Motor questions and a rotary suggestion

I just bought a 1/12 HP, 5000 RPM  variable speed DC motor and I have 
a couple of questions.  First, is this powerful enough to use to drive a 
rotary gap?  Secondly, can I get  DC to drive this motor by simply 
running the output from my variac through a full-wave bridge, or should 
I put in some filter caps to smooth out the ripples?

And a suggestion for Ed concerning your rotary gap:  instead of adding 
more rotating electrodes to get higher break rates, it might be easier to 
add a second set of stationary electrodes positioned to fire halfway 
between the first set.  This would effectively double your break rate and 
you wouldn't need to have a new disk machined.

Steven Roys (sroys-at-radiology.ab.umd.edu)