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- To: Tesla List <tesla-at-pupman-dot-com>
- Subject: Re: Just a brush
- From: Chuck Curran <ccurran-at-execpc-dot-com>
- Date: Thu, 06 Mar 1997 21:08:08 -0600
- References: <c=au%a=telememo%p=bhpmel04%l=BHP/BHPMEL/00325971-at-bhpmel-imc01.corpmel.bhp-dot-com.au> <331ED45C.49B1-at-stic-dot-net>
Tesla List wrote: Taylor, Chris CC wrote: > > I have just recently completed building my first coil and fired it up > last night. To my utter disappointment all I got was a big racket from > the spark gap and little else. > > I have a 15/30 neon with a six element spark gap and a plate poly > capacitor, (20 plates 10x8" with an 80 mil poly dielectric, theoretical > C=0.0085 uF). I haven't got around to placing the cap in an oil bath yet > and it doesn't arc unless the gap separation is very large, the cap then > arcs around the edges and I shut down and reduce the gap separation. > Would the cap be providing 0.0085 uF without the oil bath, I can't see > why not, it is my understanding that the oil is only used to provide a > better insulator than air around the cap. > > The coil also has a 1/4" copper tubing primary with 15 turns spaced at > 1/4" in a saucer configuration, (30 degree). The secondary is 22 ga > transformer wire on a 2.8" PVC pipe with 840 turns, (22.5" long). > > All I seem to be able to get from this baby is a small brush discharge > from the tip of the secondary wire, (primary optimally tapped at turn > 5). I have also built an 11 x 3.5" toroid which when attached does not > produce any discharge. > > My questions to the lads are; > > What sort of diagnostics can I perform to point me in the right > direction for larger discharges. > > Have I missed anything, I have used a number of the circulating formulas > to roughly size various components. > > The coil is working but just doesn't seem the be very efficient. The > lowest turn on the secondary is in line with the inner turn of the > primary, do I need to lower the primary to get better coupling. > > Is my secondary too long for efficient coupling, (H/W ~ 8.5) I have read > this may be a bit large. > > The addition of the torus increases the resonant frequency, do I > increase or decrease my tank capacitance as the secondary frequency > increases and how do I adjust the primary tap as the secondary resonant > frequency increases. > > Any help would be greatly appreciated and will speed me on my way to > coilers nirvana. > > Chris Taylor > Perth, AUSTRALIA Hello Chris: I would suggest that you should calculate the capacitive reactance of your .0085 mfd cap--I get about 312K ohms at 60 Hz. Not sure if you use 50 or 60 Hz power, but the point is that would result in a current draw of 48 milliamps on your 15,000 volt transformer and it is rated at 30 milliamps, per your comments above. That will cause the current limiting feature of your neon to kick in and result in less than spectacular Tesla activity. Double check my numbers, I did that pretty quick! Chuck
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