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Harold Gough
26th February 2017, 04:59 PM
We have on of those on-the-wall clocks which is kept accurate by radio signals. We have had it for many years. The accuracy is somewhat enigmatic, in that, a few weeks after inserting a new battery, the second hand stops moving.

I have previously remedied this by fitting a fresh battery. However, some closer observations have revealed the following.

A couple of weeks ago, I found that removing the old battery and putting it back in again got the second hand moving again. By checking the clock against the radio pips, I found that the minute hand was correct but the second hand was out by about 20 seconds and did not reset on the hour.

Watching the sweep of the second hand, I saw that on the upwards part, between the 8 and the 12, it seemed to hesitate briefly. A closer monitoring showed that it moved back up to four times on the upward sweep. That seems to have gone down to two, once between the 8 and the 9 and once between the 9 and the 10. It actually moves back the distance for half a second or a whole second, which is the longer or shorter +/- alternating.

I can believe that a worn part might cause a slip or a pause but to move backwards leaves me puzzled as to the mechanism.

Harold

Petrochemist
26th February 2017, 09:19 PM
If the issue is on the upward swing only the cause is probably gravity, combined with a stripped tooth on one of the cogs.
I've often had battery clocks that struggle on the upward side, as the battery is failing.

PeterBirder
26th February 2017, 09:43 PM
I agree with Petrochemist.

These movements seem to use a chain of nylon gears. Once the second hand has moved "out of synch" with the minute and hour hands it will not reset when the movement is reset by the radio signal. You can buy replacement movements on E-Bay etc. but probably no more expensive to replace the clock.

Regards.*chr

Harold Gough
27th February 2017, 08:03 AM
If the issue is on the upward swing only the cause is probably gravity, combined with a stripped tooth on one of the cogs.
I've often had battery clocks that struggle on the upward side, as the battery is failing.

Mike,

Thanks. It is clearly related to gravity. This morning, I placed the clock flat on its back and stopped the symptoms. On replacing it on the wall, the first circuit produced 5, possibly 6 half-second step-backs. A couple of minuits later, it was down to 2, just below the 7, where gravity effects would be minimal.

Harold

Harold Gough
27th February 2017, 08:06 AM
I agree with Petrochemist.

These movements seem to use a chain of nylon gears. Once the second hand has moved "out of synch" with the minute and hour hands it will not reset when the movement is reset by the radio signal. You can buy replacement movements on E-Bay etc. but probably no more expensive to replace the clock.

Regards.*chr

Thanks, Peter.

We are currently redecorating the room and the clock is unlikely to match the colour scheme, so it will be replaced. It was the backward stepping of a half second or a second which intrigued me.

Harold

OM USer
27th February 2017, 12:48 PM
Wrist watches with a chronograph function can often go out of sync this way. When you reset the stopwatch hands they do not go back to zero. There is usually a way of manually moving the hands to the upright zero position to reset the reset.