Escapement mechanism
The heart of a pendulum clock is an escapement mechanism, which slows down the fall of a weight into a steady, accurate rhythm. One of the simplest escapement mechanisms is an "anchor escapement" - the pictures below show how such a mechanism can be built out of LEGO bricks.
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| Escapement mechanism - anchor |
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| Escapement mechanism - escape wheel |
We need to transmit the gravitational force pulling the weight into a rotational movement of the escape wheel.
We will need to use some gears to ensure that for each rotation of the escape wheel, the weight falls down just a little bit. The gears will also help to translate the fast and jerky movement of the escape wheel into a slow and smooth movement of the clock's hand.
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| Clock mechanism |
How long a clock will keep going depends on how far the weight can travel, before it eventually stops at the ground level. Therefore, we need to suspend the clock's mechanism as far above the ground as possible. To build a sturdy, rigid tower we can use the "truss" technique, typically found in bridges. Notice how the width of the clock's mechanism (and the Pythagorean theorem) makes it easy to use a right triangle in our construction.
A pendulum equation shown below tells us that we can make the clock go faster by shortening the length of the pendulum or we can make it go slower, by lengthening the length of the pendulum. You can try to change the position of the wheel that acts as pendulum weight and measure how fast the clock's hands travel (i.e. how long it takes them to go from 12 o'clock to 6 o'clock).
