The Valveless was an English automobile manufactured, after lengthy development, from 1908 until 1915 in Huddersfield, Yorkshire. The successor to the Ralph Lucas Valveless, the car marked the entry of the David Brown & Sons group into the manufacture of motors. Its engine was a 20 or 25 hp duplex two-stroke model which was advertised as having "only six working parts"; these included two pistons, two connecting rods, and two crankshafts, which were geared together and counter-rotated. This is a type of engine configuration known as a split single since it is effectively a single cylinder split into two.
Models 1908 20 hp 2-cylinder 133 × 140 = 3.891 litres 1909–1911 25 hp 2-cylinder 133 × 140 = 3.891 litres 1911-1915 15 hp 2-cylinder 112 × 127 = 2.503 litres 1913 15 hp 2-cylinder 118 × 127 = 2.503 litres 1913–1914 19.9 hp 2-cylinder 127 × 127 = 3.217 litres 1915 19.9 hp 2-cylinder 127 × 133 = 3.546 litres The cars with smaller engines had slightly shorter wheelbases and so were lighter.
See also List of car manufacturers of the United Kingdom
References
David Burgess Wise, The New Illustrated Encyclopedia of Automobiles.