SRSG Newbie questions

["Alan Sharp" <AlanSharp-at-compuserve-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Message text written by INTERNET:tesla-at-pupman-dot-com
>Hello,
I'm preparing to build a SRSG that can handle up to 2 - 2.5 KW:

What determines the diameter of the disk I should be spinning? I have seen 
many in the range of 7" - 12"  Which size is correct?
My next question is about motor HP.  How much HP do I need?

I'm handling 6-8kW with an async 390BPS. disc is about 8* diameter.
1/4 HP would be sufficent.
I'm using a 1/2 HP modified electric grinder which works well.
Another trick that I use - 
is that instead of using 8 rotating electrodes and 2 stationary
electrodes, I use 4 rotating electodes and 2 sets of stationary
electrodes offset by 45 degrees.

full details on my website on the "Bride of Frankenstien" page
http://ourworld-dot-compuserve-dot-com/homepages/alansharp/

Alan Sharp (UK)