The boys' book of engine-building

Front matter

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Contents

CHAPTER PAGE

I. — The First Engines I

II. — Two Simple Steam Turbine Engines . . 24

Chapter I

Hero Invents the Steam Engine — Branca Devises a New Engine — Papin Gets up the Piston Engine — Newcomen Makes the Engine Work — The Boy Who Made it Self Acting — Watt Puts on the Flywheel — The Development of the Steam Boiler — The First Steamboats — The Invention of the Locomotive — The Modern Steam Turbine — Some Other Kinds of Engines : The Compressed Air Engine; The Hot Air Engine; The Gas Engine.

About the beginning of the Christian era, a babe named Hero first saw the light of day in far off Alexandria in Egypt, and this child was destined to make a lasting impression on the human race.

Even as a boy he built apparatus and machines of all kinds, even as you do now, but this was doubly hard in his day for few inventions had been made and tools to make them with were just about as scarce, for science had not yet come into its own.

Hero Invents the Steam Engine.— But Hero was not discouraged and he began to invent and make things for himself. To tell you of all the experiments he made and all the apparatus he built would take a whole book of this size, but his greatest invention and the one that interests us now is his steam engine, for he was the first who ever made steam do useful work.

Hero called the steam engine which he invented and built an eolipile (pronounced a-ol'-i-piV) and this curious word he coined from two Latin words, the first of which is Eolus, the name of the god of the winds, and the other one pila, which means ball.

Let's find out now just why Hero named his engine the god of the winds plus a ball ? In the first place he made his engine of a hollow metal ball ana he fitted two short bent pipes into holes on the opposite sides of it. Next he mounted the ball on a pair of hollow pipes, or trunnions as they are called, so that it would revolve easily and the lower ends of these pipes were fixed to a boiler, all of which is shown in Fig. 1.

When he built a fire under the boiler the steam passed through the trunnion pipes into the ball and then out of the bent pipes into the air. As the steam struck the air with considerable force

Fig. 1. Hero's Reaction Engine or Eolipile it acted much the same as a rubber ball does when it strikes a sidewalk, that is it reacted on the hollow ball forcing it to turn in the opposite direction and at a fairly high speed, like unto the winds let loose by the god Eolus. This is the reason an engine of this kind is called a re-action engine.

Branca Devises a New Engine. — Strangely enough nothing more worth while was done in the way of transforming the energy of steam into mechanical motion during all the long centuries from the year i to 1609.

Then an Italian named Branca devised another sort of rotary steam engine. He made a paddlewheel and when the steam from a boiler was directed through a spout, or more properly a

Fig. 2. Branca' s Impulse Engine or Turbine

nozzle, against the paddles, or blades, as shown in Fig. 2, the force of the impulses of the steam striking them made the wheel revolve. For this reason an engine of this kind is called an impulse engine.

In those early days the Italians put an artistic touch on everything they made — indeed they haven't got over the habit yet — and so it was perfectly natural for Branca to give his boiler the head and body of a human being and he added to the life-like effect by having the steam blown from its mouth.

Now you may think out loud that a reaction ball like Hero's or an impulse wheel like Branca's is not a real steam engine but if you do you are quite mistaken for it so happened that within the last twenty years both of these ancient toys have led to the last word in steam engine building and that is — the steam turbine.

Papin Gets Up the Piston Engine. — The first steam engine in which steam in a cylinder moved a piston forth and back, or up and down, came shortly before Branca devised his rotary engine but these engines were used only for pumping water, for no one knew how to change the reciprocating motion, as the to and fro motion of the piston is called, into rotary motion, as the complete turning of a wheel is called, for another hundred years or so.

To begin at the beginning of the first invention of the piston engine, we have to start with Dennis Papin, a Frenchman. In 1610 he got up the scheme of using a piston in a cylinder and moving it by steam ; I say scheme because it did not work successfully when he built it. The trouble with his engine was that he made the boiler and the cylinder in one piece.

The way he tried to use it was to pour a little water in the bottom of the cylinder, which stood in a vertical position. Then he heated it as shown in Fig. 3. When steam was made it

Fig. 3. Papin's; The First Piston Engine

forced the piston up, the fire was then taken away, the steam cooled down, thus forming a vacuum in the cylinder, and the pressure of the air on the piston forced it down again.

Although this engine of Papin's was intended to work half by steam and half by air pressure it was called an atmospheric engine and this is the name it has always been known by.

Newcomen Makes the Engine Work. —

Nearly a hundred years later, in 1705, Thomas Newcomen, of England, and his assistant, James Cawley, made the piston engine of Papin work. They accomplished this by using a boiler that

Fig. 4. Newcomers Improved Engine

was separate and distinct from the cylinder. The piston in the cylinder was connected by a rod to one end of a lever called a walking beam and a weight to balance it was hung on the other end of the beam as shown in Fig. 4.

When steam was admitted into the cylinder from the boiler, it forced the piston up, then the steam valve was shut off and a little cold water was let into the cylinder to condense the steam, that is to change it into water again, when a vacuum would be formed; this done, the piston was pushed down by the pressure of the air on it; when the steam was turned into the cylinder again, it forced the water out through another valve.

The end of the walking beam which carried the weight was connected to a pump and hence the Newcomen engine came to be largely used in England for pumping water out of mines.

The Boy Who Made It Self-Acting. — As you can imagine the piston of Newcomen's engine worked very slowly and the steam and water valves had to be opened and closed by hand. As it was light, though tedious, work to do this, a boy was usually given the job and a youngster named Humphrey Potter happened to be one of them.

Now Humphrey was a boy of genius, and genius and humdrum work are seldom on speaking terms. So he bethought him to rig up some levers worked by strings tied to the walking beam to open and close the valves and his invention worked like a charm. He was in a fair way, at least it seemed so to him, to draw his sixpence a day while the engine worked automatically.

Instead his genius threw himself and all the other valve boys in England out of their jobs, and all he ever got out of it was undying fame.

Fig. 5. Potter's Self-Acting Engine

Humphrey's invention was at once improved upon by one Henry Beighton who connected a rod to the walking beam to work the valves and it is quite likely that, being a man, he profited by it.

Watt Puts on the Flywheel. — In your young io The Boys 9 Book of Engine-Building

lifetime you have heard enough of James Watt, of Glasgow, Scotland, to believe, probably, that he was the inventor of the steam engine, but you have seen that Papin and Newcomen and Potter

Fig. 6. Watt's ; The First Real Engine developed it to a considerable extent before Watt took it up.

What Watt did, though, constituted a mighty invention for it was he who made the wheels

The First Engines II

go round. It was in 1763 that he conceived the idea of connecting the piston rod to a crank having a flywheel fixed to it, and this made the engine useful for producing power for a thousand different purposes where before it was limited to pumping water. It is shown in Fig. 6.

To make the piston turn a crank the steam had to act on it much faster than it did in the Newcomen engine, so Watt let the steam escape from the cylinder at the end of each stroke, instead of condensing it in the cylinder by letting water run into it. Not only this, but by keeping the cylinder hot the engine used far less steam, and so it was much more economical.

Some years after Watt made two other improvements of great value, first of which was to admit steam on each side of the piston alternately, thus making the engine double acting; and the second was to cut off the supply of steam to the cylinder before the piston had completed its stroke and so using the expansive power of the steam in the cylinder to force the piston on to the end of its stroke.

Finally, Watt invented the throttle valve, so that the amount of steam which flowed into the cylinder could be controlled ; and he also invented the centrifugal governor which opens and closes the throttle valve automatically, depending on the speed with which it revolves and this in turn regulates the speed of the engine.

The Development of the Steam Boiler. — Since the first engine was the one built by Hero, we are bound to believe that the first steam boiler was the one which he used to generate steam for it. His boiler, as shown in Fig. i, was simply a hemispherical shell set on a stand and heated by a fire under it.

In the early days of the piston engine boilers were built in the shape of long boxes with fires under their entire length, but they were so weak that a steam pressure of only three or four pounds to the square inch could be used with safety. For this reason cylindrical boilers, which were very much stronger, took the place of the rectangular boilers.

The greatest improvement in boiler making came, however, when some genius put a central Hue in it and fixed the open ends to the boiler heads, or sheets, as they are called, so that there is a hole clear through the middle of the boiler.

This is surrounded by water and the heat of the fire passes through it, as shown in Fig. 7. As this scheme proved so successful, a large

Fig. 7. The Fire-Tube Boiler

number of fire tubes, as these flues are called, were then used for they gave a larger heating surface and, hence, a higher pressure could be kept up. The tubular boiler, as this type is known, see Fig. 8, is largely used for stationary engines and is the only kind used for locomotives. The First Steamboats. — Long before a steam engine capable of doing useful work had been invented, men began to think about using steam to propel boats.

Fig. 8. A Modern Tubular Boiler

The first boat actually driven by a steam engine was a packet built by John Fitch, of England, in 1787. It was a pretty crude attempt, for it used paddles at the sides and these were moved with a feathering stroke very like that used when you paddle a canoe. It ran at a speed of about three miles an hour.

Fitch built another steamboat moved by paddles at the stern, but his third boat was a great improvement over the other two, for it was driven by a small propeller. From 1785 to 1788 Miller and Symington, also of England, experimented with a steam propelled pleasure boat, but their efforts did not lead to any practical results.

In 1803 Robert Fulton, of your own United States, was in Paris and while there built a small

Fig. 9. Fulton's Steamboat the Clermont

steamboat and operated it on the Seine with great success. Coming to America he built the Clermont, in 1807, a small paddle-wheel packet, a picture of which is shown in Fig. 9, and launched her on the Hudson River.

When she started on her trial trip from New York to Albany, thousands of eager spectators lined the shore and marveled at the ease and speed with which she sailed up the river. She reached Albany without mishap and thus it was the great era of steamboats and steamships began.

The Invention of the Locomotive. — The first locomotive built was really a steam automobile, that is it was made to run on ordinary roads.

Since the engines were poor and the roads were bad, Richard Trevithick, of England, built a locomotive in 1804 to run on a track. Being fearful that the wheels would slip on the smooth surface of the rails he used a cog wheel that meshed with a cog rail.

Matthew Murray, also of England, built the next locomotive in 181 1. It had two upright cylinders set on top of the boiler ; the piston rods were connected with a crankshaft, and a wheel on this turned the driving wheels. The first engine to use a fire tube boiler was made in 1813 by William Hedley, likewise of England, and his engine was also the first to make the spent steam from the cylinders exhaust through the smokestack to give the furnace a good draft.

It was George Stephenson — he was of England too — who put the finishing touches on the locomotive in 181 4. This he did by connecting the piston rods directly to the crank pins on the driving wheels and he linked the front and back driving wheels with a coupling rod.

Stephenson built the Rocket in 1829, see Fig.

Fig. 10. Stephenson's Locomotive, The Rocket

10, and in a test on the Liverpool and Manchester Railway it ran away from its competitors, all of which were driven by sprocket wheels and chains. He not only won the prize, but fixed the design for locomotives from that day to this.

The Modern Steam Turbine. — And now we come back to the place where we started from

2000 years ago, which goes to prove the truth of the saying, "The first shall be last/' Engineers of our own time have perfected the reaction engine of Hero and the impulse engine of Branca and by combining the principles of both they have made an engine which uses far less steam and is much smaller for the horse power developed than the best reciprocating engines now in use. It is not called a steam engine, however, but a steam turbine if you please, though it is an engine just the same.

Though other men had built steam turbines, it was Gustav De Laval, of Sweden, who, in 1883, made it a practical success. He did this by driving a cream separator with it. His turbine is a highly developed Branca' s impulse engine having a single wheel mounted on a flexible shaft. The small ones run at the enormously high speed of 30,000 revolutions per minute and this is slowed down to working speeds by means of what are called reduction gears. It is shown in Fig. 11.

A year after De Laval got out his single wheel turbine, Charles A. Parsons, of England, combined the principles of the reaction and impulse engines and built the first multiple steam turbine. This turbine, see Fig. 12, developed 10 horse power when running at 18,000 revolutions per

Fig. 11. De Laval's, the First Practical Turbine

minute and its success led to the building of steam turbines powerful enough to drive the

Fig. 12. Parsons', the First Multiple Turbine

largest steamships across the Atlantic Ocean in less than five days.

Other Kinds of Engines. — There are several other ways to run engines besides using steam. Among them are by (i) compressed air; (2) hot air and (3) gas, or gasoline, which amounts to the same thing.

The Compressed Air Engine. — Any kind of an engine that can be run by steam can be run by compressed air. A simple way to compress air for running a small engine is described in Chapter V.

Compressed air is used instead of steam for running large engines when (a) the source of power must be a long way off from the engine; (b) when the smoke is objectionable as on street cars and in submarines, and (c) where the heat from the fire-box is dangerous, as in mines.

The Hot Air Engine. — The hot-air, or caloric engine as it is sometimes called, is so built that the heat of the fire is used to produce mechanical motion by acting directly on the piston.

This kind of an engine was invented by Robert Stirling, of England, in 181 6 and in 1827 he built his first practical engine. John Ericsson, of Sweden, made an improved hot-air engine in 1833, but it was not until 1852 that he built his first commercial engine, see Fig. 13, and engines of this type are largely in use at the present time for pumping water.

The Gas Engine. — In this engine a fuel gas, such as coal gas, or a gas formed of gasoline, mixed with air, is drawn into the cylinder and,

Fig. 13. Ericsson's Hot Air Engine

after it is compressed by the piston, is exploded usually by a hot tube, or an electric spark, which produces what is called the power stroke.

The beginning of the gas engine dates back to 1678 when the Abbe d'Hautefeuille, of France, conceived the idea of using the explosive power of gunpowder on a piston to make it do work.

Philip Lebon, also of France, patented an engine in which he proposed to use coal gas as the explosive fuel.

The first gas engine that actually worked was invented by Lenoir, likewise of France, in i860. He used gas for the fuel and this was exploded

Fig. 14. Otto's Gas Engine by an electric spark, but since the gas was exploded without being compressed, his engine was very wasteful and inefficient.

To Dr. Otto, of Germany, belongs the credit of having brought the gas engine to a successful conclusion in 1878. This was done by drawing in the gas on the suction stroke, compressing it on the compression stroke, exploding it to produce the power stroke and exhausting the burnt gases on the exhaust stroke. Hence this kind of a gas engine is known as the Otto four cycle engine and to its development is due not only the automobile, but that mightier marvel, the airplane.

Chapter II

Making the Boiler — Forming the Turbine Wheel — An Easily Made Alcohol Lamp — Running the Turbine — A Model De Laval Turbine — The Tools Required — Making the Turbine Wheel — Forming the Blades — Fashioning the Nozzle — The Turbine Wheel Case — The Bearings for the Shaft — Mounting the Wheel — The Reduction Gears — How the Steam Turbine Works: The Action of the Blades ; How the Nozzle Works.

A Simple Steam Turbine Engine. — Just as hundreds of other fellows before you, from Branca to the present time, have built impulse steam engines for their first models, so you would do well to follow in their footsteps and make one too.

To make a toy paddlewheel engine, or turbine, as it is now called, is a matter of a couple of hours' work and it will give you many times that many hours' pleasure, for steam in action is a wonderful power and what is equally to the point it has done more to make our world a cheerful place to live in than any other power harnessed by man, not even excepting electricity.

Now there are two chief parts to every steam power plant, however small or large as you have had occasion to observe in the first chapter, and there are, (i) the boiler which generates the steam and (2) the engine which transforms the energy of the steam into rotary mechanical motion, which means in everyday English that the force of it turns a wheel around.

Making the Boiler. — To make this little steam turbine get a /4 pound baking-powder can — empty of course — and soak it in water until the paper label comes off; this is for the boiler.

Drill or punch a %-inch hole in the can for the nozzle, about i/4 inches back from the open end and drill or punch four /46-inch holes, two on each side, at the places shown in the side and end views in Figs. 15 and 16 for the rivets; and, finally, cut a %-inch hole in the cover for the -filler, that is the hole through which water is poured into the boiler.

For the nozzle get a %-inch piece of brass or copper tube, if possible, V% inch long, or make one of tin, if necessary, and flatten one end a little.

P/JDDLE WHEEL

7X-, CORK IN LJ— FILLER

HOLE

SOLDER COVER

WIRE FRAME TO

HOLD BOILER.

■ALCOHOL

Fig. 15. Side View of Turbine

Now solder the nozzle over the %-inch hole in the can and don't be afraid of using too much solder.

Cut out two strips of sheet brass, copper or heavy tin V2 inch wide and 2 inches long for the supports that hold the wheel, and rivet these to the can so that they will be %-inch apart. You can buy small rivets or make them yourself by cutting off bits of copper wire. When you have these things done, solder the cover on tight.

Forming the Turbine Wheel. — Next make the turbine wheel. Get, or saw out, a wood wheel V2 inch thick and about 1 inch in diameter, or if you can get a spool, on which ribbon is wound, of the right size it will serve the purpose very well.

Saw 16 slots Vs inch deep at equal distances apart around the periphery, that is the rim of the wheel, and cut out as many pieces of tin V2 inch wide and V2 inch long for the paddles, or blades, or buckets, as these members are variously called. Fix the blades into the slots, using sealing wax on the edges, if needs be, to keep them in tight.

Use a piece of perfectly straight iron or brass wire, or a wire nail will do, Vs inch in diameter wtfstfm

SPINDLE

RIVETS

P/tDDLE WHEEL WASHER.

PULLEY

SUPPORT

NOZZLE

RIVETS

WIRE ERME

Fig. 16. End View of Turbine and 1% inches long for the spindle, and push it through the hole in the wheel; be sure that it fits tight and sets absolutely true and be careful not to bend the blades.

Slip a washer over each end of the spindle up close to the wheel and then spring the supports apart slightly when you can slip the spindle into the holes in them with the wheel between. Fix a V-shaped pulley to one end of the spindle and the hardest part of your job is done. Make a frame of wire, shaping it as shown in Figs. 15 and 16, and make it high enough to hold the boiler — it is no longer a baking powder can — about three inches away from the surface it sets on.

An Easily Made Alcohol Lamp. — You can make an alcohol lamp without any expense by using an ink bottle; get a squat one, not more than 2 inches high, if you can, though any kind will do. Fit a %-inch tin tube in a hole in the cork and put a cotton wick in it ; half-fill the bottle with alcohol, put the cork in it and you have a serviceable lamp.

Running the Turbine.— YidXi-hM the boiler with clean water and cork up the filler hole tight.

Set the boiler and wheel on the frame, light the lamp and set it underneath. The boiler will commence to generate steam in five or ten minutes and, when the pressure is great enough, the steam will be projected from the nozzle against

PADDLE WHEEL

FLAME

WICK

TIN TUBE

WIREFRAME TO HOLD BOILER.

-ALCOHOL

Fig. 17. The Steam Turbine Complete

the blades and the force of it as it strikes them will drive the wheel around at a great rate of speed. The completed turbine is shown in Fig.

17.

A Model De Laval Steam Turbine. — A real

De Laval turbine has curved blades, a special shaped nozzle and a flexible shaft.

The model turbine which I shall describe has curved blades and a regular De Laval nozzle but the flexible shaft need not be made. Since this turbine will run at a high rate of speed the wheel carrying the blades must be very accurately balanced and while you can make such a wheel if

Fig. 1 8. A Toy Gyroscope

you are a pretty good mechanic, I will tell you an easier way to get one.

You can buy a toy gyroscope x like the one shown in Fig. 18 for 25 cents. The lead wheel in the ring bearing runs very true considering its small cost and you would have hard work to make as perfectly a balanced wheel.

1 A gyroscope of this kind can be bought of the E. J. Horsman Company, n Union Square, New York City.

The Tools You Need. — To make this turbine you need (a) a small machinist's hammer, (b) a pair of tinner's shears, (c) a jeweler's saw frame and saws, (d) a drill stock and drills, (e) a set of taps and dies for cutting screw threads, (f) a jeweller's soldering copper, (g) a couple of files, (h) a pair of compasses for dividing off spaces and scribing circles, and (i) a needle reamer for making tapering holes.

Making the Turbine Wheel. — To make this turbine so that it will be efficient is a harder task than to make any other kind of an engine and my advice is not to start unless you have lots of patience and are willing to work painstakingly.

Begin by taking the wheel shaft of the gyroscope out of its ring bearing and from this moment on be more than careful not to bend the shaft, dent the wheel or to mar either one of them, for if you do the wheel will never run true again.

Take your compasses and draw a circle on a sheet of paper exactly the size of the gyro wheel and divide it into equal divisions % inch apart, or as nearly as you can and still make them come out even as shown at A in Fig. 19. Glue this paper pattern, or template as it is called, on the wheel and place one end of the shaft between a couple of pieces of sheet lead and then screw it up in your vise; the purpose of the lead is to keep the rough surfaces of the jaws of the vise from marring the shaft.

Put a saw blade in your jeweler's saw frame and use a blade that is the same thickness as that of the sheet tin, or brass, you intend to use for the blades of the turbine wheel. Saw a slot %e inch deep in the rim on each line of the paper and be sure to saw each slot straight across the rim of the wheel and straight down on the line of the paper so that each one will be in a radial line with the center of the wheel.

Forming the Blades. — Having sawed the slots in the wheel, the next thing is to make the blades. If the wheel of your gyro is 2% inches in diameter, which is the usual size, the circumference of the wheel will be about 8% inches, and since the blades are to be set % inch apart there will, of course, be 35 blades.

The blades should be made of sheet brass about %o inch thick and all of them must be as nearly alike as you can make them. Make each blade

/v

% inch wide and cut out the corners to form a shank % inch wide and %e inch high as shown in the drawing at B, Fig. 19.

File up all the blades nice and smooth and

Kn

Fig. 19. Construction of the Turbine Wheel then bend them into the shape shown at C. To do this get a piece of iron rod /4 inch in diameter and 3 or 4 inches long; file out a half-round groove in a piece of brass or iron until it fits the

% inch iron rod exactly. Lay the grooved form on a solid surface, place a flat blade on it, hold the iron rod over it, give the latter a sharp tap with your hammer and the blade will be bent to the proper shape.