Curtiss OX-5 - WikiHQ

The Curtiss OX-5 was an early V8 American liquid-cooled aircraft engine built by Curtiss. It was the first American-designed aircraft engine to enter mass production, although it was considered obsolete when it did so in 1917. It nevertheless found widespread use on a number of aircraft, perhaps the most famous being the JN-4 "Jenny". Some 12,600 units were built through early 1919. The wide availability of the engine in the surplus market made it common until the 1930s, although it was considered unreliable for most of its service life.

Design and development

The OX-5 was the last in a series of Glenn Curtiss designed V engines, which started as a series of air-cooled V-twins for motorcycles in 1902. A modified version of one of these early designs was sold as an aircraft engine in 1906, and from then on the company's primary market was aircraft. The basic design had slowly expanded by adding additional cylinders until they reached the V8 in 1906. They also started enlarging the cylinders as well, but this led to cooling problems that required the introduction of liquid cooling in 1908. These early engines used a flathead valve arrangement, which eventually gave way to a cross-flow cylinder with overhead valves in 1909, leading to improved volumetric efficiency. By this point engine design was a team effort; the team included Charles M. Manly, whose earlier Manly–Balzer engine had held the power-to-weight ratio record for 16 years. Curtiss continued the development of their V8 engines with demand for higher power outputs being largely driven by the US Navy’s requirement for seaplanes. By 1912 Curtiss V8’s were developing 75 hp and were known as the Curtiss Model O. The Curtiss O was further developed into the 90 hp Curtiss OX. OX series production began in 1913. The OX-5 was built between 1915 and 1919 and was by far the most popular OX variant.

thumb|Curtiss OX-5 at Canada Aviation Museum

Like most engines of the era, the OX-5's high-temperature areas were built mostly of cast iron, using individual cylinders bolted to a single aluminum crankcase, wrapped in a cooling jacket made of a nickel-copper alloy. Later versions used a brazed-on steel jacket instead. Cylinder heads were also attached to the crankcase, using X-shaped tie-downs on the top of the head attached to the block via four long bolts. Fuel was carbureted near the rear of the engine, then piped to the cylinders via two T-shaped pipes, the cylinders being arranged so the intake ports of any two in a bank were near each other. The cylinders had one intake and one exhaust valve, the exhaust valve operated by a pushrod from a camshaft running between the banks and inlet valve operated by a pull rod/tube working from the same camshaft. This arrangement caused the outer exhaust valves to have a rather long rocker arm. The push/pullrods were arranged one inside the other, the exhaust valve rod being on the inside and the intake valve rod a tube around it. The pistons were cast aluminum. The primary reason for its popularity was its low cost after the war, with almost-new examples selling as low as $20. It was often used in boats as well as in aircraft.

Reliability

The engine was considered unreliable,

A Curtis OX-5 engine, gifted by Wesley Talent, is on display at the Udvar-Hazy center.

Specifications (OX-5)

right|thumb|Top overhead view of OX-5 at Lone Star Flight Museum