User:Frogx345

= Lego Clocks =

Lego clocks are mechanically, electrically, or computer controlled clocks constructed mostly or entirely out of Lego pieces. The most common types are electronic clocks driven by motors and pendulum clocks. Almost all Lego clocks are made by dedicated Lego hobbyists.

Electronic Lego Clocks
Lego clocks driven by motors are usually simple mechanisms. A motor turns a main axle and, through a multitude of gear ratios, this axle drives the movement of the hour, minute, and second hands on the clock face.

The main difficulty to overcome with electronic Lego clocks is getting the motor to rotate at a constant, accurate speed, say one revolution a second. If the motor is off its timing by even a fraction of a degree the clock will follow suit.

Lego Pendulum Clocks
The timing of pendulum clocks depends on the period of the pendulum’s swing, which is directly proportional to the length of the pendulum. Since Lego is very versatile in the different ways to connect pieces it is easy to construct and change a certain pendulum length. A pendulum clock also needs an escapement, the mechanism which keeps the clock correctly timed. There are many different ways to construct escapements out of Lego, however, there are few Lego mechanisms which are as efficient as commercial pendulum clock escapements (such as in grandfather clocks).

The advantage of the pendulum clock is its timing. Rather than getting a motor or some other complex mechanism to run with perfect timing, ideally only the length of the pendulum will affect the timing of the clock.

Lego Clock Gearing
The hands of Lego clocks driven from one source (a motor, pendulum, etc.) involve gears which attach each hand to one another. The variety of Lego gear sizes and possible gear ratios make building a gearing mechanism for these clock hands quite simple. The second-to-minute hand and minute-to-hour hand ratios are each 60:1. This ratio must be achieved with multiple Lego gear ratios since the smallest Lego gear has 8 teeth and the largest gear has 40 teeth. The gear ratio of these gears for example is 5:1 (5 revolutions of the small gear for every one revolution of the big gear). An example of a full 60:1 gearing ratio with Lego gears could be an 8-tooth gear with a 40-tooth gear (5:1), connected to an 8-tooth with a 36-tooth gear (4:1) [4.5:1 actually], finally connected to an 8-tooth with a 24-tooth gear (3:1). This would revolve in one revolution of the 24-tooth gear for every 60 revolutions of the first 8-tooth gear (5x4x3:1x1x1 = 60:1).