Tape Drive Capstans

Josh Dersch derschjo at gmail.com
Fri Jan 30 15:41:24 CST 2015

To add a recent experience of mine, I recently rebuilt a Cipher 540 QIC
drive (in a Ridge32).

The ID/OD of the capstan wheel on this drive is (roughly) 31/64" ID, 5/8"
OD (i.e. the inner diameter is JUST a shade under 1/2"), with a thickness
of 1/4".  I found some 3/32" thick square o-rings with a 7/16" inner
diameter and 5/8" outer for $0.10 each (from http://www.theoringstore.com/)
and I ordered a few -- the inner diameter is a bit smaller than required,
but I figured it'd just make it stay on better (well, why not for the

After cleaning the goo on the capstan off (which is an ugly
procedure...) two of the rings fit snugly on the metal capstan wheel
(leaving about 1/16" at the bottom uncovered, which is ok since that area
will probably never actually need to contact the tape roller), and with a
tiny amount of glue they stay affixed quite nicely.

I've since erased/retensioned a few tapes and written a few tapes out
without issue. Also got RX/V installed on the Ridge using it.  I can't say
it'll work for a *long* time, but it has worked fine thus far and was
enough to bring a doorstop back to life.  (Well, now the power supply is
causing issues, but at least that doesn't involve getting tar all over my

- Josh

On Fri, Jan 30, 2015 at 10:44 AM, Al Kossow <aek at bitsavers.org> wrote:

> On 1/30/15 10:29 AM, Ali wrote:
>  How are you using these? Do you have the original OD and ID measurements
>> of
>> the roller and slip the tube with the right OD over it?
> Correct. You obviously have to have one surviving roller to be able to do
> this.
> Brad Parker fixed some TU58's a while ago and sent me a 1' piece of
> Norprene that
> a friend of mine cut for me. You end up with a lot extra because you have
> to buy
> 10' minimum. He also just did a few for the 9145s we have. You put
> a dowel inside the tube and cut using dish soap as a lubricant. He used an
> Xacto
> Saw blade.
> I guess creating a table for tubing diamaters that work with common pinch
> roller
> types would be a good thing. There are some rollers that may be difficult
> to do.
> The early DEI 1/4" cartridge drives have very small rollers. There hasn't
> been
> much experimentation yet as far as how much the outer diameter can vary.
> Most of
> the cartridge tapes I know of use self-clocking encoding formats, so it
> might
> actually be quite a bit.

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