In 1911 the Macomber Rotary Engine Company of Los Angeles marketed one of the first axial internal-combustion engines, manufactured by the Avis Engine Company of Allston, Massachusetts. A four-stroke, air-cooled unit, it had seven cylinders and a variable compression ratio, altered by changing the wobble-plate angle and hence the length of piston stroke. It was called a “rotary engine” because the entire engine rotated apart from the end casings.
Ignition was supplied by a Bosch magneto directly driven from the cam gears. The high voltage current was then taken to a fixed electrode on the front bearing case, from which the sparks would jump to the spark plugs in the cylinder heads as they passed within 1/16 inch from it. According to Macomber’s literature, it was “Guaranteed not to overheat”.
The engine was claimed to be able to run at 150 to 1,500 rpm. At the normal speed of 1,000 rpm, it reportedly developed 50 hp. It weighed 230 pounds (100 kg) and it was 28 inches (710 mm) long by 19 inches (480 mm) in diameter.
Pioneer aviator Charles Francis Walsh flew an aircraft powered by a Macomber engine in May 1911, the “Walsh Silver Dart”.