Strutt Epicyclic

The  Strutt Epicyclic Clock is unusual in design.

Designed by William Strutt of Derby in the 1820's it was manufactured in small numbers by William Wigston who had an engineering firm.

The epicyclic or sun and planet gear formed the going train, and an ingenious Ferguson's Paradox like system consisting of two gears on the same shaft and a lantern pinion produced the 12:1 reduction for the hour hand.

This version deviates from the original in that it is made of wood and has is different in appearance, but has the original teeth counts for the wheels. 

All wheels are Module 1.5

A video of it in action can be seen at the bottom of the page.

The Strutt Clock

The escapement is a 36 tooth inverted recoil escapement

 

 A six tooth escapement pinion meshes with a large ring gear that has 168 teeth externally and 144 teeth internally.

The planet gear of 68 teeth runs around the internal of the ring gear, being mounted  on a counter balanced carrier arm. Here the counter weights are 2p coins. The minute hand is mounted on a shaft projecting forward from the carrier. 

An eight tooth lantern pinion on the planet gear meshes with two sun gears. The innermost one has 72 teeth and the outer one has 66 teeth and is prevented from rotating.

Although they have different numbers of teeth they have the same pitch diameter, but they still mesh adequately with the lantern pinion. 

By a geometrical process that I don't understand this arrangement means the inner wheel rotates at once per twelve hours and is thus connected to the hour hand.

This image shows the means of fixing the rotation of the 66 tooth sun wheel by prongs projecting from an escutcheon plate engaging a crossing of the wheel.

The escutcheon plate is fixed to the dial.

The large ring gear is driven from a gear mounted on the same shaft but  between the plates. The motive power is supplied by a weight running a short arc around the periphery of this gear. The weight is a motor which gets switched on when it is low on the gear by a mercury switch and a 3 second timer, which lifts it up while still maintaining motive power to the clock.

The pendulum bob is just for display. There is an adjustable brass weight further up the pendulum shaft which is the real bob and regulator.

The biggest challenge in making this clock was to fabricate the large ring gear so that it was flat and round enough to mesh properly with the 6 tooth pinion. I decided to make it in six segments to avoid any warping of the admittedly cheap plywood. The segments are laser cut and pegged and glued together with additional support from the spider carrier.