Re: Fused quartz pendulum - temperature coef


On the subject of temperature sensitivity when I changed over to a lead bob I noticed that the original gray cast iron bob had, in principle, just the right coefficient of expansion (1.08 10-5 ºC-1) and height to compensate for an invar rod (1.21 10-6 ºC-1) when the two are rigidly connected at the bottom of the bob. Does anybody know if this design feature is typical of all synchronomes?
In principle for a given bob weight, one can always compensate exactly for the pendulum temperature coefficient with the right choice of materials and bob aspect ratio, so that the problem changes from finding the smallest coefficient material to the best known coefficient material. I would also be curious to know if anybody has attempted to measure thermal expansion experimentally with decent precision other than from period vs natural ambient temperature fluctuations.

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