Wooden Clock Spot: Franklin Three Wheeler

This is my interpretation of the clock designed but never made by Benjamin Franklin around 1758. A description of the clock was recorded by James Ferguson in about 1773.

A limited edition of 1000 clocks has been made by Thwaites and Rees.

The clock is very simple, consisting of 3 wheels, a pendulum and weights. It was wall hanging with a long pendulum and an anchor escapement.The most noticeable feature was the dial with the single hand which went once round the dial in 4 hours. This necessitated having multiple hour markings at the same place on the dial. The time was capable of being read to the nearest minute but I have to admit it is not perhaps the easiest dial to read.

My version has been constructed as a mantel clock with a smaller compound pendulum, a shorter fall of weights with automatic rewind and a grasshopper escapement. And of course it is made largely of wood.

The original clock had an anchor escapement but I decided to use a grasshopper. The grasshopper is virtually silent, visually intriguing and works very well in wood because it does not have any sliding action at its pallets, That John Harrison knew a thing or two.

The compound pendulum has a beat of 2/3 of a second.

The grasshopper escapement

The largest wheel of 160 teeth at a Module of 1.5 was too large to cut in on go on my laser cutter so was fabricated from 5 sections and a boss.

The two weights are rewound by an electric motor in the base which rewinds the barrel via a wooden chain and epicyclic maintaining power. The rewind is triggered by the weights bridging contact electrodes on the base and starting a relay timer which runs for30 seconds. The wooden chain has been described before in my Regulator clock.