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Re: Another First Light! (fwd)
---------- Forwarded message ----------
Date: Tue, 19 May 1998 18:27:02 -0600
From: "Patrick J. Gustafson" <gustafpj-at-uwec.edu>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Another First Light! (fwd)
Gary:
For tuning the coil, I did put a tack on the toroid, and I was still getting
secondary streamers shooting for my garage door. I would like to build a
larger toroid, or just stack them for that matter, but this a coil that I built
for the physics department here at the university and I probably won't see it
much longer (I'm moving on the 30th of May to Madison). My first coil and I
already have to leave it (sigh). I did also have the 1K resistors coming off
of the NST's like you mentioned, but they were only rated to about 5W (I know
they should be around 30W but I had to give them a try), needless to say, they
got smoked. I can't tell any difference without them. Thanks for the bypass
cap info, never knew about that. You are correct about my secondary being as
low as I can get, I'm not getting an racing sparks at all. Is there anywhere
that I can post pictures of my coil?
Thanks to Jeff Corr for his excellent advice in getting my coil running.
Patrick Gustafson,
Leaving his First coil behind, in Eau Claire Wisconsin
Tesla List wrote:
> ---------- Forwarded message ----------
> Date: Tue, 19 May 98 08:54:25 EDT
> From: Gary Lau 19-May-1998 0811 <lau-at-hdecad.ENET.dec-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Another First Light! (fwd)
>
> Damn good for a first try! My thoughts:
>
> Each time your main gap fires, your safety (bypass) discharges it's
> charge and this energy dissipates in non-productive (and possibly
> destructive) ways. If your main cap is .01 uF and your safety cap is
> .001 uF, this means that .001/(.001+.01) * 100% = 9.1% of your
> transformer's power is going to no-good. You might want to use a
> smaller value bypass cap. You also must use series damping resistors
> (1K or so) when using chokes to dissipate all that power. Even so, use
> of chokes is controversial.
>
> I started out with a flat primary with my 4" secondary, and the single
> greatest improvement I made was converting to a 15 degree conical (also
> with a 15Kv/60mA NST). I'll bet your secondary is as low as you can get
> it and you still don't see any racing sparks to indicate overcoupling.
>
> Re. your gap, if there is a single gap segment that is .225", I think
> this be the weak point that affects quenching. The total gap length
> seems right but it shouldn't be lumped like that. Build another RQ gap
> in series. You do have a fan on it, right?
>
> Re. your toroid, if you put a nail on it and you still get multiple
> streamers, you might try going to a 6" cross section X 24" (and re-tuning).
> While I think the multiple streamers look nicer, when trying to measure
> your longest arc as a goal, a single streamer is necessary.
>
> Let me know how your 6" secondary works out. Using #28 may be kinda
> small though, and the inductance with that many turns may be too high for
> your primary to tune. I'm still using the 4.25"x23", #22, w/ 42" sparks.
>
> Regards and congrats,
> Gary Lau
> Waltham, MA USA
>
> >Date: Mon, 18 May 1998 22:26:13 -0600
> >From: "Patrick J. Gustafson" <gustafpj-at-uwec.edu>
> >To: Tesla List <tesla-at-pupman-dot-com>
> >Subject: Another First Light!
> >
> >Hello All:
> >
> >With schoolwork, and finals week here I haven't much time to work on my
> >first coil, but I did nonetheless complete it and give it some initial
> >runs. The specs are as follows:
> >
> >primary - flat pancake with .25" copper tubing (15 turns)
> >power supply - (2) 15kV 30mA NST's paralleled
> >chokes - 100 mH on each leg of the NST's
> >spark gap - RQ type (6 section (.1" combined) plus adjustable brass
> >gap(.225")) set at .325
> >capacitor - .0125 micro farad rolled polyethylene (.062"), filled with
> >transformer oil
> >safety cap - .001 micro farad, filled with transformer oil
> >safety gaps across the NST's and main cap
> >twin variacs rated at 17 Amps
> >toroid - 4" cross section x 25" diameter
> >grounding - 8' x 1/2" dia copper ground rod
> >secondary - see below
> >
> >I had a two layer 6"dia x 22" length secondary wound with #28 magnet
> >wire, but I had a problem with the inner winding being shorted out
> >somehow, so I replaced it with an alternate secondary that I had wound
> >(4"dia x 20" with #22 magnet wire). The tuning took quite awhile,
> >beginning with zero spark length, and now properly tuned I'm pulling
> >around the 30-35" mark (loud as %&*-at-) Not bad for my first coil eh?
> >And plus I'm using the lower inductance secondary. Can't wait to
> >re-wire the 6" and see what I get.
> >
> >Patrick Gustafson, Ozone plentiful in Eau Claire, Wisconsin