Sync motor modification

From:  Gary Lau  28-Jan-1998 0803 [SMTP:lau-at-hdecad.ENET.dec-dot-com]
Sent:  Wednesday, January 28, 1998 7:36 AM
To:  tesla-at-pupman-dot-com
Subject:  Sync motor modification

>> I have both acheived good outputs from neon systems using sync gaps,
>> without any tranny failures, but only time will tell how effectively the sync
>> gaps "protect" the trannies.  Perhaps if more folks start using sync gaps
>> on their neon systems, a long term consensus (on tranny longevity) 
>> will emerge. 

>Funny you should mention that.. I am in the process of seeking out 
>the directions to modify a motor to sync operation for just that reason.
>[More power for less..] I figure if I smoke the tranny now, well, it
>gave me a good result, and I can't really learn too much more from it.

I'm just about ready to test out my sync RSG with a 15KV/60mA NST.  For a
motor, I bought a 1/8 HP 1725 RPM motor for $4.95 from H&R Surplus.  This
unit has a 3.5" dia rotor.  I milled four flats onto it, each being
1.00".  While the flats should have been 1.30" to each cover 1/8 of the
circumference, I thought it safer to remove less and see if it works.  It
sync's right up so I'll stick with the 1" flats.  Only problem is, there
are four angular positions, each 90 deg apart, from which the motor will
stall if started there.  Perhaps if the RSG works out well, I'll buy
another motor and remove more material and see if that resolves the

A question on adjusting the phase of a sync RSG.  It would be best if I
could do this without attempting the subjective test of when I have the
longest spark, turning off power each time.  I did a dry run last night
without my secondary installed, and as I rotated the motor case, saw a
clear point of maximum gap arcing.  Is this a valid indicator of the
correct rotor phase for when the TC is completely assembled?

Gary Lau
Waltham, MA USA