The Atkinson Cycle Engine.

Opened: 30 Sept 2008
Updated 13 Oct 2008
Another drawing of 'Cycle' engine added

The Atkinson engine shown here was an extremely ingenious design which not only successfully evaded the stranglehold of the Otto patents, but also promised increased efficiency because it could give greater expansion of the combustion gases. The piston was not driven directly from the crankshaft, but via a mechanical linkage which made the expansion stroke longer than the compression stroke.
James Atkinson called this the "Cycle" engine to distinguish it from some other ingenious and unconventional engines he had developed. Atkinson was born in 1846 near Manchester, into a family of engineers. He was originally concerned with steam engines and ships, but by 1879 his attention had obviously turned to internal combustion, for in that year he took out a patent for a hot-tube igniter. In 1883 the British Gas Engine and Engineering Company of London was set up to build 2-stroke engines; Atkinson was the managing director.

Left: The Atkinson Cycle engine patent: 1887.
The connecting rod E drives the piston indirectly via the links E and C, the kinematics being such that a complete four-stroke cycle is completed in one revolution of the crankshaft; it was this feature that got round the Otto patents.
The exhaust expansion stroke was 1.78 times longer than the intake stroke.
The British Gas Engine company built more than a thousand of these engines between 1886 and 1893, so it has to be called a success.
From US Patent 367,496 of 2nd Aug 1906

There is quite a good Wikipedia article on the Atkinson cycle though it includes some rather speculative stuff about rotary Atkinson engines. There seems to be no reason why a rotary Atkinson engine should be any more successful than any other sort of rotary engine.

Left: The Atkinson engine in action.
Note how the exhaust stroke is made longer when the swinging link is in the top position, and the lower lip of the cylinder has to be cut away to accomodate the connecting rod.

Another fine animation by Bill Todd

Left: An Atkinson engine.
This one was built by Manlove, Alliot & Co of Nottingham, who built them from 1889 to 1892.
(This company later became known as Manlove, Alliot & Fryer. It was founded by Edward Manlove and Alexander Alliott in 1837; their Bloomsgrove Works were in Ilkeston Road, Nottingham. This versatile firm also made steam trams, laundry machinery, vacuum pumps, and centrifuges for purifying palm-oil. They were still going in 1949, but I have not been able to find out if they still exist today) They took out a US patent in 1969.
This version of the engine has the crankshaft above the swinging link. Note the cam-operated push-rods to work the valves. The hot-tube ignition can be seen at the extreme bottom, with the rod that opens communication to the cylinder at the appropriate time.

Internal F

Left: Layout of Atkinson engine with the crankshaft above the swinging link.
This gives a horizontal cylinder, rather than an angled one, which may have been more convenient. Note the patht traced out by the connecting-rod bearing.
Internal F