The Duthiel-Chalmers engines were early French designs, in which the cylinders were all arranged horizontally.
Except for the first 20-h.p. air-cooled two-cylinder model used in Santos-Dumont’s Demoiselle, all of the later engines were water-cooled.

A series of Duthiel-Chalmers horizontal engines of two, four, and six cylinders and rated at 20, 40 and 60 h.p., respectively, were built with 125 mm. (4.92 in.) bore and 120 mm. (4.72 in.) stroke. The 20-h.p. engine, of 179.52 cu. in. total displacement, was said to weigh 165 lbs., or 8.25 lbs. per rated h.p. The four-cylinder 40-h.p. model had 359.04 cu. in. total displacement and weighed 264 lbs., or 6.6 lbs. per rated h.p. The six-cylinder engine of 538.56 cu. in. total displacement weighed 374 lbs., or 6.23 lbs. per rated h.p.

An interesting feature of these engines was the two spark plugs located in a valve. Either of the spark plugs could be removed while the engine was running by turning the internal tapered plug.