SIMPSON & SHIPTON'S SECOND ENGINE: 1851

Left: Simplified diagram of the second Simpson & Shipton engine. This intriguing engine was introduced by two Manchester engineers, Joseph Simpson and James Alfred Shipton. It should not be confused with a similar machine that was patented by them in 1848; see Page 2. This engine was shown driving textile machinery at the London Exhibition of 1851, and "attracted no little attention" according to Reuleaux. But he also said: "In the form before us, however, the machine is in the highest degree impractical, in no respect as advantageous as the common direct-acting engine."

Left: Side view of the second Simpson & Shipton engine, with the cylinder part-sectioned. Note the heavy flywheel to the left, more than twice as big as the engine.

Left: Section of the second Simpson & Shipton engine. g is the eccentic driving the valvegear. This simplified section does not make the modus operandi any clearer. (to me, anyway) From "The Steam Engine- Its History & Mechanism" by Robert Scott Burn,

Left: End view of the second Simpson & Shipton engine. The slide valves are driven by the eccentric, via a bellcrank on layshaft Z at the left. Note once again that enormous flywheel; did this engine have particularily variable torque in its cycle? It is very clear is that the number of moving parts is not much less than a conventional steam engine.

Left: Animation of the Simpson & Shipton rotary steam engine. Here it can be seen clearly how the axle of the rotor slides back and forth in the slot on the side of the casing, allowing rotation. It is also very clear that there is a line contact between the rotor and the inside of the casing, one that looks particularly difficult to seal. This superb animation is kindly provided by Bill Todd

The Simpson & Shipton engine is one of the few engines for which detailed drawings exist. And even better, you can build your own!

Left: A model of Simpson & Shipton's second engine. Parts to build this model are sold by pollymodelengineering.co.uk, who very kindly provided this image. See the model here They also sell parts for several other unusual steam engines, such as Murray's Hypocycloidal Engine

THE NAPIER ROTARY ENGINE: 1851

Left: The Napier Rotary Engine: 1851 "An eccentric mounted cylinder on a shaft concentric with the shell. There are two sliding wings in slots in the shell, held to their bearings by springs or cam wheels on the shaft outside with connecting bars. There are two pair of ports." In the diagram, it appears that on the right side of the two sliding doors, the upper pipe is the steam inlet and the lower is the exhaust. However, in the left part of the casing there appears to be direct communication between the steam inlet and outlet ports, which would hardly be conducive to economy. This could be prevented by the addition of valve gear to cut off the steam admission on the non-working side of the casing, and probably this is what Napier intended. If so, it would detract from the beautiful simplicity that most rotary engine designers aimed for. Diagram from "Mechanical Movements, Devices and Appliances" Hiscox, 1899