I’ve made rack and pinion mechanisms before, but I really wanted to use the mesh gear design that I have been using with standard gears. Here’s what I have come up with so far. Click on the picture to see the Instagram animation.

The idea with the mesh gears is that they can be made from simple flat shapes. This is, I think, in keeping with the ethos of paper engineering. The flat shapes are then meshed together at ninety degrees to each other. I’ve used the same technique with this rack and pinion mechanism. As the pinion turns the orange tube (the rack) is driven back and forth along the blue inner tube.

Here’s the next stage prototype with new tooth profiles on both the pinion and the rack. The box holds the parts in alignment.

I finished off the box by adding a big crank wheel to the front.

As well as being interesting as a pure mechanism I’m sure that the rack and pinion will come in useful as the core of some interesting automata projects.

By attaching a thin paper loop it can be used for pulling a model across the top of a box…

…or by cutting a long thin slot in the box top it should be possible to make a mouse scuttle…

…or a tortoise peep out of its shell.

Next step – I’ll be completing the parts layout and releasing the rack and pinion as an Essential Mechanism for you to make for yourself.