Re: RSGs

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

Original poster: "G by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bog-at-cinci.rr-dot-com>

Howdy!

I got great performance from my 11k rpm grinder. The 8" diameter 
rotor (zero cost!) was made from 3/4" furniture-grade plywood. I used 
3/16" tungsten electrodes and the rotor trued up with one well-placed 
drywall screw. It ran great until the pinion gear sheared off a few 
teeth and dead locked the rotor. ( $12.00 chinese model) Well, I 
should say the shaft deadlocked. The rotor became a great model of 
kinetic energy as it shot across the room (through the safety shield, 
too)!

Happy day,
Gregory

>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
>  >
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