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Re: RSG -- rotary spark gap
Subject:
Re: RSG -- rotary spark gap
Date:
Tue, 01 Apr 1997 16:33:02 -0500
From:
"Edward J. Wingate" <ewing7-at-frontiernet-dot-net>
To:
Tesla List <tesla-at-pupman-dot-com>
References:
1
Tesla List wrote:
>
> Subject:
> Re: RSG -- rotary spark gap
> Date:
> Mon, 31 Mar 1997 20:54:58 -0500
> From:
> "Edward J. Wingate" <ewing7-at-frontiernet-dot-net>
> To:
> Tesla List <tesla-at-pupman-dot-com>
> References:
> 1
>
> Tesla List wrote:
> >
> > Subject:
> > RSG -- rotary spark gap
> > Date:
> > Fri, 28 Mar 1997 10:06:08 -0700
> > From:
> > "DR.RESONANCE" <DR.RESONANCE-at-next-wave-dot-net>
> > To:
> > "Tesla List" <tesla-at-pupman-dot-com>
> >
> > A 5/8 inch thick G-10 glass laminate makes a good rotor disc. For 5-15
> > KVA
> > systems use a 1725 RPM 3/4 HP motor equipped with 10 electrodes on a 12
> > in.
> > dia. disk. 3450 RPM seems to overquench. We use 1/2 dia. brass thru
> > holes
> > that have been precision reamed .001 oversize and brass is press fit
> > with a
> > small press. The brass is 1 1/2 inches long and each end fitted with a
> > standard tungsten-molydenum screw in electrode. They seem to last about
> > 7
> > years in rotary service. We use a 1 inch dia. screw in electrode for
> > the 4
> > fixed electrodes and replace them once every 3 years (that assumes
> > museum
> > is doing 3 presentations a day x 6 days per week). They are a little
> > expensive but in experimenter service should last about 40 years or so!!
> >
> > Type LE and CE phenolic (carmel colored) seems to soften slightly so
> > safety
> > becomes an issue with these materials. Never try to build the rotor
> > yourself --- always have a machine shop do it so absolute precision is
> > maintained -- never mind expense either -- how much is an eye worth???
> > A
> > machine shop should balance the rotor to 5000 RPM. Again cost enter the
> > picture but these rotors can be dangerous so safety has to become a
> > strong
> > concern. We have been making our rotors this way for over 20 years
> > without
> > ever having a single rotor explosion (knock on wood).
> >
> > DR.RESONANCE-at-next-wave-dot-net
>
> Dr. Resonance,
>
> G10, is indeed, a great material for spark gap rotors. I regularly run
> the series rotary on my magnifier system between 7000 and 8000 RPMs with
> no problems. G11 has a little more resistance to heat but is quite a bit
> more expensive. Balancing is very important at these speeds and I do
> both static and dynamic balancing on all of my rotors.
>
> I disagree, however on the choice of a 1725 or 3450 RPM induction motor
> for the average Tesla experimenter's rotary gap. A better choice is a
> 1/2 or 1 hp AC/DC universal motor run either straight from a small
> variac or powerstat on AC, or, for a little cooler and smoother running,
> on DC by using a bridge rectifier with the variac. Fixed speed motors
> are fine for museum displays, where the setup will never be changed, and
> maximum performance is not all that important, but for Tesla coil
> experimenters they do not allow the wide range of speed adjustment
> sometimes needed to bring a coil into synergistic operation. If I were
> limited to only one gap, it would be a variable speed without a doubt!
> When experimenting, versatility is the name of the game.
>
> Press fitted studs can work loose, as can screw in inserts and I feel
> much safer with a rotary that uses setscrews installed in the outside
> periphery of the rotor to positively hold the studs in place. Solid
> tungsten studs are also a safer bet to prevent self- disassembly at high
> speeds. 1/4" to 3/8" Lexan (polycarbonate) or 3/4" plywood covering the
> gap is cheap insurance too! A supersonic piece of tungsten killing a
> friend or an observer would not make for an enjoyable afternoon.
>
> BTW, I must be missing something....
> How do you press fit a stud into a .001 oversize hole? ;-)
Either my mail tool or the list mail tool cut off my ending salutation,
so....
Best Regards,
Ed Wingate