Left : 1931 Square Four instrument details Above : Square Four 1957 4G Mk11 and 1946 4G
L ike so many motorcycle pioneers , and ultimately manufacturers , Ariel began in the bicycle business during the early part of the 20th century . It wasn ’ t until 1928 that an engineer and designer , with a special interest in four-cylinder engines , designed an unusual machine after joining the Ariel company . His name was Edward Turner . Ironically , he is the same engineer who in 1937 would design one of the most iconic twin cylinder motorcycles in history , the Triumph Speed Twin . It was , however , his creation of the Ariel Square Four that first brought him to the attention of the motorcycle world .
STAR OF THE OLYMPIA MOTORCYCLE SHOW The story of the square-four engine begins with Turner having drawn a square four
engine layout on the back of a cigarette packet and , without much success , trying to sell the idea to the British motorcycle industry . AJS initially seemed interested , but then turned it down . It was Jack Sangster from Ariel who gave Turner the chance to make good his creation . The result was the birth of the Ariel Square Four , which became the star of the Olympia Motorcycle show in London in 1930 . The first Square Four was ready for distribution in 1931 . It had a 497cc engine , consisting basically of two vertical twins on a common crankcase , and geared together at their centres . Power output was 24bhp at 6000rpm , with a top speed of 85mph ( 137km / h ). At 330lbs the bike was surprisingly light .
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