Ariel 1937 model 4G 997cc Square Four frame # AX 528 engine# DD1188
Ariel unveiled the all new SQ 4 to the motorcycle world at the Olympia show in 1930.
It was a brainchild of design genius Edward Turner and was powered by an OHC engine with 2 parallel crankshafts, mounted in a crankcase transversely across the frame.
The two cranks were geared together in the center uf the unit, so in effect there were two vertical twin engines running in opposite directions.
The result was a silky, smooth power output with instant response to the throttle.
In 1932 the capacity was increased to 600 cc and at the Olympia show in November 1935 a new 4 was unveiled , this time of 1000 cc and with pushrods instead of the chain-driven overhead cam.
The roller conrod bearings were also dropped in favour of plain bearings and the coupling gears were moved from the center of the engine and placed in a case on the left side. Power output was about 36 HP, top rpm approx. 5800.
This new model attracted much attention but the public had to be patient because the first machines were actually produced almost a year later, in September 1936.
This well-restored square four is a sought after model because of its smooth acceleration ( 10-100 mph in top gear!), reliability and compactness.