Re: Last light >:-| (fwd)
---------- Forwarded message ----------
Date: Mon, 18 May 1998 19:22:19 -0500
From: Chuck Curran <ccurran-at-execpc-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Last light >:-| (fwd)
Too bad about the difficulties on your last test. I have to admit that some
of what you described is similar to what happened on my coil last spring,
when I first fired it up. The first item that caught my attention is the
toroid size, which you already pointed out. On my 8" diameter secondary
from two years ago I employed a 6" by 40" toroid with great success. I
simply placed the toroid on top of a 6" high piece of PVC tube and then ran
the wire from the secondary up to a connection point near the center line of
the toroid. This is the toroid that I stiffened with some 3/32" thick
modeling plywood. I jammed the wire in between the ply and the toroid
surface and it caught fire on about the 5 th or 6th run. Sorta neat with
little resulting damage. I would really recommend a larger toroid before
your next run and I would also review the coupling.
On my 15" secondary I got arcing from primary to secondary, which shorted a
turn just like yours. This one had the toroid that was about 10" x 56".
This secondary had a very heavy coat of the good ol' Behr Super Build 50
product on it and it didn't help at all. You asked about wire size, I also
used #22 on the 8" diameter secondary, not too much different than your
coil. One item that I'm not sure of from your note Chip -- did you have
another larger toroid above the 10 x 3" corona shield one?
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Sunday, May 17, 1998 11:33 PM
Subject: Last light >:-| (fwd)
>---------- Forwarded message ----------
>Date: Sun, 17 May 1998 22:29:22 -0600 (MDT)
>From: Chip Atkinson <chip-at-pupman-dot-com>
>Subject: Last light >:-|
>I finally got the right conditions of readiness, wind and light to fire up
>my 9" coil outside. Mike Hollingsworth and I fired up this coil in the
>garage a few weeks ago and it seemed to work well. This time when I fired
>it up outside, it self destructed in a matter of seconds. In fact, I
>don't recall even seeing any break out at all before seeing gobs of sparks
>up and down the secondary, as well as sparks from the top turn (?) to the
>main body. These sparks were not "attached" to the coil form, but sort of
>arched out. Since there was a very thin coating on the windings, the arcs
>quickly burned a hole in the insulation and fused a turn. It's amazing
>how fast a shorted turn on the secondary will heat up. I noticed a little
>smoke escaping and quickly shut it down. Inspection in the light showed
>that there were two burned areas that had bare copper. Bummer.
>One thing perhaps someone may have some comments on is the way I did the
>toroid this run. When Mike was over, I had the coil set up with a
>conductive tube on top of the coilform bulkhead. This 10" section of Al
>tape coated PVC pipe then lead directly to the toroid. This time, I put a
>10x3" toroid on top of the coilform and then the 10" riser followed by the
>toroid. I suspect that this small toroid, rather than providing extra
>corona shielding allowed spark breakout at the top of the turns and
>the subsequent arcing from the top to the middle of the coil.
>Ok, so what did I learn? I think I'm going to skip the smaller toroid
>"corona shield". I don't want to destructively test this though, so I'm
>going to just shy away from the new configuration and go with the tried
>The other thing is that I now feel that a good coating on the secondary is
>important. I believe that this extra insulation may have allowed the coil
>to last long enough to fuss with it and fix it up before it totally fried.
>Well, back to the winder. BTW, what gauges are people using for 9-10"
>coils? I used 22ga.
> Chip Atkinson
> --- If I can't fix it, I can fix it so it can't be fixed --