The Megola had a unique design, laid down by Fritz Cockerell in 1920, using a rotary engine mounted within the front wheel. The engine contained five cylinders with side-mounted valves, each of which displaced 128cc, with a bore/stroke of 52x60mm, and a total displacement of 640 cc (39 cu in). The crankshaft rotated around the front axle at 6x the wheel speed; thus while the crankshaft was at its maximum of 3600rpm the front wheel was turning at 600rpm, or roughly 60mph (given the wheel diameter). A hand-controlled butterfly valve was located in the hollow crankshaft to regulate throttle. Power output was a modest 14 bhp (10 kW) but was applied directly to the wheel. This arrangement produced a very low centre of gravity and provided for excellent handling.
"The 5 cylinder star-engine was mounted in the front wheel, and the wheel turned around six times slower than the crankshaft did." 
The engine was very flexible, lacking both a clutch and a transmission. Starting it required a person to either spin the front wheel while the bike was on its stand, or to push-start. The cylinders could be disassembled without having to remove the wheel spokes in order to service the engine. The tires were tubed with the front inner-tube being a circular sausage shape rather than a complete doughnut-like torus shape, so that it could be changed without removing the wheel and engine. The box section frame contained the main fuel tank which fed by gravity a smaller tank mounted on the axle. The front suspension consisted of semi-elliptical springs.
The top speed was 85 km/h (52 mph) resulting in a win at the German Championship in 1924, while later, sportier models were said to be capable of 140 km/h (88 mph). A total of ~2000 Megolas were built, and perhaps only 10 rideable examples remain, and one was displayed at the Guggenheim Museum 'Art of the Motorcycle' exhibition in New York, USA.
Killinger and Freund