Re: Disk size for 3600 RPM sync TTY motor

In a message dated 99-06-08 16:49:33 EDT, you write:

> I was wondering what size disks others have been using with 3600 RPM TTY
>sync motors?  Is the problem one of rotating mass, where it just can't
> get over the startup hump, or is it air drag, where any attempt at such
> prominent rotating electrodes would be too much drag for this motor?
> Regards, Gary Lau
> Waltham, MA USA


My guess is it's air drag that's the problem.  The sync motor I used
at 3600 rpm is a 1/12HP teletype unit, and I used a 3/8" thick 8" dia.
lexan rotor with 2 or 4 spinning electrodes.  The electrodes are 3/8"
threaded rod with nuts on either side of the rotor to hold them tight.
The motor locks up synchronously at about 75 - 80 volts, so there's
some good leeway during normal 120 volt operation.  I also have a
similar, but smaller 1/20th HP motor, but I never tried it with a rotor.
But my guess is the 1/20HP would not be quite enough for my rotor,
nor yours.  Did you try using 140 volts from a step up variac to see if
that helps?  Is yours the 1/20HP type?  I have some doubts that my
1/12HP motor would handle the pipe type electrodes.  It is possible
that a 1/4 or 1/2HP motor would be needed.

John Freau