RE: Synchronous motors for rotary gaps (fwd)

---------- Forwarded message ----------
Date: Fri, 03 May 96 09:49:00 PDT
From: Richard Hull <RICHARDH-at-whitlock-dot-com>
To: bin <bin-at-poodle.pupman-dot-com>
Subject: RE: Synchronous motors for rotary gaps

Skip, all,

I haven't heard this mentioned in this conversation so I'll throw it out. 
 Bill Wysock in California has long championed the Synchronous rotary 
system.  He has used "salient pole motors"  This are synchronous motors 
which also lock to the same point each time they are started.  That is the 
same point on the shaft will align with a given point on the case every 

For a long time, this was a deep dark secret.  This motors are made up from 
common, garden variety squirrel cage induction motors (el cheapos). 
 Two/four flats are milled or plained off of the armature rotor in a fashion 
which does not disturb the copper conducting bars within the armature.  In 
this manner, anyone can make a nice salient pole synchronous motor.

Recently, TCBOR good buddy and long time correspondent, John Freau of the 
Tesla coil Builders of New Jersey has done a huge amount of research into 
these motors and the synchronous system in general.  He has fashioned a 
number of motors with crude hand tools and a drill press.  (no milling 
machine).  All of them work well.  All of his finished gaps work well, too.

Again, what one hand gives the other takes away.  It seems that if you take 
a 1/4 hp induction motor and turn it into a salient pole motor, you will be 
lucky to retain 1/2 to 1/3rd its original horsepower rating!!!  Thus your 
old 1/4hp might now be a 1/10 hp unit, but synchronous.  This is not bad if 
you start with a 1/2 hp motor, but don't experiment with milling flats on a 
large unit like this!!  If you screw up, you now have a worhless motor!  If 
you decide to piddle with salinet pole motors,  get a fist full of  surplus 
1/8-1/10 hp units and dink around until you have a feel for the work.

John has shown no real advantage exists in the synchronous system over say a 
normal fully controlled variable speed rotary.  This is based on actual 
tests with working coil systems, where a like non-synchronous gap is swapped 
out after the synchronous gap is run.  The synchronous system has a very 
distinct spark pattern and can be recognized instantly at sight by the 
adroit coiler.

I am not a booster for synchronous systems, but it sounds like a few of you 
might be.  I hope this info is of some value.  John Freau like myself, tends 
to use the non-synchronous gap most often in his medium sized magnifier 

Richard Hull, TCBOR