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

by Ward L. Goodrich

Fig. 152.

The position which the barrel and great wheel should occupy is worthy of serious consideration. In most of the cheap regulators, as well as in a few of a more expensive order, the barrel is placed in a direct line below the center wheel, as is shown in [Fig. 152]. This arrangement admits of a very compact movement, and it also allows the weight to hang exactly in the center of the case, which some think looks better than when it hangs at the side, especially when there is a glass door in the body of the case. But while a weight hanging in the center of a case may be more pleasing to the eye than when it hangs at the side, this is an instance where looks can, with great propriety, be sacrificed for utility, because when the weight hangs in the center it comes too close to the pendulum, and is very liable to disturb its motion. In proof of this statement, let any reader who has a regulator with a light pendulum and a comparatively large weight hanging in front of it, closely watch the length of the arc the pendulum vibrates when the weight is newly wound up and when it is down opposite the pendulum ball, and he will observe that the length of vibration of the pendulum varies from five to fifteen minutes of arc, according to the position in which the weight is placed; that the pendulum will vibrate larger arcs when the weight is above or below the ball than when it is opposite it; and if the clock has a tendency to stop from any cause, that it will generally do so more readily when the weight is opposite the pendulum ball than when it is in any other position. For this reason I would dispense with the symmetrical looks of the weight hanging in the center of the case, which, after all, is only a matter of taste, and construct the movement so that the weight will hang at the side, and as, far away from the pendulum as possible.

[Fig. 153] is intended to represent the effect which placing the barrel at either side has on throwing the weight away from the pendulum. A is the center wheel; B and C are the great wheels and barrels with weights hanging from them; D is the pendulum. It will be noticed by the diagram that the weight at the left of the pendulum is exactly the diameter of the barrel farther away from the pendulum than the weight on the right. On close inspection it will also be observed that on the barrel C the force of the weight is applied between the axis of the barrel and the teeth of the wheel, while on the barrel B the axis of the barrel lies between the point where the force is applied and the point where the teeth act on the pinion; consequently a little more of the effective force of the weight is consumed by the extra amount of pressure and friction on the pivots of the barrel B than there is in C.

Fig. 153.

Notwithstanding this disadvantage, I would for a regulator recommend the barrel to be placed at the left side of the center wheel, because the weight may thereby be led a sufficient distance from the pendulum in a simple manner. If we place the barrel at the right, and thereby secure the greatest effective force of the weight, and then lead the weight to the side by a pulley, we will lose a great deal more by the friction of the pulley than we gain by the proper application of the weight.

In a regulator with a Graham escapement but little force is required to keep it going, and there is usually accommodation for an abundance of power; therefore we cannot use a little of this superabundant available force to better advantage than by placing the barrel at the left side of the clock, and thereby throw the weight a sufficient distance from the pendulum in the simplest manner.

The escapement we assume to be the old dead beat, as for timekeeping it is equal to a gravity escapement while possessing advantages undesirable to sacrifice for a doubtful improvement. The advantages it possesses over any form of gravity escapement are: it has fewer pieces and not so many wheels; it takes very much less power to drive; is not liable to fail in action while winding, if the maintaining power should be rather weak; while for counting, seconds and estimating fractions, its clear, definite, and equable beat has great superiority over the complication of noises made by a gravity escapement.

Full directions for making this and other escapements have already been given, but in a regulator there are some considerations which will not be encountered in connection with the escapements of ordinary clocks, where fine timekeeping is not expected. We have previously stated that the center of suspension of the pendulum should be exactly in line with the axis of the escapement and we will now endeavor to state plainly how important this is in a fine clock and the reasons for it. Mr. Charles Frodsham, the noted English chronometer maker, has conducted a series of careful experiments and the results were communicated in a report to the British Horological Society, as follows: