THE LATEST AUTOMOBILE ENGINE
OUR BOY FRIEND AND THE SCIENTIST LOOK OVER THE FIELD OF GASOLINE
ENGINES AND SEE SOME BIG IMPROVEMENTS OVER THOSE OF A FEW YEARS
AGO
While we are following the conversations of the scientist and his
young friend about new inventions, we must not overlook some of their
most interesting times in keeping abreast of the vast improvements
that are being made every year--almost every day--in the inventions
of a dozen years ago.
For instance, there is the gas engine. Ten years ago it was a very
imperfect machine, as every boy who has heard the old jokes about
"auto-go-but doesn't," "get a horse," etc., will remember.
Then there is the wireless telegraph. No invention of recent years
has shown a more remarkable development than that of Guglielmo
Marconi for sending messages without wires.
But these are only a few of the things that the two friends talked
about. They looked into the wonderful advancement in the art of
photography about which every boy knows something, and they
investigated the latest achievements of science in electric lighting.
Ten years is a very short time, even in this fast moving age of ours,
and we shall see that many inventions made years ago are still being
worked upon by the original inventors and others.
First, let us see a few of the ways the gas engine has been improved,
for we are all more or less familiar with it in automobiles, motor
boats, or the hundred and one other places that it has become an
invaluable aid to man in carrying on the world's work.
Our young friend brought up the subject one day when he asked the
scientist for a few pointers on getting better results with his
motor-boat engine.
"We will look it over together," said the man. "Of course you
know that every gasoline engine has its own peculiarities, and
crankinesses, so it's hard to tell just what's the matter with one
until you see it. I don't know very much about them; I wish I knew
more, but I have been talking with my automobile friends a good deal
lately about the new motor invented by Charles Y. Knight."
"Oh, I know," replied the boy, "it is called the 'Silent Knight'
motor because it doesn't make any noise, and it is used on a great
many high-priced automobiles."
"That's it. If you like we will go and have one of these engines
explained to us. At any rate the automobile man can tell you more
about your motor-boat engine than I can."
The expedition was made shortly after the conversation. "You
understand, of course," said the scientist on the way, "that the
Knight motor represents only one of the many, many improvements in
the gas engine, but it is what we call a fundamental improvement, as
it is a development in the main idea of the gasoline motor, rather
than merely an improvement of one of the parts. Most of the evolution
of gas engines has consisted merely of the improvement and perfection
of the various parts for more power, and more all around efficiency.
"You remember what you found out about gasoline motors in general
when we were spending so much time talking about aeroplanes. The high
speed motor, as we know it now, was invented, you know, by Gottlieb
Daimler, a German inventor, in 1885, and with the ordinary four-cycle
engine it takes four trips, or two round trips of the piston rod,
to exert one push on the crankshaft of the engine. In other words,
the explosion drives down the piston giving the power, and on its
return trip the piston forces out the burned fumes. On the next
downward stroke the fresh vapour is sucked into the cylinder and on
the fourth trip, or second upward trip, the gas is compressed for
the explosion. The carbureter on your motor-boat engine, and all
others, as you know, is the device that mixes the gasoline with air
and converts it into a highly explosive gas, and the sparking system
is the electrical device that ignites the gas in the cylinders for
each explosion which makes the 'pop, pop, pop' so familiar with all
gasoline engines.
"In the old gas engines the ignition was derived from a few dry-cell
batteries and some sort of a transformer coil, whereas nowadays the
magneto takes care of this work. As you know there are many kinds
of magnetos, and inventors have spent years working out better and
better ones. Also, in the old style motors the carbureter was more
or less of a makeshift, with a drip feed arrangement, and a hand
regulating shutter for admitting the air. Now a special automatic
device regulates this, so that it is no longer a toss up whether
the gas is mixed in the proper quantities or not. Then, too, the
oiling systems have been improved, so that the function is done
automatically. In short, the motor has been made a perfectly reliable
servant instead of a very capricious plaything.
"All these improvements made no fundamental change in the valves
through which the gas was admitted to the cylinders, and the
exhausted vapours expelled--and from your own experience you know
that you are just about as apt to have trouble with your valves as
with any other part of your machine.
"It is in these valves that the Knight motor departs from the usual
style, and by this it eliminates the well-known 'pop, pop, pop' by
which gas engines have been known all over the world."
As they looked over the engine, an expert in gasoline motors
explained all the parts of the "Silent Knight" and showed the
scientist and his boy friend just how the machine worked.
He said that the only big difference between the Knight motor and
other standard makes of engines is that the Knight substitutes for
the intake and exhaust valves an entirely new device composed of two
cylinders, one within the other, sliding upon each other so as to
regulate the flow of gas and the exhaust of fumes.
Early in his career as an inventor, while living in his home city of
Chicago, Knight decided that gasoline engines had entirely too many
parts--that they were too complicated--and he set about trying to
simplify them. For one thing, he made a careful study of valves, and
collected a specimen of every kind known to mechanics. The sliding
locomotive valve seemed to him to hold the greatest possibilities for
his work, and he began a series of experiments with sliding valves
until he finally brought out his first engine in 1902.
Strange as it may seem, Knight's work was not recognized in his own
country until after he had gone to Europe, where his engine was
taken up by some of the biggest automobile manufacturers of England,
France, Germany, Belgium, and Italy. After that it was taken up in
the United States, and only now is coming to be generally known. The
inventor now lives in England, where he was first successful, and he
is still at work on improvements of his engine.
The motor expert went on to explain that the advantage of the Knight
motor lay in the fact that the two sleeves or cylinders, which go
to make up the combustion chamber or engine cylinder, sliding up
and down upon one another, give a silent, vibrationless movement,
as against the noisy action of the old style poppet or spring valve
motors.
"But," interrupted the boy, "there are lots of other engines that run
without making a noise nowadays."
"That is true," the man answered, "but most of them run quietly only
when at low speed, or stationary. When they begin to hit the high
places the noise of the poppet valves is very noticeable. A few years
ago, when most engine builders were satisfied to make motors that
would run, regardless of noise, they paid no attention to some of the
finer mechanical problems, but since they have become more skilful,
they are cutting down on the noise. But, as I say, the explosions
are plainly heard when these engines are running at high speed. With
the 'Silent Knight' the only noise is that of the fan and magneto,
whether at low speed or the very fastest the motor can run. There can
be no noise, for there is nothing for the sleeves to strike against."
The expert then went on to explain the motor in detail. The
combustion chambers of the four or six-cylinder "Silent Knight," he
explained, are made up of two concentric cylinders or sleeves, or, in
other words, one cylinder within another. There is only the smallest
fraction of an inch between them, and as they are well oiled by an
automatic lubricating device they slide up and down upon each other
with perfect ease. Of course the sleeves, which are made of Swedish
iron, a very fine material for cylinder construction, are machined
down inside and out so that they are perfectly smooth to run upon
each other.
The two sleeves which go to make up one cylinder work up and down
upon each other by means of a small connecting rod affixed to the
bottom of each sleeve connected to an eccentric rod, which is driven
by a noiseless chain from the engine shaft.
The most important features are the slots cut in each side, and close
to the upper end of each sleeve, so that, as the sleeves move upon
one another the slot in the right-hand side of the inner one will
pass the slot of the right-hand side of the outer sleeve, and also
the same with the left-hand side.
Then when the left-hand slots of the outer sleeve open upon, or come
into register with the left-hand slots of the inner sleeve, a passage
into the cylinder is opened for the new gas to enter. When a charge
of gas has been drawn into the cylinder, one sleeve rises while the
other falls, so that the openings are separated and the passage is
tightly closed. The compression stroke then begins with the piston
rising to the top. At this juncture the igniting spark explodes
the compressed gas and the downward or power stroke takes place.
During the upward compression stroke and the downward impulse stroke
the slots have been closed, allowing no opportunity for the gas to
escape. When the explosion has taken place and the piston has been
driven to the bottom of its stroke, the right-hand openings in the
inner sleeve and those of the outer sleeve come together, providing a
passage for the exhausted gases to escape with the fourth or exhaust
stroke. Thus it is plain that the motor is of the four-cycle type and
it should not be confounded with two-cycle motors.
As the expert explained the motion he showed how it was carried out
on an engine from which the casing had been partly removed. The
careful mechanical adjustment of the eccentric shaft, which operated
the connecting rods that pull the sleeves of the cylinder up and
down so that the openings for the entrance of the fresh gas and the
expulsion of the exploded fumes come together at just the proper
second, was what took the boy's eye.
In connection with this the scientist handed the boy a magazine
to read. It was a copy of the _Motor Age_ in which an expert said
editorially:
"Those who pin their faith to the slide-valve motor do so for
many reasons, chief of which is that with this motor there is a
definite opening and closing of the intake and exhaust parts, no
matter at what motor speeds the car be operating. Two years ago
one of the leading American engineers experimented with poppet
valves and discovered that frequently at the high speeds the
exhaust valves did not shut, there not being sufficient time
owing to the inability of the valve spring to close the valve in
the interval before a cam returned to open it again. With such a
condition it is certain that the most powerful mixture was not
obtained. With the sleeve valve such failure of operation cannot
be, because no matter how fast the motor is operating there is a
definite opening and closing for both intake and exhaust valve.
"It is a well-known fact that with poppet valves the tension
of the springs on the exhaust side varies after five or six
weeks' use, and consequently the accuracy of opening and
closing is interfered with. Carbon gets on the valve seatings
and prevents proper closing of the valve, with the result that
the compression is interfered with and the face of the valve
injured. These troubles are, as far as can be learned, obviated
in the sleeve valve."
The friends of the Knight motor claim that it is simpler than the
ordinary types of engines, having about one third less parts, that it
is economic, powerful, and, as previously pointed out, runs silently.
Beside these advantages, there are claimed for it many technical
virtues that we need not enter into here.
The lubricating system of the Knight motors is another interesting
point, as it serves to illustrate one more way in which the gasoline
engine has been improved upon of late years. The manner of oiling
used is known as the "movable dam" system. Located transversely
beneath the six connecting rods are six oil troughs hinged on a shaft
connected with the throttle. With the opening and closing of the
throttle these troughs are automatically raised and lowered. When the
throttle is opened, which raises the troughs, the points on the ends
of the connecting rods dip deep into the oil and create a splashing
of oil on the lower ends of the sliding sleeves. These sleeves are
grooved circularly on their outer surfaces in order to distribute the
oil evenly, while toward the lower ends holes are drilled to allow
for the passage of oil.
When the motor is throttled down, which lowers the troughs, the
points barely dip into the oil and a corresponding less amount of oil
is splashed. An oil pump keeps the troughs constantly overflowing.
The motor is cooled by a complete system of water jackets, and it is
fitted with a double ignition system, each independent of the other.
Of course in the adoption of the sliding sleeve type, mushroom
valves, cams, cam rollers, cam shafts, valve springs, and train of
front engine gears all are eliminated, the sliding parts fulfilling
their various functions.
Before Mr. Knight ever achieved success with his motor it was
subjected to some of the severest tests on record in the whole
automobile industry. In France, Germany, and England, it was only
accepted by the leading manufacturers after being tried out for
periods extending over several months of the hardest kind of usage.
Now, that it has proven itself a practical success, automobile men
declare that the sliding valve principle, never before applied to
gas engines until Knight began work, will undoubtedly have a lasting
effect on the whole industry.
The compact little two-cycle motors represent another big fundamental
development in the field of gas engines. There are many different
makes of two-cycle motors, of course, and all have their various
merits. They are used in practically all the work for which gas
engines are employed, including automobiles, motor boats, and
aeroplanes. It will not be necessary to describe these engines
further than to say that the name describes the fundamental
difference between them and the four-cycle motors. Instead of the
piston making four strokes for every explosion--that is, an, upward
stroke to clean out the burnt vapours, a downward stroke to suck
in the fresh gas, an upward stroke to compress it, and finally the
downward explosion or power stroke, all this work is done in two
strokes.
For the general development of the gasoline engine, it is only
necessary for a boy to look about him. Everywhere motors built on
the same ideas as laid down in earlier inventions, but improved in
every detail, are in use. Not only do we see them on fine pleasure
automobiles, motor boats, and aeroplanes, but on our biggest trucks,
fire engines, and in business establishments where light machinery is
to be run.