Arial Square Four Pictures
The Ariel Square 4, or "Squariel" was the first four cylinder "sporting" motorcycle, with previous attempts having the four cylinders mounted either longitudinally or transversely -- both of which forced the bike to be either too long or wide.
The designer behind the design was Edward Turner who was later to be responsible for the Triumph Speed Twin. Turner came up with the initial design based on a 497cc overhead cam, square four and approached several manufacturers with a view to making it into a commercial offering. It was Jack Sangster of Ariel who took it on and showed the initial version at Olympia in 1930. Amazingly, the machine weighed in at just 330lbs. However, this initial version was prone to overheating with the rear cylinders not getting enough cooling -- often resulting in warped cylinder heads.
As the Ariel soon became very popular for sidecar work, a bored out 597cc (Model 4F) was soon offered alongside a 997cc (Model 4G) version. After the Second World War the smaller Square Four was dropped and all development continued on the 4G. By this time, despite the use of a new light alloy cylinder head and block, the Squariel had become a very heavy motorcycle with its weight over 500lbs.
The Mark II, the final Square 4, was introduced in 1954 with the biggest difference being the use of four separate exhaust pipes leading to twin silencers. Production finally ceased in 1958, as Ariel focussed on their new range of two-stroke twins.
Production: 1930 to 1958
Engine: 997cc OHV square four, four stroke
Power: 42 bhp (28 kW) at 5800 rpm.