Re: Rotor & sync motor
Sent: Tuesday, September 16, 1997 10:28 AM
Subject: Re: Rotor & sync motor
In a message dated 97-09-16 11:24:13 EDT, you write:
> I think I will build a rotor that will fire one time for every 60 Hz AC
> peak. I don't see any reason to make it fire more than once for each peak.
> 2 rotating electrodes on a 9" disk and 2 stationary electrodes using an
> RPM sync motor will give 120 Hz. It will fire on each + and - AC peak.
For an 1800 rpm sync motor you need 4 spinning electrodes
and 2 stationary electrodes to give one firing on each + and -
AC peak. If you use a 3600 rpm motor, 2 rotating and 2 spinning
electrodes would be correct.
> 2 additional stationary electrodes opposite the other 2 stationary
> electrodes will give me 4 gaps with them wired in series.
For an 1800 rpm motor you'll need four spinning electrodes. Yes, the
2 fixed, the 2 additional stationary electrodes opposite the other
2 stationary electrodes will give four actual firing series gaps with
them wired in series.
> How does this look so far? Does anyone have any suggestions.
>I called my friend at the motor shop about a sync motor. He said they don't
> make sync motors any more with out special order and they are very
> expensive. True sync motors have a wound armature with slip rings and
> brushes. No used sync motors are available.
> Some information on the internet says 4 flats can be milled in the armature
> to make a 1750 RPM run sync. Most AC motors are 1725 RPM. My question is,
> will this work on a 1725 RPM motor? My next question is, will the flats
> a 1725 RPM motor run at 1800 RPM?
Yes, the flats will make both a 1725 and a 1750 rpm motor run
synchronously at 1800 rpm. And yes 4 flats are needed. Use 2
flats for a 3600 rpm motor. 1725 and 1750 motors are built the
same way, it's just a matter of how they're rated for their load, since
their speed will vary with the load (just a little trivia here).
> My friend at the motor shop said he thought the flats would make a 1725 RPM
> motor sync at exactly 1725 RPM's. And a 1750 RPM motor would sync at 1750
> RPM. But it seems to me like the flats will have to sync with the 60 Hz AC
> and run exactly 1800 RPM's. Has anyone tried this? Does this really work?
You must not have read my numerous posts over the last few months
in which I describe in detail how I have modified these motors. I use
a modified motor in my present coil. But I prefer the 3600 rpm motor
with 2 flats. But 1800 rpm is fine. Skip Greiner, Dr Resonance, and
many others often use 1800 rpm. The 1725 and 1750 rpm motors will
of course run at 1800 rpm when modified. Yes, this really does work.
> I have a 1/4 HP 1725 RPM 120 VAC motor I can use to make a sync motor. If
> this really works I will mill flats in the armature and use the motor on a
Well, there are two points to keep in mind when using 120 BPS sync-
1. If you have been previously using a rather high break-rate,
such as 300 or 400 ACTUAL BPS (there's a BIG difference between
gap presentations and actual gap firings), then you will find that you
will need to use a considerably larger main capacitor to maintain the
same spark length. If you keep the same size cap, both the power
input and the spark length will decrease, (most likely). What actually
happens will depend on whether you acheive proper resonant charging
in the new set up. In my TC which gives 42" sparks using a .007uF
cap, at 680 watts, at around 14kV input, the caps reach a peak
voltage of 32kV, using a 120 BPS sync-gap.
2. When you modify an induction motor for sync operation, you will
lose some power. I modified a 1/4 hp 1725 rpm motor for sync
operation, and it still gave enough power to lock up a 9" rotor in sync
operation. Depending on just how heavy and how much air resistance
your rotor has, and how heavy and how air resisting the electrodes are,
it is possible that the motor may lack sufficient power. Bottom line is
"ya don't know 'til ya try it", so I say "go for it Gary", and join the ranks
of the syncho-folks.
> Gary Weaver