FW: Magnifer & rotary problems

From:  Greg Leyh [SMTP:lod-at-pacbell-dot-net]
Sent:  Tuesday, June 23, 1998 1:20 AM
To:  Tesla List
Subject:  Re: Magnifer & rotary problems

Michael Nolley wrote:

> > Aluminum rotors have always worked well for me, they're cheap,
> > good conductors.  Aluminum has a very high edge speed rating,
> > and is easy to machine and dynamically balance.  An aluminum
> > rotor also carries the waste heat away from the electrodes.
> > -GL
> Why, then, do most use lexan or some other non-conductive plastic
> for their rotors?  If metal is superior, and it doesn't compromise the
> quenching, why use plastic?

I think that it comes down to personal preference.  
Metal rotors are stronger and have greater dimensional
stability, but require the shaft bearings to be 
insulated from ground.  I personally prefer to make
the stationary bearing support blocks out of insulating
material rather than the rotors themselves, since the
rotors must survive far greater mechanical and thermal 
stresses than the stationary framework.

The thermal heat capacity of the metal rotor mass can 
absorb a considerable amount of heat, and offers a 
large rotating surface area for removal of that heat.
Typical heat rise on the 40kW rotors is about 5-10degF.
Bert Pool has a picture of this rotor assembly at:
Also, in the unfortunate event of a rotor crash, such
as an interference with a stationary electrode assembly,
a metal rotor gets bent, but an unlaminated plastic
rotor explodes.