St. Nicholas/Volume 40/Number 1/Nature and Science/Watch Machinery

The Machinery of a Watch

The power to keep in motion the machinery of a watch is supplied by the mainspring. In winding a watch, this spring is coiled in the central part of its holder, known as a “barrel.” The mainspring in its constant endeavor to uncoil turns this barrel in one direction, and its power is transmitted through the teeth on the outer rim of the barrel to the “train” of wheels.
The mainspring, coiled in the “barrel” is the power of the watch
(Magnified about five times.)

The motion is prevented from being too fast by what is known as an escape-wheel, the cogs of which work in connection with the “pallet and fork.” This lets the motion “escape” in a series of short stoppings, well known as the ticking of the watch. In connection with the “pallet and fork” is the balance-wheel, whose vibrations regulate the speed at which all shall move. This balance-wheel serves the same purpose in a watch that the pendulum does in a clock.

The vibrations of the balance-wheel are the result of the action of two forces, one being the force of the mainspring acting through the “train” of wheels and the escapement, to turn the balance-wheel on its axle, and the other being the opposing force of a very small spring, known as the hair-spring, coiled loosely about the balance-wheel, and which thus tends to regulate the power of the mainspring.

The bearings for the ends of the tiny shafts of the wheels give better service if they are not made of metal but of some hard mineral or jewel, as, for example, garnet, chrysolite, ruby, etc. The lower-priced watches have these jewels in only some of the most important bearings. The better classes of watches have more jewels. If all the important wheel bearings have these minerals, the watch is said to be “full-jeweled.”
The under side of the balance-wheel.
This regulates the speed.
(Magnified about five times.) The jewels are held in place by screws so small as to be almost invisible without the aid of a microscope. Very small screws are also used in other parts of the watch.

Ask some one you know to let you look at the works of his watch, or, better still, as watches nowadays are often made with a protecting plate that conceals all but a few parts of the mechanism, ask some friendly jeweler to let you see the machinery of a watch from which he has removed this outer plate, and to explain it to you.

Twelve tiny screws and six jewel-pins.		An escape-wheel.	An escape-pinion.
(Magnified and photographed with the head of a medium-sized pin to show relative size.)

The Wonders of a Watch

It is a matter of every-day occurrence for a person to say to his watchmaker, “Here is a
Three tiny screws holding a small jewel.
(Greatly magnified.) watch which you sold me ten years ago. It has gone well till lately, when it has taken to stopping without any apparent cause.”

The people who speak in this way little think of the amount of work that a watch has performed in this space of time, and may be astonished at the following figures:

“In ten years,’ says London “Answers,” “which include two leap-years, and consequently a total of 3652 days, the hour-hand has made 7306 and the minute-hand 87,648 revolutions. The end of an average minute-hand has traveled more than 10,280 yards—more than six miles. The second-hand has made 5,258,880 revolutions, and its extremity has traversed on the dial a distance of nearly 123 miles. The escape-wheel has made 52,588,880 revolutions, and as it has fifteen teeth, it has come 788,832,000 times in contact with each pallet. The balance-wheel has made 1,577,064,000 vibrations, and any point on the outside of the rim has covered a distance of about 50,000 miles, and that is equal to twice the circumference of the earth.”

These amazing statements and figures have been submitted to the Elgin National Watch Company of Elgin, Illinois, and Mr. George E. Hunter, the superintendent, says that they are almost right for an Elgin watch, small changes being due to the size of the watch. In the Elgin No. 16 size, the end of the minute-hand in ten years travels 11,473 yards; in No. 18 size, 12,238 yards. The second-hand in No. 16 travels 130.38 miles; in No. 18, 143.42 miles. A point on the outside rim of the balance-wheel of 16 and of 18 respectively, travels 44,511 and 48,891 miles.

Interesting as these figures are, and surprising as are the distances traversed, one’s interest is increased by a knowledge of the amount of force,
The “pallet and fork” which works in connection with the escape-wheel.
(Magnified about three times.) in horse-power, required to drive an Elgin watch, size 18. Of this Mr. Hunter says: “All watches are built to run for at least thirty hours, and on that basis, the power required to drive an 18 size watch is approximately 192-10,000,000,000 horse-power.” One hundred and ninety-two ten-billionths of one-horse power! The distance traveled is enormously great, the power needed is enormously small, if I may be allowed to use such an expression, and one’s astonishment is increased when he remembers that a single horse-power is the power to lift 33,000 pounds one foot in one minute.

A copy of the item from the London publication was also sent to the Waltham Watch Company of Waltham, Massachusetts. Mr. E. A. Marsh, of that company, adds the following even more astonishing facts as to the accurate work done by a watch:

“In addition to the above it ought to be said that, however astonishing the statements as to the enormous amount of work which is performed by the pocket watch, the truly remarkable feature concerning it is the marvelous accuracy with which that work is done. The following brief statements will help to show how wonderfully accurate the work of a running watch really is:

“In nearly all modern watches the mechanism is so designed that, in order to obtain accurate ‘mean sun time’, the balance-wheel must vibrate exactly eighteen thousand times (18,000) every hour. We say ‘exactly eighteen thousand’, for if there should be one vibration in each hour less than the required number, the watch would lose two and two fifths minutes in a month. Such an error would be serious.”

An interesting comparison may be made in this way: in a No. 16 watch (the ordinary size for men), the balance-wheel makes about one and one quarter turns for each vibration, and its rim, in each vibration, will travel two and three quarters inches. In a single day this will amount to rather more than sixteen and one half (16.61) miles, or farther than most persons care to walk in a day.

If you planned to walk exactly the 16.61 miles, and should fall short of that distance by only ten feet, or by only about five steps, it would be a trifling matter; but if the watch balance should make a similar failure, it might become serious in its results, for the watch would then lose nine and four fifths seconds a day, or four and nine tenths minutes a month. A watch that kept no better time than that would be exceedingly unsatisfactory.

Wonderful as are the achievements of a watch, it is still more wonderful that man has been able to invent machinery of such marvelous delicacy, that, when set in operation, it will automatically manufacture the microscopic parts required.