More fascinating terms – the language of clocks

Regular reader and contributor JC suggested a few more clock terms I thought readers and fellow horologists might find interesting.

My source for this article is the Watch and Clock Encyclopedia by Donald de Clarke, published by Bonanza Books (1984) which is still available on Amazon.

Gridiron pendulum: A pendulum consisting of alternating steels and brass rods coupled together to compensate for downward expansion so that the centre of oscillation of the pendulum remains consistent with changes in temperature, invented by John Harrison in 1725.

final look
Gridiron pendulum on a Junghans Crispi wall clock

Broaches: To broach is to open and enlarge a hole. A Broach is a steel cutting or smoothing tool with a tapered or parallel sided edge used to cut or “finish” holes in a clock plate. Used to enlarge and then finish (smooth) a newly installed bushing on a clock plate.

Swiss made smoothing broaches
A set of Swiss made smoothing (or finishing) broaches

Motion Works: The train or wheels of a clock directly connected with the hour and minute hand.

Great wheel: The teeth that form part of the barrel of the going barrel. It is also the wheel to which the mainspring is attached.

The motion works of a clock; the largest wheel on this movement is the great wheel (Pequegnat Clock Co.)

Maintaining Power: A method to maintain the driving power while the weight is being lifted or mainspring with fusee is being wound. In effect keeping the mechanism going while winding.

Weight driven movement with maintaining power
Weight driven movement with maintaining power, (unmarked Vienna Regulator)

Huygens Endless Rope Drive: It is a method of providing maintaining power to drive the clock while the weight was being raised. The endless cord passes over pulley A which is attached to the great wheel and supports the driving weight B, it then passes over pulley C which has a ratchet to support small weight D. As cord E is pulled down to wind the clock ratchet C turns under it’s click to raise weight B which continues to drive the clock as it supplies torque to wheel A. This ingenious system is found in some 18th century long-case clocks.

Huygens endless rope
Huygens endless rope

Locking Wheel (or Count Wheel): A count wheel is the wheel that determines the number of blows to be struck in striking mechanisms.

The left wheel with notches is the count wheel

Ratchet wheel: A toothed wheel into which a click engages permitting the wheel to revolve in one direction only.

Click replaced
Toothed ratchet wheel and click

Cam: Usually a disk so that upon revolving it transmits movement to or exerts pressure upon a connecting unit.

Arrow showing location of a cam
Arrow showing location of a cam, the fly is located in the upper right

Fly: Often called the governor or controller of a chime or strike train. It is the last piece in a train of wheels.

The language of the clock world always amazes me. There are a plethora of other clock terms that I will be happy to explore in future blogs.