The Claw: Gear Ratios & Power Using LEGO Cranes
Students learn about gear ratios and power by operating toy mechanical cranes of differing gear ratios. They attempt to pick up objects with various masses to witness how much power must be applied to the system to oppose the force of gravity. They learn about the concept of gear ratio and practice calculating gear ratios on worksheets, discovering that smaller gear ratios are best for picking objects up quickly, and larger gear ratios make it easier to lift heavy objects.
Figure 1: A crane made with LEGO pieces.Copyright 2012 Zachary Nishino, Polytechnic Institute of New York University
Gears are incorporated into almost all mechanical machines. From cars to cranes, different gear ratios provide ways to increase or decrease torque depending on the task at hand. Engineers figure out what torque is needed for each situation and the corresponding gear ratio for a fixed power.
After this activity, students should be able to:
- Measure gear diameters.
- Compute gear ratios used in a simple machine.
- Describe the characteristics of different gear ratios, including speed and torque.