The Niel Engine
Sent to us by Richard D. Hamp, 1772 Conrad Avenue, San Jose,
California 95 I 24-4501
A novel type conical rotating valve is employed in the Niel
engine for controlling the whole distribution of the charge and the
exhaust. By means of suitable gearing the valve is made to rotate
once for every two revolutions of the crank, and during this period
it effects successively the admission of the mixture to the
cylinder, the ignition, compression, and expansion and finally the
exhaust of the burnt gases. An ingenious arrangement ensures
sufficient gas tightness and prevents the valve from sticking.
Although the four-stroke cycle is used, suction only takes place
during two-thirds of the forward stroke, and the quantity of gas
drawn in is therefore less than the volume of the cylinder. From
this there results a certain economy, as the expansion is not so
great and the compression is less. The incandescent tube
arrangement introduced by Leo Funck in 1883 is adopted for the
ignition.
The Martini, Sombart, Adam, Roger, and Kientzy Engines
Although built by different makers, these engines, which work on
the Otto cycle, differ from one another in unimportant details
only. Considering also the absence of any novel features it is
unnecessary here to do more than mention their names.
Lablin Engine
Mr. Lablin of Nantes devised what may be considered as the gas
type of the Brotherhood steam engine, that is to say, an engine
combining the greatest possible power with the minimum weight and
size. To quote Mr. Lablin’s words, the engine was devised with
a view to increasing the ‘dynamical density’ of the gas
engine, and he so far succeeded in being able to construct engines
of half a horse power weighing only 88 lb. and engines of 8 HP
weighing less than 3 tons with a consumption of 35 cu. ft. of town
gas or 1 lb. of gasoline. The engine works on the Otto cycle but
three cylinders arranged radially around one crank are used, and
the system of working is such that an explosion takes place in each
cylinder successively, there being thus three driving strokes per
revolution of the common crank. A flywheel of the minimum
proportions may then be used, as the driving effort is practically
uniform. When the crank occupies the position shown in Fig. 344,
and when the direction of motion is that indicated by the arrow,
explosion occurs in cylinder A, and its piston drives the crank.
Exhaust of the waste gases commences from cylinder B, and the
piston of C finishes the suction stroke preparatory to the
compression of the mixture. Between the end of one driving period
and the commencement of the next the interval does not exceed
one-sixth of a revolution. Firing of the mixture may be effected
either by the use of a heated ignition tube or by an electric
spark, the former method being usually adopted when the working
substance is gas, and the latter for oil vapours. The speed of the
engine was controlled by a centrifugal governor which acted upon
the gas-admission valve.
The National Engine
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.
Charon Engine
Mr. Charon sought to prolong the duration of the expansion by
means less complicated than those devised in the first instance by
Mr. Atkinson. His gear consists of a shaft having a double-stepped
cam controlled from the governor.
One half of the double cam operates the admission, and the other
half a special valve, through which a portion of the explosive
mixture is driven into a large pipe or reservoir during the
compression. The compression of the portion of the charge in the
cylinder is thus reduced, while the expansion is more complete, and
is, at the same time, entirely under the control of the governor.
As a result of this increased expansion a very satisfactory
consumption was obtained.
Letombe Engine
Messrs. Mollet Fontaine, of Lille, built the Letombe engine,
which embodies several novel and interesting features. The engine
is double-acting, and the stages in the action on the two faces of
the piston follow one another at intervals of half a revolution, so
that during each revolution of the shaft there is one driving
impulse. As a result of this the uniformity of the motion is equal
to that obtained with two-stroke cycle engines, and the economy is
also increased to an important degree by the lengthening of the
expansion, as in the Charon engine.
VAPOUR ENGINES Durand Engine
It is claimed for this engine that it is able to work equally
well on gas or petroleum and that it works regularly without
attention, and is not costly although strongly constructed. To a
certain extent these claims are justified by results; but the
mechanism is somewhat complicated, and the design is not carried
out on well-proven lines. It is a four-cycle engine with electric
ignition, the spark being produced by the interruption of the
current from a small magneto machine driven by the engine itself,
Fig. 368. Governing is done by throttling the gas supply at the
admission valve, and the air supply is sucked directly by the
piston over a sieve heated by a special arrangement in which the
exhaust gases circulate. From this initial heating of the air a
certain economy of gas results. The carburetor is automatic and
self-regulating. It consists of a hermetically-sealed cylindrical
vessel filled with the oil supply. On the surface of the oil there
floats a mass of cork, into the centre of which the air to be
carbureted is led through a pipe in the cover. The cork acts as a
sponge and soaks in the volatile spirits which are thus brought
into close contact with the air. The evaporation is always
superficial, and the impurities remain in the bottom of the vessel.
Petroleum having a specific gravity of about .7 is used, as it not
only costs somewhat less than gasolene, but is also more readily
procurable. As already stated, the one serious defect of the Durand
engine consists in the number and the complication of the parts. In
the case of gas engines, which are subjected to continual severe
shocks, the fewer of the working parts the better, as otherwise the
wear becomes very considerable and the difficulty of efficiently
lubricating the working surfaces and the cylinder is increased.
Bruhot Engine
Messrs. Bruhot, of Vierzon, have introduced a gas engine which
can be run equally on the light volatile oils, and is particularly
suitable for agricultural purposes. The engine, as arranged for
town gas, differs from those already described in details alone. It
works on a four-stroke cycle, and the firing of the mixture is done
by means of a small battery, or by a magneto driven from the engine
shaft. To make the engine suitable for running on oil vapour a
carburetor and the necessary oil reservoirs are added. Air is
sucked in by the motion of the pistons over the petroleum or other
volatile mineral oils contained in the carburetor cylinder, and
becomes charged with hydrocarbon vapours. In connection with the
carburetor chamber is a tank containing a reserve supply of several
pints of oil, and a special regulator keeps the level in the
carburetor always constant, however variable the demands may be.
The arrangement, which is both simple and strong, makes the engine
particularly suitable for agricultural purposes.
This feature will continue in a future issue, when we will
begin with the Capitaine, an oil engine.
