Three Layer Gears

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I have a large project to complete for a local museum where I’ll be making a series of automata depicting local historical characters. These will be on display in the museum, powered by electric motors operated by a push switch. Hopefully the finished models will be on display for a long time so I need to be able to make repairs when pieces wear out. Obviously wooden dowels axles are out, I’m replacing them with brass tube. The problem remains, how to fit the gear to the axle so that it can be changed if necessary. Through a process of trial and error I think I’m pretty close to the laser cut gears that I want.

I’ll add a download file with this post for anyone who wants to try this out.

The gear is made from three main parts in 3mm ply plus two axle parts from 6mm ply. I’ll added a little alignment triangle to each of the gear rings mainly so I know which is the front and which is the back.

I’ve also cut out a small section of rack with the same pitch as the gear teeth. This helps lining up the layers as they are glued together.

One triple thickness gear. Twenty three teeth. That’s a prime number that is.

I punched a dent close to the end of the brass axle piece. It might be better if I put a solid filler piece in the tube whilst I do this. I then drilled through one side only with a 1.5mm drill bit.

I drilled a hole into the side of a hub piece. One side only again.

I pushed the hub onto the axle then twisted them round until the holes lined up.

I then inserted the drill into the hole and drilled right the way through and out the other side.

Finally I fitted a split pin through the hub and the axle.

I finished of by threading the axle though the hole in the gear wheel and gluing the hub and gear together. Finished off by gluing a second hub on the back of the gear.

Here it is meshing with a 47 tooth gear. Looking good! If I need to change a gear wheel in a completed model I’ll be able to pull out the split pin and slide it off the axle. Perfect.