Sunday, June 17, 2012

Basics of how a clock works

Before I confirmed that I would make a clock, I obviously researched a bit about if it is really achievable. I looked through some book in our school library. I found one book which names all the vocabulary of all the pieces of a clock, which I thought would be very usefull when I would go buy the pieces. Only later I came with the idea of making all the pieces from wood. So I photocopied it and put it here:
















There are another book which explains a bit confusinly how the basics of a clock work. But I figured it out mainly by common-sense.

You have two types of Mechanical Clocks, one that works on weight, one that works on springs. If you have a clock that works on springs it means that you tighten the spring which holds potential energy and pushes a wheel round. If it works on weigth it also hold potential energy, because the gravity will pull the weight down, and the weight are attached to a wheel, so the weights will turn around the wheels.

How the wheels work is easy: when one wheel starts turning, the other once will aswell and eventually it will get the teeth of the clock to work. The next bit is a bit hard to explain just by words, but I'll do my best. One wheel is directly attached to the minute teeth, but one wheel (a bigger one) is touching it. because the wheel is bigger, the smaller one has to turn more times for the bigger one to go around once, in other words the big one will go slower. Then above the big wheel is another wheel. These are attached to eachother, not just touching. So whenever the big one goes around once, so will the other one. The 'other' one is smaller, and is touching another bigger wheel. So the small one will go really slowely, but it has to turn several times before the big one has turned once. Therefore the big one goes even more slowely. Mathmatically calculated the made sure that the speed of this one is acsactly 60 times slower that the minute teeth, which makes the hour teeth. Are you with me?

Then you have another problem. If the weigths or the spring makes one of the wheels go around, why doesn't it very quickly make all the wheels go around really fast and then stop? This is solved by the pendulum.

In the book it also explains how an electronic clock works, but that doesn't really help me in my project, and in the back it also explains a bit about the history of the clock. But this was only a small paragraph, so I just quoted it:

"Clocks

A rack-and-pinion gear was used in a water clock build by the Greek inventor Ctesibius in about 250BC. The water clock was an ancient device in which water dropped at a constant rate into a containter, the level of the water indicating the time. Ctesibius improved it by having a float raise a rack that turned a pinion connected to a pointer on a drum. The pointer turned to indicate the time in the same ways as the hour hand of a mechanical clock.
The oldest surviving mechanical clocks date from the late 1300s. Gears transmitted the constant movement of a regulator to the hands or to a bell. A good regulator appeared only with the discovery of the pendulum in 1581 by the great Italian scientist Galileo, who timed a swinging chandelier with his pulse and realized that chandelier with his pulse and realized that the time taken for each swing was always constant. Even so, it took nearly a century for the first pendulum clocks to appear."

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