ARIEL SQUARE FOUR - RED HUNTER (Engines Framed) The 1950 Ariel 997 cc Square Four The Ariel Square Four was the brainchild of Edward Turner, perhaps the most commercially successful designer the motorycling world has known (he gave us the Triumph Speed Twin, its descendants, the Cub, the Tina and the Tigress Scooters). The square layout was conceived to make a four fit a conventional frame. The prototype 500, way back in 1928, was so compact that even with a unit gearbox it slotted into the current 250 Ariel frame. Beefed up and separated from the gearbox, the first production 500 (1931, overhead camshaft) fitted the frame employed for the big-single range. It was enlarged to 600 cc the next year but retained a tendency to overheat. For 1937 it was redesigned with pushrod valve operation and enlarged to 1000 cc, a 600 cc version being added later. For 1950 the switch to ligh