"NY" wrote in message
...
My wife has a small clock, of sentimental value only, which has a spring
with a weight on the bottom which oscillates vertically to operate the
escapement. It runs for a couple of seconds but the movement that the
spring exerts on the escapement quickly decays to a point that the
escapement no longer operates because the claws do not move far enough to
release one tooth at a time. I presume the escapement is not providing
enough "driving force" to keep the spring oscillating.

https://i.postimg.cc/50Kt1njT/20201013-131035.jpg

The spring has a peg trapped between its coils which causes arm 1 to move
clockwise/anticlockwise about a pivot as the spring oscillates. This
causes two claws to operate the escapement. There is a second arm, arm 2,
but that plays no part in the escapement - it just operates a moving bird
on the clock face!

The clock used to work perfectly, but has been in storage for several
years because we couldn't find a key to wind it until recently.

I can't see anything that looks obviously bent or out of place. The main
spring is fully wound. The coils of the "pendulum spring" are roughly
evenly spaced when the spring is extended - one coil of the spring is not
more stretched than another. The spring is securely attached at the top,
so it can't have rotated to move the peg onto the wrong turn of the
spring, which would cause the escapement claws to be unbalanced: it takes
about the same amount of movement of arm1 either side of its neutral
position to release either the upper or lower claw.

If the clock is placed face down so there is no load on the spring, the
spring can be manipulated so the escapement oscillates very rapidly and
the gears turn, which proves that the mainspring is driving the escapement
and there isn't excessive bearing friction.

Any suggestions?


This is the clock https://www.youtube.com/watch?v=dEwiuIjWXts - a standard
German mechanism, apparently