Wright Engines and Propellers

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Wright Engines Taking advantage of a recent technological advanced in "precipitate-hardening" aluminum, the Wright were among the first to build internal combustion engines with aluminum cases, saving hundreds of pounds without sacrificing power. Their engines, like their airplanes, developed from finicky experimental devices to commercial power plants renowned for their reliability. The power they delivered grew from 12 horsepower in 1903 to 75 by 1915.

A replica of the 1903 Wright engine their first aircraft motor with the crankcase exposed.

A late model Wright "6-60" six-cylinder engine, circa 1915. This was one of the last engines produced by the Wight Company.
1903 Engine The gasoline engine that powered the first flights on December 17, 1903 delivered 12 hp when it was started, then dropped somewhat when the motor heated up. It was built along a then-standard 4-4-4 design 4 cylinders, each 4 inches (10.2 cm) in diameter with a stroke of 4 inches (10.2 cm). It had no spark plugs; each cylinder had electrical "points" that sparked when they opened. This was called a "make-and-break" ignition. The combined weight of the engine, water, and oil was about 180 hundred pounds (81.6 kilograms).

The 1903 Wright engine was a "horizontal" engine the pistons moved horizontally in the cylinders. There was no carburetor; the Wrights dripped fuel into the intake at the top of the engine.

The 1903 Wright engine installed on the 1903 Wright Flyer. It was a hot-running engine the ignition chamber glowed a dull red after the engine had been running for a few minutes, even with the radiator connected.
1903 Propellers The propellers that drove the 1903 Wright Flyer through the air were the result of careful thought, innovative mathematics, and combative arguing between Orville and Wilbur. In the end, they agreed to treat their props as if they were rotating wings. As such, the props had cambered blades to increase thrust. After several experiments, the Wrights ended up with two slow-turning (350 rpm) props 8.5 feet (2.6 meters) long. Each turned in a different direction. This canceled out the sideways torque generated by the spinning props.

Two views of a 1903 Wright propeller. Note that the blade is cambered it was designed as a wing the camber produces lift in a horizontal direction  The design was remarkably efficient for its day, converting 66% of the mechanical energy used to turn the props into thrust.

The propellers mounted on the 1903 Flyer now on display at the Smithsonian Air & Space Museum.
1904-1905 Engines Upon returning from Kitty Hawk, the Wrights built two horizontal engines. One of these they mounted on their 1904 and 1905 Flyers. The other was an experimental "bench" engine, used to test ideas to improve power, reliability, and cooling. The Wrights would modify the experimental engine to investigate an idea, and then transfer that modification to the airplane engine if it worked. In this way, they eventually boosted the output of their engines to 25 hp.

The 1904 experimental engine, also known as Wright Engine No. 3, is on display at the Dayton Engineer's Club in Dayton, Ohio.

The 1904-05 airplane engine Wright Engine No. 2 mounted on the 1904 Flyer. It was later cannibalized for parts when Orville restored the 1903 Flyer in 1916.
1905-1915 Bent-End Propellers In 1904, the Wrights noticed their propeller blades had a tendency the flex  at flying speed, altering the  angle at which they met the air. This in turn reduced thrust.  At first Will and Orv tried prevent this by increasing the width of the blade, but this worked only partially. They next added "little jokers" triangular extensions   to the trailing edges of the blades so that when the prop flexed at speed, the blades would be at the proper shape and pitch. This did the trick and evolved into a distinctive shape known as the Wright "bent-end" propeller.

Wright propellers evolved through several designs from 1904 to 1905. The end result was the distinctive "bent-end" propeller that revolved between 400 and 500 rpm and was 78% efficient. By comparison, modern propellers are 82-83% efficient.

Bent-end propellers continued to be used on various Wright airplanes that were manufactured through 1915. This particular prop was designed to be used on the 1915 Model K, a large float plane the Wrights built for the U.S. Navy.
1906-1912 Vertical 4-Cylinder Engine In 1906, the Wrights designed a vertical 4-cylinder engine for use on their commercial airplanes. It had individual cylinders that could be disassembled one at a time to make maintenance easier. It also had spark plugs and a high-tension magneto to make the ignition system simpler and more reliable. The first Wright "vertical 4" engine produced 28 horsepower, but later improvements boosted this to nearly 40 hp. In later years, the engine was referred to as the "Wright 4-40" 4 cylinders, 40 hp.

The Wright 4-40 also had a water pump (lower left) to increase cooling.

Wilbur lubricates a Wright vertical 4-cylinder engine in France in 1908. Although more powerful, the engine was actually slightly lighter (180 lbs or 81.6 kg) than the Wrights' original horizontal-4 engines.
1911-1916 Vertical 6-Cylinder Engine As the need for more power and speed grew, the Wrights developed a "straight six" engine six cylinders in a straight line. This wasn't just a stretched 4-40, there were significant improvements in the way the engine operated. This was the first of the Wright engines to employ standard carburetion, giving it a range of speeds at which it could be operated. Both the heads and the cylinders were water-cooled, so it ran much cooler. And for the first time the exhaust was ported away from the engine (and operator) through exhaust tubes. The enlarged and improved engine produced over 60 horsepower and was designated the "Wright 6-60."

The Wright 6-60 was also the first Wright engine in which both the intake and exhaust valves were operated by a camshaft. Previous Wright engines had automatic (spring-operated) intake valves.

The Wright 6-60 was first used on the Wright Model C, an upgraded version of the Model B. It proved to be too much engine for the airplane, pushing it too fast. But later Wright airplanes with stronger aerodynamic airframes particularly Models F, G, and H seemed to grow into the engine.

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