Hour-Wheel and Snail.
escapement is that called the dead-beat or lever escapement, found to be the best for time-keeping, and least likely to get out of order. Upon the set-hand arbor, used for setting the hands on the dial to time, are two springs or keys to keep in place a wheel fitted loosely on the arbor, and working in the teeth of the centre-wheel. The hands are set by means of the set key which fits on the end of the arbor in front. At the back end of the same arbor is a joint by means of which an iron rod connects the clock to the dial, and works the outside hands. The whole of the arbors are turned with suitable pivots into brass bearings screwed into the uprights, and all bolted to the bed or frame by stout bolts and washers. On the front upright is fitted an index or set-dial by which to set the outside hands, and two wheels and pinions, termed the motion or dial-work, fitted on sockets and working on iron studs which are screwed into the upright. Upon the largest wheel, known as the hour-wheel, is fixed a snail having twelve steps in it for regulating the strokes to be given at the different hours. The striking-train consists of a barrel similar to the going-train, only that it has a camm or toothed-wheel fitted on the back of the barrel-wheel for the purpose of raising the hammer which strikes the bell, a lever being used called the hammer-tail. This barrel is fitted into bearings in plummer-block, and bolted on frame. The train of wheels and pinions fitted in arbors, and working in brass bearings, consists of,—the pallet pinion fitted tight in the pallet arbor and working in the teeth of the barrel-wheel; at the front end of this arbor is a pallet of steel working in the teeth of the rack (see next illustration), and gathering it up as the blows of the hammer striking the hours are given on the barrel. Above the pallet arbor is a pinion running into the teeth of the pallet wheel and termed the fly-pinion, as it is used for regulating the blows or strokes. Fans are attached to the fly-pinion to assist in regulating the striking,—the intervals between the strokes being thus made longer or shorter as desired. Fitted to the fly-frame is a ratchet with two clicks and springs, these being used to prevent the train being stopped too suddenly, and the damage likely to arise therefrom. At the right-hand side of the clock frame is an arbor to carry the work for the maintaining power, by means of which work the clock is kept going even while it is being wound up, and injury to the escapement is at the same time prevented. But for this maintaining power during the winding-up, whilst the pendulum is vibrating to and fro, the pallets are liable to catch the teeth of the wheel, and these are so fine as to be
The Rack.
readily injured. As properly fixed the clock cannot be wound up unless this maintaining power is put in action by means of a lever passing in front of the barrel-square, so that the winder cannot be put on the square until the lever is raised and puts this power in action. The repeating work for the striking-train is fitted on brass sockets working on wrought-iron studs screwed into the front upright, and consists of the Rack-hook, Warning, Locking, and Lifting pieces. The Rack is a portion of a circle with a number of half-circular teeth cut on its edge; at the end of the Rack is the Rack-arm fitted with a spring having a nib or pin in it, which nib or pin falls upon the steps of the before-mentioned hour-snail, and thus the different strokes are given at the hours; as the nib falls nearer the centre the rack drops a greater
Pendulum Rod.