Re: Source for Universal Motors???

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

At 07:30 14/01/03 -0700, you wrote:
>Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><dhmccauley-at-spacecatlighting-dot-com>
>
>I'm looking for a source for universal motors.

Easy, just cannibalize a vacuum cleaner. The motor inside is a universal 
motor, 400 to 1200 watts depending on model of vac, and good for 
10,000-12,000 rpm at least. Leaf blowers have a similar motor. Washing 
machines also have universal motors but the shaft is designed for belt 
drive so less convenient for attaching a rotary gap disk. With a vac/leaf 
blower you could just unscrew the fan from the motor and screw the disk on.

Be warned, universal motors can overspeed and self destruct if run at full 
voltage without a mechanical load. Also as I'm sure you know, balancing is 
absolutely crucial at these speeds. If you're trying to balance the rotor 
in situ using the "spin it and see where it stops" method then you need to 
take out/retract the motor brushes or the friction will be too great and it 
won't work.

Good construction is vital too because the centrifugal forces are 
tremendous even if the rotor is perfectly balanced. You can minimize these 
by using a light but strong rotor of the smallest possible diameter, and 
the lightest flying electrodes possible. It would be wise to know the 
strength of your materials and familiarize yourself with the math so you 
can calculate the stresses involved and design in a safety margin. All nuts 
and bolts on the rotor should be threadlocked and a steel or lexan guard to 
catch any flying bits is compulsory. I assumed you were building an ARSG 
but I suppose these precautions hold for anything spinning at 12000 rpm.

I'm currently trying to make a mini ARSG using the tiny 150 watt motor from 
a "Magic Broom". I'm hoping to have a 3.5" diameter disk spinning at 12,000 
rpm.

Steve C.