rotary design

From:  Bill Noble [SMTP:william_b_noble-at-email.msn-dot-com]
Sent:  Tuesday, June 30, 1998 1:16 AM
To:  Tesla List
Subject:  rotary design

it seems that there are two kinds of rotary gaps:
type 1 = an insulating disk carries conductive "shorting bars" that cause
the gap to conduct when they pass between two electroded

type 2 - a conducting (in particular HEAT conducting) disk carries
conducting extensions that cause a gap to conduct when they align with a

There has been a lot of dicsussion of the problems of the first type of gap
and of the need to use special materials because of heat build up - a 1/8
inch tungsten rod held in an insulator has to absorb a lot of heat.

It seems to me from an engineering perspective that the "type 2" gap should
be superior because the heat build up on the electrodes can be conducted
away (not radiated) along the whole disk.  Just mount the disk on a
non-conducting shaft.  With one "gap" per disk, you may need several disks,
but cooling, hence quenching should be measurably superior.


>From:  Barton B. Anderson [SMTP:mopar-at-uswest-dot-net]
>Sent:  Saturday, June 27, 1998 10:17 PM
>To:  Tesla List
>Subject:  Re: Magnifer & rotary problems
>Greg, Bill, and all,
>Thought I'd add my 2 cents here.
>I'm running a 10kva, 6 joule capable system utilyzing an all alluminum 8
>electrode rotory on an 1800 sync setup. I built it from on-hand materials.
>I'm using 1/4 inch copper electrodes which extend .75" out from the outer
>ring. It spins on an insulated shaft. It has performed nicely and does give
>me a good feeling knowing the electrodes are very secure (safety measures
>used regardless). So far, the electrodes have barely warmed. I am using
>G6 fiberglass covers over the flywheel and electrodes to aid in quenching.
>still have plans to upgrade to a G10 disc setup, but FWIW, alluminum
>flywheels can perform very well.
>Tesla List wrote:
>> ----------
>> From:  Greg Leyh [SMTP:lod-at-pacbell-dot-net]
>> Sent:  Wednesday, June 24, 1998 12:43 PM
>> To:  Tesla List
>> Subject:  Re: Magnifer & rotary problems
>> Bill the arcstarter wrote:
>> >  We are using a slightly different type of aluminum rotor.  This gap is
>> > composed of a non-insulated induction motor (non-sync) with a 4 inch
>> > plastic hub (don't know what material) mounted on the shaft.  Onto the
>> > plastic hub is mounted an aluminum ring, with an o.d. of about  14
>> > inches.  Stainless steel contact mounted near the edge provide the
>> > arcing path.
>> >
>> >  The point here is that we insulated the disk from the motor via the
>> > plastic hub disk.
>> >
>> > This is an alternate construction technique.
>> And a fine design it is, since you are utilising metal
>> in the rotor construction to contain the hoop stresses,
>> to support the centripetal forces of the rotating electrodes,
>> and to dissipate the heat from cathode spots on the electrodes.
>> The 130kW RSG uses an insulated axle, as there are multiple
>> ganged rotors in series, all at different voltages.  The
>> central bearing crossmember floats at mid-voltage.
>> --
>> -GL
>> www.lod-dot-org