Motion work. In clockmaking , generally designates the work contained in the space between the dial and the plate of a watch or clock (Clockmaking Plates VI, VII, and XI), but more specifically the part of the repeating work in a repeating watch or clock contained in that space.

In ordinary watches, the motion work comprises the cannon pinion, the minute wheel, and the hour wheel. These two wheels turn the hour hand, mounted on the hour wheel for this purpose: the cannon pinion revolves once in an hour and has 12 teeth, and it engages the minute wheel with 36; the latter has a pinion of 10, which engages the hour wheel with 40. Thereby one revolution of the cannon pinion moves the hour wheel 1/12 of a revolution; in other words, 12 revolutions of the cannon pinion equal one revolution of the hour wheel, so the hand mounted on this wheel will show the hours. All conventional watches, repeating or otherwise, always have these three wheels for turning the hour hand. In clocks, also, there is always a motion work to move the hands, and it is designed on the same principles.

In repeating watches or clocks, as we have said, in addition to the parts we have mentioned, the motion work comprises a part of the repetition work, the rest being contained inside the cage. These parts are the rack, the all-or-nothing, the quarter piece, the finger, the star, and the hour snail; the jumper, the quarter snail, and the surprise; the mute, the two pulleys, the hammer springs, the lifters, and all the springs required for the action of these various parts.

Since the construction and the arrangement of these parts in relation to each other can vary greatly, it is easy to imagine that a great number of motion works have been made that are very different from one another; but of all those motion works only three or four are ordinarily used. These are English-style, Stogden, French-style, and M. Julien Le Roy's. See the article Repetition. See also [Plate VI], Figure 31, [VII], 34, 35.

The quality of a motion work consists chiefly in the accuracy and reliability of its action; the latter condition is especially essential, for otherwise it often happens that the repetition mechanism goes out of order and causes the watch to stop.

Several clockmakers have attempted to locate all the repetition parts in the motion work , but they have been unsuccessful so far. That would be a great advantage, for since the cage would contain only the movement, is could be made as large and as good as that of plain watches.

In defining motion work , we have said that it was contained between the dial and the plate, but although true in general, it seems that clockmakers understand by motion work more particularly the assemblage of parts we discussed above, whether located between the dial and the plate or elsewhere. Therefore, in a repeating clock designed by M. Julien Le Roy, with those parts located on the rear plate, they have kept the name of motion work . See Clock, repeating.