James Atkinson built and patented this machine in 1886. He didn’t want to change the world by constructing this engine, but at that time, N.A. Otto had already claimed the most patents referring to four stroke engines.
So it’s a special detail of this machine, that the cams are not – as usually – placed on a separate camshaft, geared with a 1:2 speed: Atkinson placed the cams directly on the crankshaft; his machine has no camshaft at all. –
But his engine really runs in a four stroke rhythm:
This is achieved by a motion link and the main rod connector interlocked with the crankshaft.
( …Please excuse my bad translation, I hope you understand my rudimentary explanation attempts! )
The centres of rotation are positioned in this way, that the engine has 4 strokes, but each with a different length: In relation to the outlet stroke , which is the longest stroke with full length, the aspiration stroke has 1/3, the condensing stroke ¼, and the working stroke 2/3 of full stroke length. Thereby the expansion can be used more efficiently and the fuel consumption is reducedto its minimum rate. -

Video Atkinson


Bore : 29 mm
Stroke: 44, 19, 11, 37 mm
Height: 195 mm
Diameter of
Band wheels: 197 mm


Technical description:
Liquid-cooled four stroke engine; the model is no full scale decrease, because otherwise the engine parts would have been built up in a nearly closed case. The outfit of the outer shape, however, is corresponding to the original engine. The Atkinson engine can either be run with gasoline or propane. -

Casting set with CAD drawing, piston rings and insert springs (valves): 348,00 €
Finished engine: 1400,00