Legendary designer, Edward Turner, left us in 1973, but his legacy is still being felt today.
Turner built his first bike in 1927, a 350cc OHC single. The Motor Cycle published a photograph of Edward Turner’s patented engine, mounted in his motorcycle called the Turner Special. The Special was registered for road use with the London County Council as YP 9286. It used Webb forks, and a three-speed Sturmey-Archer gearbox.
In 1928, Turner conceived the Square Four engine. At this time he was looking for work, showing drawings of his engine design to motorcycle manufacturers. The engine was essentially a pair of ‘across frame’ OHC parallel twins joined by their geared central flywheels, with a one-piece four-cylinder block (or Monobloc) and single head. BSA rejected the idea but Ariel took up the design, which is why there’s no such thing as a BSA Square Four.
In 1936, Triumph’s car and motorcycle business was split. Ariel owner, Jack Sangster, bought the motorcycle side and changed the name to Triumph Engineering Co Ltd.
Sangster made Edward Turner General Manager and Chief Designer. In July 1937, Turner introduced the 500cc Speed Twin, which fitted snugly into the existing Tiger 90 single-cylinder chassis. This new combination had magic in name, looks, and performance, and set the tone for the British motorcycle industry for the nearly 50 years.
Turner retired in 1963 but, from the sidelines in 1967, he sketched out a direct challenge to the Honda CB450, whose performance nearly equalled his aging line of 650cc Triumph twins. Turner poached a few Triumph employees to build up a running prototype of his double-overhead-camshaft, twin-cylinder 350cc bike with a short-stroke, 180degree crankshaft – exactly the spec of the Honda, but with 100cc less capacity. Turner was confident his decades of experience squeezing power from his twins would yield excellent performance from this smaller engine, and so it proved to be. The little bike hit 112mph in tests, about 7mph faster than the Honda. It never made it in to production after problems were found during testing.
The restored prototype
Short Interview with Edward talking about the Speed Twin
