Re: Disk size for 3600 RPM sync TTY motor

"I was wondering what size disks others have been using with 3600 RPM
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?"

	Although I haven't looked at mine for years, believe that they are all
1800 RPM jobs.  Because of the gear reduction used in TTY machines,
can't see any extra value in 3600 RPM operation.  The windage is
certainly an important factor as the disk size goes up.  Have an NACA
paper on "Drag of Rotating Disk" somewhere.  Seem to remember that the
windage power loss goes up as the FIFTH power of the diameter and as the
cube of the speed!  I once tried to spin a thin 36" diameter wheel at
3600 RPM with a 5 HP sync motor, and we could never get it to "pull
in".  Eventually added a clutch which let the motor come up to speed and
then applied the flywheel load, but then the thing hunted so badly as to
be useless for the intended purpose.