The well known builders L.Dutheil y R. Chalmers, who were building motorcycles for a long time, built gasoline engines of the finned air-cooled type.

There is the air-cooled 8 CV (1908-1909) with two horizontally-opposed cylinders that only weighed 25 kg.

It was used in the USA by Mathew Sellers on his ultra-light quadriplane.

Other information says that the engine gave 20 CV with the same characteristics. The truth is that the aerodyno weighed 110 lbs.

“Dutheil et Chalmers”

The air-cooled 20 CV, also known as the 18-20 CV at 1,500 rpm, has two pistons of 120 mm of diameter and 120 mm of stroke. It had a curb weight of 65 kg.

-This engine we see in its original packaging together with its propeller. This is the information that says it is the original Sellers engine between 1908 and 1913.

“20 CV image”

-The method of the 20 CV cylinder lubrication by air is interesting.

-We can see the drop by drop lubricators that affect the cylinder walls.

"Dutheil et Chalmers 18 CV"

-It was the engine that was used during the first Santos Dumont flights with the Demoiselle between 1907 and 1908.

-On the airplane no 19, on November 17, tests were carried out with the same water-cooled 20 CV engine.

"20 CV, water" (PiP)

-The water-cooled 20 CV seen from the rear on the same aircraft.

-It is the one that was mounted on Santos Dumont's Demoiselle XX and other aircraft.

"25 CV, front view"

-From the water-cooled 20-25 CV 2-, 4-, and 6-cylinder versions were made with powers between 25 and 100 CV.

-It is known that there were two series of Dutheil et Chalmers engines, those of type A (at 1200 rpm) with a single crankshaft in the center and those of type B (at 1000 rpm) where the cylinders were opposed by the cylinder heads, which gave an engine with two crankshafts, rotating in opposite directions for two-propeller aircraft. We do not have any illustration of this type of engine, for now.

"35 CV, water"

-The engine that gave 35-37 CV at 1,000 rpm was liquid cooled, weighed about 200 pounds, and was installed on the Bleriot XI among others.

-The four-cylinder engines were not so well known or famous because the airplanes that used them did not do the exploits of the previous ones.

-That is the case of Bonnett-Labranche 4, Dutheil et Chalmers-Farman, Pischoff and Koechlin, etc.

"Dutheil et Chalmers, 4-cylinder"

-It is not a photograph of the 4-cylinder, but a drawing.

-We transcribe a part of the found text: "It is also worth mentioning the excellent hemispherical combustion chamber, which suppresses all the space that is harmful to the mixture-explosion performance".

-The six-cylinder, from which we neither have graphic information, gave 60 CV and 72 CV. They were from 1910 and 1912.

-The 60 CV had 524 cu. in. of displacement.

-In 1920, they continued with 4-cylinder engines giving 75, 97 and 100 CV. All of them were water cooled.

-The 75 CV and 100 CV had both the same displacement of 699 cu. in.

-The 97 HP however, had 898 cu. in. of displacement with its four cylinders.

-Finally, we bring here a different and hardly known Dutheil et Chalmers.

-On the 24 CV, twin-cylinder engine, it is observed that it does not have classic valves on the head, but a mechanically operated rotary valve.

"Rotary valves"

From Appendix 6: Around 1910, L. Dutheil and R. Chalmers built a 20 CV model in their Paris company. It was similar to the one used by Santos Dumont on the Demoiselle, but this time it was air-cooled.

"Dutheil et Chalmers at the Smithsonian museum"

-Interestingly, like other old engines at this Museum, magneto, carburetor, intake manifold, and spark plug wires are missing.

-However, the 20/25 CV water-cooled one on the demoiselle exposed on its own plane at the Paris Air Museum, is splendid and complete, as we see below.

"Dutheil et Chalmers in París"

-The picture below shows the Dutheil et Chalmers engine presented at the London Olympia Air Show in 1909.

-As it is mentioned in the main text, they made 2-, 4-, and 6-cylinder engines.

-The engine shown below is the one with six horizontally-opposed cylinders.

"Dutheil et Chalmers with 6 cylinders"

-And now we show the horizontally-opposed cylinder engine presented at the 1909 Paris Air Show with its original architecture that is similar to the Italian SPA (or vice versa).

-Actually ir was the Eole built by Dutheil et Chalmers. There was the 4-cylinder 40 CV and the 8-cylinder 100 CV.

"Dutheil et Chalmers, 8-cylinder, 100CV"

From Appendix 9: Schematic diagram for the engine that appears in the main text mounted on an airplane that has a propeller with shovel-blades.

"Dutheil & Chalmers boxer"

-Presentation of some Dutheil et Chalmers engine images received from the south of France. it is the water-cooled, horizontally-opposed, 4 cylinder boxer from 1909. It gave 40 CV.

"Dutheil et Chalmers' 4-cylinder boxer"

"desaxe cranks"

From Appendix 10: New illustrations taken from the German Flugsport magazine prior to WWII.

“Three 4-cylinder boxer views”

-And a group of two engines joined by combustion chambers, with their own propeller each.

"Two engines linked by combustion chambers"

-There also is a 2-cylinder V engine attributed to Dutheil et Chalmers.

“The recent found 2V engine of this brand” (PiP-Flu)

-Dutheil et Chalmers engine on Santos Dumont's Demoiselle at the Air and Space Museum in Paris.

“Dutheil et Chalmers, 35 CV at the MAE"