l web
of the shaft is bent to bring the centres of the crank pins as close
together as possible, leaving only room for the connecting rods, and
the pins are 180 degrees apart. Nickel steel valves of the cone-seated,
poppet type are fitted, the inlet valves being automatic, and those for
the exhaust cam-operated by means of push-rods. With an engine having
such a number of cylinders a very uniform rotation of the crankshaft is
obtained, and in actual running there are always five of the cylinders
giving impulses to the crankshaft at the same time.

An interesting type of pioneer radial engine was the Farcot, in which
the cylinders were arranged in a horizontal plane, with a vertical
crankshaft which operated the air-screw through bevel gearing. This was
an eight-cylinder engine, developing 64 horse-power at 1,200 revolutions
per minute. The R.E.P. type,in the early days, was a 'fan' engine,
but the designer, M. Robert Pelterie, turned from this design to a
seven-cylinder radial, which at 1,100 revolutions per minute gave 95
horse-power. Several makers entered into radial engine development in
the years immediately preceding the War, and in 1914 there were
some twenty-two different sizes and types, ranging from 30 to 600
horse-power, being made, according to report; the actual construction of
the latter size at this time, however, is doubtful.

Probably the best example of radial construction up to the outbreak of
War was the Salmson (Canton-Unne) water-cooled, of which in 1914
six sizes were listed as available. Of these the smallest was a
seven-cylinder 90 horse-power engine, and the largest, rated at 600
horse-power, had eighteen cylinders. These engines, during the War, were
made under license by the Dudbridge Ironworks in Great Britain.

The accompanying diagram shows the construction of the cylinders in the
200 horse-power size, showing the method of cooling, and the arrangement
of the connecting rods. A patent planetary gear, also shown in the
diagram, gives exactly the same stroke to all the pistons. The complete
engine has fourteen cylinders, of forged steel machined all over, and
so secured to the crank case that any one can be removed without parting
the crank case. The water-jackets are of spun copper, brazed on to the
cylinder, and corrugated so as to admit of free expansion; the water is
circulated by means of a centrifugal pump. The pistons are of cast-iron,
each fitted with three rings, and the connectin