A Mechanical Accelerometer from 1904

Mechanical Artist
The history of engineering is marked by the achievements of individuals who were inventive, single-minded, persistent and, above all, passionate about their subject.

This is especially true of Frederick William Lanchester (1868-1946), described by Harry Ricardo as a great engineer and a true artist in mechanical design.

Lanchester made major contributions to aeronautical and automotive theory and practice and is best remembered for building the first all-British petrol-driven car in 1895. His story is that of the individual's
determination for progress against the odds. He remarked that his achievements had been gained solely through spending his own money and that he had never been backed by funds, or been in a position to take advantage of resources from external sources.

Lanchester left a legacy of successful inventions related to the internal combustion engine, including the balanced reciprocating engine and the torsional crankshaft damper. His most creative period of invention
spanned the final decade of the Victorian era and it was during this time that he developed his idea for a pendulum accelerometer.

The accelerometer was devised to measure and to record tractive and brake effort and was eventually used by Daimler. It consisted of two tracing pens, one centred and one pendulum mounted, above a paper scroll. The scroll was housed on two clockwork driven drums operated by a winding handle. Before its invention, the only method of measuring acceleration was by observation.

The accelerometer was initially tested on the railways with the aim of assessing braking conditions. The engineers wanted to measure accurately the rate of change of acceleration of rail vehicles. The rate
of change needed to be limited to manage wear and tear hut also to prevent harm to passengers. Accelerometer diagrams revealed problemscaused by driving wheels slipping as acceleration could be seen to fall dramatically and only resume again when the wheels gained a proper grip.

The accelerometer was also used on road vehicles to help designers spot weaknesses and faults in areas such as carburettor design and to render improvements. The accelerometer could also be used to measure lateral
stresses on tyres when a vehicle turned corners or took curves. An example of this fine piece of engineering is held by the IMechE Archives and can he viewed by visitors. Lanchester developed the accelerometer in 1889.
It was a home-made affair but he spent time perfecting it and it is the improved 1904 version that can be seen on display today.

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