HP2648A tape drive capstans

CRC technobug at comcast.net
Thu Feb 16 02:22:19 CST 2006

I've been following this thread with interest since I'm in the midst  
of restoring an HP Dynamic Systems Analyzer with two of the same tape  
drives installed. Both capstans were gooey. I considered the various  
suggestions and came up with an easy, inexpensive and accurate way of  
restoring the rubber coating on the capstan. Plasti Dip International  
<http://plastidip.com/consumer/index.html> makes a coating for tools,  
insulating, weatherproofing, etc. You dip the object you want to coat  
as many times as necessary to build up the necessary layer. The  
product has just about the right consistency to replace the old  
capstan rubber and appears to have excellent wear characteristics.

I was able to add 0.021" [53.3] coating to the capstan in three dips  
to bring the diameter to the proper value. The diameter varies less  
than 0.001" [0.025] over several measures and the run-out is around  
0.002" [0.051]. This was on the first try. The drive appeared to run  
the tapes on hand properly.

A couple of hints:
- stir the stuff well. However, not so fast as to introduce bubbles.
- attach an extension to the can of dip and add one or two drops of  
solvent to the top of the dip. This will ensure that the area above  
the surface of the dip is saturated with solvent and will prevent  
- coat past the capstan onto the shaft. The added weight is  
negligible and will ensure that the coating is uniform over the  
capstan's surface.

My next try will be on a capstan for a DEC 7-track tape drive  
belonging to a friend.

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