Wolfgang Seidel designed and built several custom radial engines. The ST 540, ST 770 and ST 996 were among the smaller series of radial engines that were used in 1/5 scale and 1/4 scale model aircraft. These engines varied in size from about 8 inches to 11 inches in diameter. This engine is 9″-long, 8″-wide, and 9″-high.
The ST 540 is the smaller 5-cylinder 40cc (2.43 cubic inch) radial engine with a speed range of 1,100 to 6,800 revolutions per minute, using a 22-6 propeller. It burns methanol with castor oil mixed in for lubrication, and it is capable of producing 2.8 horsepower.