Clocks and watches by Overton George L

Author:Overton, George L
Language: eng
Format: epub
Tags: Clocks and watches
Publisher: London, Pitman
Published: 1922-03-25T05:00:00+00:00

the fourth wheel, and two for the third wheel, making a total of fifteen.

The acting pallet surfaces of clocks often take the form of jewels, which are also sometimes used for the escape wheel and the pallet bearings in high-class clocks. In some French clocks, the pallets consist of jewel pins, and these escapements are arranged so that the escape wheel is in front of the dial and the action of the escapement visible.

One method of reducing the friction, which has been extensively used in scientific instruments, is the employment of friction wheels. This method has not been used to any extent in clocks; but in the Science Museum there is an exceptional example, in which friction wheels were employed by Benjamin Vulhamy in a clock made for King George III. This clock was the principal timekeeper in His Majesty's private observatory at Kew, and was afterwards the property of George IV and William IV. Each pivot rests upon a pair of wheels, which move through a much smaller angle than that through which the pivot rotates, with the result that there is a reduction in the friction. The wheels supporting the bearings for the pallets are arranged symmetrically below the axis ; but for the other bearings of the train, one of each set of friction wheels is placed partly to the side of the pivot, in accordance with the direction in which the pressure of the pivot acts. An arrangement is provided whereby the great wheel can be lifted from its delicate bearing during winding.

Henry Sully, a famous horologist, who settled in France, used friction wheels in a chronometer constructed in 1724 ; and they were also employed by Harrison and Mudge.

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