1951 ARIEL SQUARE FOUR BACKGROUND
The original Ariel Square Four was created by legendary engine designer, Edward Turner in 1930. In its original form, it displaced 500cc and had four cylinders arranged in a ‘square’. It was unusual in that it had two crankshafts, one behind the other, each with two cylinders. These cranks were geared together 180 degrees out of phase. The cast iron one-piece cylinder block and removable head had a single overhead cam (SOHC). Also rare for the times, it had horizontally-split crankcases made of aluminum alloy. Before its official 1932 introduction, it was expanded to 601cc. In 1937, it was completely redesigned as a 995cc pushrod-operated OHV 4-cylinder and was dubbed the Model 4G, but carried the nickname “Squariel”.
1951 ARIEL SQUARE FOUR DESIGN
The Model 4G ditched the rigid rear frame in 1939 in favor of an Anstey-link plunger rear suspension, and a new frame to go along with it. In 1946, when civilian production resumed after World War II, a new telescopic front fork replaced the old girder forks. In 1949, the old cast iron cylinder block and head were dropped in favor of aluminum alloy pieces, which both saved weight and aided cooling. This and other changes allowed the new Mark I, as it was called, to reach 90 mph-plus.