural "hot spot" of resonance, just like a musical string has it's natural note. A function of the coil, and it's natural resonance, is such that it offers low impedance at the base for currents that match it's natural resonate frequency. So if the coil has a natural resonance of say 250 kHz, and current at 250 kHz is fed into the base, the coil will take it up. Current will flow. Current of any other frequency sees a very high impedance. But at the top of the resonating coil you do not see current. The coil "converts" the base current into a voltage at the other end. Since this voltage rises as you go higher and higher up the coil, and reaches it's peak at the top; Tesla was able to determine the voltage at the top of the coil is the first 1/4 wave voltage peak of the RF current fed into the bottom. A good term to introduce here is VSWR, for Voltage Standing Wave Ratio. The coil at resonance establishes a standing wave of the resonate frequency. The bottom of the wave is a low potential, such as your RF ground. From this low potential base, the standing wave is established, and voltage increases as we move higher up to the top of the coil. In order to get a handle on the true resonate frequency of a coil I use a signal generator, o'scope, and a frequency counter. The signal generator produces about a 2 volt signal that can be varied in frequency. I place a 1K resistor between the signal generator output and the o'scope input. Now the o'scope measures voltage. The higher the wave on the scope, the higher the voltage present in the signal generator output. The output of the frequency generator is fed to the base wire of the coil, and the frequency of the output is varied while watching the o'scope. When the frequency of the signal generator matches that of the coil, the coil takes up the current. Because current flows into the base of the coil at resonance, there is a voltage drop in the signal generator output line. This voltage drop is measured by the o'scope (across the 1K resistor) and is know as a "grid dip". The wave on the scope drops to nearly a flat line. When I see a grid dip I know I have matched the signal generator output to the coils natural resonate frequency. By also running a frequency counter connected to the signal generator, I can tell precisely the frequency of the input current. So in this little example, with a coil resonating at 250 kHz; the coil is resonating at 250 kHz and accepts 250 kHz current at the base. The current flow is high, the base impedance is low. As you measure voltage up the coil, the voltage rises until you get to the top of the coil. At the top of the coil you find the maximum voltage peak. This is the first voltage peak of the RF current fed into the base, and represents the 1/4 wave point of the input frequency current. So you have a 250 kHz coil, with a 1/4 wave voltage output. 250 kHz input, 1/4 wave voltage output, helical resonator; or 250 kHz 1/4 wave Tesla coil. We know the coil does not require current fed to the base to become excited. Oscillating magnetic field flux at the resonate frequency will highly excite the coil. The coil also having the property of inductance. So the coil can become highly excited by placing it in close proximity to a high powered oscillator, which is the Tesla tank circuit. Excitation by field flux produces equal energy output from both ends of the coil. Current from the bottom, and voltage from the top. It becomes clear now why such heavy RF grounds are required for Tesla coil work, and why the RF ground must be isolated from all other equipment. DH> ::Status report:: DH> Got some PVC pipe - flimsy stuff but I will use wooden DH> braces to hold it circular while I wind it. Actually, will DH> probably cut out some plexi circles and glue them in... Plug the ends of the coil form with something to hold it round while it is wound. Once wound, the wire will stiffen the coil form and hold the shape. When you glue the end caps on the form, it will be plenty sturdy. DH> Question - there are some very cheap cutting boards DH> available made out of a high-density polyethylene plastic - DH> was thinking of using them for the "breadboard" for the DH> transformer protection stuff as well as the base of the coil DH> - do you have any feedback on the Q of this material? Pretty good choice of material for a filter board. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-23-93 23:43 From: David Tiefenbrunn To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ On 11-19-93 Richard Quick wrote to David Tiefenbrunn... RQ> New lab so far is looking good. Expensive, contractor wants RQ> $32.50 per square foot. Have you "shopped" the local contractors much? I would thing you could get a pretty good deal with the terrible recession were in.:) In CT things are still slow, anyway. RQ> BTW I will trade tapes happily if anyone has goodies I would RQ> be interested in. Video tape is an excellent way to archive RQ> our little projects; I agree. I still sometimes forget to get the dang thing before "throwing the switch" though. RQ> not only are they useful as a personal reference, but they RQ> are amazingly effective teaching tools. Nothing explains RQ> something like a coil project as well as the designer/ RQ> operator pointing to, and talking about, the operational RQ> working equipment. Of course, most of my projects haven't been as striking as the 10KVA Tesla coil, but it is nice to have them on record. BTW, is that Tesla Coil Builders Association sticker on the big control panel for real? I never in 1K years would have thought there was such a thing. Dave (203)345-7635 (1:320/5967) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-24-93 01:29 From: George Powell To: Richard Quick Subj: Re: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ I bet tesla was a fun person to live by..made the locals life real interesting.. ;) (1:2460/21) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-27-93 00:52 From: Richard Quick To: David Tiefenbrunn Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ DT> On 11-19-93 Richard Quick wrote to David Tiefenbrunn... RQ> New lab so far is looking good. Expensive, contractor wants RQ> $32.50 per square foot. DT> Have you "shopped" the local contractors much? DT> I would thing you could get a pretty good deal DT> with the terrible recession were in.:) In CT DT> things are still slow, anyway. Yeah, I'm going to go "shopping" as soon as I can get motivated to spend 100G. Right now I am catching my breath from the sticker shock. The building should go up fast, and I don't plan to start until spring or early summer. This will give me a chance to shop around. DT> BTW, is that Tesla Coil Builders Association sticker DT> on the big control panel for real? I never in 1K years DT> would have thought there was such a thing. Yup It's for real. Tesla Coil Builders Association Harry Goldman #3 Amy Lane Queensbury, NY 12804 ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-27-93 01:26 From: Richard Quick To: George Powell Subj: Re: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ GP> I bet Tesla was a fun person to live by..made the locals GP> life real interesting.. There are several good (and true) stories about the local disturbances Tesla created. One of the best concerns an electro-mechanical steam powered oscillator he constructed. Now the oscillator was built to provide a constant frequency field current for a RF alternator in his radio work. But he played around with the thing. In New York he had a lab in the loft of a building for awhile, I don't have the exact address, but I can easily reference it if required. The building had a heavy iron center post in the construction. The post came up through the center of the loft and supported the roof peak. The base of the post was sunk into bedrock, and carried a considerable portion of the building load. Tesla bolted the oscillator output shaft to the post and fired it up. As steam pressure in the boiler increased, so did the frequency of oscillation. He sat in a chair and observed the effects of the mechanical vibrations on objects at hand. Each object having a resonate frequency would begin to vibrate and move as the frequency of the oscillator matched it. After about 30-40 minutes Tesla began to notice the building itself begin to sway, and saw beams unseat. He went to shut down the machine. To his dismay he found that his jury rigged steam line was too hot to approach, and/or the valve was seized. He looked around the lab for a minute or two and finally attacked the problem with an axe, severing the steam line and blowing clouds of live steam into the building. As the steam cleared, he heard a knock at the door. Two of New York's finest stood in the doorway. Now Tesla was apparently no stranger to dealing with the authorities. He explained to the cops that they had arrived too late for the demonstration, and that an unfortunate problem prevented him from reproducing the test while they waited. He invited them back later in the day, and showed them out. It seems the police had received frantic calls from people in a radius of several blocks reporting an earthquake. Walls, sidewalks, and foundations cracked, windows shattered, street lamps tilted askew, and stuff was falling out of cabinets and shelves. The police realized that the station itself was only subjected to a slight tremor, but officers reporting to the scene of the calls found the intensity increased as the drew near Tesla's lab. It did not take them long to figure out where the commotion was coming from. As I mentioned, Tesla was no stranger in dealing with local authorities. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-26-93 23:28 From: David Tiefenbrunn To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ On 11-23-93 Richard Quick wrote to David Tiefenbrunn... RQ> DT> *Quite* awesome... Previously the largest Tesla coil RQ> DT> I had seen was in a science museum in Boston, MA. RQ> DT> It's spark was maybe 1/2 of the >small< coil in your RQ> DT> video. I *used* to think it was a big one. RQ> RQ> Yup, we have one in our science museum too. Small system RQ> putting out about 2' of spark. I decided I could do a little RQ> better if I put my mind to it. You sure did. :) RQ> DT> At what power level does it become dangerous to RQ> DT> draw spark with the pole? RQ> RQ> This is a very good question. Very good. I routinely pull RQ> spark off of my coils with a key, pipe, or other conductor. ... RQ> Power arcs leaving the body and hitting the ground are very RQ> dangerous, especially for those who are more shock RQ> sensitive than myself. I do not experience "shocks" in these RQ> instances, but do feel the RF burns. I have also had a few RQ> RF burns from change, keys, etc. on my person, as well as RQ> having lost all the magnetic strips on my bank and credit RQ> cards. My brother lost a nice digital watch once. RQ> RQ> But, if you know what you are doing, and the system is well RQ> set up in proper tune, it is OK to take up to 5 kVA output RQ> through a conductor to your person. But this is not RQ> recommended for amateurs. Reminds me of one of my dad's T shirts: I am a professional. DON'T try this at home. You should get one :) It would seem that the important thing is to not allow a spark to jump directly to or from the body. The first coil I made (back in grade school days) only threw a spark about 1/2 inch long. But I would let it jump directly to a finger with no shock or burn. Not enough power to do damage. I do feel shocks (and burns), so I would hesitate before trying that with a large coil. RQ> DT> I'm going to show a few friends your tape. RQ> Please do. All I ask is that you do not make copies without RQ> my permission. O.K. (203)345-7635 (1:320/5967) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-26-93 01:00 From: Guy Daugherty To: George Powell Subj: Re: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ GP>I bet tesla was a fun person to live by..made the locals life GP>real interesting.. ;) You might say it brightened up their lives. Brought a little spark into them, so to speak. (209)472-0843 (1:208/216) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-30-93 12:15 From: Richard Quick To: David Tiefenbrunn Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ RQ> DT> At what power level does it become dangerous to RQ> DT> draw spark with the pole? RQ> This is a very good question. Very good. I routinely pull RQ> spark off of my coils with a key, pipe, or other conductor. DT> ... RQ> Power arcs leaving the body and hitting the ground are very RQ> dangerous, especially for those who are more shock RQ> sensitive than myself. I do not experience "shocks" in these RQ> instances, but do feel the RF burns. I have also had a few RQ> RF burns from change, keys, etc. on my person, as well as RQ> having lost all the magnetic strips on my bank and credit RQ> cards. My brother lost a nice digital watch once. RQ> But, if you know what you are doing, and the system is well RQ> set up in proper tune, it is OK to take up to 5 kVA output RQ> through a conductor to your person. But this is not RQ> recommended for amateurs. DT> Reminds me of one of my dad's T shirts: DT> I am a professional. DON'T try this at home. DT> You should get one :) DT> It would seem that the important thing is to not DT> allow a spark to jump directly to or from the body. Yes I would tend to agree with this, especially at higher powers. The charge density and amount of power alone can be dangerous, despite the output of the coil being clean RF. I don't know if the resolution on the tape is good enough to see but in the shot where I am pulling a few feet of spark off the coil with a copper pipe, there are some 6" - 8" sparks coming off my feet. Since I am standing on an insulated platform, and my shoes socks are sweaty, I only get a tingling sensation. Another thing to caution about is being in series with a power arc from the discharge terminal, even if the actual arc leaves a conductor such as a pipe or what not. Again the charge density is just too high on a big coil to make this safe. I have been placed in an uncomfortable position or two where this has happened, and the operator of the coil needs to have a cool head and be very familiar with the controls. I wish I had these incidents recorded on video tape. When doing the million volts through the body trick, or other HV RF experiments when in physical contact to the output, discharge must be radiated or arced through the air, not to ground. Power arcs to ground while in series with the circuit is "eye opening" to say the least, and can make your fillings really sing. ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-23-93 10:28 From: Dave Halliday To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ > DH> Geeez Richard - and I thought *I* had too much going on > DH> at once what with my boat, woodworking shop, metal shop ( > DH> lathe, wirewelder and torches ), music studio, > DH> homebrewing, BBS, computers and printing... RQ> DH> This takes the cake RQ>Isn't it funny how intelligence and imagination breeds havoc? Havoc... Now *that's* a polite term for it RQ>Mark Lawton (spel) sent me a post about all of his concurrent >projects too. It seems we landed in a nice spot to exchange a >few ideas and interests. This conference is not too crowded, >yet several people end up with similar sets of hobbies and >interests. Great! I am looking to connect to a local source for FIDO just for this conference... RQ>BTW to keep somewhat on topic, I really hope your coiling >efforts are moving along. I have tried to dump as much as >possible in the last few days, and have spent several hours >per day in organizing my thoughts and getting them out. I sent you a status report a couple days ago - just getting stuff together right now. I will be going to the Boeing surplus place today and will see if they have anything of interest - they are closed on Monday - they put all the new stuff out then so Tuesday is the primo day to go there... TTYL - Dave ð:-) 301-794-6496 (1:109/546) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-23-93 10:36 From: Dave Halliday To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ RQ> DH> Used to work for the public aquarium in Boston and we had > DH> grounding problems like you wouldn't believe - I was RQ>A few months back when our local sysop first added this >conference, there was an thread on grounds and grounding that >you just would not believe (well maybe you would), anyway, the >misunderstandings and misconceptions about grounds and >grounding, and the bizzare things that happen when equipment >and systems are not properly grounded... I can well imagine - I also did PA systems for bands for a while and some of the perceptions about power and signal grounds were amazing. Not so much for their blind ignorance and lack of common sense but for the fact that some of them were still alive RQ>By reading the Colorado Springs Notes it is quite clear that >Tesla struggled to get a good ground on site for his system >and cited the local geology (sand & rock) as the source of his >problem. He eventually had to run water 24 hours a day over >his ground. Interesting - the water table there is probably pretty low so that would be a problem. In Seattle, the reverse is true - where I live is fairly close to Lake Washington and the ground is pretty wet all year round. I will probably drive a couple lengths of copper pipe into the earth for the coil ground - the ground for the house is a 6' copper rod but from what you say, the more the merrier! RQ>His control, or line frequency, ground was the water pipe. >Tesla was capable of producing serious ground currents from >the machine. Some of the effects were reported many miles >away; sparks coming off the shoes of horses which caused >the animals to spook, clouds of insects covered in St.Elmos >fire, in addition to the locals getting sparks from their >water taps. Must have been fun to live near there RQ>When he went on to Wardenclyff, he spent half of the tower >construction cost on the well with 18" copper plated steel >pipe driven into bedrock 50' below the water table. He did not >intend to mess around. Jeeezzz! I guess not!!! That is getting a bit serious! Anyway, TTYL - Dave 301-794-6496 (1:109/546) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-23-93 10:38 From: Dave Halliday To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ RQ> Harry Goldman > TCBA > 3 Amy Lane > Queensbury, NY 12804 > Tel: (518) 792-1003 RQ>Tell him I sent you!!! Thanks! Will do 301-794-6496 (1:109/546) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-23-93 11:16 From: Dave Halliday To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ RQ> Primary coils Me again... This is exactly the info I need! I was wondering what would work best. >primary coil should be large. I have seen lots of holdovers >from the classic age of coil building who insist on 2-3 turn >primaries and HUGE capacitors to achieve the proper frequency >of operation in the tank circuit. RQ>This is wrong. RQ>A tank circuit with a small capacitor, and a large primary >inductance, will reach down to the same frequencies of >operation. A tank circuit of this design will use less power, >and therefore require a smaller step up xfrmr. The capacitor >will be smaller, which further reduces the cost of the system. Makes a lot of sense! Also, because of the losses in the capacitor, using a lower value will result in less loss... RQ>So to give some advice to my friend Dave Halliday, who is >building a 6" secondary coil sometime in the near future, >plan on winding a primary coil from a conductor material that >I have listed above, and use a conductor length of around 75 >feet. Your primary should end up about as wide as, or wider, >than your secondary is tall. Got it! I was thinking of using some 3/8ths refrigeration tubing but since the surface area is important, I'll probably get a reel of 3/4ths or 1/2" tubing ( gotta check on pricing first ) Also, I wasn't thinking about the length of the primary and I only have about 20' of the small tubing. I'll be going to Boeing today so they might have something there too. Again - many thanks for the info - I have a pretty good handle on what is needed - like I said, probably building the capacitor over the Thanksgiving weekend - I'll be closing the store then... Trade some videos / photos once I get something to show. 301-794-6496 (1:109/546) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-20-93 18:24 From: Joseph Freivald To: Richard Quick Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ For those of us who are wanna bees, What's a tesla coil, and why does it get at least 10 posts per day? Just trying to catch up, Joe 301-794-6496 (1:109/546) ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ Date: 11-23-93 17:49 From: Dave Halliday To: Joseph Freivald Subj: 10KVA Tesla Coil ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ JF>For those of us who are wanna bees, What's a tesla coil, and >why does it get at least 10 posts per day? JF> Just trying to catch up, > Joe Hi Joe - the Tesla coil is basically a high-frequency resonant air transformer - oscillator system. It was developed by a wonderful genius / wildman Nikola Tesla ( 1856-1943 ) as a means of generating very high voltage as well as power transmission. Richard has a great two hour video tape of his work which he will send to you for the following: ten bucks, a blank good quality tape, and postage paid mailer It is well worth it! His "big" coil is about 4' tall and fires continuous bolts of lightning from nine to fifteen feet! This is a point-to-point measure too so add in about 30% for the twists of the arc! I used to be into them when I was a teenager and had always thought about getting back into it but the stuff he is working on has convinced me! I will be working with a couple friends ( sharing work 'n money ) and we are starting work on parts of it this thanksgiving holiday. It is interesting too because the "classical" design for a tesla coil is quite different from the actual best design. The classical design goes for long thin coils ( maybe 30" by 3" dia.) and just two or three turns of wire for the primary whereas the actual best design calls for much shorter / fatter coils and lots of primary turns ( 10 - 15 ) My friends and I have arrived on a basic design - 6" diameter and 30" long, fixed spark gap, 12kV neon sign transformer and homemade capacitor. Richard mentioned that he once built one just like this and he was able to get 5' bolts! Anyway, the posts are well worth saving, send away for the video tape too - it makes for fantastic viewing! 301-794-6496 (1:109/546)