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126 Masterpiece 3 • The LEGO Turning Machine

Bricks & Chips….

Gray Pins or Black Pins?
For this step, we recommend using gray pins. When using a touch sensor, gray
pins are preferred over black pins because the gray pin’s ability to rotate. Their
shape is also more precise when pushing the button on the touch sensor.

The Direction Control II

This is the second part of the Direction Control sub-assembly, where we connect the
motor and the touch sensor. Later, we will connect the Direction Control II sub-assembly
to the Direction Control sub-assembly.
In this sub-assembly, we use an 8T gear to slow the motor down to a reasonable
speed, by gearing it down to 1:5.

Bricks & Chips….
Gears and Gear Ratios

The fundamental property of a gear is its number of teeth. It is so important that
we even name the gears after it: for example, a 24-tooth gear becomes a 24T. By
connecting two or more gears with a different number of teeth, you can control
their speed. Think of connecting a 24T gear to an 8T, and slowly turning the 24T:
You see, for every turn of the 24T the smaller gear makes three turns. This is a
gain in angular velocity. In simple terms, angular velocity means a gain in speed.
This conversion unfortunately has a cost: The torque of the system, that is the
strength, is reduced exactly the same way (except for a small part of it that is lost
due to friction) to one third.
Continued