https://www.instructables.com/Knex-ForwardReverse-Transmission/
K'nex Forward/Reverse Transmission : 7 Steps - Instructables
K'nex Forward/Reverse Transmission: Hello there! Say you are in the middle of making an awesome new k'nex project, and you need a motor. You run to your junk...
forward reverse transmissionk nex7 stepsinstructables