Disadvantages
Scientists in the 1800s found that the gridiron pendulum had disadvantages that made it unsuitable for the highest precision clocks. The friction of the rods sliding in the holes in the frame caused the rods to adjust to temperature changes in a series of tiny jumps, rather than with a smooth motion. This caused the rate of the pendulum, and therefore the clock, to change suddenly with each jump. Later it was found that zinc is not very stable dimensionally; it is subject to creep. Therefore another type of temperature-compensated pendulum, the mercury pendulum, was used in the highest precision clocks. Both types were superseded by pendulums using low-expansion materials such as Invar and fused silica.
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