What Makes It Tick?
WHAT makes the rhythmic tick in a watch? That is a question almost every little boy has asked, and perhaps quite a few little girls. Could you answer their question?
The tick is much more frequent than you may have realized. Did you know that a watch ticks an average of 18,000 times an hour? That is five times a second, 300 times a minute, 432,000 times a day—and about 13 million times a month!
Compared with other methods of keeping time, the watch is a relatively new device. Humans probably first kept time by observing the sun or by measuring the angle of shadows of trees. Eventually sundials were introduced. These instruments mark off time by measuring the shadows. But on a cloudy day, or at night, they leave man without his clock.
Obviously another type of timepiece was needed. Many early civilizations used a water clock or “clepsydra.” Although these varied, the principle was the same. Water or some other substance was permitted to flow from one vessel to another. The amount that flowed could be measured, and in this way the passing of time was marked off.
The introduction of a mechanical means to measure time was a real improvement. It seems that the first such timepieces appeared in Europe in the fourteenth century. Then, in about 1500, a locksmith in Nuremberg, Germany, invented a portable clock. However, it was so heavy that it had to be hung from a belt around the waist.
Besides being bulky, early watches were not very accurate. In fact, they had only an hour hand. But improvements were made, and eventually precision timepieces were produced. All of these early watches were handmade.
Then, about the middle of the last century, the principles of mass production were applied to watchmaking. Over the years refinements have been made in production techniques, so that watches are now produced that keep almost perfect time.
Watches can now be made that will fit into a dainty ornamental ring for a lady’s finger. The screws used in their manufacture are so tiny that thousands of them could be put in a thimble! Also, some of the holes in which the tiny pivots of the wheels operate are so small that a human hair will not pass through them!
How It Works
But how does a mechanical timepiece work? How does it keep time? What makes it tick?
To help visualize the function of a watch, you might mount a spool of thread on a nail on the wall. Then use a little glue to attach a toothpick to the end of the spool. This toothpick will serve as the minute hand. Now slowly pull the thread of the spool. This will turn the spool and the attached toothpick, the minute hand. If you pull the thread at just the proper rate, the minute hand will make one complete revolution in an hour. Thus, you will have an instrument for measuring time—although a very crude one.
A mechanical timepiece does essentially the same thing. It moves pointers or hands around the face of a watch at precise rates of speed to mark off the day in time units of seconds, minutes and hours. However, the mechanism for maintaining the correct rate of movement of the hands, as well as their synchronization with each other, is indeed complex.
First, a watch must have a power source to move the hands. In the above illustration the power was provided by pulling the thread. This turned the spool, which turned the toothpick, or minute hand. In an ordinary watch the power is supplied by a “mainspring.” This is a thin, narrow ribbonlike piece of highly tempered steel.
The mainspring is inside a barrel that has gear teeth around its outer circumference. To store up power, there is a winding mechanism by means of which the mainspring can be wound. Thus when you wind your watch, you are storing power in the mainspring. The mainspring is attached to the inside of the barrel in such a way that it turns the barrel around as it fights to uncoil itself.
Thus, as the barrel turns, it drives the center wheel. This wheel, in turn, drives a suitable number of other wheels. The series of wheels is called the “train.” Its purpose is to carry the very slow motion of the barrel throughout the watch. The train is thus a series of reduction gears that expends the mainspring’s power a little at a time so that it will last longer.
Attached to certain of the wheels are the watch’s second, minute and hour hands. By means of various ratios between the number of gear teeth, the size of the wheels and their speed of movement, the hands are driven at the proper speed to measure the time.
But how is the flow of power through the wheels regulated so that they turn at the right speed to register correctly the passing of time?
This is the job of the “escapement,” the heart and brain of the watch. The accuracy of the watch is dependent upon its precision, quality and condition. Perhaps you can visualize to some extent the operation of the escapement by considering again the illustration of the spool of thread attached to the wall.
Suppose now that you carefully carve teeth in the outer rim of the spool. Then below the spool of thread, mount to the wall a specially designed fork having a pendulum. Mount it to the wall with a nail at the fork’s pivot point. Position the fork so that its two points enmesh in the teeth of the spool.
Now if you pull the thread, one tooth of the spool will push one point of the fork away from the spool, and this will move the pendulum to one side. This will cause the other point of the fork to enmesh with a tooth of the spool. As you continue pulling the thread, the pendulum will return and the first fork point will enmesh with the following spool tooth. As this action continues, the connecting and disconnecting of these parts will make a rapid tick. In your watch this tick normally occurs five times every second.
A wristwatch generally employs a highly refined escapement, using a fifteen-tooth escape wheel and two ruby jewels at the tips of the fork. In a watch this is called a pallet fork. There is another wheel known as a balance wheel in a watch. This is connected about where the pendulum is located in our illustrated escapement. The speed at which the balance wheel moves back and forth is governed by a hairspring. The balance wheel and hairspring are coordinated to swing back and forth five times a second or 18,000 times an hour.
Self-Winding and Electric Watches
Some modern watches are self-winding. They have a swinging weight geared to the mainspring. As the wearer moves his arm, the weight is swung and the mainspring is wound. The self-winding watch usually costs $15 to $20 more than the ordinary hand-wound watch, and it may cost about 50 percent more to service.
Electric watches employ a very small electric cell of approximately 1.35 volts. This energy is switched into a coil of wire (electromagnet) that is mounted on a balance wheel. The balance wheel then drives the hands in exactly the reverse manner of a mainspring-driven watch. In 1957 the electric watch was introduced in the United States.
One electric watch uses a tuning fork that drives a ratchet wheel, which in turn drives the hands. It does not use a switch, but a transistor to connect the power to its coils. This combination results in a very accurate timepiece. It does not tick, but hums. The second hand does not move in jumps as is true in most watches, but moves smoothly like a second hand of an electric clock. This watch was introduced in 1961.
If Your Watch Runs Erratically
If your watch should start to lose or gain time, or stop altogether, what probably is the trouble?
First it is good to realize that many watches contain nearly 200 tiny parts that are very carefully fitted together and properly adjusted. Although some parts run without oil, the very small pivots rotating in the jewels employ an extremely small amount of very highly refined and expensive oil, usually fish oil.
Now, it is possible to imagine what happens to this oil in a year or two. It may dry up, and the watch will run erratically or stop. Keeping your watch near a source of heat will cause the oil to dry up sooner than normal. Lack of oil is the number one cause of watch failures.
Oil is applied by the watch repairman with a small tool similar to a screwdriver, or with a glass tube that has a minute metal pipe at the end, about the size of a human hair. A tiny dot of oil about one-fourth the size of the period at the end of this sentence is applied to each jewel. If your automobile required one gallon of this type of oil to fill the crankcase, it would cost over $200 for an oil change!
If you see fog or moisture in your watch crystal, take it to a watch repairman right away. It should be serviced or else the oil will be damaged. If it has been submerged in water and you cannot get it to a repairman soon, it can be submerged in alcohol. This will absorb the moisture, although it will damage the dial and hands. The expense of refinishing a dial and hands, however, is minor compared to replacing a ruined watch movement.
Women sometimes forget to remove their watch when washing the dishes. And men who do heavy work perspire freely, thus exposing their watch to the corrosive effects of the acid in the perspiration. Snow, although fun to play in, is a major cause of watch failure in some places.
Also, dirt or lint in the watch’s movement will jam up the very small gears and eventually stop a watch. Sometimes a watch that has stopped is brought in for repairs and a microscopic piece of material is found between the jewel and the balance staff. The obstruction must be removed before the watch will run properly again.
The complexity of a timepiece is reflected in the cost of repairs. Generally, though, a thorough cleaning and lubrication will take one and a half to two hours and the cost can vary greatly, depending on locality.
However, if a watch repairman ever tells you that you have wound your watch too tight, ask for the watch back and go elsewhere. A watch can only be wound so far, and if it is in condition it will run. Also if he tells you that he has to send it to the factory, he is stalling for time, or he is incompetent. Find someone who knows his business.
The Watch-repairing Skill
Perhaps you are intrigued by watches. You may want to know more than just how they tick. You may enjoy working on them. Watch repairing is a skill that can be developed. It is interesting, challenging and sometimes frustrating. But it can also be compensating.
If you want more information, you can locate a watch-material house in the telephone book of any of the larger cities. Have them recommend a good book or watch course. About $100 to $200 worth of tools will get one started. It will take some time and quite a bit of patience before one can begin to do this as an occupation. But some have used this trade to provide a means of support while spending most of their time in pursuing a more important career. They have obtained work from jewelers who are too busy or those who are jewelers and not watch repairmen. The work can be performed at home at one’s convenience.
Even if you are not interested in learning how to repair watches, it is good to know what makes them tick. Knowing something about them will help you to give yours better care.
[Picture on page 18]
An escape wheel and oscillating pallet fork of a watch