The speed of the motions of the components of the planetarium is controlled by a balance-wheel clock, and the entire mechanism is driven by the mainspring of that clock. The mechanism below the platform consists of a system of 95 gears, which together with assorted eccentrics and levers move the visible part of the planetarium.

As much as possible, the original structure and components have been kept in place. Some badly worn parts of the clock were replaced. The wood platform on which the mechanism is mounted had shrunk over the decades, requiring hand-filing of some gears to reduce binding, and two broken gears were replaced.

While the mechanism is driven by the mainspring of the clock, the periodic rewinding of the clock is done by electric motor, triggered by microswitches which sense the wound/unwound condition of the mainspring.

The planetarium was restored to operating condition by Clarence Menninga (photo left), Professor of Geology, Emeritus, aided by John DeVries, Calvin College machinist.

	History of the Botjes planetarium
	Botjes planetarium home page
	Another planetarium