On 06/03/2015 12:21, N_Cook wrote:
A charming little video of the innards of one
https://www.youtube.com/watch?v=DYoD25BlSM4
I've agreed to look at /repair? one that is running fast. Anyone
familiar with clockwork mechanisms here? Curious on-demand presumably
battery powered clock-spring winder process it seems.
Not seen it yet, will turn up next week sometime

alt.horology added

I've now got inside this and a bit more info beyond that person's video.
That strange white splurged numbering is real, not wear, in conjunction
with a static black segmented mask gives an odd visual effect between
true minute digit forms.
The teeth are stripped from the 19.6mm diameter plastic cog driven by
the worm drive on the motor. Owner (given in early 1970s and used
continuously since) reported it running noticeably fast before packing
up totally.
The finesse of this escapement is probably that the spring unwinds a
specific number of turns , and so specific time, until the 2 timing cams
align and the motor comes on for that specific number of turns. So the
escapement consistently runs between 2 specific spring tensions and so
on average is more accurate than simple wound clockwork. So no fusee
required,and independent of fading battery power until exhausion point
and no more motor turning.
I suspect the motor became engaged continuously and so winding the
spring to maximum and so running the escapement fast. Whether preceeded
by tooth stripping or that came after motor jamming , don't know. The
motor runs well, now not jammed or constrained by worm and cog train.
The escapement drive cog off this spring seems to take 6 minutes to back
off 1 turn. I cannot work out the double cam action for the motor
switch, whether every 6 minutes of even say 10 times that, 1 hour, that
I don't know. I suspect the whir of the motor once an hour would be the
designed repeat rate , rather than every 27 minutes 22 seconds or
whatever. For every 6 minutes would not require the double cam
mechanism, just a simple single cam.
So if I get this working again it would be a matter of over-riding the
motor switch a bit and measuring the escapement until the 10 spring
turns is in the right range, I suspect something like 20 turns available
in total, but some residual tension has to be there at all times. Plus
the balance wheel spring adjuster for final adjustment.
Just as well I salvaged "useful parts" from scrapped cassette audio tape
machines. A plastic cog of right tooth pitch and axle size is available
to replace the broken one, just requiring a hole made in the disc to
take the spring anchor hook.
There is condensed nicotine goo on the balance wheel etc. I own a small
ultrasonic bath, use that? immersed in what chemical/s to clean off the
nicotine?