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Re: My 1st capacitors



Tesla List wrote:
> 
> Subscriber: gweaver-at-earthlink-dot-net Tue Dec 31 10:32:32 1996
> Date: Tue, 31 Dec 1996 09:38:35 -0800
> From: Gary Weaver <gweaver-at-earthlink-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: My 1st capacitors
> 
> My 2 new capacitors the 1st that I have ever built.

<Biggg SNIP>

Congratulations, Gary!! There's lots of good ideas here! 
  
> I bought a roll of .006 mill clear polyethylene at the lumber yard.
> The roll was 10' by 100'.  I cut it into strips 14" wide by 222"
> long by rolling the plastic around a pipe first then cutting around
> the pipe with a razor knife.  

Nice approach for rapidly slitting to size, since 6 mil poly seems to
only come in 10' widths! But its CHEAP and readily available!

> I laided the strips out on the carpet
> floor in the house.  I put 9 layers of poly in a stack.  Then I laid
> the aluminum plate on the stack of poly and folded the poly over the
> top of the aluminum plate.  Now there is 9 layers of .006 poly on both
> sides of the plate.  Its made like a sandwitch with poly on both sides
> and the aluminum plate in the middle.  The poly hangs over each side of
> the plate 2" and hangs over the tab end 3".

Good idea. In order to prevent pickup of lint and other junk from the
carpet, you might want to put a layer of clean kraft paper fown first
(it's relatively cheap by the roll as well...). 

<SNIP>


> I returned home and didn't waste any time removing the glass plate
> capacitor from the TC and put on 1 of the new poly caps.  It has been
> about 2 hours sence I finished them both.  The output was more than twice
> what I had before and I didn't change anything except the capacitor.
> The output use to be 13" sparks on the secondary and now its 32" with
> one new cap using a 6.5" dia by 23" long secondary wound with # 24 wire.
> The primary is 3/8" copper tubing spaced 3/4" center to center helix
> wound at a 30 degree angle with 18 total turns.  The tap is on turn
> 13 my lucky number.  I then added the 2nd cap in parallel with the 1st
> and the output went down a little.  I have too much capacitance for my
> power supply.  Another transformer or 2 will fix that.   I need .015 uf
> and I have .016 or maybe .0178 uf.  The power supply is 3 neons 15,000
> volts at 90 ma in parallel.

Sounds great! Although three neons at 90 MA should be OK for driving
this tank cap size, 4 would be better... or a pair of 60's if you can
find some.

<SNIP>

> I noticed that the Richard Quick spark gap made with copper tubing is
> burnt and very black.  I built another spark gap today.  It is another
> Richard Quick spark gap except this time I used tungston carbide
> tool inserts for the electrodes.  I cut a 4" pelexiglass circle to
> fit inside the 4" pvc pipe to plug up the air flow threw the pipe.
> Then I drilled a .375 dia hole exactly on center with each spark gap.
> The fan will force the air in threw the holes directly across the arcs.
> I replaced the old spark gap with the new one an tried it.
> 

Are you using 1.5" diameter tubing in a 6" pipe? The power level you're
running at generates a fair amount of heat, and you'll need at least 12
or more individual gaps to share the load at 15 KV. Fewer gaps at wider
spacing will heat the pipes more and burn them earlier. You may want to
look at making a vacuum or air blast gap now that you've got some good
caps! :^)

<SNIP>

> I ran the Tesla coil hard for about 45 minutes.   I designed these new
> capacitors to hold up to 40,000 volts and if they are going to fail I want
> them to do it now.   

At 108 mils, your caps will certainly outlast your neons!

> I ran the TC until one of the choke coils shorted out
> and caught on fire.  I was a little worried about setting the ceiling on
> fire with all the arcs that are going to the ceiling for such a long time.

A very valid concern. At least one other person on this list HAS set
their cieling on fire this way!
> 
> I have my secondary bottom end connected to the primary.  When I
> connect the secondary to earth ground along with the center tap of the
> transformers like it should be the output at the secondary is reduced
> by about half.

Remove any connection from earth ground to the primary winding! Let the
primary float. Only connect the secondary base and neon cases to earth
ground. Tieing the primary to ground effectively only uses half of your
transformer output, and shorts the other half. Thats why the output is
reduced. Also, make sure your gaps are across the transformer outputs...

> Tomarrow I will work on making a new secondary and rebuilding the primary coil.
> 
> Gary Weaver

Safe cappin' and coilin' to you!

-- Bert --