Re: RE: [TCML] Toroid Problems

[Quarkster <quarkster@xxxxxxx>]

Nicholas -
   
  Your toroid (if constructed as you have described) cannot in itself  be "defective". Assuming that there are no other fundamental problems with your wiring or power supply, all symptoms point to an out-of-tune coil. The resonant point of a Tesla coil is quite "peaky"; the primary and secondary only need to be mis-tuned by a small amount to get no output at all.
   
  By your description, it sounds like when you add your toroid, you reduce the resonant frequency of the secondary system below the lowest frequency to which you can tune your primary system. Your additional two turns of primary (beyond your calculated tap point) should provide enough adjustmant range, but possibly not. 
   
  Here are some more suggestions for diagnosing the root cause of your coil's poor performance:
   
  1. Try a smaller topload. Cover various sized rubber or plastic balls with aluminum foil, and try each one, starting with the largest and working your way down. This will incrementally raise the resonant frequency of the secondary. If you start to see a significant change in streamer length, you will know which direction you need to go, frequency-wise. Use a breakout point so you will be able to see even small changes in streamer length.
   
  2. Add some more wire to your primary. This can be just #12 solid copper THHN house wiring, taped in place. This is just a temporary diagnostic measure to try to get the coil in tune. More primary turns will lower the resonant frequency of the primary.
   
  (One more question: what is the length of ALL the wiring in your tank circuit (connecting MMC, spark gap, and primary coil)? All of this wiring adds to the inductance of the primary circuit. I've seen coils that couldn't be brought into tune because there was another 5 feet of wiring in the tank circuit. All tank circuit wiring MUST be as short and direct as possible, using at least #12 AWG wire.)
   
  Regards,
  Herr Zapp
   
  
"Nicholas J. Goble" <ngoble@xxxxxxx> wrote:
  I've tested my toroid and found that it is made of the aluminum HVAC 
ducting. I remember when I bought it that it could be compressed and 
stretched due to some accordian-like structures on the tube. And by 
the way, my secondary has no gaps in the wire.

Bart asked me for the specs on my spark gap, so here they are. There 
are 5 electrodes. The electrodes consist of 1" diameter copper pipe 
pieces cut to be 4" in length. I calibrated the spacing by hooking it 
up in series to my NST, and adjusting it so that it just fired. I'd 
say the spacing for each gap is 1mm. It fires beautifully. I hooked 
up what I believe to be a "squirrel fan" that I bought from an American 
Science and Surplus store in Chicago. It isn't a leaf blower, bit it's 
stronger than any fan that I own. I can see a difference between the 
spark gap with and without the blower on it. It's blowing through the 
pipes and looks to be perfect for the application.

I'm wondering if this is simply a problem with my toroid. With the 
toroid on, I saw absolutley 0 discharge, and I was running it at night. 
Even if the coil's not tuned, shouldn't I see some sign of discharge 
from the toroid?

Nicholas Goble


Quarkster wrote:


>Nicholas -
> 
> You stated that your toroid was made from "dryer duct" material. Can 
you confirm that this is really convoluted aluminum HVAC ducting 
(formed from heavy gage aluminum foil, like disposible pie-pans are 
made from), and not the thin aluminized polyester material wound around 
a coiled spring core? You need to use the HVAC duct material, which 
comes compressed but is stiff enough to hold out at 90 degrees without 
sagging. The usual "dryer duct" material is metallized plastic film 
over a wire core (like a "slinky" toy), and is NOT conductive. I have 
seen several first-time coilers get confused by the "dryer duct" 
material, which may look similar to the HVAC duct material if you're 
looking at a photo on the internet. Quick check: take an open flame and 
apply it to the material. The aluminized polyester material will 
instantly melt,laving only the inner spring, but the flame will have 
no effect on the aluminum HVAC duct.
> 
> Otherwise, it looks like you've generally done your homework. Of 
course, to state that you've got "about" 950 turns on the secondary 
implies some lack of precision, and theres no way that you know the 
resonant frequency is actually 243.344 KHz unless you have actually 
measured it. You might want to go back and carefully measure the exact 
number of turns in an inch of winding length, and re-calculate the 
total number of turns. Also, is your secondary tightly wound, with 
essentially no gap between adjacent windings? Even small turn-to-turn 
gaps can have a significant effect on total turns count of a long 
secondary. \
> 
> Regards,
> Herr Zapp

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