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

dwight dkelvey at
Sat Nov 10 18:46:28 CST 2018

If the pulley diameter was 19.0mm, the new pulley would be exactly 22.8mm. It is a simple ratio problem. The motors rotation is synchronous to the line frequency. It turns 50/60 too slow. To speed it up is 6/5. The speed of the belt is proportional to the radius of the pulleys.
If it was a crowned belt, a fine tune can be done with the tension of the belt. A tighter belt will run a little slower because most of it rides lower on the pulley. The tension on the belt is the same everywhere, not counting bearing and drag on the disk. This means the effective rate is determined, mainly, by the where the belt rides on the pulley.

From: cctalk <cctalk-bounces at> on behalf of Chuck Guzis via cctalk <cctalk at>
Sent: Saturday, November 10, 2018 12:38 PM
To: Fred Cisin via cctalk
Subject: Re: AW: 50Hz Pulley for 8" Floppy Drive Mitshubishi M2894-63B

On 11/10/18 12:33 PM, Fred Cisin via cctalk wrote:
>>> 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.
> On Sat, 10 Nov 2018, Chuck Guzis via cctalk wrote:
>> No argument there--but the size increment is pretty small.  Consider
>> that a typical motor pulley is about 19 mm in diameter, so a 20%
>> increase would be only about 23 mm.
> Depending on the drive, WHICH pulley should be changed?

The motor drive pulley is the easiest.  You might even find a ready-made
one in an engineering findings catalog.

Alternatively, consider this YT video for a DIY frequency changer:


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