Re: My ARSG had a melt-down

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <dhmccauley-at-spacecatlighting-dot-com>

I'm surprised you used PVC in the first place.  PVC has a very low melting
point compared to other appropriate materials for a rotor.
Yes, i would definitely heed that friendly warning.  You are very lucky that
the electrodes didn't become loose enough to fly off the rotor and impail
yourself.
Definitely retire the rotor and use a better material like CE phenolic or
similar.

The Captain




 > I was running with my original ARSG last night. A 12" diameter disk with
12
 > flying brass electrodes, driven by a 1/20th HP Robbins induction motor.
I'm
 > surprised the little motor had the mojo to spin up to speed but it could.
 > This thing was built in the early nineties back when I didn't know what I
 > was doing. No Tesla list, only Lindsey's reprints from the twenties. Since
 > I planted my new RF ground recently, I've been fine tuning this coil,
 > trying to shoot for the magic K values. As it was night, the only light in
 > my shop was coming from the coil itself and the gap.
 >
 > The output was really going great; I'd started with thin purple sparks and
 > as the tuning progressed I was achieving fatter, white sparks when
 > suddenly, the output became sporadic and the tone from the gap became
 > inconsistent. The blue/white light from the gap revealed smoke billowing
 > from the gap itself. Shut down, shop lights on; I'd used a plank of 1/4"
 > hard PVC to mount the fixed electrodes. These electrodes were mounted with
 > 1.25" fender washers (to help dissipate heat, haha!) and these had gotten
 > so hot they pulled through the PVC. More like they boiled their way out.
 > Funny thing is, I had lots of run time on this gap before but was using it
 > with my old glass & foil cap. This time I was using a MMC. I hated that it
 > was destroyed but then again, the way it went out was so cool. I could
 > replace the PVC panels with either phenolic or G10 but the entire rotor
was
 > also made from 1/2" PVC. So maybe I will conclude that this incident was a
 > friendly warning from God not to use PVC for construction of a RSG and
just
 > retire the whole thing.
 >
 > One interesting side note; I never noticed this before but as I'd raise or
 > lower the rotor speed, I could hear a combination or beat tone (where two
 > different frequencies partially coincide creating a perceived third tone
 > caused by the incidence of the two frequencies adding positively and/or
 > negatively). I would slowly change the rotor speed, attempting to
 > synchronize the two pitches. When this happened, (synchronize the two
 > frequencies and the beat tone goes away) even though it would only last a
 > few seconds, the coils output would increase dramatically, then decrease
as
 > the two frequencies moved apart. Even the fluorescent tubes (which were
 > turned off but would still glow in the field of the coil) would get
 > brighter in step with the coil's output. Conversely, when the two
 > frequencies were at their maximum difference, the coil and the fluorescent
 > tubes were at their lowest output.
 >
 > This effect was the most noticeable at the lower rotor speeds, in the
 > neighborhood of 60 - 80 bps. I know that one of the two frequencies I
heard
 > was the sound of the RSG electrodes presenting and thus, firing, but am
 > unclear what the other sound was. Perhaps the output sparks from the
toroid
 > itself?
 >
 > Comments welcome,
 >
 > Daniel
 >
 >
 >
 >
 >