.I came across this design during my research into the firm of Easton & Amos. It was patented by Frederick William Stoker in 1892, whilst he was the Works Manager of the Erith Ironworks.

Stoker Engine GA

It is a quadruple expansion engine, but using only two cylinders, mounted in tandem. The Steam inlet is at “S” and is controlled by the valve “V”. Steam is admitted to the top of the HP piston, and after the working stroke, exhausted below the valve V to the lower steam chest P. From here the steam passes to the upper side of the LP piston, and after the working stroke, exhausted, through the passage in the slide valve D, to the lower part of the LP cylinder.

I do not know how many of these engines were made (probably only very few!) but a twin cylinder version was exhibited at the Electrical Engineering Exhibition at the Crystal Palace in 1892.

Why the piston rod between the two pistons is shown in the drawing with grooves all along its length is not known. If you have any ideas, the please let me know!

Stoker Engine Model

David's model of the Stoker Engine