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Sticky tach

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dcoplan

dcoplan

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I've heard this is a common problem. I have a '60 Bugeye and sometimes the tach responds, sometimes it doesn't. When it does, if it does, the reading seems to be inaccurate and the needle sometimes doesn't drop back down to zero. The cable engages on both ends but I don't know how to tell if it's worn. I pulled the entire gauge apart yesterday and gave it a good dose of WD40 but still no luck. The delicate spring is working, but seems to be weak - but maybe that's how it's supposed to be?

I know I can send it in to be rebuilt, but would like to give it a shot myself both for experience and to save money. Any advice?

Dan
 
Google for the 27 page PDF by Anthony Rhodes "Repairing Jaeger & Smiths Speedometers". The mechanical tachs are identical to speedometers except for the lack of the odometer components.

The drag cup assembly that the needle attaches to should not be lubed. Oil will attract dust and get gummy. That can result in the needle going all the way around the gauge face and ruining the hairspring. You are correct that the hairspring is weak and delicate. Don't mess with it if you don't have to.

Were this my tach I would take it apart and carefully lube only the entrance point where the cable connects. Clean and degrease the other areas supporting the spindle the needle is on. Leave the lower needle bearing on the spindle "dry" and be sure to clean out the small hole that it goes into. If this is a tach that connects to the generator, pay attention to that end of the cable. Your errors may also be coming from the drive end of the cable, not just the gauge end.
 
I forgot to ask - some of the white and black paint on the needle has chipped off. What do you recommend for repainting this part? Touch up paint? Model hobby paint? Other?
 
For the needles I typically use flat, white Testor's model paint. However, the choice is obviously yours.

The printing on the face will be very delicate so avoid too much contact with it. Do not use cleaners. If you are lucky, you may find that any incidental dirt can be removed using clean water and cotton swabs.
 
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