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Re: rotary spark gaps

 In response to querries about rotary spark gaps:
 
 I am using a rotary gap with my coil.  I am using an old transmitter transformer
 and running about 2KW  ( about 12KV).
 
 By the way, for your interest, my capacitor is built up of 16 1 uF 1000V 
 snubber capacitors all in series. (With equalization resistors across each
 cap.)    I got these for a buck a piece surplus!  The bank has been running
 for years - and I did find some data-sheets for the caps - their high-freq.
 response is great.
 
 Anyway, back to rotary gaps....
 
 I built my rotary gap from an old keypunch.
 
 It had a 1/4 hp synchonous motor with a 'plastic' gear (about 4" diameter)
 already mounted.  I figured, why mess with this part?  The bottom of the 
 keyboard had a stainless (!) metal plate attached.  I took this plate and
 cut and eight sided star that was  about 9" in  'diameter.'  I also cut a hole
 in the middle that was about 3 1/2 inches in diameter.  After carefull centering
 of the start wheel on the plastic gear, I screwed the two together.  In this
 manner, the entire disk is the conductor, but everything is isolated from the
 motor.
 
 For the stationary part, I used two 'C' shaped pieces of 1/4 inch copper pipe.
 The two pieces were mounted:  ( )
 I drilled three holes in each  'C'  and inserted stainless bolts (and nuts to
 tighten everything down.)
 
 The interesting thing about this rotary gap is how it fires.  Because the
 star is eight sided and there are six startionary electrodes, one  gets many
 make-breaks for each rev of the motor.  (One doesn't need to run the motor
 very fast due to this.  (Although no choice for me with a sync. motor.))
 I run the motor and tighten down each screw until I hear it 'ting' on the 
 star, then back off about 1/2 turn.
 
 As with the capacitor back, this gap has served well for a couple of years.
 About every hour of operation - I just turn the screws a little.
 
 For my next coil (higher power), I am planning to do approx. the same thing,
 except I will use eight screws on the  ( ) parts.  In this manner, all of
 the contacts will be in line at one time.  This is the same as having four
 gaps in parallel, so they should quench faster since each pair of gaps only 
 needs to deal with 1/4 the current.  Comments???
 
 
 rob