Re: RSGs

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>" <youngs-at-konnections-dot-net>

Greg,

Sounds like a winner.

Some cheap angle grinders have some axial play in the drive shaft - not the
best bearings.  In my case, I have a horizontal rotor, and when the RPM got
high enough and the wind loading increased enough, the gears overcame the
force of gravity on the rotor and lifted it up, causing the rotating and
stationary electrodes to crash into each other and get bent up.  I had to
rig up an external bearing arrangement to keep the rotor from being able to
lift up.  You may need to do the same if you have axial play in your
grinder.

I would worry about an 11,000 RPM RSG!  If it were me, I would keep it below
5,000 RPM and use more electrodes.  The bigger diameter is a good idea, but
be sure to leave plenty of rim beyond the rotor electrodes and secure them
well to withstand the centrifugal forces.

If your supply is DC, then definitely the additional air blast will help
with quenching.  If it is AC, then probably the air movement from the rotor
will suffice.

--Steve
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, January 03, 2002 12:46 PM
Subject: RSGs


> Original poster: "Mr Gregory Peters by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>
>
> First and foremost, I would like to thank you all for your advice
> lately. It has been most helpful.
>
> Today I bought a cheap and dirty 700W 11000 rpm angle grinder. I'm
> going to use only 4 electrodes for up to 733 BPS (even higher if I wind
> up the variac to 270v). The motor throttles quite smoothly with my
> small variac. I intend to use an 8" diameter disc, with the 1/4"
> electrodes at 7" diameter. The disc is 5 blank PCBs, glued together.
> I'm actually tempted to make a bigger disc to make the dwell time
> shorter. The rotary will be used in series with an air blast gap to
> allow better quenching, reduce flaming on the rotary and improve the
> lifespan of the electrodes. What do you think.
>
>
> Cheers,
>
> Greg Peters
> Department of Earth Sciences,
> University of Queensland, Australia
> Phone: 0402 841 677
> http://www.geocities-dot-com/gregjpeters
>
>
>
>
>