Chapter V: Some Simple Models for Beginners

I. HOW TO MAKE A BOAT WITH A SCREW PROPELLER.

BY F. CHASEMORE.

To make a model steamboat that will go is the ambition of most boys, but the high price of engine and boiler deters many from doing so. In this chapter instructions are given for making a model screw steamboat, the machinery for which every boy can make for himself, by the exercise of a little ingenuity, at a very trifling cost--which machinery, too, may be fitted into any boat, the rigging of which may have gone by the board off the dangerous coast of the duck-pond.

First you must procure your boat; but if you should wish to make the boat yourself you will need no instructions from me, as several capital chapters on boat-building appear in another part of this volume. The only directions I need give are, that your craft shall be very light, and hollowed out as thin as possible, be twenty-four inches long, four inches wide at midships, and three and a half inches deep; the sternpost to be about an inch and a half within the stern, to be raking, and two and a half inches high, as marked in Fig. 1; a strip of lead one-eighth of an inch thick to be fastened along the bottom of the keel; the bows to be sharp, and the boat to have a clean run aft. When the boat is finished paint it, and when dry put it into water, and mark on the sternpost the height the water comes. Now you must bore a hole in the sternpost right through into the boat, in the direction of the top of the stem. This must be done with a red-hot wire; the hole is to be three-eighths of an inch across.

The next thing to do is to get a brass tube from the gasfitter’s, or get a tinman to make you one of tin three-eighths of an inch inside measurement. This tube must be long enough to reach from the sternpost to three and a half inches beyond the top of the stem. Four inches from one end of this tube solder a strip half an inch wide and one and three-quarter inches along, bending the middle of it half round the tube, and bending the ends outwards; punch a hole in each end of this strip; in this end of the tube cut four teeth like saw-teeth, one-eighth of an inch deep, like Fig. 2. Put this tube in the boat thus. Push the end, without the tin strip, through the hole in the sternpost from the inside of the boat, so that the tube is flush with the wood, and fasten the other end by driving tacks through the holes in the tin strip into the boat. Put some putty round the tube where it goes through the wood, to keep the water out. Now make the deck of board one-eighth of an inch thick, plane it, and fix it in its place by pins, leaving a gunwale of half an inch all round. Stop up with putty, and mark with a pencil the boards on the deck. Bore a hole near the stern one-sixteenth of an inch wide right through the deck and boat, coming out under the counter one inch from the sternpost. This is the rudder-hole. To make the rudder get a piece of brass wire one-sixteenth of an inch in diameter, and six inches long; cut your rudder out of tin, and solder it on to the wire, so that the heel of the rudder is flush with one end of the wire. Now push the other end up through the hole in the counter, and bend it down on to the deck; this will form the tiller, and, by pressing tightly on to the deck, will keep the rudder firm and in its place for steering.

Two inches abaft the middle of the deck cut a hole three-quarters of an inch in diameter for the chimney, which is a tube of tin three-quarters of an inch in diameter and four inches long. Bore two more holes in the deck three-eighths of an inch in diameter, one halfway between the stem and chimney, the other halfway between the rudder and chimney; these are for the masts, which are made of wood, and should stand about nine inches above deck; put a pin into the end of each mast, and cut the head off, leaving about half an inch of the pin projecting; put the masts in their places, and the pins will keep them firm by being pushed into the bottom of the boat.

Make the propeller out of a circular piece of stout tin two inches in diameter, cut as in Fig. 3. The dark parts are to be cut away. The projections are to be three-quarters of an inch long. Punch a hole one-sixteenth of an inch in the centre, and fix a piece of brass wire one-sixteenth of an inch, two inches long, in the hole, to form an axle for the propeller. Twist each of the fans of the screw out of the plane of the circle about a quarter of an inch, in the manner of the sails of a windmill, as in Fig. 4. Now make two little wooden plugs three-quarters of an inch long, and half an inch wide at one end, tapering to a quarter of an inch at the other. Bore a hole through each from end to end one-sixteenth of an inch wide. Take the propeller, and put a glass bead, that will fit easily, on the wire, and push the wire through one of the wooden plugs from the large end; bend the wire into a loop at the small end. Next take another piece of wire, two and a half inches long, and make a similar loop at one end, and put the other end through the other little plug, from the small end, and bend the wire into a handle (Fig. 5). Now the only thing we want is the power. This is a strip of strong elastic about three and a half feet long and a quarter of an inch wide; tie the ends together to make a band--a large stout elastic ring will do, or two smaller rings looped together. Fasten a string to the elastic, and pass the string through the tube in the boat, from the stern end; hook the loop on the propeller-wire into the elastic, and push the wooden plug into the tube so that the screw is clear of the rudder; draw the elastic, by the string, through the other end of the tube, and hook the wire in the other plug into it; take off the string and push the plug into its place. You must cut the plug away so that the handle can catch in the teeth cut in the tube. Now the boat is ready for use.

To use it wind up the elastic by the handle at the end of the tube, holding the screw firmly with the other hand. As soon as wound up enough set the rudder and put the boat into the water; release the screw, and the boat will go till the elastic is quite unwound. The distance it will travel will be regulated by the extent to which the elastic is wound up.

II. HOW TO MAKE A SMALL MARINE ENGINE FOR A BOAT FOUR OR FIVE FT. LONG.

BY FRANK CHASEMORE.

I have already described the method of making a small boat move through the water by means of an elastic band, which is simply twisted up and then released, but I have no doubt that many readers would like to possess a simple model boat to work by steam.

Such models can now be purchased at all shops where mechanical toys are sold, at prices varying from one shilling, the smallest, eight inches in length, to about twenty pounds, the largest, five feet in length. Although all these boats really go by steam, the application of the power is different in the different sizes.

The small boats are of course the simplest. In these the steam from the boiler is conducted through a short pipe to the sternpost of the boat, where by its pressure on the water in escaping it forces the boat along.

The next class have a further development of the application of steam-power. In the centre of the boat, close behind the boiler, is a fan-wheel, turning on an axle, which in the case of a paddle-boat carries the paddles, and in the case of a screw carries the propeller. The steam is conducted from the boiler through a short pipe to the front of the fan-wheel, which it blows round as it escapes.

The third class are the steamboats proper, varying in price from five shillings upwards. In these the steam-power is applied as in ordinary engines. The cheapest have one single-action oscillating cylinder, and the better sorts two double-action cylinders.

As the two first-mentioned classes are, after all, only imitations, I do not think it worth while to describe them; and of the third class I have chosen the largest to describe, as I think that if it is worth while making a model at all, it is worth while to make a good one, and the small engines take almost as much time to make, and quite as much care to fit, as the large ones, and unless they are well fitted the loss of power by friction and waste of steam is very great.

The engine here described is a model of a real screw-engine, with a pair of double-action oscillating cylinders, having reversing gear and boiler complete, ready to be put into the boat. It will be capable of driving a boat from four to five feet long, provided it is well hollowed out and that the engine is made and fitted with care, to reduce friction and waste of steam as much as possible.

In this section the exact dimensions of the several parts are given when possible, but, owing to small differences in the size of the cylinders, I am only able to approximate in some cases--in which cases, however, I have used the word ‘about,’ at the same time explaining how to obtain the exact measurements.

In all engines the most important parts are the cylinders, which must be well fitted. Boys who have a turning-lathe and the requisite practice in metal-turning can buy rough castings of all the parts of the engine for a few shillings and finish them up themselves. But as only a few of my readers may be so favoured, I will suppose that the cylinders are purchased ready for use. For these cylinders there is a great range in the prices quoted by different firms, the prices varying for the No. 4 cylinder from eight shillings at one firm to twelve shillings and sixpence at another. Messrs. Theobald and Co., of 20, Church Street, Kensington, quote the lowest prices to me, and have further consented to supply the No. 4 double-action oscillating cylinders for this engine at seven shillings each to any one mentioning this section.

The dimensions of these cylinders are three quarters of an inch in the diameter of the bore, and an inch and a half in the length of stroke--_i.e._, an inch and a half difference in the length the piston-rod projects from the top of the cylinder when in and out to its fullest.

Get a pair of these cylinders which have the steam-blocks, pivot-pillars, and screw-crossheads complete. Ask for the No. 4 double-action oscillating cylinders. When buying them see that the piston-rods work true, and not to one side; see also that the small indentations on the opposite sides to the steam ports are correctly drilled, so that when the cylinders are swung between the blocks and pivots they work true. To test this, place the block on its back on the table, and put the cylinder on it, with the pivot in the proper hole for it. Now turn the cylinder round on the block and place a pin in the indentation, and if it is truly drilled the pin will not move; but if not, the point of the pin will describe a small circle. You can find out by this pin the exact spot where the pivot-hole ought to be drilled.

We will now set to work at the construction of the engine, and the first thing to be done is to make the top plate (Fig. 1). For this get a small brass plate four inches long and three inches wide, and an eighth of an inch thick, with a projecting piece an inch and a quarter square at one end of it, as in the figure. Get two of these plates, as the second will be required for the bed-plate, but will not have the square projecting piece. Take the first of these plates and square it up, so that each corner is a right angle. Now proceed to mark it as in Fig. 1. Divide the large part lengthwise into two equal parts by the line C D, and crosswise, also into two equal parts by the line A B, these two lines intersecting in the point O. From this point mark off, each way along the lines O C and O D, the following distances. O to _x_ a quarter of an inch, and _x_ to _y_ an inch and a quarter; and through these four points draw the lines _e-g_, _f-h_, _k-m_, and _l-n_, making them two inches long each, and projecting one inch on each side of the line C D. Join the points _e-f_, _g-h_, _k-l_, and _m-n_.

Cut out the two rectangles so formed carefully, so as not to injure the lines. This can be done easily by first drilling a small hole, about an eighth of an inch in diameter, near one corner, and then putting a fretwork saw through it and fixing it in the frame, and sawing the metal away just inside the lines. The saw must be kept well moistened with water. The corners can be left circular, which will add to the finish of the plate, and make the cutting with the saw easier.

After the holes are cut they must be finished quite up to the lines, but without injuring them, with a fine-cut flat file. Through each corner of the plate a hole must be drilled an eighth of an inch in diameter, and about an eighth of an inch from the edges, as in Fig. 1. The top plate is now ready for mounting the cylinders on, which we will set about doing.

Take the two steam-blocks (Fig. 2) and draw a pencil mark on each from the centre hole to the bottom, and at right angles to it (Fig. 2). Next place the two blocks back to back on the middle of the top plate, between the two large holes, so that the pencil marks coincide with the line C D, and so that the bottom edges of the faces coincide with the lines _f-h_ and _k-m_. Be very careful in setting these blocks right. When in their places mark the top plate through the screw-holes in the projecting bases of each, and drill four holes straight down through the plate, making them a little smaller than the holes in the bases of the blocks. Now replace the blocks and fasten them there with two small screws each. These screws correspond with the size of the cylinders, and can be purchased by the dozen, together with taps, for each size, to make the thread in the holes with.

Next take the pivot-blocks and mark them with pencil, as the steam-blocks were marked, and put them on the line C D on the outer sides of the large holes, using the same care to get them properly centred along the line C D, and at right angles to it, and about an eighth of an inch from the lines _e-g_ and _l-n_. Mark the screw-holes and drill them as before, and fasten the pillars in their places.

Now the cylinders can be hung. Unscrew the pivots about a quarter of an inch and place the cylinders in their places, with the spindles in the proper holes for them in the blocks. Now screw in the wire pivots till they catch in the indentations drilled for them in the sides of the cylinders. They will now swing freely between the blocks and pivots.

Now to cut the bed-plate (Fig. 3). Take your second brass plate and divide it by the lines A B and C D as before. From the point O mark off each way along the line C D the distances five-eighths of an inch from O to _x_, and three-quarters of an inch from _x_ to _y_. Through these points draw four lines two inches long, and projecting one inch on each side of the line C D, and parallel to the line A B. Join the lines in pairs as before, and cut out the rectangles so formed. Finish up the edges, and bore a hole in each corner, as in the top plate. On the line A B, and half an inch from each end, bore two holes an eighth of an inch in diameter, and countersink them at the top, as in the figure.

Now the bearings for the crank-shaft must be made. Fig. 4 is a perspective view of one of these. Get two pieces of brass one inch long, half an inch wide, and a quarter of an inch thick, as Fig. 5. Along the face of each block draw a line, dividing it lengthwise into two equal parts, and in the centre of these lines drill a hole right through the brass one-eighth of an inch in diameter. Cut the brass away at the ends (as in Figs. 4 and 5), leaving the projecting pieces a quarter of an inch long and a little more than one-sixteenth of an inch thick. Through each of these flanges drill a hole, to screw the bearings to the bed-plate by. Drill two holes down through the top of the block, passing one on each side of the bearing-hole (as in Fig. 5, the dotted lines showing the positions of the holes). Drill a small hole through the top of the cap into the bearing-hole, for oiling purposes. Cut the block in two along the line passing through the middle of the bearing-hole with a stiff-backed saw. This will make the block as in Fig. 6, having a movable cap which can be fastened in its place with two screws. Screw these bearing-blocks in their places, one at each end of the bed-plate, using the same care to get them properly centred along the line C D and at right angles to it.

We must now make the crank-shaft. This can be made with bent wire one-eighth of an inch thick. But when made in this way it very seldom works steadily and true. The best way is to build it up. You must get a piece of iron wire a quarter of an inch in diameter and about two feet long. Part of this will be required for the screw-shaft; straighten and smooth the wire and polish it up. Cut from the end three pieces, one an inch long, the second two inches long, and the third one and seven-eighths of an inch long. Next get four pieces of flat iron plate one-eighth of an inch thick, one inch long, and half an inch wide. Cut them into the shape shown in Fig. 7. The distance between the centres of the holes is to be a little less than three-quarters of an inch. The largest hole is one-eighth of an inch square, and the smallest hole a little less. The metal is to be left one-eighth of an inch wide round the holes. Take the shortest piece of iron wire and cut one end of it away, leaving a square pin and shoulder; the pin is to be three-sixteenths of an inch long, and one-eighth of an inch square (Fig. 8). Cut both ends of the two-inch piece and one end of the remaining piece in the same way. Counter-sink the largest holes in the plates (Fig. 7) and rivet them on the pins of the portions of the shaft, being careful that they are at right angles to the rods. The plates on the two-inch piece must be at right angles to each other. The pins should fit very tightly in the holes, to make them firm when riveted.

Cut two pieces of iron wire one-eighth of an inch in diameter and five-eighths of an inch long, and at each end of each piece make a pin and shoulder to fit the small holes in the plates, leaving a full quarter of an inch of the wire between the pins untouched. Join the cranks together in pairs by riveting in these wires, being careful to keep the cranks at right angles to the shaft, and also to keep the several pieces of the shaft in the same straight line. Place the shaft on the bearing-blocks in the position it will occupy, with the cranks over the holes in the bed-plate and with the longest end to the after end of it. Mark on the shaft the position and thickness of the bearing-blocks, and cut the metal of the rods away in these places till it is reduced to one-eighth of an inch in thickness, so that it will work freely in the bearing-holes. The crank will now look like Fig. 9.

The next step is to connect the top and bed-plates by four pillars. The length of these will depend on the length of the piston-rod. They must be made of four pieces of brass wire a quarter of an inch thick. Take one of the cylinders and a sheet of paper; on this paper draw a line about six inches long, and at one end mark the point A (Fig. 10). Push the piston-rod in as far as it will go, and push the pivot of the cylinder through the point A, and mark on the line the point B, exactly under the hole in the crosshead of the piston-rod. Now draw out the piston-rod as far as it will go, and mark the point C exactly under the hole as before. Bisect the portion of the line between B C in the point D, and measure the distance between A and D. Reduce this length by the distance the centre hole in the steam-blocks is from the lower edge, and add to it a quarter of an inch for the height of the centre of the bearing-block from the upper surface of the bed-plates, one-eighth of an inch for the thickness of the bed-plate, and a quarter of an inch for riveting.

This will give you the length of the pillars including the pins. File a pin and shoulder at each end, as in Fig. 11, making the pins one-eighth of an inch in diameter and a quarter of an inch long. Rivet a pillar firmly in each corner hole of the bed-plate, and put the top plate on the top ends of the pillars, and rivet them firmly in. Be careful that the pillars are upright. Rehang the cylinders and unscrew the caps of the crossheads. Fit the cranks into the holes in them and screw on the caps.

If the cylinders are made without screw-crossheads the pin of the cranks must be placed through the hole in the heads before riveting the cranks together. Unscrew the caps of the bearing-blocks, and put the crank-shaft into the bearing-holes, and screw on the caps again. Oil all bearings and parts that work together. Now you must get a heavy brass fly-wheel three inches in diameter, which can be purchased with the other things, and costs about two shillings. This wheel has a screw-bolt through one side of the centre block to fix it to the shaft by. Fix this wheel on the long end of the shaft by tightening the screw. It would be better to make a small hole in the shaft for the point of the screw to enter. The wheel must have two iron pins, about one inch long, in the face of it.

Now if all the fittings are well made and oiled, the engine ought to work easily and smoothly without noise if the fly-wheel is spun round.

Fig. 26 at the end of this section represents the engine as finished.

We must now turn our attention to the boiler. For this you must obtain some sheet copper; get the size known as 12-lb. copper--that is, the sheet two feet by eight feet weighs 12 lb. You must also procure some copper tubing one-third of an inch in diameter. Get also the following articles; two brass gauge-taps, 1s. 3d. each; one steam-tap with union, 1s. 6d.; man-hole or water-filler, 1s. 6d.; spring safety-valve set to 30 lb. the inch, 1s. 4d. If these are not already fitted with screw-blocks get them so fitted when buying them. Fig. 12 represents the safety-valve with the screw-block.

Cut out of your copper a piece (Fig. 13) eighteen inches and three-quarters long and nine inches wide. Draw a line A B at right angles to the two long sides, and bisecting them. From A and B mark off the distances shown in the figure. Bore the holes, C, D, E, and F, the sizes marked, and in the places indicated. Bend the plate so that the middle eight inches form a semicircle with a radius of two and a half inches, and the five-inch parts are straight and five inches apart. Turn in the remaining half inch at each side to form a foot for the boiler to stand on. The copper will now be like Fig. 14, and will form the body of the boiler. Take two small sheets of copper eight inches long by six inches wide, and mark one as in Fig. 15 and the other as in Fig. 16. Cut them out carefully, and in Fig. 15 bore two holes one-eighth of an inch in diameter in the places marked. Turn up the edge all round the sides and circular portions of both plates, a quarter of an inch wide, till it is at right angles to the other part of the plate, as in Fig. 17. Fit one of these pieces on each end of the boiler body, so that the turned-up edges of the ends fit outside the boiler body. The Fig. 16 is to fit over the end of the boiler that has the two holes in the top. Solder or braze the ends to the boiler body.

I should strongly recommend all the joints of the boiler being brazed, as in the event of the vessel steaming far from shore, the water running short, and the lamp still burning, it would melt the solder, and the boiler would fall to pieces, but if brazed it would not be injured if made red-hot. If you solder the parts together you can do it yourself from directions given in the section on the magic-lantern, but in soldering copper or brass together both surfaces of the joint must be first tinned over.

If you decide to have the joints brazed you can get it done at the ironmonger’s, if you first cut out and fit the parts together and explain what you require. The floor of the boiler is made out of a piece of sheet copper nine inches long and seven and a half inches wide. Mark it as in Fig. 18. Bend it along the lines into the shape shown in Fig. 19. In the middle of the top make a hole one-third of an inch in diameter. Bore seven holes one-third of an inch in diameter along each of the sides and half way up. Cut a piece of the brass tube six and a half inches long, and braze one end of it into the hole in the top, as in Fig. 19. Cut seven pieces of the tube four and a half inches long each, and connect the holes on opposite sides by brazing the tubes across into the holes, as in the figure. Take the screw-block off the safety-valve and solder it over the hole marked D in Fig. 13 on the inside of the boiler. Solder the screw-block of the steam-tap inside over the hole marked F, and solder on the inside the two blocks of the gauge-taps over the holes in the end of the boiler. The block of the man-hole must be brazed on the outside over the hole C, Fig. 13.

Now fit the floor of the boiler in its place, passing the end of the tube, fastened to the top of it, through the hole marked E in the top of the boiler, and projecting about half an inch, and braze it in. Fig. 20 will show the position of the boiler floor. The top of it is to be two inches from the bottom of the sides. Braze it in firmly, being very careful to make all the joints steam-tight. Screw in the man-hole cover, safety-valve, steam-tap, and gauge-taps. On the top of the boiler and over the projecting pipe solder a piece of brass tube seven inches long and an inch and a quarter in diameter, raking aft a little, for the funnel. Now the boiler is finished and ready to be connected with the engine. But before this can be done we must make the reversing-gear.

Procure a block of brass, three-quarters of an inch wide, one inch long, and half an inch high. Square this up true, and bore a hole right through it from top to bottom, three-sixteenths of an inch in diameter. With the end of a rat-tailed file taper the hole to a little more than a quarter of an inch at the top. Get a piece of brass rod a little more than a quarter of an inch thick, and file one end of it taper to fit the hole, and square off the bottom end of it, making the taper portion half an inch long. Smoothen this with fine glasspaper, and then oil it and dust over it some fine emery-powder, and put it in the hole in the block and grind the two together till they fit perfectly. Cut the taper portion off exactly the length of the depth of the block.

Cut the brass away at the ends of the block, leaving a flange at the bottom, at each end, a quarter of an inch long and one-sixteenth of an inch thick, as in Fig. 21. In each flange bore two small holes, to screw it to the top plate by. Drill four holes, one through each side of the block one-eighth of an inch in diameter, right into the centre hole and at right angles to each other, as in Fig. 21. Wipe the plug and hole quite clean from the oil and emery, and replace the plug. Put a needle-point into one of the side holes, and lying on the bottom of it and pressing against the plug. Turn the plug round in the socket. Now move the needle-point to the top of the hole and turn the plug round again.

Take out the plug, and there will be two lines one-eighth of an inch apart scratched all round it, as in Fig. 22. With a small round file cut two grooves opposite each other in the plug, by filing between the scratched lines, leaving the brass between them one-sixteenth of an inch or less thick, as seen in Fig. 22. Drill a hole one-eighth of an inch in diameter and a quarter of an inch deep down the top end of the plug, and another up the lower end, to fit one of your small screws. Be careful that neither of these holes enters the grooves.

Cut a small circular plate of copper seven-sixteenths of an inch in diameter, and drill a small hole in the middle of it. Give this plate two or three taps with a small hammer in the middle to hollow it a little. Put the plug in its place in the block, and turn it over and place the circular plate on the bottom, with the concave side to the plug, and fix it there with a screw. This will keep the plug from coming out of the block. Solder an iron wire one-eighth of an inch thick and six inches long into the hole in the top of the plug. Fasten the block on to the square projecting piece of the top plate, first cutting out of it a circular hole half an inch in diameter, to let the circular plate at the bottom of the plug drop into. The valve must now be connected with the steam-blocks. Take two pieces of steam-pipe three-sixteenths of an inch in diameter and an inch and a quarter long, and bend them the shape of Fig. 23, so that the distance apart of the ends is the same as from one hole in the top of one block to the corresponding hole in the other.

Cut a hole in one side of the bent piece, as in Fig. 23, large enough for the end of another piece of the pipe to fit into when tapered a little. This piece is to be about three and a quarter inches long, and bent so as to pass from the steam-blocks round the cylinder to the hole in that side of the reversing-valve block. Fit the end of this pipe into the hole in the bent tube and braze it in the following way. Rub a small lump of borax on a moistened tile and rub the joint to be brazed with the mixture of borax and water. Cut a small piece of silver off a threepenny-piece about the size of a large pin-head, and put it on the joint. Now hold the end of the tube in the left hand, covered with a cloth, and with a blow-pipe direct the flame of a spirit-lamp or gas-jet on to the joint till it is red-hot, when the silver will melt and flow round the joint and fix it. If you cannot do this yourself a jeweller or watchmaker will do it for you. Make two of these bent tubes with double ends, and solder them in their places, connecting the steam-blocks with the reversing-valve. You must enlarge the holes, to let the ends of the pipe in before soldering.

Bend a piece of steam-pipe, a quarter of an inch in diameter and eight inches long, so that about two inches of one end stands at right angles to the other part. The bend must be circular, or it will compress the pipe. Solder this end firmly into the front hole in the reversing-valve. Bend another piece of the pipe about the same length so as to go into the after hole of the valve and be parallel with the other pipe. On the top of the boiler solder a piece of pipe about six inches long; one end is to be bent up about one inch and inserted through a hole in the bottom of the funnel, and directed upwards inside, the other end is to project about one inch from the end of the boiler.

In the end of the steam-pipe solder the union of the steam-tap. Next make the stand for the engine and boiler. Make it out of a piece of deal eighteen inches long, five inches wide, and half an inch thick. Screw the bed-plate of the engine on one end of it, so that the after end of the plate is flush with the stand. The wood must be cut away under the square holes, to let the cranks work in. Screw two strips of copper at the other end, for the turned-in feet of the boiler to slide under. Put them so that the end of the boiler will be about three and a half inches from the fore end of the bed-plate. Put the boiler in its place, and bend the steam-pipe so that the union can be screwed to the steam-tap and the exhaust-pipe so that the end of it is opposite the projecting pipe from the boiler, and connect these two ends with a piece of indiarubber tubing.

The spirit-lamp must be in the shape of a closed box, made of sheet copper, four inches wide, eight inches long, and three quarters of an inch deep. In the top cut five holes, as in Fig. 24, a quarter of an inch in diameter. In these holes solder five tubes half an inch long, and projecting from the top a quarter of an inch. These are for the wicks. At the front end of the top solder a screw filling-tap. At this end solder also a piece of small pipe four inches long. This is to be bent so that it will stand upright outside the end of the boiler, and is to act as a vent, to prevent the spirit being forced too freely up the wicks. Fill the wick-holes tightly with cotton. Now fill the lamp half full of spirit. Pour hot water into the boiler till it just flows out of the top gauge-tap. See that all the taps are turned off. Light the lamp and put it under the boiler, and while steam is getting up oil the engine well with sewing-machine oil. In a short time the steam ought to be up and the engine at work. Try the reversing-gear and see if it acts properly. The engine ought to work smoothly and without noise, and the frame ought not to jar.

We must now make the screw propeller. The boat, which I suppose already made, is to be five feet long, ten inches wide, and eight inches deep, without the keel, and hollowed out to about a quarter of an inch thick at the gunwales and three-quarters of an inch thick at the bottom, and must be rather flat-bottomed, as steamships are, so that the inside at the bottom is five inches wide.

Put the engine and boiler in the boat so that the boiler is a little abaft the middle. Cut away the dead wood of the stern to make a hole four inches high and two inches wide, as in Fig. 25. Bore a hole from the hole in the dead wood right through into the interior of the boat, as shown by the dotted lines in Fig. 25. This hole is to be directed to the centre of the fly-wheel of the engine. The shaft is made out of the quarter-inch wire. Cut a square pin and shoulder three-eighths of an inch long and an eighth of an inch square at one end of the shaft. Cut a piece of the same wire three and a half inches long and drill a square hole in the middle, and rivet it on the end of the shaft crosswise. In the hole in the stern of the boat you must fix a tube and stuffing-box, which may be got--together with the screw, which is to be a three-fanned one, measuring three inches across the fans--with the other things, of Messrs. Theobald and Co., and similar houses.

Put the shaft in its place inside the boat, with the cross-piece resting across the pins in the fly-wheel, about half way. Mark the end of the shaft so that it will project an inch and three-quarters, and cut it off there. The bearing must now be made out of a strip of brass one-sixteenth of an inch thick, three quarters of an inch wide, and two inches longer than the width of the inside of the boat. In the middle of this bore a hole a quarter of an inch in diameter, and bend one inch of each end at right angles to the other part. In each bent piece drill two small holes, to screw them to the sides of the boat by. Slip a piece of tubing, one inch long and of a size to fit tightly on the shaft, close up against the cross-piece. Put the shaft through the bearing and stuffing-box tube, and put the cross-piece on the pins in the fly-wheel, and screw the bearing to the boat, so that it is close against the tube on the shaft. The screw has a screw-bolt like the fly-wheel to fix it to the shaft by. Drill a small hole in the shaft for it, and put the screw on the end of the shaft and fix it by tightening the screw.

The deck of the boat must be cut the shape of the inside of the gunwales, out of quarter-inch board, and is to be fixed so that the gunwales are one inch high. It must have a hole cut in the middle to go over the boiler and pipes. A hole must also be cut over the engine, and one also in the front part of the deck large enough to admit your hand, to allow of your removing and lighting the lamp. These two holes ought to be covered by movable skylights. A hole must be bored in the deck just in front of the after-skylight for the wire from the reversing-valve to project about half an inch. A wire handle must be fixed by riveting to the end of this, and two pegs driven into the deck, one on each side, in front, to prevent the handle being turned too far to either side. It should only turn one quarter of the way round.

If you have followed these directions your boat ought to steam for two hours and a half without refilling the boiler; though the lamp would not burn all that time. But if you solder a short piece of tube a quarter of an inch in diameter into the front end of the lamp and quite at the bottom edge of it, and have a closed tin tank with a like tube to it in the front part of the boat, and this tank is filled with spirits, and connected to the lamp by a piece of india-rubber tubing joining the two tubes, the lamp will supply itself from the tank as it gets low. The spirit from the tank will not fill the lamp, but will just cover the hole of the tube and keep at that height so long as there is any spirit in the tank. Such an engine as here described would cost to purchase about £7 10_s._, and the boat with engine complete, quite double that sum.