Gear Ratio Explorer

Run the Gear Ratio Explorer MicroSim Fullscreen

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Description

Set a gear ratio, a motor speed, a motor torque and an efficiency, and watch a small motor gear turn many times for each turn of the output while the output speed and torque update. Then solve five gear problems. Used in Chapter 5.

The picture shows a small motor gear, a gearbox and a large output gear. The gears turn in slow motion while the pointer is over the MicroSim, and each gear has one marked spoke so that you can count its turns. The two formulas are output speed = motor speed / N and output torque = motor torque × N × efficiency. The values in Explore mode are illustrative. The 42 rpm and 1.62 N·m figures in the problems come from the STS3215 worked example in Chapter 5.

Lesson Plan

Grade level: Middle school and up (age 12+). Time: 10 to 15 minutes.

1. Predict first. Before you move the gear ratio slider, say what will happen to the output speed and to the output torque.
2. Explore. Double N. The output speed halves and the output torque doubles. Now lower the efficiency. Which of the two outputs changes?
3. Problems. Five problems in a fixed order. Type the answer in the unit shown and press Check. You get one try for each problem, and 4 of 5 is mastery.
4. Think about it. The leader arm uses 147 : 1 gearing on some joints and the follower uses 345 : 1. Why is the leader easier to move by hand?

Watch the units in problems 3 and 4. A motor torque is given in millinewton-metres (mN·m), and 1000 mN·m is 1 N·m.

Specification

The learning objective, evidence of mastery and content for this MicroSim are specified in Chapter 5: Actuators and Sensors.