Double-acting rotative steam engine by Boulton & Watt, 1797. Atkinson's Engine, formerly Maud's Engine. In use at the chemical works at 66 Aldersgate Street until c. 1884.

This engine was constructed by Messrs. Boulton and Watt, and erected in 1797 for John Maud, chemist and druggist, at 66, Aldersgate Street, E.C., subsequently Atkinson's Chemical Works, where it continued working until 1885, when it was taken down and presented to the Museum. The engine was of 8 nominal h.p., and had a cylinder 16 in. diam. and 4 ft. stroke, but in 1806 it was altered by the makers to a 12 h.p. engine, the diameter of the cylinder being increased to 19.25 in. It is a low-pressure condensing engine, with sun and planet gear, similar in general construction to No. 73, but the valves are driven by a crank motion instead of by tappets, and there is a separate cut-off valve moved by a cam motion to give expansive working. The crank and cam are both on a counter- shaft driven by spur gearing, at one-half the speed of the flywheel shaft, which, on account of the sun and planet gear, makes two revolutions for each double stroke of the engine. The connecting rod from the valve crank-pin is made with a gab end, so that it can be disengaged, and the valves be worked by hand levers when required in starting the engine. The engine was probably made with a tappet motion in the first case, and the motion above described added at the later date.