Yellow Earl Progress Report

YellowEarl-b01My continuing mission to work out a work flow for designing and making wooden automata has borne fruit.
Having made up a prototype box from corrugated card – previous post – I’ve set about dividing up the automata into its various mechanisms.
Firstly, the parallax hills. The two smaller gears (14 and 22 teeth respectively) are fixed onto a single shaft. The two larger gears are where the magic happens. The 37 tooth gear is fixed to a 7mm tube, the 43 tooth gear fits onto a 6mm rod threaded through its centre. The hill profiles are fitted to these coaxial tubes. As the small gear turns, the front hill turns faster than the rear hill producing the illusion of movement.

YellowEarl-b02Next, the legs. I’ve made up the mechanism as a complete unit. This fits inside the box. The legs of the Yellow Earl fit down into the top of the two fingers. As the gear turns the fingers are driven back and forth moving the legs in the process.

The final mechanism is the thought bubble window. As the Yellow Earl trudges onward ever onward towards the North Pole he is haunted by the memories of the various women in his life. In a ‘thought bubble’ window behind his head the pictures flips past showing portraits one after another. The mechanism is driven by a ratchet and pawl.


Mechanisms in hand, I visited Archive this morning to see how everything fits together with Dawn’s splendid puppets.

YellowEarl-b04Dawn has done a fantastic work making her distinctive puppets to match with my mechanisms. The Yellow Earl is no exception. Everything fits together in the prototype form.
Having taken measurements and made sure everything works we’ve arranged to meet up again early next week for final assembly. Exciting stuff!

Geneva Drive – Laser-cut


The automata in the Archive Project use all kinds of different mechanisms to make all kinds of different movements. The one I’m working on at the moment uses a particularly interesting mechanism. There is a little window in the background of the model. Through the window you can see a portrait of a woman. As the mechanism runs I need the picture in the window to change to another portrait, then another, then another… and so on. I need the picture to be stay still for a set amount of time then flip quickly to the next picture as the mechanism runs.

geneva-a01This is the perfect tesk for a Geneva drive.. In my test version I went for an eight step drive.

The mathematics of the parts layout is fairly straightforward. I wrote a blog post about it a while back here. The key centres for an eight step drive are based around a right-angle triangle with a 22.5° angle. The angle is worked out by dividing 360° by eight, for the eight steps, then halving it.



Having designed the parts in Illustrator, I’ve cut out the resulting mechanism from 3mm plywood and used 12mm and 9mm hardwood dowel for the axles. The drive pin is then fitted onto a 26 tooth gear which will be driven direct from the automata mechanism. This prototype works a treat!