HP-97 Printer Replacement Gear

[Jim Goeldel]

Hello. We have a HP-97 Calculator, everything is functional on it (as well as the two others we have laying around), except for the printer mechanism. It seems there is a small gear made out of rubber (or some sort of plastic), which gets chewed up over the years. We are down to our last working gear, and don't know how much longer it will last. It is also making a squealing noise when the printer is working. I can't figure out if this is because of the gear. I have tried using WD40 to lube it up, but it still is making the noise.

Does anyone know of a source to get a replacement? I have checked with a local machine shop about making one, but they want upwards of $800 to make a dozen of them.. (too much setup time and such..)

Thanks in advance,

Jim Goeldel
jimgo@voyager.net

[Tony Duell]

Where exactly in the printer mechanism is this gear? I don't know of any rubber gears in the HP9x printers, but there's a train of plastic gears between the motor and the leadscrew. Is it one of those?
WD40 may well be contributing to the problem. WD40 (no matter what is says on the can) is NOT a lubricant. I have had problems caused by it to last a lifetime. What typically tends to happen is a
piece of fine machinery (clock, camera, etc) develops a fauly and the user sprays it with WD40. This has no effect on the fault and the unit then lands on my bench. I both have to cure the original fault and do a total strip-down and clean to remove the WD40 residue.
And also, petroleum based oils (which WD40 is) will attack some plastics. I only ever use silicone lubricants on plastic gears.
As to a replacement, have you tried a local model enginering club. If there's a member who makes clocks, then he may well be set up for gearcutting. It's not a simple job, but it is possible to do in a well-equipped home workshop.

[Katie]

Take a look at the article that I wrote here. It describes how to fix your problem exactly and relatively cheaply.

http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=84

[Ellis Easley]

I've always heard silicone lubricants recommended but I've never heard any brand names. Can anybody name a brand that would be available in the U.S.?

[Ren]

Inre: WD-40

A locksmith told me years ago that the "WD" stands for
Water Dispersant, developed by NASA to get water off
of electrical circuits. I always used to carry a can
behind the seat of my pickup to wash out the inside
of the distributor cap during wet weather.
To repeat what you said, it is NOT a lubricant. Though it will work on a rusty gate hinge, don't lube anything of value with it.

[Tony Duell]

Yes, WD40 is Water dispersant/displacement (I've seen both). I believe the '40' means it was the 40th formula tried :-)
It's great for keeping the rain out of your car ignition system, or preventig garden tools (or the steel bars you keep in stock for mechanical projects) from rusting. I use it all the time for things like that.
But what it is not is a lubricant, and certainly not a lubricant for precision machinery. It is advertised as that (at least in the UK), but it does a lot more harm than good.
An example. I have a reasonable 35mm SLR camera here (old, mechanical thing) that I bought non-working, second hand. The original fault was a sprint had come unhooked in the slow speed mechanism. Time to repair, about 5 minutes (remove tripod mount (3 screws), remove baseplate (4 screws), hook the spring hack). Unfortunately, the previous owner sprayed it at random with WD40. I am going to have to totally
dismantle it (even things like the exposure meter movent are gummed up!), clean all the parts, put it together and do all the adjustments. A lot of work.
No, round here, 'WD40' stands for 'Wanton Destruction' :-)

[Ellis Easley]

What are some U.K. brands of good silicone lubricants (both grease and oil types)?

[Scotty]

I don't know anything about UK brands of silicone lubricants, there is a very good German products manufactured by WURTH PTY LTD. The ones I use are silicone spray grease any a silicone spray dry lube, some teflon sprays are also available. WURTH products are sold all around the World and in my experience are very high quality. Regards Scotty Brisbane Australia