Per Group
Place the RISE girls into cooperative groups of two or three. Have the girls work together to share the responsibilities of recording data and manipulating materials.
1. Draw a pencil line down the middle of the craft stick.
2. Measure the width of the stick and divide by two. Mark a dot on the line at this distance from one end of the stick. This will be the location of the main hole.
3. With the center of the main hole as zero, mark an additional dot every two centimeters until you reach each end of the stick. Number the holes 2, 4, 6, etc., according to how many centimeters they are from the main hole. On the other side of the stick, mark "for 10-tooth pinion."
4. Using the 5.5 mm or 7/32" bit, drill the main hole.
5. Using the 7/32" bit, drill additional holes at each of the marked spots.
6. Make another stick in the same way, except this time use a 65 mm or 1/4" bit for the main hole. Mark this stick "for 12-tooth pinion."
7. Push the l0-tooth stick over the pinion on the electric motor. Hold the motor at the edge of the table and connect the spring scale to one of the holes in the stick.
8. Turn the motor on and measure the force in newtons with the scale. Keep the scale perpendicular to the stick.
9. Record your measurements on the Torque
Data Sheet.
1. What was the torque of your motor? Select a nylon gear with 62 teeth on one gear and 10 teeth on the other. Lay it flat on the table with the 10-tooth side up.
Put the "main hole" of a 10-tooth stick over the 10-tooth pinion and press the stick down so that the 10-tooth pinion comes through the hole.
2. Push an axle into the gear from the side that doesn't have the wooden stick.
3. Repeat the process with a l2-tooth stick, forcing it into the 12 tooth pinion on a 48/12 gear.
4. Mount the motor on the bottom of the chassis (the side without the lettering) and place the chassis on the edge of the table.
Insert axles and gears to make the gear train, with a gear with an attached stick as the last gear in the train.
5. Measure the torque at the last gear in the train. Record the torque. Make a drawing of the arrangement of gears.
For each revolution of the motor, how many revolutions does the last gear in the train make?
6. Design a different gear train and repeat the process. Record the torque.
Make drawing of the arrangement of gears for each revolution of the motor, how many revolutions does the last gear in the train make?
Challenge: Can you come up with a way of predicting mathematically what torque a particular gear train will produce, if you know the motor's torque?
Torque is a measure of the force exerted by the motor. Most times when we think of force we think of push and pull. However, your motor neither pushes nor pulls, it turns.
The measure of the strength of twisting and turning that a motor has, is called its torque. This is measured normally by measuring the force at some distance from the center of the shaft of a motor.
In effect, what we are measuring are two things: force and distance.
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