A rack and pinion is a clever mechanical device that can be useful in many projects. And this set up is really neat because the gear teeth both for the rack and the pinion are simply the corrugations taken right out of cardboard.

A rack and pinion is a clever mechanical device that can be useful in many projects. And this set up is really neat because the gear teeth both for the rack and the pinion are simply the corrugations taken right out of cardboard.

You turn the round gear (the pinion) and the rack will move horizontally back and forth. Conversely you could move the rack back and forth so the gear turns.

Watch the video to see it in action (11 seconds) :

I will show you a little bit more about how to make something like this.

Cut strips of cardboard across the flutes. Cut your strips long enough so you only have to use one piece for the rack and one piece for the pinion. (If possible) this will make the gear meshing easier.

Then carefully peel off the top layer of craft paper. If you have trouble you can brush on some water. That will dissolve the starch.

They look good.

One important thing to consider when choosing the cardboard for these pieces : Use the same box for both pieces. This is because different boxes can be made up of flutes that are different sizes and at different intervals.

Here is a picture showing the flutes from two different boxes. You can see that one piece has more flutes per inch than the other. These pieces would not mesh well and your rack and pinion would not work very well.

Want to learn more about cardboard types and fluting? I have a great description and explanation of it right here.

Here is how to make the pinion.

I simply cut four circles out of cardboard. They are 2 1/2 inches in diameter. Then I glued them all together to make a stack. That stack is about one half inch thick which is the same as our corrugated piece.

Glue the corrugated piece all the way around.

Make the rack in a similar fashion. It is four pieces of cardboard glued to make a stack. Then along one side of the stack I glued the corrugated strip.

Those two wooden dowels sticking out are important. You need at least two of them. Otherwise the rack would not travel in a straight line.

Those dowels slide in a slot.

Secure the pinion gear with a dowel it can rotate freely on (red star) and add a handle you can turn (Yellow star). Then you can pierce a hole and mount it right up against the rack so the corrugations match nicely.

And that's it! You have made a rack and pinion out of cardboard. You can tailor the size to any application you need.

Want to see more mechanical devices made out of cardboard including pulleys, bearings, and cams? I Have a list of them right here.