Jim Scott wrote:
I have an old (Victorian) pendulum spring wall clock. I finally got it to
keep good(ish) time by adjusting the pendulum length.
Recently it has taking to losing 11 minutes then it continues merrily on
its way not losing any more. It's always ~11 minutes (ie not 8 or 13). If I
reset it, it will sooner or later do the same thing.
Any ideas?

Pendulum length is set correctly once only in the life of the clock. If
it then drifts I would suspect friction due to muck in the mechanism,
rust, things like that. It is better to clean rather than just oil,
since accumulation of crap is too often the problem with old kit.

I've no experience with clock mending, but from working with other
assorted historical mechanicals this is what I would suspect, rather
than a pendulum length error.

Why would it lose at one piont and keep time the rest? Probably a bit
of muck on only one part of a wheel.


NT