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:

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.