The Boy's Book of New Inventions

by Harry E. Maule

"How did you come to invent your turbine while you were busy with your wonderful electrical inventions?" Tesla was asked.

"You see," he answered, "while I was trying to solve the problem of aerial navigation by electrical means, the gasoline motor was perfected; and aviation as we know it to-day became a fact. I consider the aeroplane as it has been developed little more than a passing phase of air navigation. Aeroplaning makes delightful sport, no doubt, but as it is now it can never be practical in commerce. Consequently I abandoned for the time being my attempts to find the ideal airship motor in electricity, and for several years studied hard on the problem as one of mechanics. Finally I hit upon the central idea of the new turbine I have just been showing you."

"What is this principle?"

"The idea of my turbine is based simply on two properties known to science for hundreds of years, but never in all the world's history used in this way before. These properties are adhesion and viscosity. Any boy can test them. For instance, put a little water on a sheet of metal. Most of it will roll off, but a few drops will remain until they evaporate. The metal does not absorb the water so the only thing that makes the water remain on the metal is adhesion—in other words, it adheres, or sticks to the metal.

"Then, too, you will notice that the drop of water will assume a certain shape and that it will remain in that form until you make it change by some outside force—by disturbing it by touch or holding it so that the attraction of gravitation will make it change.

"The simple little experiment reveals the viscosity of water, or, in other words, reveals the property of the molecules which go to make up the water, of sticking to each other. It is these properties of adhesion and viscosity that cause the 'skin friction' that impedes a ship in its progress through the water, or an aeroplane in going through the air. All fluids have these qualities—and you must keep in mind that air is a fluid, all gases are fluid, steam is fluid. Every known means of transmitting or developing mechanical power is through a fluid medium.

"It is a surprising fact that gases and vapours are possessed of this property of viscosity to a greater degree than are liquids such as water. Owing to these properties, if a solid body is moved through a fluid, more or less of the fluid is dragged along, or if a solid is put in a fluid that is moving it is carried along with the current. Also you are familiar with the great rush of air that follows a swiftly moving train. That simply means that the train tends to carry the air along with it, as the air tries to adhere to the surface of the cars, and the particles of air try to stick together. You would be surprised if you could have a picture of the great train of moving air that follows you about merely as you walk through this room.

"Now, in all the history of mechanical engineering, these properties have not been turned to the full use of man, although, as I said before, they have been known to exist for centuries. When I hit upon the idea that a rotary engine would run through their application, I began a series of very successful experiments."

Tesla went on to explain that all turbines, and in fact all engines, are based on the idea that the steam must have something to push against. We shall see a little later how these engines were developed, but it will suffice for the moment to listen to Doctor Tesla's explanation.

"All of the successful turbines up to the time of my invention," he says, "give the steam something to push upon. For instance"—taking a pencil and a piece of paper—"we will consider this circle, the disk, or rotor of an ordinary turbine. You understand it is the wheel to which the shaft is attached, and which turns the shaft, transmitting power to the machinery. Now it is a large wheel and along the outer edge is a row of little blades, or vanes, or buckets. The steam is turned against these blades, or buckets, in jets from pipes set around the wheel at close intervals, and the force of the steam on the blades turns the wheel at very high speed and gives us the power of what we call a 'prime mover'—that is, power which we can convert into electricity, or which we can use to drive all kinds of machinery. Now see what a big wheel it is and what a very small part of the wheel is used in giving us power—only the outer edge where the steam can push against the blades.