msg hath wroth:

Nice hearing the various techniques mentioned in this thread. I have
restored digital tape transport capstans by removing the deteriorated
rubber and layering back to the original diameter using multiple dips
in liquid vinyl; the capstan needs to be spun at low rpm with the shaft
horizontal until each vinyl layer has set. I did a capstan for an
HP-85 awhile ago that required quite close tolerances and this technique
worked well; the result was a bright red surface however ;-)

The HP85 drive roller is mostly metal with a relatively thin coating
of rubber. See photos at:
http://www.voidware.com/calcs/hp85rep.htm
See page 2 of 3 pages. Resurfacing such a roller will work just fine.
However, the Sony and Gerrard idlers have a much thicker layer of
rubber. The deformation depth of the capstan is also substantially
deeper than the HP85 drive roller, requiring a much thicker deposition
of added rubber. It's probably possible, using the suggested freezing
the rubber and machining it down to the diameter required. As I
indicated in a previous message, I think it will work with the
relatively wide Sony idler, but will not work with the fairly narrow
Gerrard idler.

Current status is that I'm gathering an assortment of chemicals and
concoctions, along with a variety of rubber parts. I'll try some
experiments next weekend, and then apply the least disgusting fix to
the customers antique tape recorder and turntable.

Thanks for all the suggestions and hints.

Incidentally, this is how I repaired an HP65 calculator drive roller:
http://802.11junk.com/jeffl/pics/hp65/slides/Hp65-Drive-Roller.html
The "rubber" is a piece of vinyl tubing, conveniently with the correct
diameter. The only good way to cut it to size is with a razor blade.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558