Ariel Motorcycles Square Four 4f 1931
The original Square Four design developed by Edward Turner has been described as a masterpiece although it was too costly to produce commercially and Valentine Page, Ariel’s chief designer, was instructed by the company board to make alterations that would reduce production costs.
The production version was unveiled at the London Olympia Show in November 1930 where it caused a sensation. It was launched onto the market in 1931.
The Square Four was intended as a luxury touring motorcycle featuring a 500cc, chain-driven, single overhead-camshaft engine with enclosed valves. Designed to be accommodated in the frame of the existing 500cc Sloper model, the square configuration can be regarded as two parallel twins with bore and stroke dimensions of 51mm x 61mm sharing a crankcase although the cylinder block and head are each one-piece castings. The two 180-degree crankshafts are geared together by geared central flywheels so that the crankshafts rotate in opposite directions and two diagonal pistons are at TDC when the other two are at BDC so that vibration is minimised. Wet-sump lubrication is via two gear pumps and fuel mixture is provided through an X-shaped intake tract from a single, front-mounted Amal carburettor. A hand gearshift is used to operate a four-speed Burman gearbox, Turner’s original integrated gearbox being one of the costly design items discarded by Page. In 1932, the Square Four was enlarged to 600cc. Sales of the 500cc model totalled 927 units.
This particular example was restored by Gordon Cansdale of Glenhaven, New South Wales, from a bike that had been abandoned on the banks of the Nepean River where it was partly submerged at full tide. A truck driver had found the bike and sold it to Gordon as a rusty mess. Although he found that the frame and gearbox were salvageable, the engine and cycle parts were very damaged. Gordon had recently purchased two Square Four motors, a 500cc and a 600cc, from a N.S.W. Ariel enthusiast and had the 500cc motor rebuilt by Peter Scott, a local magneto and electric motor rewinder who raced vintage motorcycles, mostly Rudges. The con rods from the rescued bike were used in the rebuild and other parts including the primary chain case, exhaust pipes, wheels and mudguards were sourced from swap meets in Australia and the UK. The original petrol tank was rusted beyond repair and a tank from a 1930s Sunbeam was modified to fit and to accommodate the instrument panel.
When Gordon moved into a retirement village, he sold the bike along with his collection of 45 other vintage motorcycles, many of which he had restored from ‘basket cases’. He was a mechanic in the Fleet Air Arm and worked on Spitfires and Fireflies. His first restoration in 1943 was a 1927 AJS flat tanker. The Ariel went to Western Australia from where it was acquired for the NZ Classic Motorcycles collection in March, 2009. Others went as far afield as Germany, the Netherlands, the US and the UK.