[TCML] Tesla Coil Help

[Barton B. Anderson]

Hi Ben,

Hard to help with that. The coil is just so small. Small coils like that 
are some of the hardest to build. The problem is to tune in correctly. 
I'm looking at it and the secondary is a bit over 2 MHz. The primary is 
however hard for me to imagine with a dual layer helical?. Javatc can't 
do dual layers (I'm not sure I understand the primary configuration). 
But, if it's 14 turns at 2" height (boy a picture would help here), 
Javatc will want about double your capacitance to get it in "near" 
tuning range. The problem here is that the primary coil adds a lot of 
external capacitance to this little coil and the position of the primary 
(and actual geometry) along the secondary can change it's tune point 
considerably.

I think your basically getting a force feed situation with the small 
sparks at this point. You should get at least 3 inches, but don't expect 
9" numbers. Those numbers are based on coils of the normal 3" and larger 
coil sizes. I don't think anyones performed a study on such a small coil 
before as far as spark length versus power.

Take care,
Bart

Ben Sneath wrote:
> hello all,
>
> can anyone help me with my coil problems,
> i built a small 1" coil and it is only making thin wispy 3/4
> inch sparks, yet I'm putting about 30W into 
> the thing. i don't know if the PVC pipe i used in the
> secondary is absorbing all the power (its 1" dia., 
> with about 2.5 mm thick walls, bit too much plastic) or from
> overcoupling. here are the specs:
>
> Secondary: 1" x 3", about 500 turns, 38ish gauge wire
> Primary: helical, 14 turns (2 layers) 20 Amp electrical
> wire, 2" dia.x1" high
> Tank Cap: .42nF MMC 
> Topload: 12mm x 40mm foil coated wooden toroid 
> Power: 10kv induction coil, running at 230Hz
> Gap: 4 round head bolts, spaced so they just fire
> Runs at about 2.5MHz
>
> any help would be a great help, thanks
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