Signedpunched on the front bar, punched: R. L. KETCHEN
on the back bar, punched: R. L. KETCHEN 1990
Inscribedcast into main weight: 2 oz
FunctionThis is a working model that demonstrates how the verge escapement operates. It can function for about a half hour. Verge escapements like this one operate by the interaction of a dented wheel and a vertical rod that has two carefully angled pallets at its point of contact with the wheel. As the wheel tries to turn (driven by the weights wound around the spool), it pushes one of the pallets, which makes the rod rotate and puts the other pallet in a position that blocks further rotation of the rod. The rod starts to rotate in the opposite direction and the cycle is repeated.
The net effect is the transformation of the rotational movement of the wheel to a periodic back and forth rotation of the rod, which can be used to drive a mechanism. The speed of the ticking will depend on the rod's inertia, which in this case is controlled by the weights on top.
Historical AttributesCommissioned and used by William Andrewes, Curator of the Harvard Collection of Scientific Instruments (1987- 2000), to teach "Instruments of Time and Space."