g rods are of high grade
steel, machined all over and fitted with bushes of phosphor bronze;
these rods are connected to a central collar, carried on the crank pin
by two ball-bearings. The crankshaft has a single throw, and is made
in two parts to allow the cage for carrying the big end-pins of the
connecting rods to be placed in position.

The casing is in two parts, on one of which the brackets for fixing the
engine are carried, while the other part carries the valve-gear. Bolts
secure the two parts together. The mechanically-operated steel valves
on the cylinders are each fitted with double springs and the valves are
operated by rods and levers. Two Zenith carburettors are fitted on the
rear half of the crank case, and short induction pipes are led to each
cylinder; each of the carburettors is heated by the exhaust gases.
Ignition is by two high-tension magnetos, and a compressed air
self-starting arrangement is provided. Two oil pumps are fitted for
lubricating purposes, one of which forces oil to the crankshaft and
connecting-rod bearings, while the second forces oil to the valve gear,
the cylinders being so arranged that the oil which flows along the walls
cannot flood the lower cylinders. This engine operates upon a six-stroke
cycle, a rather rare arrangement for internal combustion engines of the
electrical ignition type; this is done in order to obtain equal angular
intervals for the working impulses imparted to the rotating crankshaft,
as the cylinders are arranged in groups of seven, and all act upon the
one crankshaft. The angle, therefore, between the impulses is 77 1/7
degrees. A diagram is inset giving a side view of the engine, in order
to show the grouping of the cylinders.

The 600 horse-power Salmson engine was designed with a view to fitting
to airships, and was in reality two nine-cylindered engines, with a
gear-box connecting them; double air-screws were fitted, and these were
so arranged that either or both of them might be driven by either or
both engines; in addition to this, the two engines were complete and
separate engines as regards carburation and ignition, etc., so that
they could be run independently of each other. The cylinders were
exceptionally 'long stroke,' being 5.9 inches bore to 8.27 inches
stroke, and the rated power was developed at 1,200 revolutions per
minute, the weight of the complete engine being only 4.1 lbs. per
horse-power at the normal rating.

A type of engine spec