Re: desperate need for info on sync gaps
In a message dated 99-10-24 08:33:46 EDT, you write:
<< hi i read that post a week ago about the 6"x24" coil with 28 gua wire and
> 12/30 nst and was amazed to hear that it got 3 foot sparks. i know all
basic >construction methods for
> rotary but dont have the slightest idea of how to modify a standard ac
> motor to syncronous operation. a very well
> made brushless ( can you use brushless) 1/6 hp 3500 rpm 60hz motor, and a
> blender moter of unknown value.
> ps. what exactly are the characteristics of a sync moter ie. oh and
> about that 12/30 coil design would it run properly on a static gap like the
> one i currently have
> very much thanks in advance Chester Lowrey
That was my TC, the one that gives 42" sparks using the 12kV, 30ma
NST. To create a sync motor, start with an induction motor. These
have no brushes, and are found in washing machines, clothes dryers,
etc. These motors run real quietly. Bench grinders use an induction
motor also. The 3500 rpm motor you have is probably 3450 rpm right?
If it's an induction motor, it would be perfect for your project. It will
run at 3600 rpm after it's modified. To modify it, grind TWO flats onto
the armature opposite from each other. If the armature is 3.3" in dia,
then make the flats about 1.2" wide or so. The grinding can be done
with a milling machine, edge grinder, or even with a large hand file.
There are some websites that show the process, someone will probably
mention them. Make sure the flats are equal in width, and parallel to
each other, to help keep the motor balanced. At 3600 rpm, balancing
is more critical than at 1800 rpm, but not too bad. Make sure the rotor
and electrode assemby is not large or heavy, or you might have trouble
getting the motor to lock up synchronously.
You can see a sync gap I made at my webpage at :
I also offer videotapes for sale that cover sync motor modifications,and
many other Tesla coil topics, and shows the 42" spark in operation. THe
tapes are $16 each.
A sync motor spins at an rpm that is an an exact multiple of the 60Hz
line frequency. And it stays in phase so that the gap firing always
occurs at the same point along the ac sine wave. We want it to fire
when the cap is fully charged for max output from the system.
Some provision has to be made to permit the phase to be adjusted
for initial setup. Either the motor can be mounted in a cradle so it can
be rotated, or the electrodes can be placed in a special rotatable assembly,
or the disc can me rotated relative to the motor shaft. I consider the
rotatable motor method to be the simplist, and I always use that technique.
Adjust the phase for best operation of the TC.
If you do build this project,
you will be the first one that I know of other than myself. I'd be glad to
hear how it works out, and you're more than welcome to e-mail me with
questions or if you run into any problems.