컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� Msg#: 851 Pvt Date: 12-08-95 22:42 From: Richard Quick Read: Yes Replied: No To: Rmr@christa.unk.edu Mark: Subj: Salt Water Caps 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 * Carbons Sent to: tesla@grendel.objinc.com usa-tesla@usa.net Quoting Ryan Ruel : > I have completely finished my coil except for the capacitor. > I'm planning to build some rolled polyethylene caps as soon as > I gather the required materials and find the time. Until then, > I would like to easily construct a salt-water capacitor so I > can play with the coil until I build a better unit. I was not > really able to find anything online about salt-water caps, but > I keep seeing references to them. What would be required to > build one capable of withstanding a 15 kv, 60 ma neon system? > The secondary is 24 inches, 6 inches diameter, 880 turns 22 awg > magnet wire. Primary is 14 turns, conical spiral, 1/4 inch > copper tubing. Spark gap is a 6 inch, 16 electrode disk rotary > system. Any advice would be greatly appreciated! Before I jump into salt water capacitors I would note that the rotary gap is overkill on a neon power supply. The rotary may even cause a premature failure in a neon. This is not to say the gap won't work, it will, I just prefer a decent static gap when using internally limited (read neon) transformers... Now, on to the subject at hand, salt water capacitors: Tesla used salt water capacitors in the primary circuit of the industrial sized Colorado Springs coil. He took ceramic standoff insulators and placed them on wooden planking layed down over the wooden floor. On top of the insulators he placed another layer of wooden planking. This formed an insulated raised platform. On top of the raised platform Tesla placed seven square metal tanks. The tanks were made of tin or galvinized sheet steel and had soldered seams to prevent leaks. Each tank was about three feet square and two feet high. An excellent photo of these tanks appears on page 324 of the Colorado Springs Notes. Inside of the tanks, Tesla placed a number of glass mineral water bottles. Using a saturated solution of rock salt and water (brine), Tesla filled the bottles about 2/3 of the way to the top and inserted an electrode into each bottle so that the conductor was in contact with the brine. Each electrode extended out of the top of the bottle. The bottles in each tank were grouped into three equal parts or sections. Each group had their electrodes wired together to form a high current buss. Once the bottles in a tank were filled and connected, brine was carefully poured into the tank until the level of salt water in the tank and the level of salt water in the bottles were the same. This is a salt water capacitor. The brine in the tank forms one of the two capacitor plates. The glass bottles are the dielectric. The brine inside of the glass bottles forms the second plate of the capacitor. Tesla had some simple covers that fit over the tops of the tanks. There were three holes in each cover. A high voltage buss cable passed through a porcelain insulator placed in each hole. Each cable represented 1/3 of the capacitance of a tank. Salt water capacitors of this type are messy to build, difficult to maintain, and very lossy; but they do work. In order to supress corona losses, prevent flashovers up and down the sides of the bottles, reduce churning of the liquid plates during pulse operation, and prevent evaporation of the brine plates; both the bottles and the tank were topped off with several inches of heavy mineral oil. For today's coiler a smaller and somewhat simpler salt water capacitor may be easily and cheaply constructed for use until a suitable plastic film capacitor can be constructed/purchased. The most common is the beer bottle/brine cap. I have heard all of the jokes about these... That you don't really need the brine, just get a case of cheap long-necks and let nature take it's course:-) But anyway, you do need about a case of long neck bottles (clean with labels removed) and beer bottles do work very well. You will also need the twist off caps. Buy a standard Rubbermaid plastic dishpan (11-1/2 x 13-1/2 x 5-1/4 inches, Wal-Mart under $7.00). Shop around at a hardware store(s) and buy twenty-four 1/4 inch diam. by 6 inch long galvinized steel carriage bolts. You will also need seventy-two, 1/4 inch thread, nuts that will thread onto the carriage bolts. You will need a few quarts of the cheapest grade, straight 30W, non-detergent, motor oil; don't spend money for multi-viscosity high detergent oil; you can use the best mineral oil in a pinch, but it works no better than cheapest straight grade engine oil. You will need some heavy duty aluminum foil, and you may want to get a large tube of clear silicone sealant. Get a 1/4 inch diam. by 1 inch long brass screw and two nuts. Using a hole punch, punch a 1/4 inch hole into the center of each twist-top bottle cap. If you punch from the top of the cap down it will bend, so flip the caps over and punch them through from the bottom. Run a nut down the threaded shank of the carriage bolt about an inch, slide a bottle cap over the threaded shank, then run another nut down and tighten. This should produce an electrode that will drop down inside of the long neck bottle and will secure with a twist on the bottle cap. After fitting and adjusting, you may want to remove the top nut and the cap. By bedding the cap to the electrode with silicone sealant you can prevent leaks and stop the nuts from loosening. After completing the electrode assemblies for all of the bottles, mix up a few gallons of warm saturated brine in a five gallon plastic bucket. I use the cheapest grade of rock-salt which is readily available here in the winter season. In many parts of the country water softener salt is available year around. Fill each bottle with brine to a depth of about 4-3/4 inches, insert the electrode part way, then top the bottle off with a couple of inches of motor oil. Use a small funnel or "squirt bottle" here to prevent sloshing and do not overfill with the brine or oil. Now if things are going right you have a bottle with the elect- rode assembly inside and held over to the side. Before fully inserting the electrode assembly and cinching down on the cap you can smear some silicone sealant around the threads on the cap and around the top of the bottle. This will prevent leaks. Cinch down firmly on the cap. Fold a very large sheet of aluminum foil over double and scrunch it down into the bottom and sides of the plastic dishpan. Some dishpans have a hole molded into the lip, if yours doesn't then cut or drill one. Get a 1/4 inch diam. by 1 inch long brass screw and two nuts. Roll up a bit of the foil at the hole end of the dishpan, punch a hole through the foil, and make a terminal by passing the brass screw through the plastic lip and foil. Secure with one nut. The second nut is for securing the connection to the tank circuit. Set the bottles into the dishpan. You will find that only 16 of the bottles will comfortably fit, but you will most likely need the other eight bottles and a second dishpan to get a .012 MFD capacitor. One dishpan with 16 bottles gives about .008 MFD. Wire the tops of the bottles together with some stout copper cable, strap, or copper tubing that is pounded flat and drilled for the 1/4 inch carriage bolt electrodes. You can use some strips of aluminum flashing with holes punched through if you smear a little electrical corrosion inhibitor on the connection. When everything is set and settled down, fill the dishpan up with brine to within a 1/2 inch or less of the rim. Pour a thin layer of oil over the brine to suppress corona. With the dishpan this full it is not fair to say this capacitor is portable. It will slosh over if moved. It is probably best to fill the pan right where you intend to use it. There are as many variations on these capacitors as there are coilers building them. Heavy plastic bottles or buckets give a much higher Q factor, but the dielectric constant ("K") of the plastic is a low ~2 compared to the much higher K of bottle glass which comes in ~7. This means the capacitors must get physically larger. I have seen a pretty nice vertical stack brine capacitor made from five gallon plastic buckets. A strip of stainless steel strap was hung across the bottom of the bucket, up the side, and over the rim. About 1.5 quarts of brine was poured in. Another bucket was firmly seated inside of the first, another strap, more brine, another bucket, etc. The guy was processing 8 KVA from a pole pig through this corona glowing ozone producing monstrosity. Like I said, these are messy, inefficent, high maintanence... but they are very cheap and they do work. Richard Quick ... If all else fails... Throw another megavolt across it! ___ Blue Wave/QWK v2.12 � Area: UUCPE-Mail 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� Msg#: 1051 Pvt Date: 12-10-95 04:04 From: Richard Quick Read: Yes Replied: No To: Usa-tesla@usa.net Mark: Subj: Re: Catching up, + help! 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 * Carbons Sent to: tesla@grendel.objinc.com Quoting James Peters : Moving again. Hopefully it will be the last time in the foreseeable future. All of that iron, copper, and oil... I easily have over a ton of Tesla equipment, easily. I threw away hundreds of pounds of stuff two years ago when I moved last. I am getting a house with a full garage and basement. Knowing I would have room for larger setups and more storage, I must have accumulated back the same poundage that I scrapped two years ago. Only the quality of the junk has improved with the turnover. I will be back to burning barns again in short order. > 1. What is your personal opinion on bottle caps? (in terms of > quality, loss etc) As far as quality goes, they suck. When you factor in the cost, time, and availablity of construction materials, their image improves. I know of more than one coiler who used a brine/glass capacitor to get them sparking on their first serious project. > 2. How does glass compare to mylar as a dielectric? (in rf > applications) I don't have access to these figures. As far as RF dissipation factors are concerned, even Mylar, as poor as it is, beats bottle or plate glass. There are specialty glasses that have acceptable dissipation/thermal properties in RF applications, but you will not find bottles molded from it. If you have access to PYREX containers (i.e. flasks) this would be an improvement over bottle or plate glass when RF losses, dielectric constant, and dielectric strength are considered. This is a better dielectric when looking at dissipation factors, but because the dielectric constant of plastic is so much lower than glass (2 vs 7), the size of the capacitor grows pretty large, nearly four times so. As the size increases you come across another problem in brine capacitors; the plate mass and surface area go way up. This mass is electrically part of the tank circuit, it's like having many pounds of conductor wired in that is not doing anything. The large surface area of brine means high corona losses and much lower Q factors. It is hard to get a good trade off with brine caps. This is not to say it is impossible with a good design and the right dielectric. > suggestions? A good brine capacitor works fine for a coiler who is looking for some spark pending a capacitor upgrade. It is better to build and run a brine cap than not to fire at all for lack of a capacitor. Since they are very cheap and easy to build, they should not be ignored by the novice-intermediate coiler. I was just out at the convenience store this evening getting washer fluid for the car. Having just written a short paper on a brine/bottle capacitor yesterday, I noticed some 1 pint long neck bottles of beer sold as singles. A green ST PAULI GIRL came home with me. I think I could make a nice PORTABLE salt-water/glass capacitor with these bottles inside of a 5 gallon plastic bucket. With everything else that is going on now I don't have time to mix up a batch of brine and measure the capacitance of the bottle, but judging by eye, it should work pretty well. I should think you could get a .01 at 15 kvac rms in a five gallon bucket. > I finally have a toroid. It was free! It is a commercial > aluminium one that comes off the top of a van de graff > generator. This should combine the advantages of a sphere and > toroid discharge terminal as it is dome- shaped. I got it from > the physics department at school. ideas, suggestions? > Oh yeah, it's a 16" outside diameter. Use it. If the sparks tend to leave to discharger upwards rather than to the side, then make a true toroid. I know the commer- cially made units look spiffy in the fit & finish dept., but the homemade toroids work every bit as well for pennies on the dollar. > I now have an industrial compressor. I think I'll make an air > blast gap. Upgrade your capacitance before you invest time building an air blast gap. Air blast and other fast quenching gaps eat second rate capacitors for breakfast. > Thanks for your time and trouble, Now and in the past! No problem! Richard Quick ... If all else fails... Throw another megavolt across it! ___ Blue Wave/QWK v2.12 � Area: UUCPE-Mail 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� Msg#: 1227 Pvt Date: 12-10-95 21:01 From: Tesla@grendel.objinc.com Read: Yes Replied: No To: Richard Quick Mark: Subj: Re: Salt Water Caps 컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 From: tesla@grendel.objinc.com To: EDHARRIS@MPS.OHIO-STATE.EDU, GCerny@ix.netcom.com, Date: Mon, 11 Dec 1995 09:01:08 +0700 Subject: Re: Salt Water Caps From mrbarton@ix.netcom.com Sat Dec 9 07:12 MST 1995 >Received: from ix3.ix.netcom.com (ix3.ix.netcom.com [199.182.120.3]) by uucp-1 .csn.net (8.6.12/8.6.12) with ESMTP id CAA18900 for ; Sat, 9 Dec 1995 02:27:53 -0700 Date: Sat, 9 Dec 1995 02:00:18 -0800 From: mrbarton@ix.netcom.com (Mark Barton) Subject: Re: Salt Water Caps To: tesla@grendel.objinc.com Sit back and I will tell the tale of my first salt water capacitor. It consisted of 7x7 rows (that's 49) one liter glass 7-UP bottles. They were placed in a wooden tub that had a galvanized steel liner. A solution of super-saturated brine was poured into each bottle up to about 4" from the top. The tub was filled to the same level. It is now obvious that the water in the tub is one capacitor plate and the water inside each bottle is the other. The bottle, of course, is the dielectric. A 1/2" dia copper tubing T fitting above each bottle was fitted with a piece of pipe going down into each bottle to contact the solution, and horizontal pipes to connect to each other. This capacitor stood up to 14,400VAC at about 6KVA. Each bottle was good for about 900pF. This capacitor worked well and was next to free to make. However, the difference in spark when we went to real store-bought capacitors was more than subtle. The sparks went from OK but kinda wimpy to mean snapping white discharges. You will get the same result with your homebrew polypropylenes. Good luck. Incidentally, Tesla used bottles in Colorado Springs from the Manitou Water company in nearby Manitou Springs. When I was there a few years ago, I combed the many antique shops for a Manitou Water bottle from that era. The dimensions and a sketch of the bottle are given in Tesla's Colorado Springs Notes so I knew what I was looking for among the zillions of old bottles in the antique shops. The shop employees and patrons thought my girlfriend and I were crazy measuring old glass bottles going "Nope, not the one. Next." I quickly learned not to even try to explain what I was doing and why the bottle had any particular significance. I finally found one that was real close and bought it. Zap, Mark