Three curved rectangular form brass castings, by James Watt, Glasgow, Scotland, 1758-1769. These castings were intended as the vanes of a small rotary steam engine.
This item is part of the contents of the workshop that Scottish engineer James Watt developed at his home, Heathfield, at Handsworth, Birmingham. Although Watt is best known for his work on the steam engine, his workshop contains a wide variety of objects from many different projects, from chemistry to sculpture-copying.
The description of the item was written by Edward Collins, the land agent responsible for Heathfield when the workshop was given to the Science Museum in 1924. Collins could not always identify what he was looking at, but always described what he saw clearly. This has allowed his descriptions to form the basis of subsequent research.
These are fragments of Watt's 1782 rotary steam engine. Watt, as well as constructing traditional steam engines using beams, also attempted to make an engine without a piston and cylinder, using pure rotary motion. In this, a steam jet spun the three blades around a shaft. Although it leaked and hit technical difficulties, Matthew Boulton wrote excitedly that ‘if we had a hundred wheels ready made’ he could easily sell them. It was premature – an effective rotary steam engine did not arrive until 1884 with the Parsons turbine.
The pieces comprise three undressed brass castings of rectangular form but curved out of a plane. One straight edge is thickened. These were intended as the vanes of Watt's small rotary steam engine, jointed to a hub - parts from which shared the same home in the workshop. It may be observed that, when finished, the rotor formed of 1924-792/1394 and /1400 might have been housed in a drum of the same size as that of the semi-rotary engine now found on the workshop table, of which some parts were formerly in this box. This should be considered in relation to Watt’s letter, describing how his first “steam wheel” was altered into a “reciprocating circular engine …”