Page 45 - The Unofficial Guide to Lego Mindstorms Robots

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Of Geared and Ungeared Motors

There's one more topic related to gears that's important. M ost electric motors turn too fast and with too little power to be
u seful. Gears are usually used to swap speed for power until a good balance is achieved. This process is called gearing down or
gear reduction.

The motors that come with RIS are internally geared, which means that the motor case actually contains an electric motor and
some number of gears. The output shaft is already adjusted to turn at a reasonable spee d with a reasonable amount of power.
This means you can attach wheels directly to these motors to drive your robot around.

The LEGO group makes four different kinds of motors that can be driven from the output s of the RCX:

st andard motor
This has been the standard motor of the LEGO TECHNIC line for many years. It is an ungeared motor, which means its output
shaft rotates very rapidly, with little power, when electricity is applied. To do any useful wo rk with it, you'll probably have to
use gears to reduce its output speed.

m icro motor
This is a tiny motor with low speed and low power. You probably can't use this motor to move your robot, but it could be
useful for lighter tasks. It's harder to find than the other motors.

geared motor
Two of these motors come with the MINDSTORMS RIS kit . They are internally geared so that the output shaft has enough
p ower to drive your robot around. They are more efficient than the standard motor. The geared motor is shown in Figure 2-14.

Figure 2-14.
The geared m otor