The same conditions that arc met with while winding the weight-clock present themselves in the use of the fusee and chain; that is, the tension of the spring while being wound cannot act, as the fusee during this ope ration is turned backward; hence it is necessary to apply the already described maintaining power to any time-keeper with fusee and chain.
This is unnecessary, however, when the barrel and the great wheel become one part, since the barrel turns in the same direction as its arbor while the winding of the spring takes place, as demonstrated in Figure 10 (fi/. 123). Figure 7 represents the upper part of such a barrel, which shows also the click s and ratchet-wheel r for the purpose of winding the spring round the arbor. The ratchet r is fixed to the arbor, which projects through the barrel. If, now, arbor and ratchet-wheel are turned in the direction indi cated by the arrow, the spring inside the barrel is wound upon the arbor, and is prevented from turning back by the click s, which, being fastened to one of the plates between which the barrel is placed, is pressed into the teeth of the ratchet-wheel by the spring f (fig. 7), which produces the condition explained in Figure ro, and causes the barrel to turn in the direction in which the arbor is turned while winding the spring.
The Slop-work.—In addition to the ratchet-wheel and click, the barrel is provided with another arrangement (fig. 8) called the " stop," whose object is to prevent the spring from being wound up too tightly. Upon the cap of the barrel is placed another smaller wheel u, half of whose periphery is toothed; the arbor by which the winding is effected carries a single-toothed wheel (s), which at every revolution rotates the wheel u to the extent of one tooth. If in a few turns the solid portion of the wheel's periphery comes in contact with the tooth of the wheel s, the latter cannot be turned any farther and the spring has attained its desired tension. While the spring is running down, this mechanism repeats its movements in the opposite direction, and collies again to a stop when s collies in contact with the other side of the solid portion of the wheel u; this last stop prevents the spring from losing its tension below a certain fixed point, and makes winding necessary to renew the impelling power.
The defined in the general classification (p. 36o), the train is a series of toothed wheels impelled by the motor for moving the pointers or hands over a dial to indicate the hour and its subdivis ions. Figure 4 (pi. 124) shows a pendulum-clock train, of which the great wheel B has already been mentioned (p. 361) in conjunction with the motor. This wheel has one hundred teeth, and gears into the pinion C of the centre-wheel D, which has eighty teeth; the centre-wheel gears into the pinion E of the third wheel F, which has sixty teeth; and finally, the third wheel gears into the pinion G of the escape-wheel H. The num ber of teeth of the pinions C, E, G are respectively 8, 8, and io. The centre wheel D makes one revolution every hour, consequently the escape-wheel II X ci-2 = 6o revolutions. To effect this is the object of the escapement and pendulum, which in their co-operating action prevent the escape-wheel from revolving uninterruptedly by stopping each tooth of the wheel twice during its complete revolution. In the Figure the escape-wheel, having thirty teeth, will therefore be compelled to make sixty stops at every rev olution, and, moreover, the escape-wheel, as it is required to make this number of stops at each revolution, will have to be stopped at intervals of one second.
continuation of the train is the motion-work (pi. fig. 4) for indicating the time by the hands on the dial; it is generally placed outside on the clock-frame, and is operated by the projecting arbor of the centre-wheel. Terminating in the pinion A, and fitting tightly on the protruding arbor of the centre-wheel, is a tube which carries the minute hand, and makes, with the centre-wheel, one revolution every hour. The wheel R is also fastened to a tube, which fits loosely over the tube of the wheel A, and carries the hour-hand. The hour-hand, however, must travel twelve times slower than the minute-hand, which is accomplished by the intermediate wheel and pinion B, C, the number of teeth of A, B being so calculated as to reduce the speed of C in that proportion.