Fig. 103
A torpedo-tube for use on model destroyers and battleships is shown inFig. 104.First two disks of wood are cut. Then a circular piece is cut, as shown. Two brass 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 illustrated inFig. 104and no further directions need be given. If the model-builder has a small piece of brass tube on hand suitable for use in this case, it will make a much better appearing tube than the piece of wood illustrated.
A wireless antenna is shown atFig. 105. This is a fitting that will do much toward improving the appearance of any craft. Very fine copper wire is used for the aërial. 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 aërial by winding it around each one of the aërial waves. The aërial should be suspended between the masts of the vessel. Afew 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 inFig. 106. The same small brass 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.
Fig. 105
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 issoldered 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 inFig. 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 brass 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 oftin, as shown. A hole is made in the bottom of this, so that the nail that passes through the barrel of the gun will also pass 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 atAis a very simple type made out of a solid piece of wood. The one atB, however, is made out of two pieces of wood fastened together with a pin, as shown. The bottom piece of the anchor shown atBshould 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 atFig. 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.
Fig. 115
A cargo-hoist for use on model freight-boats is shown inFig. 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, likethose on the life-boat. A little hook bent to shape from copper wire is placed on the end of the thread, as shown.
Fig. 112
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 lastsmokestack. 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
Fig. 114 shows the method of making spray-cloths for the top of the pilot-house. Small brass 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 inFig. 115. The rudder-post should be a piece of brass rod so thick that it can be split with a hacksaw. The sheet brass 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 inFig. 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 brass and filing little notches in it. The lever of the rudder rests in thesenotches, 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. 116illustrates such an arrangement.
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. Bythis the author means that the workman can design his engine to meet the materials he has on hand.
NoticeFig. 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.
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. SeeFig. 118. Steam enters the steam-chest through the pipeA. The slide-valve is shown atD. When the slide-valve is in the position shown, steam enters the cylinder, and by the time the cylinder has arrived in the positionshown by the dotted lineC, the slide-valve moves over, closing the passageB. The steam under pressure forces the piston to theoppositeend of the cylinder. When the piston reaches the opposite end of the cylinder, steam that has entered through the passageFagain 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 studyingFig. 118the action of theDvalve will be understood. The connecting-rodEis connected to the crankshaft and in this way the engine is caused to revolve.
Fig. 118
A cylinder similar to that shown inFig. 118is called a double-acting cylinder. Thisis 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 theDvalve 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 from3/8of an inch to 11/2inches. 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 of7/8inch and a cylinder-bore of3/4inch.
At this juncture the author would caution the more inexperienced young mechanics not to build double-acting engines. The valve mechanism is somewhat intricate and very difficult to regulate. The construction is also much more complicated, and this also holds true of the designing. On the other hand, single-acting engines, while not so powerful for a given size, will do very nicely in driving model boats, and will deliver sufficient power for all ordinary purposes.
Fig. 119
Your attention is directed toFig. 119. This shows a design for a model single-cylinder, single-acting steam-engine. The reader should carefully study each drawing before continuing to digest the following matter. The cylinderLcan be made from a piece of tubing. This can be either brass or copper. Aluminum should not be used, owing to the fact that it is difficult to solder and difficult to work with. The piston is made so that it will fit nicely into the cylinder and move up and down without binding. It will be seen that a groove,M, is cut aroundthe piston near the top. String soaked in oil is placed in this groove. This is called packing, and the presence of this packing prevents steam leakage between the piston and the cylinder walls and thereby materially increases the efficiency of the engine.
In this case the connecting-rodRis made in a circular piece. It is attached to the piston by a pin,F. The connecting-rod must be free to revolve upon this pin. The engine shown has a stroke of7/8inch. Therefore, the crank-pinKon the crank-diskNmust be placed1/2of7/8or7/16inch from the center of the diskN, so that when this disk makes one revolution, the piston will move7/8inch in the cycle. Thus it will be seen that the distance of the crank-pinKfrom the center of the crank diskNwill depend entirely upon the stroke of the engine. It may be well to mention here that the worker should always start designing his engine by first determining the bore and stroke. Everything depends upon these two factors. It is also well to mention here that the piston should never travel completely to the top of the cylinder—a small space must alwaysbe left for the steam to expand. One eighth of an inch is plenty of space to leave.
It will be noticed that the valve mechanisms on the particular engine shown bear no resemblance to theDvalve previously described. The holesGwhich are bored around the cylinder are the exhaust ports. It will be seen that when the piston is at the end of its downward stroke it uncovers these exhaust ports and permits the steam to escape. The momentum of the flywheelApushes the piston upward, closing these holes. As these holes are closed the valveHuncovers the entranceIand permits steam to enter from the boiler throughJ. By the time the piston has reached the upward limit of its stroke a considerable steam pressure has developed on top of the cylinder, and this again forces the piston downward. Thus the same cycle of movement is gone through repeatedly.
The valve on this little engine is extremely simple. It consists of a circular piece of brass drilled out, as shown. A hole (IandJ) is drilled transversely through this. The little cylinder shown in the insert atOslidesin the larger hole, and when it is at its upper limit it cuts off the steam. At the proper intervals the valve is pulled down by the eccentricC. It will be seen that the moving parts, i.e., the valve and the piston, must be properly timed. That is, the eccentricCmust be mounted on the crank-shaftBso that the valve will close and open at proper intervals. When the engine is made, the eccentric can be shifted about by means of a set-screw,Q, until the engine operates satisfactorily. This set-screw is used to hold the eccentric to the crank-shaft. The word eccentric merely means "off center." Thus the eccentric in this case is formed by a little disk of brass with the hole drilled off center. The distances these holes are placed off center will depend entirely upon the motion of the valve. It will be seen that the valve is connected to the eccentric by means of the valve-rodE. The valve-rod, in turn, is held to a circular strap which is placed around the eccentric. A groove should be cut in the surface of the eccentric, so that this strap will not slip off. If the strap is not put on too tightly and the eccentric is freeto revolve within it, the valve will be forced up and down as the eccentric revolves.
The crank-shaftBrevolves in two bearings,D D. The flywheel is held to the crank-shaft by means of a set-screwS.
Most small engines with a bore under one inch will operate nicely on from 20 to 30 pounds of steam, and this pressure can easily be generated in the boiler that was described in the chapter on model-boat power plants.
AS many of the readers probably know, a dry-dock is used in assisting disabled vessels. Some dry-docks are permanent, while others are built so that they can be floated or towed to a disabled vessel that is not able to get to a land dry-dock. The land dry-dock operates as follows. It is first filled with water, and the disabled boat is towed in by tugs. After the tugs leave, the gates are closed, and the water in the dry-dock is pumped out, leaving the boat high and dry. Large props are put in place to prevent the boat from tipping.
The dry-dock here described is a model that is towed to a disabled vessel. It is then sunk until it passes under the boat. The sinking is brought about by filling the dry-dock with water. After it has sunk to the proper depth it is passed under the boat tobe repaired, the water is pumped out, and the dry-dock rises, lifting the disabled boat with it. Repairs can then be made very easily.
The model here described does not possess all the fittings and additions of the original. However, it is able to rise or sink as required, carrying the machinery necessary to bring about these functions.
Fig. 120
A general view of the completed model is shown inFig. 120. The first part to construct is the framework for the hull. Four pieces of wood will be required for this, and they should be cut to the shape and size shown inFig. 121. To make this it is bestto cut the two side parts first, as indicated by the dotted lines. This done, the bottom piece can be clamped on from behind by means of pieces of lath. These are for the two end pieces. The other two pieces are made in the same way, except that they contain holes for the water to pass through, as shown atB. The wood for these frames, or ribs, should be not less than1/4inch thick in order to accommodate the pieces used in the construction of the remainder of the hull.
When the builder has made the four ribs, he should proceed to construct the lower deck, which consists of a single piece of wood nicely planed and finished, measuring 141/2inches long by 8 inches wide and1/8inch thick. This piece must be nailed to the bottom of each of the ribs, one at each end, and the other two containing the holes at equal distances apart. Tiny nails, similar to those used on cigar-boxes, will be found very suitable for this work. Some old cigar-boxes may be broken apart to obtain the nails for this purpose. Before nailing on the board it should be marked out to present ordinarydeck-boards. The reader is referred back to Chapter 9 which describes this process, using a straight-edge and knife.
When this board is nailed in place, the next requirement will be two pieces for the sides the bottom edges, of which must rest on the top of the deck-board. These boards are the same length as the deck. They should reach to the top of the ribs, and be fastened in the same way as the bottom deck. It is good practice, when doing this, to place a little white lead on the bottom edge before finally driving the nails in place. This will tend to produce a water-tight joint. This done, three pieces of wood5/8inch square must be screwed in place, flush with the bottom ends of the ribs, to form a flat keel. They should be firmly fixed since a lead keel is afterward screwed on the bottom of the boat. Attention should now be directed to fitting the two middle decks. These are placed 4 inches from the top and are 4 inches wide. In this space the engine and pumps are placed. Therefore, the top deck is made in the form of a lid, and the outside plate made to draw out. In this way the mechanismbelow the deck can be made very accessible.
The framework of the dry-dock is now completed, and the builder can proceed to fix on the side plates. These are made from sheet tin with a width of 141/2inches. The length must be sufficient to reach from the top of one side, around the bottom of the hull, to the top of the other side. Having cut the tin to the required size, one side is put in place with small nails, spacing them an equal distance apart.
Before securing the opposite side, the builder must first arrange the inlet-valve. This particular member is constructed as follows. First, obtain an old gas-pipe union which measures about5/8inch in diameter and3/4inch long. With a hacksaw this is cut off in a sloping direction with an angle to correspond with the slope in the bottom of the dry-dock. When this is done, a lid must be fitted to the top by means of a long rod, as clearly shown inFig. 122. On the under side of this lid a small piece of sheet rubber should be glued, so that when the lid is screwed down the valve will be made water-tight.The valve must now be soldered to the inside of the hull. It is placed in such a position that it will rest just under the center of one of the upper decks when the controlling rod is upright.
Fig. 122
The top end of the rod must contain a thread for about 1 inch, and a round plate made to screw on. This plate should be about3/4inch in diameter, and contain three small holes around the edge. These holes are used in fastening the plate to the deck. The top of the rod is fitted with a small crank-handle, which is used in turning the rod in either direction. In this way the valve can be either opened or closed. At the bottom of the rod a small swivel should be provided, as indicated inFig. 122.
The plate or sheet of tin on this side of the hull can now be permanently fixed in place. When this is done a light hammer should be used around the edges to turn the tin into the wood.
With the plates secured in place, thebuilder must next fix a flat wood keel along the bottom of the dry-dock. This should be screwed to the inside keel, screws passing through the tin plate. A lead keel is then screwed to the wooden keel, and when this is done the dry-dock can be launched. If the foregoing instructions have been carried out carefully the dry-dock should ride lightly on the water.
As a trial the inlet-valve is now unscrewed and water is permitted to enter the hull. When the water rushes in, the hull will begin to sink. The water should be allowed to enter until the hull sinks to within an inch of the lower or inside deck. The valve should then be closed. The exact position of the water should now be found, and a line drawn all around the hull, which can afterward be painted in.
The engine and boilers must now be constructed and placed on the dry-dock, so that the water that was permitted to enter may be pumped out. As a temporary arrangement, a thin rubber tubing is inserted through a hole in the lower deck and allowed to hang outside the water-level. The siphon canthen be formed by simply drawing the water up by suction with the lips. A continuous flow will result, emptying the hull within a short time.
Fig. 123
Attention is now directed to the construction of the boiler and pumps. The boiler, which is rectangular in shape, is made of thin sheet copper, and measures 4 inches long by 3 inches wide by 2 inches deep. A hole is made in the top, and a brass or copper tube 6 inches long and about3/4inch in diameter is soldered in position, as depicted inFig. 123. This tube acts as a chimney on the dry-dock, but it is really used for filling the boiler, and the top is supplied with a tightly fitting cork.
The ends of the boiler also act as supports, and they are made 4 inches long. The bottom edge is turned up for about1/4inch to enable the boiler to be screwed firmly to the lower deck. The boiler occupies a position at one end of the hull, and should fit easily in between decks. A small spirit-lamp is used to furnish heat, and no description need be given of this particular part of the equipment. Before the boiler is firmly fixed in place a small hole should be made near the top at one end. The feed steam-pipe is inserted in this, and soldered in place.
Two small oscillating cylinders, similar to those made for the engine on theNancy Lee(Chapter 6), should be made. They should not be more than3/4inch in length, with a3/8-inch bore. If the builder has any old model steam-engines in the shop, he may take the cylinders from them instead of constructing new ones for the dry-dock.
The engine is set up as shown inFig. 124. The first job is to make the frame or standards, and this is in one piece. Two pieces of brass (A), measuring 51/2inches long by1/2inch wide and1/16inch in thickness, arecut. Next the builder should mark off 11/2inches from either end, and carefully bend at right angles, after which holes are drilled to accommodate the crank-axleB. Two holes must also be made for screws to enable the machine to be screwed to the deck.
Fig. 124
The flywheel should be 11/2inches in diameter, while the bent crank has a throw of3/16inch. The steam-cylinder is fixed on the outside of one of the uprights, and the steam-pipe must, of course, be fitted from the inside.
The pump-cylinder is composed of a small piece of brass tube 1 inch long and3/8inch in diameter. The plunger is1/2inch long, and the diameter is just sufficient to enable it to work freely up and down inside the brass tube. One end is shaped as shown inFig. 125. This contains a saw cut that enablesthe pump-rod to be placed between and connected with a pin. The bottom end of the cylinder is now fitted with a brass disk in which a hole is made and a3/32-inch tube soldered in place. The inside surface of this piece of brass should be countersunk, and the piece is then soldered into the end of the cylinder. Before the plunger is inserted a small lead shot is dropped in, which should be larger than the hole at the bottom of the cylinder, thereby covering it. A hole is drilled in at the side of the cylinder, and a small bent pipe fixed in it. At the top of this pipe a short piece of3/8-inch brass tube is fixed in place, as indicated. This piece of tubing is closed at both ends. The bottom end is treated like that of the pump-barrel and supplied with a large shot. An outlet-pipe is soldered into the side of the delivery-valve chamber and leads to the side of the hull.
The pumpEis fixed at the bottom midway between the engine uprights as indicated inFig. 124. The suction-pipe passes through a hole and down through the deck nearly to the bottom of the hull. After theengine and boiler are connected, a trial can be made. If the foregoing instructions have been carried out, the engine will run at a good speed and a continuous flow of water will be pumped out of the hull. All parts of the engine and pump should be carefully oiled and water should be poured into the pump in order to prime it before its start.
It is understood that two complete boilers and pump units are made for the model, and one is mounted on each side. If the builder desires to increase the capacity of the pumps and install a more powerful boiler and engine, only one pump will be necessary. Otherwise the water will not be pumped from the hull very rapidly.
When the builder has finished the pump units, he should turn his attention to the remainder of the fittings. Two small cranes are made, and one is placed at each side of the hull. They are made of tin. The cab of each crane measures 21/2inches high by 2 inches long by 13/4inches wide. A small roof is fitted on, and a piece of wood fitted to the bottom to serve as a floor. The jibmeasures 6 inches long by3/4inch at the base, and tapers to1/2inch. It has1/4inch turned down at each side, thus adding considerable strength. The jib is fitted to the cab by means of a wire passed through the sides, and two guy-ropes are arranged as shown. A small piece is now cut out at the top, and a pulley wheel fixed in position by means of a pin passed through the sides.
Fig. 126
The winding-drum can be made of either tin or wood. The axle passes through both sides of the cab, the crank being attached to the outside.Fig. 126shows the completed crane, which is held to the deck by means of a small bolt and nut. A washer should be placed between the bottom of the crane and the deck, to allow the crane to turn freely with little friction.
A hand-rail, made of fine brass wire, is placed around the deck.
Dummy port-holes are fixed to the sides of the dry-dock for the purpose of lighting up the interior of the engine-room. These are furnished from top rings taken from gas-mantles. Anchor-chains are fixed at each end of the dry-dock. The whole dry-dock is painted with two coats of gray paint and the water-line painted in bright red.
Fig. 127
Fig. 127 shows the dry-dock with a model boat in position.
THE flash steam method of propelling model power boats of the racing type produces a far greater speed than would otherwise be possible. Flash steam plants are far more complicated than ordinary steam-propelled power plants, and for this reason the author devotes a chapter to their description.
A considerable equipment of tools and not a little mechanical ingenuity are required to produce and assemble a workable flash steam plant. However, such plants have gained great popularity in the past few years, and all of the hydroplane racing craft are propelled with such outfits. These power plants are capable of delivering such a tremendous power that speeds as high as thirty-fivemiles an hour have been reached by boats measuring 40 inches long.
The illustration,Fig. 128, shows a flash steam plant and its various parts. Each part and its function will be described in this Chapter in detail. The gasolene tankAis used to hold the fuel, which is fed to the gasolene burnerC. The gasolene burner operates on the principle of the ordinary gasolene torch. First the tank is filled about three-quarters full with gasolene. An air-pressure is then produced in the tank with a bicycle pump. The pipe leading from the gasolene-tank at the top is coiled around the burner, and the free end of it is bent and provided with a nipple, so that the gasolene vapor will be blown through the center of the helix of the coil formed by the pipe bent around the burner. This is quite clearly shown in the drawing.
Fig. 128
The cylinder is merely a piece of stovepipe iron bent to shape and provided with several air-holes at the burner end. To start the burner, the vaporizing coils must first be heated in an auxiliary flame. The flame of an ordinary blow-torch is suitable for thispurpose. After the coils have become sufficiently hot the valve at the top of the gasolene-tank is opened, and this causes a stream of gasolene vapor to issue at the nipple. This produces a hot flame at the center of the vaporizing coils, and in this way the coils are kept hot. The purpose of heating these coils is further to vaporize the gasolene as it passes through them on the way to the burner. Once started, the action of the burner is entirely automatic. The vaporizing coils are made of Shelby steel tubing with an internal diameter of1/8inch.
It will be seen that the flame from the gasolene-torch is blown through the center of the boiler coilsB. Thus, any water passing through these boiler coils is instantly converted into steam. In other words, the water "flashes" into steam. The heat of the blow-torch is so great that most of the boiler coils are maintained at red heat even while the water is passing through them.
Notice the water-tankG. A little scoop, formed by a pipe of small diameter, protrudes through the bottom of the boat, so that the forward motion of the boat willcause water to rise in the tankG. An overflow is also provided, so that, should the water not be sucked out of the tank quickly enough, it will not flood the boat. The overflow pipe hangs off the side of the boat.
The water pumpEsucks water from the tank, and pumps it through the check-valveK(this valve permits water to pass in one direction only) into the boiler coils. The boiler coils, being red-hot, cause the water to flash into steam the instant it reaches them. By the time the steam has reached the opposite end of the boiler coils, it is no longer steam, but a hot, dry gas at a terrific pressure. From the boiler coils the steam passes into the steam-chest of the engine, and thence into the cylinder, where it expands, delivering its energy to the piston.
It will be seen that the water-pumpEis geared to the engine. Owing to this, it is necessary to start the water circulating through the boiler coils by the hand pumpF. This hand pump forces water through the boiler coils just as the power pump does. After the hand pump is started the engineis turned over a few times until it starts. The valveHis then closed, which cuts the starting pumpFentirely out of the system, because when the engine starts it also drives the water pumpE, and therefore the action becomes entirely automatic.
The relief-cockLis placed in the system to be used if the engine stalls. By opening the relief-cock the pressure in the complete system is immediately relieved. At all other times the relief-cock is closed.
A second pump,I, is also included in the system. This, like the water-pump, is geared to the engine and driven by it. It is the duty of this pump to convey oil from the lubricating tankMinto the steam feed-pipe just before it enters the steam-chest. In this way the live superheated steam carries a certain amount of lubricating oil with it in the cylinder.
Owing to the high temperature of the superheated steam, it is impossible to use brass cylinders on the steam-engines employed with flash steam systems. Steel seems to be the only cheap metal that is capable of withstanding the attack of flash steam. Brassis out of the question, since its surface will pit badly after it is in use a short time.
The boiler of a flash steam plant is covered with sheet iron so as to prevent drafts of air from deflecting the flame from the center of the boiler coils. The cover is provided with ventilators, so that the burner will not be smothered. If enough oxygen does not enter the interior of the boiler coils, poor combustion will result, and the gasolene flame will not develop its maximum heat. Upon referring again to the diagram, it will be seen that the exhaust steam pipe from the engine discharges into the stack of the boiler covering. This discharge greatly facilitates the circulation of air through the boiler coils.
After a flash steam plant has been started it will work automatically, providing all the parts are in good running order. Flash steam plants, however, are difficult to get in the proper adjustment, and once adjusted they are easily disturbed by minor causes. Owing to the fact that every square inch of surface in the flash coils is heating surface, the amount of water supplied to the boilermust be exactly what is needed. The heat must also be regulated so that the temperature of the steam will just meet the engine's needs. Many times an increase in heat causes the steam to reach such a temperature that it will burn up the lubricating oil before it reaches the cylinder of the engine. This is liable to cause trouble, because sticking is apt to occur.
Model power boats with speeds as high as thirty-five miles an hour have been made in America. Such high-speed boats must be assembled with infinite care, owing to the fact that the mechanism they carry is more or less erratic in its action, and unless it is well made results cannot be expected.
Fig. 129
There are probably few sports more interesting than that of model power-boat racing. The Central Park Model Yacht Club of New York city is one of the most progressive clubs in America, and its members not only have a sail-boat division, but they also have a power-boat division. The members of the power-boat section have races regularly once a week, and the most lively competition is shown. It is indeed amusingto watch these little high-speed boats dash across the pond, their bows high in the air and their little engines snorting frantically. Owing to the difficulty of keeping these small racing boats in a straight line, they are tied to a wire or heavy cord and allowed to race around a pole anchored in the center of the pond, as illustrated inFig. 129. The top of the pole should be provided with a ball-bearing arranged so that the cord to which the boat is fastened will not wind around the post. In this way the boats are caused to travel in a circle, and as the cord to which they are fastened represents the radius of the circle, the circumference can readily be found by multiplying theradius by 2, which will give the diameter. The diameter is then multiplied by 3.1416 to obtain the circumference. If the boats were permitted to travel wild they would run into the bank, a fatal procedure when they are running at high speed.
Speed boat hulls are usually of the hydroplane or sea-sled type. This type of hull is extremely easy to make. Such a hull is shown inFig. 130. It will be seen that it has an aluminum bottom. The propeller and propeller strut will be noticed in this illustration.