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>

Hello Terry and all!

The wood rotor is still in great shape. I mounted it to a 3450 rpm 
hard drive motor and it is used in my present coil setup. I am glad 
to report that no charring has occurred at the electrodes. The only 
issue I have with the wood is that it is not flat across the 
diameter. This causes a slight amount of vibration perpendicular to 
the rotor. I am pleased with how well the wood has worked. My main 
motivation to try it was economic. I hope this has answered your 
questions. Btw- I emailed the US distributor about a replacement 
pinion and was told it was cheaper to buy a new grinder. Go figure.

Gregory
ps- has anyone one else here noticed Coiling interfering with their 
personal lives/ productivity? :)

>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
>>>   >
>>>   >
>>>   >
>>>   >
>>>   >
>>