Boys' Book of Model Boats Part 7

[Ill.u.s.tration: FIG. 99]

[Ill.u.s.tration: FIG. 100]

[Ill.u.s.tration: FIG. 104]

[Ill.u.s.tration: FIG. 101]

A small life-boat is shown in Fig. 100. This can easily be carved to shape from a small piece of soft white pine. The center is gouged out, and tiny little seats made of thin strips of wood are glued in place.

Two small screw-eyes are placed in the boat, for fastening it to the davits. The davits are shown in Fig. 101, at _A_ and _B_. They are made by bending a piece of small bra.s.s rod, as shown. One end of the rod is hammered flat, and a hole is made in it with a very small drill. Holes a little under size are drilled in the deck, and the davits are forced into these. The method of suspending the life-boat from the davits is shown at _B_, Fig. 101. The little blocks of wood are glued on to a thread to represent pulleys, and they are, of course, only imitation or dummy pulleys.

[Ill.u.s.tration: FIG. 102]

The method of producing port-holes is shown in Fig. 102. A hole is first bored through the wood with a bit of the proper size. The size of the port-holes depends entirely upon the size of the boat. A piece of bra.s.s tubing is then cut off with a hacksaw to form a bra.s.s bushing. The outside diameter of this tubing should be the same as the size of the bit used. For instance, if a 1/2-inch bit is used, bra.s.s tubing 1/2 inch in diameter should be purchased. Such tubing can be obtained from any hardware store. Celluloid, such as that used for windows in automobile curtains, is glued to the inside of the port-holes. This makes a splendid subst.i.tute for gla.s.s. It can be obtained at garages and automobile supply stores for a few cents a square foot. The model boat builder can also use either mica or gla.s.s for this purpose, although thick gla.s.s looks somewhat out of place.

A binnacle is shown in Fig. 103. This is made from a solid piece of wood cut with a semi-spherical top. The steering-wheel is made of a wheel from an old alarm clock. The teeth of the wheel should be filed off.

Tiny pieces of wire are then soldered in place on the wheel, as shown. A pin driven through the center of the steering-wheel is used to fasten it to the binnacle. The binnacle itself can be held to the deck either by glue or by a small screw.

[Ill.u.s.tration: FIG. 103]

A torpedo-tube for use on model destroyers and battleships is shown in Fig. 104. First two disks of wood are cut. Then a circular piece is cut, as shown. Two bra.s.s nails are then driven through this piece into one of the disks. An upholstering tack is driven into the end of the circular piece, as pictured. The method of attaching the torpedo-tube to the deck is clearly ill.u.s.trated in Fig. 104 and no further directions need be given. If the model-builder has a small piece of bra.s.s tube on hand suitable for use in this case, it will make a much better appearing tube than the piece of wood ill.u.s.trated.

A wireless antenna is shown at Fig. 105. This is a fitting that will do much toward improving the appearance of any craft. Very fine copper wire is used for the aerial. The little spreaders are cut to shape from wood, and a tiny hole is punched through them through which the wire is placed. Black beads slipped on the wire serve very well as insulators.

The lead-in wire which drops to the wireless cabin is attached to the aerial by winding it around each one of the aerial waves. The aerial should be suspended between the masts of the vessel. A few words should be said about masts in general. If there is one way in which a model-builder can destroy the appearance of a model boat, it is by using badly proportioned masts. The average boy seems inclined to use a mast of too great a diameter, which makes it out of proportion with the rest of the boat. It is better to have a mast too small rather than too large.

The method of producing railing is shown in Fig. 106. The same small bra.s.s rod that was used for the davits can be used for the rail stanchions. One end of the stanchions is hammered flat and drilled out.

The stanchions are fastened to the deck by first drilling small holes and forcing them into it. Thread or very fine wire is used for the railing. Fine wire is preferred owing to the fact that it will not break so easily under strain.

[Ill.u.s.tration: FIG. 105]

[Ill.u.s.tration: FIG. 106]

[Ill.u.s.tration: FIG. 108]

[Ill.u.s.tration: FIG. 107]

[Ill.u.s.tration: FIG. 109]

[Ill.u.s.tration: FIG. 110]

Fig. 107 shows a good method of producing stairs. It must be remembered that stairs are often used in model-boat construction. First a strip of tin is bent as shown. Then two more strips, which act as side pieces, are cut. One of these strips is soldered to each side of the stairs.

Then six stanchions, which can be made from heavy copper wire, are soldered to the side pieces, as shown. The railing can be made from copper wire or black thread.

Fig. 108 shows a small skylight placed on the deck. This is easily made from cigar-box-wood glued together. The holes in the top pieces for the windows are cut with a very sharp knife. It will be necessary to use a little patience in this, to prevent the piece from splitting and to prevent cracks. A piece of celluloid is glued underneath the top pieces before they are finally glued in place.

A small quick-firing deck-gun is shown in Fig. 109. This is a very simple fitting and can be made with very little difficulty. The base of the gun is formed by cutting a thread-spool in half. A piece of small bra.s.s tubing is used to form the barrel. A little piece of sheet tin is looped over the back of the gun to represent the breech. A tiny piece of wire is held to the side of the breech with a drop of solder, to represent a handle. The shield of the gun is cut from a piece of tin, as shown. A hole is made in the bottom of this, so that the nail that pa.s.ses through the barrel of the gun will also pa.s.s through this hole and into the spool. The center of the spool should be plugged to hold the nail. After the gun is painted gray or black it will appear very businesslike, considering the small amount of labor spent in producing it.

Anchors are more or less difficult to make (Fig. 110), and unless the builder is endowed with a great amount of patience he will not be able to file them out of solid metal. A dummy anchor can be easily cut out of wood, however, and when painted black it will answer instead of a metal one. The anchor shown at _A_ is a very simple type made out of a solid piece of wood. The one at _B_, however, is made out of two pieces of wood fastened together with a pin, as shown. The bottom piece of the anchor shown at _B_ should be rather thick to get the proper effect, and the two points should be tapered nicely. The center of the bottom piece should be hollowed out to accommodate the vertical piece.

A common hatch is shown at Fig. 111. This can be made in the form of an open box from cigar-box wood, and glued to the deck. It is not necessary to cut a hole in the deck for this purpose.

[Ill.u.s.tration: FIG. 115]

[Ill.u.s.tration: FIG. 116]

[Ill.u.s.tration: FIG. 111]

[Ill.u.s.tration: FIG. 113]

A cargo-hoist for use on model freight-boats is shown in Fig. 112. This is a very simple piece of work and will need little description. Several stay-wires should be fastened to the main-mast and held to the deck with small screw-eyes. The boom should be made a trifle smaller in diameter than the mast. The pulleys are dummy, like those on the life-boat. A little hook bent to shape from copper wire is placed on the end of the thread, as shown.

[Ill.u.s.tration: FIG. 112]

[Ill.u.s.tration: FIG. 114]

Fig. 113 shows a method of making a whistle and an engine exhaust. The engine exhaust is made of a piece of wood, and the furled top is produced by an eyelet such as those used in shoes. The engine exhaust is always placed immediately back of the last smokestack. The whistle is a simple device made almost entirely of wood. The whistle-cord is of thread attached to the small piece of wire, as shown.

Fig. 114 shows the method of making spray-cloths for the top of the pilot-house. Small bra.s.s brads are driven into the top of the pilot-house, and white adhesive tape is placed on the brads, as pictured. Advantage can be taken of the adhesive substance on the tape which holds it in place on the brads.

A rudder is shown in Fig. 115. The rudder-post should be a piece of bra.s.s rod so thick that it can be split with a hacksaw. The sheet bra.s.s that forms the rudder proper is placed in this split and soldered. In the case of an ornamental boat the rudder can be fixed as shown in Fig.

115. It will be seen that it is quite impossible to keep the rudder in adjustment in this way.

If the rudder is to be kept in a certain adjustment a quadrant is necessary. This is made by using a semicircular piece of heavy sheet bra.s.s and filing little notches in it. The lever of the rudder rests in these notches, and by this means the rudder can be held in any one position, so that the boat will either turn in a circle or go straight.

Fig. 116 ill.u.s.trates such an arrangement.

CHAPTER X

THE DESIGN OF MODEL STEAM-ENGINES

INSTEAD of describing the construction of several model engines of different design, the author thinks it advisable to put the reader in possession of the fundamentals of model steam-engine design and construction. In this way the model engineer will be able to design and construct model steam-engines according to his own ideas and in accordance with the raw materials and miscellaneous parts he may find in his workshop. Unless the young mechanic is in possession of a very well equipped workshop, it is quite impossible to construct a steam-engine according to certain specifications. However, if he has in mind the fundamental principles of steam-engine design, he can go ahead and design his engine, for which he will have no trouble in machining or producing the parts that enter into its construction. By this the author means that the workman can design his engine to meet the materials he has on hand.

Notice Fig. 117. This is a cylinder into which is fitted a piston. If steam is forced into the cylinder the piston will be forced to the opposite end of the cylinder. If some means is then provided so that the steam can escape and the piston come back, another impulse can be given it by admitting more steam, and thus a continuous motion may be produced. This is how the steam-engine works.

[Ill.u.s.tration: FIG. 117]

Having learned how motion is imparted to the piston by the expansion of steam under pressure, attention is directed to what is known as the "D"

slide-valve. This slide-valve permits steam to enter the cylinder and to exhaust at proper intervals. See Fig. 118. Steam enters the steam-chest through the pipe _A_. The slide-valve is shown at _D_. When the slide-valve is in the position shown, steam enters the cylinder, and by the time the cylinder has arrived in the position shown by the dotted line _C_, the slide-valve moves over, closing the pa.s.sage _B_. The steam under pressure forces the piston to the opposite end of the cylinder.

When the piston reaches the opposite end of the cylinder, steam that has entered through the pa.s.sage _F_ again forces the piston back to its original position. This is caused by the slide-valve shifting its position, because of the impulse it received at the opposite end of the cylinder. Thus it will be seen that when the piston is at one end of the cylinder the opposite end is exhausting. By carefully studying Fig. 118 the action of the _D_ valve will be understood. The connecting-rod _E_ is connected to the crankshaft and in this way the engine is caused to revolve.

[Ill.u.s.tration: FIG. 118]

A cylinder similar to that shown in Fig. 118 is called a double-acting cylinder. This is because the steam acts on both sides of the piston.

Single-acting cylinders are cylinders in which the steam expands on only one side of the piston. In the single-acting engines the _D_ valve is modified.

The "stroke" of a steam-engine depends upon the length of the cylinder; really, the stroke is the distance travelled by the piston. In model engines it ranges from 3/8 of an inch to 1-1/2 inches. The bore of a cylinder is its internal diameter. The bore is usually a trifle smaller than the stroke. Thus it is common to have a stroke of 7/8 inch and a cylinder-bore of 3/4 inch.