Gummy wheels for 41 series card readers



It has been a long while since I have been on this site. Lots of exciting things have been going on I see. Sad, what has been happening to hp. I really hope the ships Captain knows where he is sailing!
I am sure this question has been asked before, but does anyone know the size of the O rings that go in the card readers? I purchased my card reader for my 41C in 1990, and the O rings finally degraded or whatever they do. Motor runs, but card barely feeds. Sounds bogged down. I guess I am lucky the O rings have lasted this long. There is a shop not far from where I live that claims they carry or can get any O ring made. I would like to try the repair.

I had to go back to Using my 41 since my 49G+ keyboard malfunctions too much. I have to watch it like a hawk, as it types in too many digits on several keys. Never was able to get it repaired properly. I believe a ROM update was tried that was supposed to help, and it was sent back to hp once, the calculator returned with no change. It has been shelved. Too bad, as I rather liked that calculator aside from it's crazy keyboard.

I used a TI N-Spire CX-CAS the other day, wow! Lots of bells and whistles and I like the color screen! It looks like a really fine learning machine.

Be well and Thanks.


They are easy to find at any Lowe's or Home Despot. Problem is I am not at home and don't have any with me and don't remember the dimensions off the top of my head. I am sure someone will be able to help there but I can tell you the you will need two of them (at least the ones I usually use). You can also use silicon tubing but it is usually more work.




two options, my preference is silicon tubing with MIL specs, fancy way of saying the hole in the tube is centered. found at the local hobby shop or remote controlled vehicle outlet (gas powered model planes, cars and etc.)

The o-rings are listed below as well as some pictures of the pinch roller

Silicon tubing
inner diameter = 2.5mm
outer diameter = 5.5mm

inner diameter = 2.6mm
outer diameter = 6.1mm

Edited: 29 Aug 2011, 2:21 p.m.


Hi Geoff;

Thanks for the repair tips. Really great pictures too! I'll try to get some of the milspec fuel line, I want to look at it. The guy at the O-ring place says he can get o-rings in different materials also. He says there are "application materials" now. When I go there and If I learn something of interest, I'll share it with everyone.

He supplies Duke University labs and research facilities in Triangle park. Yes, I do not live in North Dakota anymore. I live near Durham N.C. now. Great weather! My wife seems to think the wheels on my card reader lasted so long because of the frosty North Dakota air, ha ha. Thanks for your effort.


The correct o-rings are US size 005.

Size Fractional Actual
005 7/64" 15/64" 0.101" 0.241"


Hi Randy;

Thanks for your reply. The size you gave is what I was looking for. I'll give the O-ring fellow those specs, he thinks he can come up with O-rings made of a different material that would be more suited to that application. I'll see what he comes up with and pass it on here with info and pics. Thanks Randy

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