Powering the Aerodrome
Anatomy of an Ultralight Propulsion System
Source: Langley Memoir on Mechanical Flight
Background Image: National Air & Space Museum Archives
Aerodrome No. 5’s propulsion system consisted of four major components: the aeolipile, the boiler, the engine, and the propellers.
AEOLIPILE
The aeolipile was, in essence, a pressurized gasoline torch. It started with a copper air chamber that was charged with compressed air before each flight. The air was connected to a gas reservoir by a copper pipe, which pressurized the gasoline in the reservoir. The gas reservoir contained enough gasoline for a total running time of two minutes and thirty seconds. Flow of gasoline from the reservoir was controlled by a needle valve at the bottom of the copper vessel. Another copper pipe delivered gas to an evaporative coil, which converted liquid gasoline into gas vapor. The gas vapor was ignited at the burner, sending super-heated exhaust through the boiler and out the exhaust smokestack.
BOILER
The aerodrome’s boiler system consisted of a separator, a pump, copper coils, a mica heat shield, and copper tubing. The separator was a copper vessel that served as both the water reservoir and steam drum. Water within the bottom of the separator was fed into a mechanical pump located below the separator. The pump, which was powered by the engine shaft, pumped water into the copper coils of the boiler, where it was superheated into steam by the burner. Steam exiting the boiler reentered the separator. Copper pipes leading from the top of the separator fed the piston cylinder at the front of the engine and a pressure gauge. The boiler was capable of producing 130 lbs of steam pressure after running the burner for 1 minute.
ENGINE
Unlike modern internal combustion engines, Aerodrome No. 5’s combustion system (the aeolipile) occurred externally from the engine. The engine itself consisted of a steam cylinder, piston, crankshaft and a bevel gear. Pressurized steam arrived at the cylinder through copper tubing where its force pushed the piston back and forth longitudinally. At the end of the piston, a crankshaft converted the piston’s motion into radial motion, turning the connecting rods laterally. At the end of each connecting rod, a bevel gear transferred the lateral radial motion into longitudinal radial motion which turned each propeller.
PROPELLERS
The propellers used on Aerodrome No. 5 were constructed of white pine strips laminated together and bent to form an axial twist. Each propeller was 1 meter in diameter and weighed 0.8 pounds. At full steam power, the propellers ran at nearly 800 revolutions per minute, propelling Aerodrome No. 5 up to 30 miles per hour. In later testing trials, Aerodrome No. 5’s wooden propellers were replaced with the fabric covered propellers shown above.