[time-nuts] Non electrical time-nuttery

[Hal Murray]

namichie at gmail.com said:
> The reason that I remember a hard vacuum is not used is because the
> low pressure is used to rate the pendulum (fine tune) by slightly
> increasing or decreasing, and in a hard vacuum metals tend to weld
> together and oils evaporate so the mechanical bits seize up. 

How does the pressure change the frequency?

Why are oils a problem?  I thought typical pendulums used a spring rather 
than a bearing.


That does raise an interesting issue.  How would you fine tune a pendulum?

If you can get close enough, then you can tweak things by varying the 
amplitude, or temperature.

Big Ben is tuned by adding/removing a penny from the pendulum.
  http://en.wikipedia.org/wiki/Big_Ben  (search for penny)
That technique gets more interesting in a vacuum, but you might be able to 
rig up something equivalent.



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