and in addition to this,
so far as car engines are concerned, the method of rating horse-power
in relation to bore without taking stroke into account has given the
long-stroke engine an advantage, actual horse-power with a long stroke
engine being in excess of the nominal rating. This may have had some
influence on aero engine design, but, however this may have been, the
long-stroke engine has gradually come to favour, and its rival has taken
second place.

For some time pride of place among British Vee type engines was held
by the Sunbeam Company, which, owing to the genius of Louis Coatalen,
together with the very high standard of construction maintained by the
firm, achieved records and fame in the middle and later periods of the
war. Their 225 horse-power twelve-cylinder engine ran at a normal
speed of 2,000 revolutions per minute; the air screw was driven through
gearing at half this speed, its shaft being separate from the timing
gear and carried in ball-bearings on the nose-piece of the engine. The
cylinders were of cast-iron, entirely water-cooled; a thin casing formed
the water-jacket, and a very light design was obtained, the weight being
only 3.2 lbs. per horse-power. The first engine of Sunbeam design had
eight cylinders and developed 150 horse-power at 2,000 revolutions
per minute; the final type of Vee design produced during the war was
twelve-cylindered, and yielded 310 horse-power with cylinders 4.3 inches
bore by 6.4 inches stroke. Evidence in favour of the long-stroke engine
is afforded in this type as regards economy of working; under full load,
working at 2,000 revolutions per minute, the consumption was 0.55 pints
of fuel per brake horse-power per hour, which seems to indicate that the
long stroke permitted of full use being made of the power resulting from
each explosion, in spite of the high rate of speed of the piston.

Developing from the Vee type, the eighteen-cylinder 475 brake
horse-power engine, designed during the war, represented for a time
the limit of power obtainable from a single plant. It was water-cooled
throughout, and the ignition to each cylinder was duplicated; this
engine proved fully efficient, and economical in fuel consumption.
It was largely used for seaplane work, where reliability was fully as
necessary as high power.

The abnormal needs of the war period brought many British firms into the
ranks of Vee-type engine-builders, and, apart from those mentioned,
the most not