Ghostbusters proton pack crank knob

thingiverse

Here's how it works: The user selects the required crank knob for the gear box and then inserts a screwdriver into the recessed hole located on the side of the gearbox to turn it clockwise until it stops. This will set the correct gear ratio. Next, they must insert the crank knob into the gear box so that the threaded part of the knob is facing outward towards them. Finally, they must screw the knob clockwise with a wrench or pliers until it's snug against the gearbox.