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On 13 Jun 2005 09:11:32 -0700, wrote:
Pendulum length is set correctly once only in the life of the clock.
A pendulum will vary its length with temperature, enough to cause
inaccuracy between summer and winter. A few have a compensated
"gridiron" pendulum, but these are pretty rare (and most are just
decorative fakes).
If your clock only ever jumps forwards or back by 11 minutes, then I'd
suspect a loose hand. Does it still strike on the hour ?
If it jumps by this much but sometimes does it twice, then look for wear
allowing endfloat in a pinion. Combined with a less than flat and
perpendicular wheel, this may allow the pinion to jump a few teeth on
the wheel. This same fault can obviously cause the "single jump" too,
especially if it's freshly wound.
The most likely pinion for endfloat problems is the one forward of the
mechanism's front plate, driving the hands.
In general, don't mess with any clock older than WW1. Menders are still
around and they deserve the trade. If it's a post WW2 Smiths or
Perivale, then get the spanners out and go to it.
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