Gears

Purpose of Gears:

Gears improve the speed and agility of your wheels.  They can be used to increase or decrease speed and/or power.

Examples of Gears:

            Clocks, egg beaters, fishing poles, cars, toys, drills.

How to use Gears:

• The gear you turn (called the driver) causes the other gear (called the follower) to turn also.  The driver and the follower turn in opposite directions.

• A large driver makes a small follower gear turn faster and decreases the force.  This is called gearing up.

• A small driver gear makes a large follower gear turn slower and increases the force.  This is called gearing down.

• An idler gear makes adjacent gears turn in the same direction.  A large driver will make a small follower turn faster, regardless of the idler size.

• The crown gear can change the rotary motion through a 90-degree angle.

• Gears of different sizes on the same axle can be connected to other gears to build more extensive gearing down (and gearing up) arrangements.

• A gear ratio is a comparison of the total number of turns of input to the turns of output.  For example, a gear ratio of 1:3 (8 toothed gear turning a 24 toothed gear) means that the input axle/shaft must make three revolutions to produce one revolution of the output axle/shaft.  This also means that the output speed is three times slower, but the output force is three times greater.  (more on gear ratios below)

LEGO® DACTA, Teacher Guide 9620 Gears(1997).             

MORE ON GEAR RATIOS

To determine the gear ratios using more than one set of gears, set the gears in front of you in the order they will be mounted.  Put each ratio of gears in a column (first gear: second gear).  Remember, your second gear will become your first gear in the second ratio. 

You would set up the ratio as follows:

                        40:8                                                                40  x  8

                        8:24                            or                                 8      24

Simplify each ratio:

                        5:1*                                                                 5   x  1

                        1:3                               or                                1*      3

The next step is to multiply:

*Denotes same numeral, so that the two number “1”s are not confused.

5:3 or 5 is your ratio.

           3 

 Try this one out: 

Solution should be 5:1 or 5

                                           1

Back to Gears & Pulleys Lab or Contents