Hi Nicholas,Thanks for the gap specs. Part of the reason I asked about the gap specs was to check your NST firing voltage (wanted to be sure both sides of the hv windings in the NST were good). Based on your specs, I calculated the gap should be firing at 13kVp which is just about right for a 9kVrms NST. The NST looks good. I also saw in your specs later that you indeed had a 4.5" diameter secondary (missed that the first go around). I calc'd 933 turns, so your 950 turns is a decent guesstimate. With this data, I show the tap should be set at 10.25 turns. So enough, of what "should" be.
Gary mentioned adjusting the MMC. Sounds like a quick avenue to check if tuning is the problem. I'm by no means convinced that tuning is the issue although this procedure may identify a problem somewhere. If even one cap is shorted, it can throw off tuning by a full turn. But you mentioned that you went through all the turns, so this doesn't play well in my mind (if a cap was removed from the MMC, turns decrease for primary tuning).
Your bps is about 105 by my calculation, so probably 10 to 20% higher in reality. Thus, bps looks ok also. I am also seeing approx. 300kV at the toroid, so I don't see a problem there either.
I don't see any problem overall and that's what leads me to think there are some losses somewhere in the system that is robbing you of power (the gap is typically the cause, but not always). One thing I would do is ensure the primary is 3/8" below the secondary bottom turn and tuned to 10.25 turns. Then find where the losses are. This tap position will tune the coil where you know your very close and ensure the coil has a coupling coefficient of 0.125.
Because your coil uses a low power supply, you might want to try only 3 gaps (given the gap configuration of 1 electrode on top centered between 2 lower electrodes). Gap spacing should be at 0.075" between top and bottom electrodes. Too many electrodes at low power can be an area of loss and is the reason I'm suggesting to reducing the electrodes from 5 to 3. If cooling was a problem, you would actually see decent sparks for a few seconds and then the sparks would diminish to nothing. If you are seeing nothing right at the start, heat probably is not the issue.
Check the wiring also. Ensure a good primary tap connection. Ensure the wires from the gap electrodes are not small in size (as is ok for the charging side of the NST forward). You may also have some carbon tracks somewhere that is robbing power. So maybe take a look at all supports (cap, primary, secondary, etc..). Tracks are sometimes identified in total darkness by a dull orange glow. During inspection, they are literally thin black streaks (unless they really burn in, then the streaks get thick).
For my 4.5" diameter coil (also near 21" length and near your turns), I use a 6.25" x 21" toroid. The main difference between your coil and this one is power. This may end up playing a large part of your problems.
Take care, Bart Nicholas J. Goble 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: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.Nicholas -You stated that your toroid was made from "dryer duct" material. CanOtherwise, it looks like you've generally done your homework. Ofcourse, 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_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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