sentences:  Water was forced between the halves of a concrete mold, thereby shaping the roof.Van der Goot even built the 228 cc, 6 kW (8 hp) single-cylinder, two-stroke engine by hand, creating its connecting rod out of curved, spot-welded gas pipe.Its light weight and modular design were such that both the engine and its rudimentary three-speed transmission with centrifugal clutch could be swapped out in about five minutes with minimal manpower.