Page:Popular Science Monthly Volume 90.djvu/737

 That Wonderful Watch in Your Pocket

It breathes, and its heart beats like that of a human being By John J. Bowman

���OPEN 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.

Look into the watch when it is going, and you will see one large wheel-like part which is in ver>' 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 (i) to keep the balance in motion, and (2) to make the rate of motion visible as "time-keeping" on the dial of the watch.

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-

��The mainspring "barrel" Winding the watch wraps the mainspring around the cen- tral hub in the barrel. The effort of the spring is now to unwind itself. This effort of the mainspring causes the rotation of the barrel

��DIAL-TRAINS. HANDS MAKES BALANCE' TIMEKEEPING VISIBLE

��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- ing" of the watch. 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 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

��delicate balance 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

��MAINSPRING IN BARREL STORAGE Of PO*ER

���BALANCE CONTROLS ENTIRE MECHANISM--KEEPS TIME"

��Analysis of the watch mechanism

��less round of duty. The gear cat -'

wheels and pinions shown carry ^ ^^^^"^ °^ ^'^''1' 5°""'" t^'" t was mentioned in the begin

^, , , 1 mamspnng barrel down through. r ^1 • ^- 1 ^1 ^^l

power to move the balance, the the train and escapement to be nmgot this article, that the

source of power of course being consumed in keeping the works balance, which controls the

the mainspring. >" motion. The parts (above)

The crenr-tppth nn thp barrel ^'"^ arranged in a straight line.

1 ne gear-teetn on the Darrei j^^ ^ ^^^^^ however, they are

drive a pinion fastened to the jn a curved line to park them

shaft of the large gear-wheel in into the smallest space possible

7«1

��rate of motion of the entire watch mechanism, is es- sentially the time-keeping part of the watch. The

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