Gear Ratio Demonstrator

Step 1 of 6. Lay the 2x12 beam down flat. This is the whole chassis.

Step 2 of 6. Push a shaft down through holes 0, 2 and 6 of the front row. Leave about half a hole of shaft sticking out underneath.

Step 3 of 6. Drop one spacer over each shaft. These hold the gears clear of the beam so they can spin freely.

Step 4 of 6. Slide the gears on: 12-tooth, then 36-tooth, then 60-tooth. Check that each pair actually meshes before you go on - the teeth should turn each other with no free play.

Step 5 of 6. Lock a collar onto each shaft above the gear.

Step 6 of 6. Finish with a crank arm on the 12-tooth shaft, and a standoff through its far end for a handle. The arm points out to the side so it swings clear of the other two gears.