Page:Popular Science Monthly Volume 90.djvu/737

That Wonderful Watch in Your Pocket 0% It breathes, and its heart beats like that of a human being By John J. Bowman PEN the back of your watch-case and look at the "works"-more correctly, at the movement. The mechanism seems complicated. And so it is. There are in the average watch movement about one hundred and fifty separate parts. Many of these, to be sure, do not take an active part in the running of the watch, but simply con- stitute a frame- work, providing bearings for the moving parts. the center of the watch. This center wheel in turn drives the pinion fastened to the next wheel, and so on. Thus the power is carried to the escapement. What Makes a Watch "Tick"? The purpose of the escapement is to apply a little power to the balance at each beat of the latter, to keep it in mo- tion. It is the action of the es- capement which is heard as the "tick- The mainspring in its The delicate balance ing" of the watch. "barrel" Winding the watch wraps the mainspring around the cen- tral hub in the barrel. The Look into the watch when it is going, and you will see one large effort of the spring is now wheel-like part to unwind itself. This effort of the mainspring causes the which is in very rotation of the barrel rapid motion, "beating" in alternate directions. This is the balance. It is the balance that does the actual time- keeping. The rest of the machinery is required (1) to keep the balance in motion, and (2) to make the rate of motion visible as "time-keeping" on the dial of the watch. DIAL-TRAIN & HANDS- MAKES BALANCE'S, TIMEKEEPING VISIBLE The balance is the gov- ernor; its function is comparable with that of the pendulum in a clock. One of the illustrations shows a watch with part of the framework removed. The balance may be seen at the top of the picture. We will examine its construction in detail later on, and we shall see some wonders it performs in its cease- less round of duty. The gear wheels and pinions shown carry power to move the balance, the source of power of course being the mainspring. The gear-teeth on the barrel drive a pinion fastened to the shaft of the large gear-wheel in wheel The balance rim of brass- steel, is cut into two por- tions, for expansion and contraction, to suit the temperature. Each end is free to move inward or out- ward, toward or from center STORAGE OF POWER Of course the pow- er, as it comes down from one wheel to another, turns each wheel constantly in one direction; but the escapement is so MAINSPRING IN BARREL made as to apply the power to the balance first in one direction, and then in the opposite direction, since the balance must make its beats in alternate directions. In the past three centuries, men of highest scientific and mechanical genius have applied themselves to the problem of perfecting the escapement, which is the most complicated part of the watch.

A watch is simply a ma- chine for "making motion" -and the supreme wonder of a good watch is its uni- form rate of motion. Bear- ing all of this in mind, it is easy to understand what was mentioned in the begin- ning of this article, that the balance, which controls the rate of motion of the entire watch mechanism, is es- sentially the time-keeping part of the watch. The

TRAIN GEARING WHICH CARRIES POWER TO ESCAPEMENT ESCAPEMENT APPLIES POWER TO BALANCE BALANCE CONTROLS ENTIRE MECHANISM-"KEEPS TIME Analysis of the watch mechanism A stream of power flows from the mainspring barrel down through the train and escapement to be consumed in keeping the works in motion. The parts (above) are arranged in a straight line. In a watch, however, they are in a curved line to park them into the smallest space possible 721