Rubbery Bits Gone Gooey

From: Frank McConnell <>
Date: Sun Nov 23 12:35:00 1997

Lately a friend has been trying to copy a tape for an HP 2645

Thus far he has discovered a problem with tape drives in two
terminals. His description of the problem is that, when used, the
motor capstan in the tape drive "melts". In one case he has not
been able to get all the ex-capstan goo off of the belt capstan
in the cartridge; fortunately that was a blank tape.

My first thought was, hmm, this sounds like the problem the calculator
folks have with the rubbery wheels that go gooey.

I have one of these terminals too, but it's a bit buried in storage
and I haven't got it out yet. (In fact, the tape contains games and
he is trying to copy it because I expressed interest...of course, now
I am thinking that when I dig the terminal out I need to open it up
and check the capstans before I go and jam a tape in.) Instead I
found the May 1976 issue of the HP Journal, which was smaller,
lighter, closer to the front, and does a pretty good job of
demonstrating how proud HP was of having fit tape drives to HP
264x terminals.

What have I found out? The motor capstan has an aluminum core with an
elastomer coating that is ground to the right size during
manufacture. Said elastomer was chosen for quick recovery from the
dent that forms in it when the loaded tape isn't moving (as the
capstan is held against the tape cartridge's belt capstan).

So now I guess I have two questions. One is just what do the
calculator folks do about rubbery wheels gone gooey? And the other
is, can I do something like that for these drives? Given that the
object of this capstan is to press against and drive something less
flexible than a magnetic card (the belt capstan in a DC100 tape
cartridge) I'm not sure the same sort of material would work.

And an observation: the HP 9815A desktop calculator I have sitting here
seems to use a similar drive (at least the capstan looks similar when I
peer in the slot), and I think the HP 85 does too.

-Frank McConnell
Received on Sun Nov 23 1997 - 12:35:00 GMT

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