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Re: First big magnifier run
Tesla List wrote:
>
> Subscriber: nikki-at-fastlane-dot-net Mon Feb 3 21:17:05 1997
> Date: Sun, 2 Feb 1997 20:53:09 -0600 (CST)
> From: Bert Pool <nikki-at-fastlane-dot-net>
> To: tesla-at-pupman-dot-com
> Cc: jgore-at-cyberramp-dot-net, bemery-at-why-dot-net
> Subject: First big magnifier run
>
> Wild Bill Emery and I finally set up our large magnifier out in my driveway
> Saturday night and fired her up. We started with a 40 inch by 5 inch toroid
> on top of a 4 inch by 13.75 inch resonator coil (30 gauge). We video taped
> the runs, and then measured honest 90 inch strikes to the house and garage
> door frame. After running it, we found that I had failed to lock down one
> of the stationary electrodes on the rotary gap, and it had opened up to over
> 1/2 inch gap, and it still worked! We will redo the gap on our next series
> of runs.
>
> We first experimented with using the secondary in the driver as a
> conventional Tesla coil. It is only about 180 turns of 10 gauge wire on a
> 16 inch diameter pvc pipe, so inductance is not much. We tried the 40x5
> toroid as well as the 60x8 inch top, and all we ever got was sparks racing
> down the secondary - and this was with the coupling about as low as we could
> go without raising the secondary up (it weighs 107 pounds, so raising it up
> a foot or so is no small task.) We finally gave up on trying to use it as a
> conventional coil, and decided to use it as a driver, as it was so designed.
>
> What was absolutely incredible during this "conventional coil" attempt is
> that we had some extremely hot, violent arcs from the toroid down to the
> primary. Sometimes, but not every time when this happened, we got 23 inch
> flashovers from the bottom of the primary to the concrete driveway! We have
> the entire coil assembly sitting on top of 22 inch tall porcelain
> insulators, and the primary arced all the way to the concrete, jumping
> AROUND a 3/8 inch copper line run straight to my water main. I am still
> stunned at seeing this. I repeatedly watched this frame-by-frame on video,
> and it is weird. Apparently there is ground, and then there is ground. My
> main ground is 3/8 copper tubing screwed directly to a brass water faucet on
> the front of the house. The faucet is connected to a copper water line
> which immediately runs 30 feet under the yard to the water meter, and from
> there to the water main under the street. I dug up a section of the line
> from the meter to the house to make sure it was copper before I ever used it
> as my coil ground. I figure 30 feet of buried copper line connected to a
> buried water main is a damn good ground, so why would a strike to my
> concrete driveway just ignore a copper ground line connected to this superb
> ground? The arc had to bypass the best ground I can make and instead opted
> for some crummy concrete. I know the copper water pipe ground is adequate,
> as my coil is performing quite well. Those 23 inch strikes to the driveway
> passed within one inch of my ground and absolutely ignored it.
>
<SNIP>
>
> Bert Pool
> nikki-at-fastlane-dot-net
Congratulations on a great start with your new Maggie. How long is the
run from the base of your driver coil to the water pipe at you house?
When you get flashovers to ground, the currents are quite high, and the
frequencies are typically in the multi-MHz range. Any significant
inductance in the ground path might make this path higher impedance than
to the rebar below during a primary strike. Did your safety gap(s) fire
during these primary strikes? Interesting phenomenon for sure!!
Safe coilin' to you!
-- Bert H. ==