Avometer with sticky pointer

[Glowworm]

I found a very sad looking Heavy Duty Avometer, 1956 vintage in a junk shop (Junk Emporium, Rodney Road, Portsmouth). The sensitivity is a bit low, helped a bit by adding a small extra magnet, but the inconsistent readings were not improved by cleaning with IPA or adjusting the bearing screws. The bearings are not intended to have oil on them, but as a last resort I sprayed WD40 onto a cocktail stick and dabbed it on the bottom pivot under the hair-spring. The amount transferred is minute as the stick absorbs it. Even so this did the trick, with the needle consistently returning to zero. Maybe the hair-spring was rubbing against itself but didn't appear to be.
The effect is similar to wiping polish or cleaner onto plastic curtain rails or sticky wooden drawers; even a molecular thickness lasts a long time.

[The Philpott]

Interested to see whether the effect lasts! Never been tempted to try this approach myself.

Dave

[ScottBouch]

Oils can sometimes attract dust which may be why bearings like these are usually dry.

I'm unsure on the AVO bearing, but a lot of the aircraft instruments I mess around with contain "jewelled bearings" where the pivot pin sits in a jewel material: https://en.wikipedia.org/wiki/Jewel_bearing

A side note - I once worked in woodworking, and the machinery there was lubricated with a dry PTFE spray, it was brilliant, no sawdust clogging up the bearings!

Cheers, Scott

[The Philpott]

Yes, AVO bearings are jewelled.

Dave

[pmmunro]

Avometer pivos and bearings were not lubricated according to the service information. My concern is that the original WD40 is a Water Displacer, hence the initials. It seems to be good for freeing things but leaves behind a gummy deposit which then causes things to stick again.

I would suggest that, now the pivots are free, you should wash out the bearings with isoprpoyl alcohol.

PMM