Worm Gear (20:1)

A hand-cranked worm drive in a housing with a gear ratio of 20:1: twenty turns of the crank for one turn of the gear.

Students feel the trade-off between speed and force, and find out why a worm drive cannot be turned backwards from the gear side (used in lifts, guitar tuners and gates).

Design by bargoraj90 on Printables, shared under CC BY 4.0. The files and photos are the designer's, unchanged.

1. Print the housing halves, worm, gear, shafts, crank and handle.
2. Mark the gear and count crank turns for one full gear turn.
3. Try to turn the gear by hand: what happens, and why is that useful?