Re: RSGs

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Gregory,

How did the "wood" itself perform?  Did it survive the explosion and such?
The grinder failure (12.00 is cheap even for the "CHEAP" ones :-)) is just
one of those darn things, but I am interested to hear of your thoughts
about wood as a rotor material.

Cheers,

	Terry

At 06:36 AM 12/3/1970 -0400, you wrote:
>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
>>  >
>>  >
>>  >
>>  >
>>  >
>