1954 Ariel Square Four ?Special in Battle Creek, MI

In 1928, engineer Edward Turner was shopping a new motorcycle design to English manufacturers. BSA turned him down, but Ariel was interested. The engine was an unusual four-cylinder. V-twins and inline fours, set both lengthwise and across the frame, had been used previously but Turner?s new design had two vertical twins sharing a common crankcase. The cylinder barrels were cast as a unit in a monobloc design. Their two crankshafts were joined by a flywheel and rotated in opposite directions. By having the two pistons of one crank at top and bottom dead center and the pistons of the second shaft at half stroke, the design was ingeniously compact and the firing order made it practically vibration free. The Ariel Square Four 4F made its debut at the 1930 Olympia Motorcycle Show featuring an overhead camshaft 500cc with a hand shift for the Burman gearbox, which was integral with the crankcase. Overhead camshafts and unit construction were well into the future for most firms, so Ariel was a real pioneer. Few knew then that the bike would become a legend of the British industry, both for its performance and dependability.