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Home Made Synchronome and free pendulum

 
Since the age of 12 I have always wanted a synchronome, I had to wait until I was 
38 to build one, here is the mechanism.
And then I built a vacuum enclosed free pendulum, well it's not quite a Shortt but it
works.

There are two optoswitches at the bottom of the plate one controls the amplitude of 
the swing and the other triggers the sync pulse.  Behind the plate are some
electronics to simulate the original Shortt mechanics.  An RS latch is set by the Synchronome pulse the swing opto then triggers (or not depending on amplitude) a monostable.
The central opto supplies the sync pulse to the Syncronome and if the amplitude
mono has not been triggered impulses the pendulum via the solenoid.
 

And to monitor it, an old laptop with a couple of home built bits, an ovened VCTCXO
and a thing that counts 100kHz pulses from the osc gated by the 30s pulses from the clocks.
This data is sent serialy to the PC for recording. Yoy can just see the results of a about
10 hours running the whole screen height is 4.8mS.  When I have got a better reference
more data will be published.

 More pictures