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Re: [TCML] Improving performance
Stephen -
How do you intend to "increase quenching" with your existing single-segment spark gap? Changing the width of the gap is not the "adjustment" for changing the quenching characteristics.
In case you have not yet seen it, Richie Burnett's website:(http://www.richieburnett.co.uk/tesla.shtml)
is probably the single most informative "technical" Tesla Coil website on the planet. You will find a very concise description of the quenching process, along with animations showing exactly how quenching affects the transfer of power from the tank circuit into the secondary coil. If you are really interested in optimizing your coil's output, I think you'll that an hour or more spent on Richie's website will be more than worthwhile.
As long as your coil is not exhibiting the classic symptoms of "overcoupling", then your 15 degree primary is OK (although as you increase coil efficiency or input power level you may find that you start to have problems with overcoupling). You can calculate your primary-secondary coupling coefficient, or you can actually measure it. Classic spark-gap tesla coils generally work most efficiently when their coupling is within a fairly narrow range of values, typically between .06 and .18. As long as you achieve good coupling and good quenching, the physical form of the primary doesn't matter: conical, flat, helical, etc.
As for improving your spark gap, I'd suggest that your next step be to build a fan-cooled multi-segment copper tube gap. This style of gap has proven to be an effective, inexpensive, easy-to-build design that can give very good performance. Try 5-6 segments, 3/4" or 1" diameter copper tubing, each tube 4-5 inches long. These can be arranged in multiple ways, but I prefer to build a small open-topped plywood box, with the tube segments lying across the open top of the box, and with a high-flowrate fan pressurizing the box. The tube segments simply lie in notched phenolic plates mounted on the inside of the box. The fan creates airflow directly through the gaps between the tube segments, and the tubes can be easily lifted out of the notches for cleaning.
Maximum performance will probably be obtained with a synchronous rotary spark gap, but there's a fair amount of precision work involved in making or buying a salient-pole motor, fabricating a mechanically-precise disk, mounting electrodes, dynamically balancing the assembly, etc.
Regards,
Herr Zapp
"Stephen J. Hobley" <shobley@xxxxxxxxxx> wrote:
I think we've found the optimum tuning. I need to check with a flu tube
to see if we are at the primary osc, and not a harmonic - but so far
everything looks good.
I'm going to increase the quenching on the spark gap, but would you say
that 1/4" is about the most we should go to?
Also we have a 15 degree slope on our primary - would a flat primary,
with looser coupling help us to increase spark length?
We're going to try dual gaps, then the sucker gap, and when we've
exhausted that avenue we'll by trying a rotary gap.
Thanks again for all your help.
Steve
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of Alan
Sent: Thursday, July 31, 2008 7:16 PM
To: 'Tesla Coil Mailing List'
Subject: RE: [TCML] I guess that's 'first light'...
Great Steve!
If you saw 12 inches in the daylight, I can tell you they are A LOT
longer!
Great News
Alan Majernick
TeslaStuff.com
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf
Of Stephen J. Hobley
Sent: Thursday, July 31, 2008 5:45 PM
To: Tesla Coil Mailing List
Subject: [TCML] I guess that's 'first light'...
OK I sanded the inside of the coil - did not remove all of the trace but
abou 90% - I will work on this again later.
Cleaned the inside with alcohol, made sure not to get alcohol on the
coil.
Removed the metal connector on the top and replaced it with a nylon
bolt, relocated the top of coil to outside the form.
I ran the coil again for about 30 seconds with no evidence of streamers,
then checked inside the form to see if there was any fresh scoring -
there was none.
Re-adjusted the primary tap and got 12" streamers coming off the top.
Difficult to say how long they really were as it was sunny outside. But
it's working!
Now I can start to get it optimized...
Steve
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