1904-05 Wright Engines

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he 1903 Flyer engine was damaged beyond repair when the wind overturned the Flyer after the fourth flight on 17 December 1903. At the beginning of 1904, the Wrights built two similar motors to continue their test flights, referred to as Wright Engines No. 2 and No. 3. Each had four horizontal cylinders, but No. 2 was slightly larger than No. 3, displacing 214 cubic inches (3.5 liters) to No. 3's 201 cubic inches (3.29 liters).  No. 2 was also slightly heavier, weighing 240 pounds (108.8 kilograms) with water and oil. In both engines the volume of water surrounding the cylinders was increased for better cooling. Other improvements included a geared fuel pump, a better oil pump, and a better distribution of lubrication. There was also a compression release mechanism to aid starting and to allow the pilot to quickly cut power. This unique mechanism became a standard feature on Wright engines for years.

These engines evolved more than they were planned. According to Charles Taylor, "We didn't make any drawings. One of us would sketch out the part we were talking about on a piece of scrap paper...." Orville Wright's diary of 1904 has the entry, "Took old [1903] engine apart to get measurements for making new engine."

Engine No. 2 was used to power the 1904 Wright Flyer II and the1905 Wright Flyer III. When first built, it produced 16 horsepower, and this improved as the engine "broke in" and the cylinders smoothed. The Wrights continued to improve it over the next two years and by the time the engine was retired in 1905, the horsepower had increased to 21.

Engine No. 3 was never used on an airplane. Instead, it was used in the shop as a test-bed for engine experiments and a power source for propeller experiments. When the Wrights found something that improved the performance of Engine No. 3, it was often transferred to Engine No. 2. This third motor eventually achieved 25 hp, twice that of the original Wright motor of the same size. It was last run in 1937 at the Henry Ford Museum for the dedication of the restored Wright Cycle Shop and Wright home in Greenfield Village.

Engine No. 2 was cannibalized in 1916 to restore the engine in the 1903 Wright Flyer. In 1946 or 1947, Orville borrowed the crankshaft from Engine No. 3 to restore Engine No. 2 for the 1905 Flyer III as it was being rebuilt. This crankshaft was made new and replaced in Engine No. 3 in 2002. The rebuilt engine No. 2 is displayed on the restored 1905 Flyer III at Carillon Park in Dayton, OH. The restored Engine No. 3 can be seen at the Dayton Engineer's Club.

Specifications for Engine No. 2:

  • Cylinders: 4
  • Stroke: 4 in (10.2 cm)
  • Bore: 4-1/8 in (10.5 cm)
  • Displacement: 214 in3 (3.5 l3)
  • Horsepower:16 to 21
  • Ignition: Make-and-brake powered by low-tension (10-volt) magneto.
  • Weight: 220 lbs (81.6 kg) dry
  • Compression release, fuel injection

Specifications for Engine No. 3:

  • Cylinders: 4
  • Stroke: 4 in (10.2 cm)
  • Bore: 4 in (10.2 cm)
  • Displacement: 201 in3 (3.3 l3)
  • Horsepower:18 to 25
  • Ignition: Make-and-brake powered by low-tension (10-volt) magneto.
  • Weight: 180 lbs (81.6 kg) dry
  • Unique features: Compression release, fuel injection, auxiliary exhaust ports in cylinders.


  • Hobbs, Leonard S. The Wright Brothers' Engines and Their design. Washington, D.C.: Smithsonian Institution Press, 1971, pp 29-33.
  •  McFarland, Marvin W. (ed) The papers of Wilbur and Orville Wright. McGraw-Hill Book Co., New York, 1953, p 1214-1215.
  • Lippincott, Harvey H. Propulsion System of the Wright Brothers. In Wolko, Howard S. (editor), The Wright Flyer, an Engineering Perspective. The Smithsonian Institution Press, 1987, pp 86-87.

[Submitted by Joe W. McDaniel]

Engine No. 2 was used to power the Wright Flyer II in 1904 and the Wright Flyer III in 1905. The restored engine is on display in the Wright Flyer III in Carillon Park, Dayton, Ohio.

Like the original Wright engine, ignition Engine's Nos. 2 and 3 were powered by a low-tension magneto. The magneto was turned by a friction wheel the rubbed against the engine's flywheel.

Engine No. 3 on  display in 1937 at Greenfield Village (part of the Henry Ford Museum in Dearfield, MI). It was run at this time but shut down after it developed a crack in one of the cylinders.

The underside of Engine No. 3. The oval shapes just below the cam shaft are the oil pump and the fuel pump  The fuel pump metered the gasoline as it dripped into the intake port, providing a rudimentary form of fuel injection.

Wright Engine No. 3 on display in the upstairs lobby of the Dayton Engineers Club.

Engine No. 2 in the Wright Flyer III, as seen from the rear.

Engine No. 3 was never used on an airplane, but served as a test bed, providing the Wrights with valuable experience in engine design.

Engine No. 3 with the crank case cover removed. Note the water jacket in completely separate from the crankcase, unlike Engines Nos. 1 and 2. There are auxiliary exhaust ports (small holes) in the cylinder walls between the jacket and the case to allow hot gases to escape. This was one of the many experiments the Wrights conducted with this engine -- they wanted to see if the additional exhaust ports would help keep the engine running cooler. It apparently worked; they incorporated this feature on later engines.

Engine No. 3 was also used for experiments whenever the Wrights needed a source of power. In this 1907 investigation, the Wrights taxied along the Great Miami River on pontoons to see if their propellers and test engine would provide enough thrust to reach take-off speed from the water.

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