Step 3: The Pendulum
For our clock, we want to have a period of 2 seconds. That way, it will take the pendulum 1 second to swing to one side. With each swing the escapement will allow the escape gear to turn one tooth at a time. If the period is 2 seconds, this will basically make the escape gear our second hand since it is rotating one tooth every second. For a period of 2 seconds we need it to have a length of 1 meter. Since our escape lever will have 2 teeth, one to stop the escape gear at each end of the pendulum swing, our pendulum will need to have 30 teeth. It will make one rotation every 60 seconds. Many pendulum clocks have the escape gear on the second hand axle. That is what we are going to do.
As the pendulum swings back and forth, it rotates the escape lever in and out of the escape gear. This causes the clock gears to stop and start rotating every second. The lever is designed so that as it is moving out of the escape gear, the gear gives it a little push. This push is enough to keep the pendulum swinging.