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Re: Rotary Gap


From: 	Kenneth Pryor[SMTP:pryor-at-mmsi-dot-com]
Reply To: 	pryor-at-mmsi-dot-com
Sent: 	Monday, August 04, 1997 6:30 PM
To: 	Tesla List
Subject: 	Re: Rotary Gap

Tesla List wrote:

> From:   RODERICK MAXWELL[SMTP:tank-at-magnolia-dot-net]
> Reply To:       tank-at-magnolia-dot-net
> Sent:   Sunday, August 03, 1997 6:31 PM
> To:     Tesla List
> Subject:        Re:  Rotary Gap
>
> > Rod,
> >
> > DO NOT, under any circumstances use acrylic plastic ( plexiglas )
> for a
> > spark gap rotor. Acrylic cracks and shatters rather easily and is an
>
> > accident waiting for a place to happen when used as a rotary gap
> rotor.
> > Even small flaws from drilled or tapped holes will develop into
> cracks
> > as the material ages. Just the thought of a plexiglas rotor makes me
>
> > shudder!
> >
> > I build and sell rotary gaps and the only material I ever use is
> G-10
> > glass epoxy. G-11 has a little better heat resistance but is quite a
> bit
> > more expensive. IMHO there is no better material for rotors except
> for
> > steel or aluminum which leaves one with the added problem of
> insulating
> > the rotor from the motor. Lexan can be used, but melts at a much
> lower
> > temperature than G-10 and overheated rotor studs can work loose. I
> > regularly spin the 10" rotor on the series rotary gap I use on my
> > magnifier at 7600 RPM or better ( verified with an infrared strobe
> tach)
> > with no problems. A couple years ago while prototyping a 10"
> synchronous
> > gap, I crashed and dead stopped a G-10 rotor with 1/2" tungsten
> studs
> > from 3600 RPM on a 2 HP motor. The rotor was trashed because of
> cracks
> > around the stud holes but was otherwise intact. The stuff is just
> about
> > bullet proof!
> >
> > So, if you want to do it safely, spring for the bucks for a piece of
>
> > G-10 or for a few bucks less a piece of Lexan, but please don't use
> > plexiglas.
> >
> > Safe Coiling,
> >
> > Ed Wingate
>
>    Thanks for keeping me out of harms way! The only place that I have
> found that sells G-10 is a plastics company that I buy my poly, and
> epoxy from. They only sell the stuff in 24" x 48" sheets, and the
> price
> works out to several hundred dollars! Sooo I'll probably use lexan.
> Thanks for your help!
>
>                               Frankensteins Helper
>                                       Max

  Just a little warning about using Lexan (polycarbonate) . Do not allow
any Loctite or
any other cyanoacrylic to come in contact with polycarbonate! Even the
smallest amount
will cause the poly to become brittle and crack under the slightest
stress. In a rotating
part this could be quite disconcerting.

--
Kenneth C. Pryor
Modular Mining Systems
3289 E. Hemisphere Loop
Tucson, AZ 85706
email: pryor-at-mmsi-dot-com
internet:  http://www.mmsi-dot-com