The Square Four had a lifespan of over 25 years and several incarnations of all sizes from 500cc to 1000cc. If you thought that all old British bikes were 650 twins then read on... Ariel's Square Four started life in 1931, designed by a young Edward Turner who drew his original idea for the Square Four on the back of a fag packet and then took it to several manufacturers. BSA weren't interested but Ariel were willing to try it out. Turner was hoping to "provide a four-cylinder engine small enough for use in a solo motorcycle, yet producing ample power for really high performance without undue compression, racing cams or a big-choke carburettor. I was aiming at the ultimate reliability with the minimum of attention". When introduced, the Square was as 500, with its remarkably compact powerplant slotted into a twin front downtube chassis similar to that used by Ariel's 500 singles, using girder forks and a rigid back end. The original OHC engine can be viewed as being similar to two parallel twins which shared a common crankcase with the two crankshafts geared together at the middle pinions, and a common cylinder block and head. The overhead camgear was chain driven. Early bikes used a hand-change, four-speed Burman gearbox. The Square grew to 600cc in 1932 to give it a little more power and was intended to be used mainly as a sidecar tug. It was very smooth but somewhat sedate, and the engine was not easy to tune for peppier performance. By the late 1930s, the 997cc Square was introduced with an OHV pushrod, all-iron engine, alongside a similarly-engineered 600cc version. The front end still used girder forks but the rear utilised Frank Anstey's sprung rear suspension system. Post-War, the Square adopted an alloy engine, saving some 30lb in weight. The 1949 machine weighed around 435lb dry, produced 35bhp at 5500rpm and matched oil-damped tele forks to the Anstey link rear end. In 1953, the most famous four-piper Mk2, still with Anstey link rear suspension, was introduced. Although Ariel built prototypes of a Mk3 with Earles forks in 1954, the model wasn't put into production, so the Mk2 ended the line when it was discontinued in 1959. The final factory incarnation of the Square cost £336.16.6 new in 1958. A non-running 1955 Mk2 4-piper was offered for private sale at the end of 2005 for £4,000.
This particular machine was supplied new by Whitby's of Acton in June 1958 and surely a rare opportunity to purchase a 'one-family' (father and son) owned machine with original purchase invoice, certificate of guarantee and retaining the original frame and engine numbers matching. Having covered a total of 55,000 miles in it's 53 years (an average of only just in excess of 1000 miles per year), this machine has been well treated from the beginning and used regularly yet sparingly over recent years. In it's early years, it was family transport and used on numerous family camping trips with a hand-crafted side-car attached (it was fitted with heavy duty fork springs especially for that purpose from new which were removed when the bike was reverted to a solo machine). Benefitting from a current MoT and historic tax '981 RMC' is ready to be ridden away and enjoyed with minimal effort! Indeed, the bike starts very easily and is an effortless ride according to the current owner.