Ariel 4F ‘Square Four’

Key facts

Year

1931
Country

Great Britain
Capacity

497cc
Cylinders

4
Performance

75mph
Price new

£70
Owner

National Motor Museum Trust
Manufacturer

Ariel Motors Ltd, Birmingham

Ariel’s famous ‘Square Four’, affectionately known as the ‘Squariel’, was a sensation when it was launched at the end of 1930. The air-cooled four-cylinder engine was effectively two vertical twin-cylinder units linked by gears. In 1932 a 600cc Square Four joined the range. This in turn was replaced by the 995cc 4G model with a re-designed overhead valve engine in 1937.

The Square Four was the brainchild of Edward Turner, a talented engineer who went on to design many famous motorcycles including the Triumph Thunderbird and Bonneville. Ariel was taken over by BSA in 1944. A Square Four model remained part of the Ariel range until 1959.