Wolfgang Seidel designed and produced many small 5, 7, and 9-cylinder radial engines for model airplanes in the early 1990s. In the late 1990s, his designs led to larger engines, including 5, 7, and 14-cylinder two-row radials. The ST 726 is a 7-cylinder 180 cc (11 cubic inch) radial that weighs approximately 16 pounds. It burns methanol with castor oil mixed in for lubrication. It swings a 32-12 propeller at 4,500 revolutions per minute. The engine is 10”-long, 14”-wide, and 16”-high.