This is the Roberts Motor Company. of Mr. E.M. Roberts. Its factory was located in Ohio

-They built 4 and 6-cylinder, 2-stroke engines.

-Roberts started building engines around 1910 and continued until 1925 when the last model was made.

“Roberts ad”

-In 1910, the 40-52hp, in-line, four-cylinder engine came out. It was water cooled.

-It rotated at 1,400 maximum rpm with a small flywheel and a displacement of 318 cu. in.

-It was installed on Benoist and Ecker seaplanes.

-The Roberts model 4X engine increased the power up to 50-60 HP. It also had four water-cooled, in-line cylinders.

“Roberts 4-cylinder with dual ignition”

-In 1911 appears the 6-cylinder, in-line, model 6X engine that gave 75 HP.

“Roberts 6X”

-We can see the manifoldless ports in the 6X model. A 200-hp, 1,195-cubic-inch 6XX model would follow.

“Roberts 6-cylinder with exhaust manifolds”

-Roberts made a fairly wide range of two-stroke aircraft engines, but its background was as a builder of speed canoe engines.

-Mr. Roberts' aeronautical vocation comes from having been a collaborator in this field with Hiram Maxim around 1894.

-Because of its proximity to Benoist Sandusky, in the same town, Roberts engines were preferably used on these devices.

-The 6Z engine, from 1925, gave 100 HP. It is curious that the ad mentions "Ask the Aviator" in terms of satisfaction given by Roberts engines.

-Below we show a new photograph of the 50 HP Roberts 4X in which more construction details can be seen.

-Highlighting the use of super light magnesium-based alloys such as Aerolight and Magnalium.

“Roberts 4X”

From Appendix 6: Contemporaries of the Elbridge engines and similar in form and conception, they were also intended for stationary, automobile, marine and finally aviation use.

“Roberts generic ad”

“Marine and aviation engines”

“Airplane with 4X and 6-cylinder marine engine”

“Another aviation and another marine”

“Roberts engine with propeller”

-More information in the main text.

-At the 2010 AEHS Convention, member Larry Rinek took some pictures of the Roberts model I-4, with a possible “mini-turbo” that we bring to this appendix due to its interest.

“Two pictures of a Roberts I-4 engine at the Smithsonian”

From Appendix 10: A nice picture of the Roberts 4-cylinder, two-stroke engine. It can be clearly seen that it is a modular engine. There is a 6-cylinder version, the 6X in two versions: 60 HP and a larger one, the 6XX with 125 HP.

-With a puller propeller.

“Nice illustration of the Roberts engine”

-Two-stroke aircraft engines built by Roberts Motors Co.

“The weight of the 4 cylinder is 170 lbs. for 40 HP"

"The previous engine in a structure and breaking in"

-These engines were designed by E. W. Roberts (M.E.). On all these engines we clearly see the quite generous exhaust ports.

“The previous engine, more developed, but with 165 lbs of weight”

-The propeller and radiator were supplied with the engine. The power was given at 1,000/1,200 rpm -which seems little-.

“Roberts 4-cylinder engine cross-sections”

-The 6-cylinder engines seem to be a development of the 4-cylinders due to the fact that they add two more power elements.

There are the following models, the 75 HP weighing 245 lbs., the 100 HP weighing 340 lbs. and the 200 HP with 690 lbs of weight, Rotating at 2,000 rpm.

“The 100 HP engine, from both sides”

-We see that on this engine the exhaust pipes are channeled towards three outlets which, by means of elongated tubes outside the plane, will avoid the contamination produced by other engines with single ports. Remember that they use a mixture of gasoline and oil and the unburnt part dirties.

“Roberts 75 HP, 6-cylinder, rear view”

“75 HP Roberts engine, right-side view”

-Here we can clearly see that the 75 HP has ports and no exhaust channeling.

-In the rear-view illustration there are gears for accessories such as water and gasoline pumps on the right, while the magneto is on the left, clearly visible. It is therefore an engine with simple ignition, like the previous ones.