AW: 50Hz Pulley for 8" Floppy Drive Mitshubishi M2894-63B

dwight dkelvey at
Sat Nov 10 13:42:38 CST 2018

He needs a larger pulley if going from 60 to 50 ( as a motor pulley ). It needs to be 20% bigger because the motor turns slower on 50 Hz. 6/5 to be exact.

From: cctalk <cctalk-bounces at> on behalf of Chuck Guzis via cctalk <cctalk at>
Sent: Saturday, November 10, 2018 8:32 AM
To: dwight via cctalk
Subject: Re: AW: 50Hz Pulley for 8" Floppy Drive Mitshubishi M2894-63B

On 11/10/18 7:55 AM, dwight via cctalk wrote:
> Typically, both the motor pulley and belt are changed as a set to keep the distance from motor to flywheel the same.
> In my younger days, a friend and I ground down a motor pulley, on a 50 Hz Shugart 800, to be a 60 Hz. We used a file while the motor ran. After getting the right size, we had to file mounting holes for the motor to keep the same belt. It was not the best way but we couldn't afford a new drive and we got the drive cheap, from surplus.
> If you change the flywheel, the distance will be to great to use the same belt or even close to the same belt. It may not even fit in the area allowed for the flywheel.
> According to the manual, for this drive, only the motor pulley needs to be changed as there is enough adjustment to use the same belt.

I was gifted a brand-new Qume 842 220V 50Hz drive many years ago.   The
220V was no problem--I had a dual-primary transformer on the power
supply, so it could be reconfigured as a 240V autotransformer and still
have enough capability for the drive electronics.  The problem was the
60Hz line frequency.  Essentially, the motor turns somewhat faster, so
you need a smaller motor pulley.  I calculated what I needed and found a
flanged toothed pulley for a timing belt that was exactly the right
size.  While the original motor pulley was crowned, the timing pulley
worked exactly as calculated.  It was not necessary to change the drive
belt--the size difference was small enough that it could be swamped out
by loosening the motor mounting bolts and adjusting.

I still have the drive today--and it still works.


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