In a conventional clock, the oscillation period depends only on the hanging pendulum length, not its mass. In a rotary pendulum, the masses and their distance from the center determine the period. Once the period is defined, the gears’ sizes and rations can be calculated.
The TEMPUS pendulum weighs 5 pounds, its period is 4 seconds. A small electric pulse from a battery keeps the pendulum oscillation amplitude constant and therefore the timing constant. Every pendulum cycle advances the six petal Maltese cross through a ratchet wheel.
There are four gears between the pendulum and the clock dial, a worm and mating worm gear, an intermediate spur gear and the minute and gear. The hands are driven through a clutch to allow setting the time. Between the minute and hour hands is the standard 12 to 1 gear set. There are eight gears and five shafts in total. The shafts are mounted on miniature ball bearings for minimum friction.