1918, that well over eighty per cent of German aircraft was engined
with the Mercedes type.

In design and construction, there was nothing abnormal about the
Mercedes engine, the keynote throughout being extreme reliability and
such simplification of design as would permit of mass production in
different factories. Even before the war, the long list of records set
up by this engine formed practical application of the wisdom of this
policy; Bohn's flight of 24 hours 10 minutes, accomplished on July 10th
and 11th, 1914, 9is an instance of this--the flight was accomplished on
an Albatross biplane with a 75 horsepower Mercedes engine. The radial
type, instanced in other countries by the Salmson and Anzani makes, was
not developed in Germany; two radial engines were made in that country
before the war, but the Germans seemed to lose faith in the type under
war conditions, or it may have been that insistence on standardisation
ruled out all but the proved examples of engine.

Details of one of the middle sizes of Mercedes motor, the 176
horse-power type, apply very generally to the whole range; this size was
in use up to and beyond the conclusion of hostilities, and it may still
be regarded as characteristic of modern (1920) German practice. The
engine is of the fixed vertical type, has six cylinders in line, not
off-set, and is water-cooled. The cam shaft is carried in a special
bronze casing, seated on the immediate top of the cylinders, and a
vertical shaft is interposed between crankshaft and camshaft, the latter
being driven by bevel gearing.

On this vertical connecting-shaft the water pump is located, serving to
steady the motion of the shaft. Extending immediately below the camshaft
is another vertical shaft, driven by bevel gears from the crank-shaft,
and terminating in a worm which drives the multiple piston oil pumps.

The cylinders are made from steel forgings, as are the valve chamber
elbows, which are machined all over and welded together. A jacket of
light steel is welded over the valve elbows and attached to a flange
on the cylinders, forming a water-cooling space with a section of about
7/16 of an inch. The cylinder bore is 5.5 inches, and the stroke 6.29
inches. The cylinders are attached to the crank case by means of dogs
and long through bolts, which have shoulders near their lower ends and
are bolted to the lower half of the crank chamber. A very light and
rigid structure is thus obtained, and the meth