Gear Train for Mary Chambers Model

The Mary Chambers model was the first of the models in the Archive Project that we completed. As parts of the process of mounting the puppetry onto a plinth I wanted to update the mechanism so that the style matched that of the later projects.

There are three main movements in this model. The soldier rows the boat, the boat rocks up and down and the waves… well they wave. All three movements  can be based round a circular crank movement but they are all at different speeds. Fastest moving are the waves with the rocking of the boat slightly slower. The rowing movement is slowest. Slow and steady. I laid out this gear train which should so the job.gear-a05Time to transfer it to the real world.

I made a simple jig onto which I can build the gears.This keeps everything at right angles and makes sure that the key slots are aligned.gear-a01These pictures show the largest gear, the thirty seven tooth gear, being constructed. The gears are made up from three layers of laser cut ply . The gear part with the spokes is sandwiched between two disks and fitted onto the jig until the glue is dry.gear-a02

With the gear centre removed from the jig I fit the outer tooth rings into place front and back and clamp them into position whilst the glue dries. You can see the short section of rack in the picture that  I use to make sure that the teeth are lined up properly.

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The finished gear.gear-a04

I’ve then constructed an arch to hold all the parts into position. Here you see the assembled parts, almost complete apart from the keys which will be fitted to the axles.

Running smooth!

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Linking a Gear to an Axle

While I’m prototyping the gears on the wooden automata I need to be able to assemble and disassemble the model so that I can experiment with designs.

I’ve tried all sorts of design variations. Brass axles, grub screws, flanges, perspex joints. Finally I feel like I have settled on a consistent design. I’m using 12mm dowel for the axles and a keyway in the gear’s axle hole to hold the gears in position.gear-a01

I drill a couple of small holes in the dowel in the place where the gear is being fitted. The holes don’t go all the way through the axle. I then make a curve-topped staple from a short length of 1mm diameter wire.gear-a02

The staple fits into the two holes, the fact that it is curve-topped ensures that the centre of the staple is raised above the dowel.gear-a03

The gear then slips onto the shaft with the keyway located over the staple. The staple works to stop the gear rotating out of position. Perfect!gear-a04

Here’s a sample of the gears in position. Looking good!gear-a05