Fig. 94. Striking Train Unlocked and Running.
One leaf, F, of the pinion of the locking arbor sticks out far enough to engage with the count wheel teeth and rotate the wheel one tooth for each revolution of D, so that F forms a one-leaf pinion similar to that of a rack striking train. Here we have our counting mechanism; F and D go around together; F moves E one tooth every revolution. A holds C out of action ([Fig. 94]) until A reaches a deep slot, when C stops the train by engaging D ([Fig. 93]).
The count wheel, E, must have friction enough on its stud so that it will stay where the pin F leaves it, when F goes out of action and thus it will be in the right position to suitably engage F on the next revolution. Too much friction of the count wheel on its stud will use too much power for F to move it and thus slow the train; if there is too little friction here the count wheel may get in such a position that F will get stalled on the top of a tooth and stop the train.
The count hook, A, must strike exactly in the middle of the deep slots, without touching the sides of the slots in entering or leaving, as to do this would shift the position of the count wheel if the rubbing were sufficient, or it might prevent A from falling (as A and C are both very light) and the clock would go on striking. If the hook A does not strike the middle of the spaces between the teeth of the count wheel, it will gradually encroach on a tooth and push the wheel forward or back, thus disarranging the count. Many a clock has struck 13 for 12 in this way because the hook was a little out. This did not occur in the smaller numbers because the action was not continued long enough to allow the hook to reach a tooth. The pin, F, should also mesh fairly and freely in the teeth of the count wheel, or a similar defect is likely to occur.
When repairing or making new count hooks, A, Figs. [93] and [94], they must be of such a length that they will enter the slots on a line radial with the center of the wheel. The proper length and direction are shown at A, [Fig. 95], while B and C are wrong. With hooks like either B or C you can set or bend the hook to strike right at one and as you turn the clock ahead the hook does not fall in far enough and at twelve it only strikes eleven. Then if you bend the same hook to strike right at twelve it will strike two at one and as you turn the clock ahead it will strike right at about five or seven. A, [Fig. 95], being of the proper length and shape will give no trouble. Many of the count wheels of the older clocks were divided by hand and are not as accurate as they should be; when a wheel of this kind is found and a new wheel cannot be substituted (because the clock is an antique and must have the original parts preserved) it will sometimes require nice management of the hook A to obtain correct striking. A little manipulation of the pinion, F, [Fig. 93] is sometimes desirable also, if the count wheel is very bad.
