Typical Gas Engines' and 'Vapour Engines'
(Page 2 of 4)
The National Engine
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Gas engines are built by the National Company in all sizes from
the smallest of 1 HP to the largest units burning producer gas.
Petrol engines are built by the same company for effective powers
of from 1 to 10 HP. All of these engines, whether gas or oil, are
provided with two large well-balanced flywheels which ensure
uniformity of the rotational motion; but this uniformity is also
partly due to the use of a novel form of centrifugal governor which
materially reduces the consumption. Fig. 349 illustrates the
outward appearance of the gas engine, and also with minor
differences that of the oil engines, which are provided in addition
with a vaporizer and lamp placed at the front and with an oil
reservoir immediately above the cylinder. Special attention has
been devoted to the reduction of the number of the parts, and the
result has been a design of the simplest possible description. One
cylinder alone is used for all engines of less than 50 HP. The
starting gear has been much simplified, and the ignition
arrangements are such that miss-fires rarely occur. Much skilled
attention is not required to keep the engine in good condition and
the lubrication is for the greater part done automatically.
Forest Engine
Reference has already been made to the two-cycle non-compression
engine first introduced by Mr. Forest, who has made the gas engine
the subject of considerable research work. Two other interesting
types of Forest engine, working on the four-stroke cycle, have also
been introduced with considerable success. In one of these types,
which is of a specially compact design, the cylinders
are open at both ends, and each contains two pistons, between
which the charge is introduced. On the explosion of the mixture the
pistons are driven in opposite directions, and their motions are
transmitted to the crank, directly in the one case by means of
connecting rods, and indirectly in the other through side levers.
The second type, illustrated in Fig. 350, has two or more cylinders
bolted together, and carried on columns over the crankshaft. By use
of two cylinders the regularity of the running is much improved, as
one driving impulse is obtained during each half revolution. For
the driving of launches, Mr. Forest, in conjunction with Mr.
Gallice, has succeeded in producing a very successful type of
petrol engine, which has been adopted by the French government, and
fitted by them to numerous boats of various sizes. By an ingenious
and simple arrangement of the cams on the valve shaft, which
controls the admission and exhaust, the motion of the engine may be
reversed instantly and at will, which, for marine work, is a most
important feature. Figs. 351 and 352 are external views of the
front and back of one of these launch engines.