RK05 spindle pulleys - trade 50Hz vs 60Hz?

Tony Duell ard.p850ug1 at gmail.com
Wed Jul 25 13:17:41 CDT 2018

On Wed, Jul 25, 2018 at 5:48 PM, Eric Smith via cctalk
<cctalk at classiccmp.org> wrote:

> I'm not sure about motors, but 60 Hz power transformers can't handle as
> high a maximum power (or current) when used for 50 Hz. The maximum power
> has to be derated. Some transformers are specified/sold with a single power
> specification for both 50 and 60 Hz use, which just means that the vendor
> has built the necessary derating into even the 60 Hz specification.
> Some products were built using different transformers for 50 vs 60 Hz
> models, and the 60 Hz models uses a transformer inadequate for 50 Hz
> operation.

This may well be true (I think it is), but the original question was about a
particular device, the DEC RK05 disk drive. According to the maintenance
manual (on bitsavers), the coversion between 50Hz and 60Hz involves changing
the motor pulley. No comment about replacing the motor, the start capacitor,
or anything else.

Does anyone have an RK05 IPB (Illustrated Parts Breakdown) manual? It would
be interesting to see if there are different part numbers for the motor (start
capacitor, blower...) for 50Hz and 60Hz versions.

Going back to a much earlier comment, I think this pulley is something that
would be a lot easier to turn (on a lathe) rather than 3D print.


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