In a mechanical engineering classes my team and I were given the task of creating a 120:1 gear ratio gear box. We were told to use cardboard for the spur gears and pencils for the shafts. It was up to us to figure out the number of gears, number of teeth on each gear, and the configuration to achieve the correct gear ratio.

Since we had the whole semester to complete this project we decided to set some deadlines.

1. The Calculations

2. Design the Gearbox using SolidWorks

3. Construct a prototype

The gear ratio calculation for spur gears are fairly straight forward. Gear ratio is equal to the number of teeth on the driven gear divided by the number of teeth on the driving gear. For example, if the driver gear has 20 teeth and the driven gear has 60 teeth then the gear ratio is 60/20 or 3:1.