Roberts Motor Company was an American manufacturer of lightweight, high-speed engines for aircraft, boats, stationary, and automobiles, based in Ohio during the early 1900s.Beverly Rae Kimes, Henry Austin Clark Jr.: Standard catalog of American Cars. Krause Publications, Iola 1989, p. 1255.George Nicholas Georgano (ed.): The Beaulieu Encyclopedia of the Automobile. band 3 : P–Z. Fitzroy Dearborn Publishers, Chicago 2001, ISBN 1-57958-293-1, p. 1342.

Company history

1905 - 1914 (Roberts Motor Company) The company originated in 1905 in Clyde and moved to Sandusky, both in Ohio, in 1908. It was cofounded by Benjamin Leacock "B. L." Roberts and his brother, Edmund Willson "E. W." Roberts, a mechanical engineer, engine designer, inventor, patent agent, and prolific author of gas engineering books."Engine Designer Succumbs; After Distinguished Career; Son of Civil War Surgeon". The Cincinnati Enquirer. March 14, 1947. p. 14. Retrieved July 7, 2025. E. W. Roberts was known for being chief assistant to Hiram Maxim in his 1894 'flying machine' project in Kent, England and a designer of a large wind tunnel for Maxim.Underwood, Paul (July 18, 1942). "Engineer Recalls Experiment with Steam-Powered Plane, Once Hiram Maxim Helper". The Cincinnati Enquirer. Cincinnati, OH. p. 16. Retrieved July 6, 2025.Knue, Paul F., ed. (October 27, 1987). "Bicentennial Capsule: Prince Hill Inventor's Ideas Soared". The Cincinnati Post. p. 10. Retrieved July 7, 2025.Angle, Glenn D. (1921). Airplane Engine Encyclopedia. Dayton, Ohio: The Otterbein Press. pg. 427 - 429 Prior to founding his company, Edmund Roberts was chief engineer at the Elmore Manufacturing Company. He was one of the top leading gas engine designers from the 1900-1915 period.

According to the Smithsonian Institution, which has a few Roberts engines in its collection, the Roberts Motor Company produced more engines during this pre-WWI period than Hall-Scott and Curtiss Motor Company put together.

1914 - 1917 (Roberts Motor Manufacturing Company) Roberts left the company in 1914 when the company faced financial trouble, and became editor of The Gas Engine magazine before starting a private consulting practice for engine design."Roberts, Edmund Willson". Rutherford B. Hayes Presidential Library & Museums. Retrieved June 28, 2025. According to an Early Bird of Aviation from Sandusky, Reinhardt Ausmus, "the company spent more in national advertizing than they took in on sales."Reinhardt, Ausmus (1969). "Reinhardt Ausmus Speech on Aviation in Sandusky". ohiomemory.org. p. 7. Archived from the original on 2022-06-21. Retrieved 2025-07-06. William H. Burke took over as president and the company produced several automobiles in 1915, powered with the company's engines. The name of the company also changed to Roberts Motor Manufacturing Company, and not much was heard from the company after 1915.

1918 - 1935 (Roberts Motors) The Roberts Motor Manufacturing Company ceased operations upon the tragic death of Thomas Benoist in 1918, who had been affiliated with the company. Earl Johnston, who had taken over as superintendent in 1915, purchased the company in 1918. Subsequently, the company shifted its focus to engines for boats rather than aircraft, and began to operate under the name, Roberts Motors. In 1935, the company became a new incorporation with a new name, the Johnston Motor Co."Sandusky Listed With Pioneers in Aviation". Sandusky Register. November 24, 1947. p. 82. Retrieved July 8, 2025.Harmon, Mel (January 6, 1967). "Flying Very Popular Here; Pioneers Started in 1909". Sandusky Register. p. 8. Retrieved July 7, 2025.

Products

Aircraft engines Model nameConfigurationPowerBore x StrokeWeightYearRoberts Model 4-XI450 hp @ 1400 RPM4.5"x5"170 lbs.1911-1912Roberts Model 4-XI465 hp @ 1200 RPM5"x5"230 lbs.1912-1916Roberts Model 6-XI675 hp @ 1200 RPM4.5"x5"243 lbs.1911-1912Roberts Model 6-XI6100 hp @ 1200 RPM5"x5"330-350 lbs.1911-1917Roberts Model 6-XI6100 hp @ 1200 RPM5"x5.5"368 lbs.1916Roberts Model 6-XXI6125 hp @ 1100 RPM5.5"x6"390 lbs.1912Roberts Model 6-XXI6165 hp @ 1200 RPM6"x6"650 lbs.1917Roberts Model 6-XXI6200 hp @ 1400 RPM6.5"x6"690 lbs.Roberts Model E-12V12350 hp @ 1200 RPM6"x6.5"990 lbs.1916-1917

Boat engines Model nameConfigurationPowerBore x StrokeWeightYearRoberts Model AI125 hp @ 950 RPM - 35 hp @ 1450 RPM4"x5"1925Roberts Model HI11.5 hp @ 750 RPM - 2 hp @ 900 RPM3"x2.5"50 lbs.1909Roberts Model 2-HI28 hp @ 1000 RPM3.75"x4"163 lbs.1919-1921Roberts Model JI48 - 16 hp3.75"x4"1922-1926Roberts Model OI12.5 @ 750 RPM - 3 hp @ 900 RPM3.5"x3"95-100 lbs.1909Roberts Model 2-OI26 hp @ 900 RPM3.5"x3"128-135 lbs.1911Roberts Model 3-PI330 hpRoberts Model 4-PI440 hp @ 1000 RPM4.5"x5"525 lbs.Roberts Model 6-PI660 hpRoberts Model RI116 - 20 hp3.78"x4"1925Roberts Model SI18 hp @ 300 RPM - 10 hp @ 400 RPM6"x6.5"300 lbs.1917Roberts Model MI120 hpRoberts Model 2-MI210 hp @ 900 RPM4"x_240 lbs.Roberts Model 3-MI315 hp @ 900 RPM293 lbs.Roberts Model 4-MI420 hp @ 900 RPM450 lbs.Roberts Model 6-Z100 hp1925

Automobile engines Model namePowerBore x StrokeWeightYearNotesRoberts 6-X60 hp4.5"x5"700 lbs.1912-1915racing engine

Other ProductSpecificationsWeightSignificanceYearEngine-compressor unit30 CFM @ 100 PSI40 lbs.Progenitor portable air compressor1910

Significance The Roberts engines were designed to be as lightweight as possible by using Germany-imported aluminum and magnesium alloys for the cylinders, pistons, and crankshaft, an alloy which the company called 'aerolite,' as well as a hollow crankshaft. All the Roberts engines operated on a two-stroke cycle for parts reduction and thus lighter weight, though four-stroke cycle engines were introduced after WWI. Despite being two-cycle, they were known for never backfiring due to a cellular by-pass in the crankcase designed by E. W. Roberts.

Some of the Roberts engines were used by prominent exhibition pilots, including Tom Benoist, Willie Haupt, Joseph Richter, Clifton Hadley, and Weldon Cooke.Hankins, Hobart Bishop (December 1911). "The Latest Engine Product of E. W. Roberts". Fly. The National Aeronautics Monthly. 4 (2). Philadelphia, PA: Aero Publishing Co.: 20–22 – via Internet Archive. Engine modelPowerRoberts engines in early aviation historyDateRoberts 4-X50 hpPowered one of the first Bleroit XI aircraft built in the United States.1911Roberts 4-X50 hpPowered the aircraft built by the first South Dakotan pilot, Saxe Pitts Gantz.March 9, 1911Roberts 6-X50 hpPowered the Ecker Flying Boat which is on display at the Smithsonian Institution.1911-1912Roberts 6-X75 hpPowered a Benoist biplane used in the first parachute jump from an aircraft, performed by Captain Bert Berry and piloted by Anthony Jannus in St. Louis, Missouri.Mason, Paul B. (September 16, 1945). "Along Aviation Lanes". The Cincinnati Enquirer. p. 13. Retrieved July 7, 2025.March 12, 1912Roberts 6-X75 hpPowered the Benoist Type XIV during the first commercial passenger airplane flight, flown by Jannus, in St. Petersburg, Florida.January 1, 1914

Gallery

References

External links

Roberts Motor Company Aircraft Engines Roberts 6x Aeroplane Engine Smithsonian Collection of Roberts Aircraft Engines Ohio museum: E. W. Roberts collection Ohio museum: Reinhardt Ausmus collection - Roberts Motor Company catalogs