This Pingstone tether boat was built by Harry A. Pingstone, of Zimbabwe, in 1933. The boat measures 12″-wide by 40″-long and is powered by Mr. Pingstone’s custom made 30cc air-cooled overhead cam engine. The engine measures 10″-high, 9″-wide, and 5″-long including the flywheel. With a bore of 32mm and a stroke of 37mm this 29.75cc (1.8 cubic inch) engine burns gasoline on spark ignition. It utilizes a pressurized dry-sump lubrication system, a pressurized fuel system; Mr. Pingstone’s custom designed gear-driven overhead cam, and his custom designed recoil starter. He fabricated all of the parts including the castings for the crankcase and gear boxes and machined everything else from bar stock. The head (as well as the cylinder) is machined from solid cast iron with 3/4″ ports and manganese valves measuring 7/8″ in diameter. The valves are set at 45 degrees, each captured by two springs and retained with split collets.
The engine was sent to Edgar T. Westbury in 1933 for his analysis and comments, which were later published in The Model Engineer and Practical Electrician in March 1934. After the engine was returned to Mr. Pingstone, he made several modifications to the cylinder and head, and fabricated a new carburetor before mounting it into his tether boat. Housed within the boat is the split fuel/oil tank each with its respective inline filter and an electric switch to turn off the ignition.