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Re: Advice on Secondary

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 05:45 PM 1/19/2005, you wrote: 
Original poster: "Medina, Benjamin Alejandro (UMR-Student)" <bamxbb@xxxxxxx>

Hello,

I am currently building a medium size Tesla Coil. Here are some of the
specs:

NST - 15kV/30ma

Capacitor- 5.37 nF made from glass plates with heavy duty aluminum foil
on the inside and outside faces

Icky... glass is quite lossy, and glass plate caps are a pain. If you want cheap, use beer bottles in a bucket with salt water.

Or, spend a few bucks and make yourself an MMC (search the list archives or google for it). String together 10-15 suitable polypropylene caps in series, each cap is 2000V, 0.15 uF. That will give you 10-15 nF.
Each cap is around $3, so you're looking at 30-40 bucks in caps. Not just any old cap will do... you need ones suited to carrying the neccessary current, but the folks on the list have spent years researching this, and the archives contain all you need to know about which part numbers to order.



Primary- 0.25" of flexible copper tubing

Secondary- 22 AWG enamel magnetic wire on 4" diameter PVC. Height- ???

I am thinking on 30". I've read that for a medium size Tesla Coil an
aspect ratio of 4.5:1 up to 5:1 is recommended. But then again, there
are no hard/fast rules.

According to WinTesla, 4"x30" with 22A WG wire yields 1090.53 turns but
the Aspect Ratio is 30/4 = 7.5. Would this be a problem?? At first we
were going to go with 22" or 23" in height (22/4 = 5.5) (23/4 = 5.75)
giving us around 800 turns, but I read that 1000-1400 turns tends to
produce better performance than lesser turns.  The difference might be
10-20% spark length.


If you're wanting more turns, why not just wind with 24 AWG or 26 AWG wire?

But... spark length is mostly a function of input power, not absolute number of turns.


What do you recommend? Please advice. Your comments and suggestions will
be appreciated. Thank you.


What are you going to use as a spark gap? (I'd start with three pieces of copper pipe a couple inches long arranged in parallel).. rig up a muffin fan to blow over it.

What are you going to use as a topload? A toroid made from aluminum dryer duct and pie pans work well.




Sincerely,
Ben Medina