Astronomia 3 axis tourbillon

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Astronomia is the name of a series of watches produced by the Swiss company of Jacobs & Co. They all feature a triple axis tourbillon with an integrated clock dial. They are exceptionally expensive costing up to 1 million dollars for the version with the solid sapphire transparent case. The original purpose of single, two and three axis tourbillons was to average out the varying effects of gravity on the watch movement as it was worn. Modern technology has largely done away with this need and they are now largely a demonstration of watchmaking skills. In a clock they are completely superfluous as gravity operates in a constant direction and can be accounted for. They are however an interesting visual feature and good fun

Some of the original watches include large diamonds!

My version is largely made of wood except for critical parts such as bearings and arbors. Two axes of rotation are accomplished by the escapement and cage and the third by rotation of the whole clock arm and escapement about the central axis.

Here I would like to thank A26 and mcmaven who are 3dprinters on www.thingiverse.com. I have taken their design for this clock and reengineered considerably for wood construction.

Drawings were made in Coreldraw and parts cut on an inexpesive K40 laser cutter bought via ebay. All wood parts are 3mm laser grade plywood, some veneered.

Two parts turned out to very difficult to maufacture. The original  English escapement has a sharp pointed tooth profile which does not work well in wood but a Swiss escapement has a club tooth profile which is good. So eventually the compactness of an  English lever and Swiss escape wheel made a suitable 'Swinglish' escapement. The hairspring was designed in Openscad and 3d printed in plastic.

The other difficult parts were the contrate wheels but eventually a design was arrived at with insertable teeth that were suitably strong to stand the torque.

Gearing to the clock face is quite interesting because unlike an ordinary clock the face has to counter rotate to keep it in a consistent orientation but the hands still have to go forward. I have to admit the logic of it all defeated me for a while.

The drive system is also interesting. I have never got on with metal springs in a wood clock because they have a lot of energy which tries to blow the clock apart. Often I have used gentle gravity with a rewind system but here this was nit viable. I finally settled on what I call, with very much tounge in cheek, a hybrid electrotension drive. This basically is a rubber band under tension driving the clock and being tightened freqently by a small electic motor. The action and mechanics can be sen at the end of the video below.

There is a potentiometer geared into the system conected to a microcontroller which defines the switch on/off points of the motor. The motor is also controlled by the microcontrller. The voltage of the system can be anywhere between 7 and 12 volts and averge current drawn is about 100mA.

The whole unit is relatively compact and works very  well.

The compete unit rotates once every 6 minutes, the carriage in 2 minutess and the escapement in 30 seconds.

The overall width of the clock is 350mm.