Motorenfabrik Oberursel

Motorenfabrik Oberursel A.G.

Company type	Aktiengesellschaft
Industry	Engine manufacturing
Predecessor	Willy Seck & Co.
Founded	1892
Founder	Willy Seck
Fate	Merged with Deutz AG in 1921; later merged with Humboldt-Deutz Motoren in 1930 and Klöcknerwerke AG in 1938; currently part of Rolls-Royce Deutschland
Successor	Klöckner-Humboldt-Deutz Oberursel facility; Rolls-Royce Deutschland
Headquarters	Oberursel (Taunus) , Germany
Area served	Worldwide
Key people	Dr. Ing. Adolf Schnürle (WWII research leader)
Products	Engines for automobiles, locomotives, and aircraft; jet engines (Rolls-Royce BR700 series)
Owner	Rolls-Royce Deutschland
Parent	Rolls-Royce Deutschland
Website	www.rolls-royce.com

Motorenfabrik Oberursel A.G. was a German enterprise specializing in the production of engines for automobiles, locomotives, and aircraft, based in Oberursel (Taunus), close to Frankfurt (Main), Germany. Throughout World War I, it provided a prominent 100 hp-class rotary engine widely utilized in various early-war fighter aircraft models. In 1921, the firm merged with Deutz AG, followed by a further consolidation in 1930 with Humboldt-Deutz Motoren, and ultimately in 1938 with Klöcknerwerke AG. From that point, it operated under the name Klöckner-Humboldt-Deutz Oberursel facility, gaining recognition primarily for manufacturing locomotive engines. Currently, it is integrated into Rolls-Royce Deutschland and manufactures a single line of their jet engines.

The Oberursel plant is reputed to be the world's oldest continuously operating aircraft engine manufacturing site.

Early years

The origins of the company trace back to 1891 when Willy Seck developed an innovative gasoline fuel injection system and created a compact one-cylinder stationary engine delivering approximately 4 hp, which he named the Gnom. The following year, he established Willy Seck & Co. to market this design, which quickly gained international acclaim. Subsequent enhancements increased the engine's power output; however, in 1897 shareholders declined Seck’s proposal to develop a Gnom-powered automobile, prompting his departure from the business. The enterprise was restructured as Motorenfabrik Oberursel in 1898 and had produced around 2,000 engines by 1900.

That same year, the company licensed the Seguin brothers in Lyon to manufacture the Gnom engine in France. Marketed under the French designation Gnome, this engine achieved great success, leading the French manufacturer to adopt the name for their company. In 1908, they introduced a rotary adaptation of the original Gnome design known as the Gnome Omega aircraft engine, followed by a series of larger variants derived from this fundamental concept. These innovative Gnome rotary engines gained widespread popularity, powering numerous early record-setting aircraft.

In 1913, Motorenfabrik Oberursel acquired licenses for both the French Gnome engine design and the comparable Le Rhône 9C. They produced these as two separate series: the U-series representing the Gnomes and the UR-series corresponding to the Le Rhônes.

Among their productions was the Gnome Lambda, a seven-cylinder rotary engine rated at 80 hp, manufactured by Oberursel as the Oberursel U.0 Umlaufmotor (the German term for rotary engine). This model served as their inaugural powerplant for German military aircraft and powered early versions of the renowned Fokker Eindecker fighter, specifically the Fokker E.I.

World War I

At the onset of World War I, the Oberursel U.I, delivering 100 hp and a licensed reproduction of the Gnome Delta 100 hp (75 kW) rotary engine, featured the highest power-to-weight ratio among German engines. This powerplant became the primary choice for many early German fighter aircraft, including the Fokker and Pfalz E-series monoplanes.

Oberursel also produced a licensed version of Gnome’s 14-cylinder Double Lambda two-row rotary engine. Known in Germany as the U.III, this 160 hp (120 kW) unit was complex to manufacture and suffered from rapid wear during use. It powered models such as the Fokker E.IV and D.III.

The subsequent noteworthy engine was the 110 hp Oberursel UR.II, a licensed copy of the Le Rhône 9J with identical power output. In 1916, Fokker acquired Oberursel to secure a steady supply of UR.II engines, a strategic move since Fokker favored rotary engines and faced limited availability of the Mercedes D.III. The UR.II powered aircraft like the Fokker Dr.I and Fokker D.VI.

By 1917, however, the UR.II had become outdated due to its limited power and subpar high-altitude performance. Although an 11-cylinder variant named UR.III was developed, it never saw combat deployment. By 1918, rotary engines were largely dismissed by both the Idflieg and pilots alike. The scarcity of castor oil and reliance on inferior mineral oil substitutes such as "Voltol" drastically shortened engine lifespan and reliability. Nonetheless, during summer 1918, the UR.II was fitted to the Fokker D.VIII. Thanks to its lightweight design and streamlined aerodynamics, the D.VIII achieved remarkable results despite using an outdated powerplant.

Following World War I, in 1921 Oberursel was acquired by Gasmotorenfabrik Deutz, another gasoline engine manufacturer that transferred its two-stroke diesel production to Oberursel’s facilities. In 1930, a merger with Humboldt-Deutz occurred but resulted in only one product line continuing. The factory ceased operations during the Great Depression in 1932 but resumed limited production in 1934.

World War II

During World War II in 1940, all diesel engine research was centralized at Oberursel under Dr. Ing. Adolf Schnürle’s leadership, focusing on developing larger and more sophisticated aircraft engines. This effort produced engines such as the Klöckner-Humboldt-Deutz DZ 700, an 8-cylinder radial engine, the DZ 710, a 16-cylinder boxer engine, and the DZ 720, a 32-cylinder H-block configuration created by pairing two DZ 710 units. Additionally, the company manufactured approximately 12,500 units of the Wehrmacht’s fully tracked artillery tractor design known as Raupenschlepper Ost. None of these engine designs reached active service before war’s end when US forces occupied the plant.

Post-World War II

In 1946, for a brief period following the war, US military forces utilized the facilities as a repair depot for tanks and trucks.

The factories were returned to Klöckner-Humboldt-Deutz ownership in 1956 and subsequently focused primarily on developing and manufacturing gas turbine technology. Over the next two decades, they produced various models, often under licensing agreements with other companies. In 1980, the entity was renamed KHD Luftfahrttechnik GmbH.

In 1990, ownership transferred to what was then known as BMW Rolls-Royce. The new management chose to leverage Oberursel’s facilities to develop a completely modern engine aimed at smaller aviation markets, initiating work on the Rolls-Royce BR700 series in 1991. These engines have since powered multiple aircraft types including those from Bombardier, as well as the Gulfstream V and Boeing 717.

Engines

Oberursel U.0

A licensed version of the Gnome 7 Lambda, this seven-cylinder rotary engine produced between 68 and 80 hp (51 to 59 kW).

Oberursel U.I

Featuring nine cylinders and delivering 100 hp (75 kW), this model had a total displacement of 16.3 litres (990 cu in) with dimensions of 124 mm × 150 mm (4.9 in × 5.9 in).

Oberursel U.III

A replication of the Gnome Double Lambda, this two-row rotary engine included 14 cylinders, generated 160 hp (120 kW), and had a displacement of 23.67 litres (1,444 cu in) with a stroke length of 140 mm (5.5 in).

Oberursel Ur.II

This engine was a copy of the Le Rhone 9J, a nine-cylinder rotary producing 110 hp (82 kW).

Oberursel Ur.III

An advancement over the Ur.II, it featured 11 cylinders and delivered 145 hp (108 kW) with a total displacement of 18.42 litres (1,124 cu in).

Oberursel 200 hp 18-cylinder rotary

Engine specifications include dimensions of 124 mm × 150 mm (4.9 in × 5.9 in).

Oberursel 240 hp V-8

Another notable engine in the lineup.

External links

• History of Motorenfabrik Oberursel – www.rolls-royce.com (in German)
• Footage showing a test run of a contemporary Oberursel UR.II replica The Vintage Aviator website

1. REDIRECT Template:20th Century Press Archives