HP CArd Readers - Longevity

[Maximilian Hohmann]

Hello!

(11-24-2017 05:35 PM)larthurl Wrote:  As most people here know, the card readers in the HP-65, HP-67, HP-41 and others become non-functional after 20, 30 or 40 years. The wheels (rubber?) used to transport the card turn to goo or at the least become soft.

It is not just the pocket calculators but the same applies to desktop calculators and laboratory equipment costing up to 100 times as much. Their card readers and tape drives suffer from the same problem.

(11-24-2017 05:35 PM)larthurl Wrote:  Do you think HP never imagined these calculators working for decades and therefore didn't use better (and more costly) material in the card reader drive mechanism?

That's a question only the engineer(s) in charge will be able to answer. My guess would be that a combination of two factors comes together:
1. The technical advance since the second half of the 20iest century has been so fast that few electronic products are used for more then a coulpe of years. Therefore they are no longer designed for "infinite life" (as it would be called in my sector: aeronautics). Just look at today's smartphones and cameras which will be replaced whilst still in perfect operational state and still 98% state of the art. Insanely crazy.
2. No long-term stability data were available for the rubber used in those drives.

(11-24-2017 05:35 PM)larthurl Wrote:  Was there even better material in the 1970s and 1980s?

Most of the materials used today for such parts, e.g. silicone rubber, nitril, polybutadiene, ... , have been around long before "our" card readers were made. Would they have lasted longer? Who knows.

(11-24-2017 05:35 PM)larthurl Wrote:  And for the card readers that are getting re-built today with O-rings, how long will these O-rings last?

It depends on the material the O-rings are made of. There are is a wide variety to chose from.

Regards
Max