R80/RA81 diagnostic experience?

From: Tom Jennings <tomj_at_wps.com>
Date: Tue Mar 9 19:32:11 2004

> > I once heard the following rumour:
> > the brake in combination with the 'heavy' motor
> > makes sure that the disk platters always rotate
> > in the same direction, never for a short instance
> > in the other direction (vibration, power flutter,


Depending on how the motor is wound, etc, it might be possible
*WHEN STARTING THE MOTOR FROM A DEAD STOP* that if initially spun
the wrong direction when power is applied, that it could spin
up reverse direction. The rotor is pushed around the stator by
discrete angular magnetic "bumps" and unless the magnetic field
is bent with shade poles or whatever the motor design uses,
it could start 'backwards'. Most motors provide for such a
thing one way or another. There are a lot of motor designs.

I have no specific information on the motor used in this drive.

> Are you suggesting that a platter, weighting several kilograms, spinning
> at something like 3600 rpm, suddenly can change spin direction at a
> millisecond notice?

This would be ummm interesting if you could make it happen... :-)
Received on Tue Mar 09 2004 - 19:32:11 GMT