From: D.C. Cox <DR.RESONANCE-at-next-wave-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Date: Wednesday, July 01, 1998 11:28 AM
Subject: Re: rotary design
We use a standard G-10 phenolic plate with 1/2 dia. brass rods axially
mounted on the disc and 1/2 dia. tungsten electrodes. We also used 1 inch
dia. stationary electrodes which conduct away most off of the heat to large
1 1/2 x 1 1/2 square brass blocks in which they are mounted. The rotating
electrodes with 1/2 dia. brass x 1 1/2 inches long work well for both RF
current conduction and heat transfer to the surface where the high speed
cools them adequately. We run this style with power levels to 40 kilowatts
without problems. If you do use a type 2 gap, be sure to use copper or
brass -- avoid aluminum due to its poor RF conductivity. It does work but
your peak currents will suffer substantially.
> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-pupman-dot-com>
> Subject: rotary design
> Date: Tuesday, June 30, 1998 9:56 PM
> 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
> 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
> 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
> 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
> >I'm using 1/4 inch copper electrodes which extend .75" out from the
> >ring. It spins on an insulated shaft. It has performed nicely and does
> >me a good feeling knowing the electrodes are very secure (safety
> >used regardless). So far, the electrodes have barely warmed. I am using
> >G6 fiberglass covers over the flywheel and electrodes to aid in
> >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
> >> > 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
> >> > 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