The Modern Clock / A Study of Time Keeping Mechanism; Its Construction, Regulation and Repair

by Ward L. Goodrich

Anyone who sees the clocks of to-day would be inclined to suppose that the first clocks were constructed with pendulums, because this is evidently the most simple and reliable system for clocks, and that the employment of the balance has been suggested by the necessity for portable time pieces. This is, however, not the case, for the first clocks had a verge escapement with a crude balance consisting of two arms, carrying shifting weights for regulation. The pendulum was not used until about three hundred years after the invention of the first clock.

After the invention of the dead beat escapement, with its great gain in accuracy by the reduction of the arc of pendulum oscillation, attempts were made to combine its many virtues with the necessarily large vibrations of a balance and thus get all the advantages of both systems. By placing the lever on the arbor of the anchor, it was possible to multiply the small angle of impulse on the pallets very considerably at the balance, and to make all connection between them cease immediately after the impulse had been given. The dead beat escapement was thus converted into the detached lever escapement and the latter made available for both watches and clocks. Another important feature of this escapement is that when properly proportioned it will not set on the locking or lifting, but will start to go as soon as power is applied to the escape wheel through the train. This cannot be said of the cylinder, duplex, or detent escapements, and it will be seen at once that this has an important influence upon the cost of construction, which must always be considered in the manufacture of cheap clocks in enormous quantities.

Fig. 61. Pin Escapement for Clocks.

The lever escapement with pins for pallets and the lifting planes on the teeth of the escape wheel, which is the one usually put into cheap clocks, is from the theoretical point of view a very perfect form, because its lifting and locking take place at exactly the same center distance and at the same angles, which again allows for greater latitude in cheap construction, while still maintaining a reasonably accurate rate of performance. These are the main reasons why the pin anchor has such universal use in cheap clocks.

As this escapement is generally centered between the plates, banking pins are dispensed with by extending the counterpoise end of the lever far enough so that its crescent shaped sides will perform that office by banking against the scape wheel arbor; [see Fig. 61]. The fork end of the lever engages with an impulse pin carried in the balance and the balance arbor is cut away to pass the guard point or dart, thus doing away with the roller table. In other constructions the roller table is supplied in the shape of a small brass collet which carries the pin and has a notch for the guard point, thus making a single roller escapement.

The diameter of the lifting pins is generally made equal to 2½ degrees of the scape wheel, which gives a lift of 2 degrees on the pallet arms, and the remainder of the lift, 6½ degrees, must be performed by the lifting planes of the wheel teeth. The front sides of the wheel teeth are generally made with 15 degrees of draw and the lever should bank when the center of the pin is just a little past the locking corner of the tooth. Other details of the pin anchor escapement coincide with the ordinary pallet form, as used in watches, and the reader is referred for them to the works of the various authors mentioned previously.

The trouble with the majority of these clocks is in the escapement and balance pivots, and to these parts are we going to direct particular attention, for often, be it ever so clean, the balance gets up a sort of “caterpillar motion” that is truly distressing, and if no more is done we may expect a “come back” job in a very short time. In taking down the movement the face wheels are left in place, but sometimes it may be necessary to remove the “set wheel” of the alarm in order to proceed as we do. Remove the screws or pins that hold the plates together in the vicinity of the escapement, leaving the others, though if screws they may be loosened slightly; pry up the corner of the plate over the lever to loosen one pivot of same and let it drop away from the scape wheel sufficiently to let the wheel revolve until it is locked by a wire or pegwood previously inserted in the train, after which the plates can be pried apart more conveniently to permit the lever being removed entirely, also the scape wheel and the one next following. As nickel clocks differ in make-up, the operator must, of course, exercise judgment as to the work in hand to accomplish this.

Have ready a straight-sided tin pail, with cover, that will hold at least one-half gallon of gasoline and of diameter large enough to receive the largest brass clock; remove the wire or pegwood and immerse the clock into the fluid and allow it to run down; this will loosen all the dirt and gummy oil and clean the clock very effectually. Let it remain long enough for all the dirt to settle to the bottom of the pail; then remove and wipe as dry as possible with a soft rag; by having no binder on the spring it is permitted to uncoil to its full, and thereby remove all gummy oil between its coils. Now peg out the holes of the wheels removed and of the lever and that portion of our work is complete.