This Robarts R780 7-cylinder radial engine was designed and built by Bob Walker, Robarts Manufacturing, Illinois, in 1993. Bob Walker modeled this engine after the Jacobs R755 commonly used in three aircraft: the Beech Stagger Wing, Cessna 195 and Cessna UC-78 Bobcat (nicknamed the “Bamboo Bomber” because its airframe was fabricated from wood).
This engine has a bore of 1.125 inches (cylinder bore or piston diameter), a stroke of 1.125 inches (length the moves up and down) with a total displacement of 7.8 cubic inches (volume displaced by all cylinders added together).
The Robarts R780 weighs 7.65 pounds and burns methanol on glow ignition. Oil is mixed in with the fuel for lubrication. The engine is 10″-long, 10″-wide, and 11″-high.