The Vee Type
An offshoot from the vertical type, doubling the power of this with only a very slight--if any--increase in the length of crankshaft, the Vee or diagonal type of aero engine leaped to success through the insistent demand for greater power. Although the design came after that of the vertical engine, by 1910, according to Critchley's list of aero engines, there were more Vee type engines being made than any other type, twenty-five sizes being given in the list, with an average rating of 57.4 brake horse-power.

The arrangement of the cylinders in Vee form over the crankshaft, enabling the pistons of each pair of opposite cylinders to act upon the same crank pin, permits of a very short, compact engine being built, and also permits of reduction of the weight per horsepower, comparing this with that of the vertical type of engine, with one row of cylinders. Further, at the introduction of this type of engine it was seen that crankshaft vibration, an evil of the early vertical engines, was practically eliminated, as was the want of longitudinal stiffness that characterised the higher-powered vertical engines.