Re: Cap break down voltages / Rotary Question

        Re: Cap break down voltages / Rotary Question
        Thu, 10 Apr 1997 00:52:44 -0400 (EDT)
        richard hull <rhull-at-richmond.infi-dot-net>
        Tesla List <tesla-at-pupman-dot-com>

>Thanks Ed Sonderman, Richard Hull for your advise.  Home made caps at
>10KV RMS are about right.

>During this run the spark gap took a hit.  For some odd reason the
>strike caused the electrodes on the rotary spark gap to colide, and self
>destruction followed.
>I would like to ask the list if the gap design I have is any good.  
>Basically I have a high speed motor (10,000 rpm) and a rotor disk made
>from fiber glass PCB copper clad board.   Two electrodes are mounted on
>the disk which are electrically connected by the copper covering.  
>These electrodes pass two stationary electrodes with a clearance of
>about 0.5mm.   I find that when the gap is running at operating speed
>the 6" disk streches and the 0.5mm gap closes almost to the point of
>I calculate that with 1/4" electrodes the dwell time:
>velocity of electrodes is
>   6*3.14*10000/60 = 3140 inches per second
>dwell time is
>   0.25/3140 = 79uS
>Flaming round problems don't seem to be a problem.  (No visable signs)
>The remaining rotor disk following the failure has lost an electrode. 
>The electrode which is 1/8" diameter has ripped a grove from the point
>it was mounted to the outer edge of the disk.  Is it possible that I am
>running the motor to the point of failure of fiber glass?
>Comments Welcome
>Julian Green

Wow!  That is not common thin PC board material is it?!!  Ouch!  Killer
If that is common PC board G-10 copper clad then you are one lucky guy! 
won't run my 1/4" thick fiberglass disk above 3000 RPM!  I am amazed a
disk like than remained stable.

I would rethink the gap big time if I were you.  good luck!

Richard Hull, TCBOR