William Murdoch - Mechanical Improvements and Inventions

Mechanical Improvements and Inventions

While based in Cornwall Murdoch had to deal with a wide range of mechanical problems related to steam engines, and this led him to make practical improvements to the basic steam engine designs used by Boulton and Watt. From 1782 there is evidence that Murdoch was discussing and collaborating with Watt on a number of inventions and improvements. There is, however, a dearth of letters from Murdoch to Watt from 1780 until 1797 in the Watt archive, possibly, as argued by John Griffiths, due to an attempt by Watt's son, James Watt Junior, to uphold his father's reputation by removing any evidence of the origin of some of the inventions he patented. It is almost certain that Murdoch's contract of employment, in common with those for other employees of Boulton and Watt, specified that anything he invented would be the intellectual property of his employers, and frequently it was they who filed, and benefited from, patents on these inventions.

One of Murdoch's most significant inventions, for which evidence exists to attribute it to him, was the sun and planet gear which allowed steam power to be used to "produce a continued Rotative or Circular Motion round an Axis or Centre, and thereby to give Motion to the Wheels of Mills or other Machines". This gear converted the vertical motion of a beam, driven by a steam engine, into circular motion using a 'planet', a cogwheel fixed at the end of a rod connected to the beam of the engine. With the motion of the beam this revolved around, and turned, the 'sun' a second rotating cog fixed to and which turned the drive shaft. This system of achieving rotary motion was patented in his own name by James Watt in October 1781 although Samuel Smiles, biographer of Boulton and Watt, attributes this to Murdoch and there also exists a drawing of the sun and planet system in Murdoch's hand dated August 1781. Other evidence attributing this invention to William Murdoch takes the form of a letter from Boulton to a colleague concerning Watt's forthcoming October patents in which he writes:

He has another rotative scheme to add, which I could have told him of long ago when first invented by William Murdock but I do not think it a matter of much consequence.

Another innovation of Murdoch's was his 1799 invention of a much simplified and more efficient steam wheel than those in use at the time. A precursor of the steam turbine, the steam wheel allowed the wheel to be directly turned by the pressure of the steam moving through it. By this time Murdoch's contract had been amended and he was able to patent this device in his own name.

Murdoch also carried out a number of experiments with compressed air and developed the first pneumatic message system which worked by using compressed air to propel a message in a cylinder through a tube to its intended destination. This system was developed by the London Pneumatic Despatch Company and became widely used; Harrods in particular used this system until at least the 1960s. Murdoch also used compressed air to ring a bell at his home to announce visitors.

Some of Murdoch's other minor inventions and experiments were: a machine developed in 1784 or 1785 in Cornwall for drilling wooden pipes, (in 1810 this was further developed and patented for stone pipes), a steam cannon which he attempted to use in 1803 to knock down a wall at Soho, a steam gun in the same year which fired 3 cm lead bullets, and machinery to grind and compress peat moss under great pressure to produce a material with "the appearance of the finest Jet".