1820 Peter Playne equipped his 1818 block with a Boulton & Watt steam engine. It could supplement the power of the two waterwheels. Probably they generated about 10 to 15 horsepower each.
He added a boiler house, housing two boilers at right angles to the mill and the chimney was in in the centre of the party wall with the mill, whereas the later chimney is at the right hand side.
The plans show this engine was located in Cooper’s mill. It generated 14 horse power, and the mill records suggest that it was only there to supplement the power of the wheels.

1855 With the rebuilding and re-equipping of the mill apparently a 25 h.p. compound beam engine, possibly by Ferrabee of Phoenix Ironworks, Thrupp, was replaced it and this engine must have had a more direct role in the production of power, now that there was such a concentration of machinery at the mill.

1873 The 1855 stone chimney was taken down and replaced by a 120 foot one housing a 32 tube Green’s Economiser. This is the chimney that survives.

1889 There was also a 10 h.p. high pressure engine, perhaps under the Willey House, as a later fire, destroying the five storey building, was reported to have started in the engine house at the bottom of the block.
Research by Ray Wilson of the Glos. Society for Industrial Archaeology reveals that the Walkers installed a 50 h.p. engine in the 1818 block, able to be coupled to the waterwheels. The wheels remain but the engine was scrapped by 1960. There was a Lancashire boiler in the Boiler House and "the engine was also coupled to a large dynamo supplying D.C. electric current to 500 sixteen candle power lights".

1914 After the fire destroyed the Willey House, a brick engine house was built housing a large Marshall horizontal cross compound engine. This was removed by 1960. The brick block has been rebuilt to the same design.