Torsion pendulum clock

The clock's gears apply a pulse of torque to the top of the torsion spring with each rotation to keep the wheel going.

Torsion clocks are unusually delicate, ornamental machines which require stable conditions to operate properly.

One reason is that the oscillation period of the torsion pendulum changes with temperature due to the temperature-dependent elasticity of the spring.

The clock can be made faster or slower by an adjustment screw mechanism on the torsion pendulum that moves the weight balls in or out from the axis.

The closer in the balls are, the smaller the moment of inertia of the torsion pendulum and the faster it will turn, what causes the clock to speed up.

The mainspring which powers the clock's wheels is kept wound by small changes in atmospheric pressure and/or local temperature, using a bellows mechanism.

In 1951, Charles Terwilliger of the Horolovar Co. invented a temperature compensating suspension spring, which allowed fairly accurate clocks to be made.