Brass casting, roughly cylindrical in form but with three sinkings in the cylindrical surface, unsigned, United Kingdom, 1790-1819. Used as the hub 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 item comprises a brass casting, roughly cylindrical in form but with three sinkings in the cylindrical surface. It has been partly dressed by filing, but remains unfinished. An axial hole has been drilled and opened to square, and it has been driven on to a steel arbor that has been broken, which would have acted as the axle.