The best way to know how a machine works is to work with it, and the next best thing to working with an actual machine is to work with a model which you have made with your own hands.
In this way you not only will become acquainted with the mechanism which is used to obtain a certain result, but if you are of an inventive turn of mind you are likely to get one or more ideas for improving it which will be of more or less value.
Now, this is just what you should do with the submarine if you really want to know the innermost secrets of how it is made and works—that is, you should build a model of one and experiment with it.
To the end that you may do this, I have given in this chapter the plans and specifications, which mean the working drawings and a full description, of a 2-foot model submarine boat which you can easily make and run yourself.
This model submarine is not only instructive but it is “amoosin’,” as Artemus Ward used to say, for while it starts out awash—that is, with its deck just about level with the top of the water—it will soon take a dive, run a ways submerged, and then bob up on the surface again, just like a real submarine.
The Parts of the Model Submarine.—There are only four chief parts to this model, and these are (1) the hull; (2) the ballast tank; (3) the power plant; and (14) the superstructure. All of this is shown in Fig 11.
The hull is of course the body of the boat. The ballast tank is a tin can in the bottom of the hull; when it is filled with water the extra weight makes the boat sink, and when the water is blown out of it by compressed air it makes the boat rise to the surface again.
The power plant includes an electric motor, the batteries to run it, the propeller-shaft and propeller, the pulleys which work the valve that lets the compressed air flow into the ballast tank to blow out the water, and finally the superstructure, which consists of the deck and the conning tower, though in this case the latter is made to hold the compressed air.
The Hull of the Boat.—The first thing to do is to make the hull; and the easiest way to build one that is light, strong, and watertight is to whittle out, or have sawed out, two tapering pieces of wood as shown at A and B in Fig. 12. The faces are shown by the dotted lines at C and D in Fig 11.
These are for the nose and tail blocks, as we will call them, and each one is 14½ inches long. The other dimensions, as well as the shapes of these blocks, are also shown in Fig. 12.
Bore four ⅛-inch holes, ¾ inch deep in the faces—that is, the flat ends of each block—at the places shown by the little circles; these are to take in the ends of the brace rods. Next bore a ¼-inch hole lengthwise through the tail block as shown by the dotted lines at B. Bore out this hole with a 1-inch bit to a depth of ¾ inch, to form a stuffing box.
Now cut off a piece of brass tube which has an inside diameter of ⅛ inch and an outside diameter of ¼ inch and force it into the hole in the tail block; this tube forms the bearing for the propeller-shaft.
Cut out a disk of brass 1¼ inches in diameter and 1/16 inch thick; drill a ⅛-inch hole through the center of it for the propeller-shaft to pass through, and three ⅛-inch holes at equal distances apart near the edge, as shown at C, so that it can be screwed to the tail block. The purpose of this disk is to keep the packing in the stuffing box. See Fig. 12.
The next thing to do is to cut off two brass rods each ⅛ inch in diameter and 16½ inches long and fit the ends of these into the lower holes in the blocks; and then cut off two more brass rods 17 inches long and set these into the upper holes. Bend these latter rods out a little until the faces of the blocks are parallel with each other, and you will have a substantial framework on which to fasten the skin of the hull.
The skin, as the sheets or plates which form the hull are called, is made of sheet tin, and to cut the tin you should have a pair of tinner’s shears.
You will need seven strips of tin altogether: one for the bottom and three for each side. The sizes and shapes of these strips are shown in Fig. 13. The widest strip is used for the bottom of the hull; bend up the edges along the dotted lines, then punch eight holes in the ends—these are shown by the little crosses—and screw it to the nose and tail blocks with flat-headed wood screws.
Next punch holes in and screw one of the lower strips to each side of the nose and tail blocks, with the hollow curved edge down and lapped over the turned-up edge of the bottom strip; punch and screw on each of the middle strips, with its lower hollow curved edge over the top of each of the lower strips; and then punch and screw on the top strips.
When you have the bottom and all of the side strips screwed on, each one will lap over the next lower one ½ inch and fit snugly up to it, and at the same time they will all curve gracefully.
After you have these strips screwed on, you must solder the lap seams to make them watertight. You can easily do this by using a regular tinner’s soldering copper—a soldering fluid made by dissolving zinc clippings in some dilute muriatic acid—and what is called wire solder.
The cover of the boat, or deck, to give it its nautical name, is a part of the superstructure, and you can cut this out later on.
The Ballast Tank.—The sole purpose of the ballast tank is to add enough weight to the boat to sink it when you want it to sink.
Use heavy sheet tin for the tank. Cut out two strips, each of which is 2 inches wide and 15½ inches long. Make a ½-inch lap seam and solder the ends of this strip together, making one strip 30 inches long. Bend the strip so that each side is 11 inches long and the ends are 3½ inches long; this will bring the ends together, forming another ½-inch lap seam, and this, of course, you must also solder.
Cut out a top and a bottom, each 4 inches wide and 11½ inches long. Cut the corners; bend up the edges ¼ inch all round, and solder the corners. And don’t be afraid to use plenty of solder, for this tank must be strong, and not only watertight but airtight as well.
About 4 inches from one end of the bottom sheet cut a ½-inch hole for the water inlet and outlet, that is the hole where the water flows into and out of the tank. In this hole solder a piece of ½-inch brass pipe ½ an inch long and flush with the surface of the tin, as shown at A in Fig 14; and also at B in Fig. 11.
Now, with a pair of dividers 1¾ inches in diameter, scribe a circle which has its center 3¼ inches from the other end of the bottom and in the middle of it. Cut out three strips of tin ¼ inch wide and 2 inches long—or wire will do—and bend over one end of each one ¼ inch.
Solder these strips to the bottom at equal distances around the circle as shown by the dotted line at B in Fig. 14, and in the cross-sectional drawing Fig. 15. The upright strips serve as guides to keep the cork float in place and yet let it move freely up and down in the tank.
Cut a hole ½ inch in diameter, 2 inches from one end of the cover, or top, of the tank as shown at A in Fig. 14. This is for the pipe of the valve mechanism.
Next cut out a hole exactly ¾ inch in diameter, and have its center 3¼ inches from the end. Take a piece of tin and make a valve seat so that its small end is 9/16 inch in diameter and solder it to the top over the hole. This valve seat must be made with particular care, so that it will be perfectly smooth and the valve plug will fit it airtight.
The valve plug is a piece of cork cut in the shape of a cone and must fit the valve seat exactly; soak it in machine oil, then run a piece of aluminum wire 1¾ inches long through it and bend it over on the bottom as shown at C in Fig. 14 and in Fig. 15.
Next solder the bottom to the sides of the tank. Drop the cork float between the upright guides as shown at B in Fig. 14. Set the cork valve plug on the cork float. Put on the cover with the aluminum wire sticking up through the hole in the valve seat; and finally solder on the cover.
The Air Control Mechanism.—Since you cannot be in your model submarine when it is stealing along submerged through the water, you must fit an automatically controlled air-valve in the pipe that connects the air chamber with the ballast tank, in order to blow out the water when it is time for the craft to come to the surface to breathe again.
There are two chief parts to the air control mechanism, and these are (1) the air-valve, and (2) the pusher control. We will describe the air-valve and its fittings now and tell you how the pusher control is made and works under the next caption.
The Power Plant.—The reason we have split up the air control mechanism in this fashion is because it is easier to solder the air supply pipe to the ballast tank at this stage of the work than it is to do it after the ballast tank is fixed to the bottom of the hull; again it is easier to do the latter job before the power plant is put in the hull; and finally the pusher control is really a part of the power plant.
If you will take a good look at the cross-section drawing, Fig. 15, you will see that the air-valve and its fittings consist of (a) the air-valve proper; (b) a small piston; and (c) the connecting pipes.
First get four lengths of pipes[9] all of which have an inside diameter of 5/16 inch; have these pipes ½, 2, 2⅜ and 2¾ inches long respectively. Thread or have these pipes threaded as follows: the ½-inch length threaded inside and all the way through; the 2-inch length of pipe threaded on the inside to a depth of 1 inch from one end and a hole drilled in it ⅝ inch from the other end, and have this threaded; the 2⅜-inch pipe threaded on both ends and one end bent over ⅝ of an inch; and, finally, thread one end of the 2¾-inch length of pipe.
Now screw the ½-inch length of pipe on the end of the 2⅜-inch piece of pipe which has the nut and washers on it. Screw a bicycle tire valve into the 2-inch piece of pipe and far enough in so that the bent end of the 2⅜-inch pipe can also be screwed in, as shown in Fig. 15. Last of all, screw the end of the 2¾-inch pipe into the threaded hole in the wall of the 2-inch pipe.
Next make a piston of a piece of brass rod ⅜ inch long and of such diameter that it will fit snugly and yet slide easily in the end of the 2-inch pipe. Drill a 1/16 inch hole through the piston and fix a stem in it tight so that it projects ¼ inch through one end and ⅜ inch through the other end. File a grooved ring around the piston to hold in the oil and slip the piston in the open end of the pipe.
This done, clean the lower end of the long pipe well; set it into the hole in the top of the ballast tank; use plenty of soldering fluid and solder it in good and tight. At the time you are doing this job see to it that the long pipe sets plumb—that is, perfectly straight up and down.
Setting the Ballast Tank in the Hull.—You are now ready to set the ballast tank in the hull. To do this you must cut a hole ½ inch in diameter, 4 inches from the face of the nose, as shown at B in Fig. 11. Set the tank in the hull so that the pipe on the bottom of it will stick through the hole which you have just cut; and then solder the pipe to the hull on the outside.
Putting in the Bulkhead.—As you will see from the end views C and D in Fig. 11, there is considerable space between the ballast tank and the skin of the hull on both sides.
As melted lead is to be poured into this space to give the boat the right weight to make it sink properly a bulkhead—that is, a partition—must be cut out of tin and soldered to the hull, on the inside of course, up against the rear end of the ballast tank. The face of the wooden nose against which the ballast tank rests will keep the lead from running out at the front end. As the lead is poured in after the motor is set in place this operation will be described later.
About the Power Plant.—While in a real submarine the power plant—the machine that converts the fuel into power to drive the boat—is a gas engine when it is cruising on the surface, and a storage battery and an electric motor when it is running submerged, in your model it is electricity first, last, and all the time.
That is to say, a battery of dry cells supplies the current to run an electric motor and this in turn drives the propeller; besides, it also furnishes the power needed to work the pusher which controls the air supply through the bicycle valve which I have just explained to you.
The first thing to do toward getting the power plant is to beg, buy, or borrow a small electric motor which will develop not less than 1/30 horsepower and at the same time run on a battery of not more than 3 dry cells.[10]
While the motor can be run to its full capacity on two dry cells it will develop more power on a three-cell battery. Now, to get three dry cells which will fit into the small space that is left in the hull of your model you will have to use rectangular cells.[11]
You will also need a small switch to open and close the battery circuit, and this is fixed to the top of the boat, or deck as it is more properly called; the way it is put on will be explained under the caption of The Superstructure.
When you want to buy one of these switches ask for a porcelain base, single pole, single throw switch. It will cost about a quarter. The way the dry cell battery, the motor, and the switch are connected up is shown in Fig. 16.
The Pusher Control Device.—Before the motor is installed in the hull the pusher control device which opens the compressed air valve must be made and mounted on top of it.
On top of the motor, as you will see by looking at Fig. 16, there is a metal name plate, which is fastened to the top of the field magnets by four screws; unscrew the latter and take off the plate.
Now make a pillow block, as the bearing for the threaded spindle is called. Saw out with a hack saw[12] a base plate of sheet brass ⅛ inch thick, 1 inch wide, and 1½ inches long; drill four ⅛-inch holes in the corners of the plate, so that it can be screwed down to the field magnets of the motor.
Also drill two ⅛-inch holes lengthwise in the middle of the plate and have the first one ⅛ inch from one end and the other ½ inch from the same end and in a line with the first hole.
Take a brass bar ¼ inch thick, ½ inch wide, and 1⅝ inches high, and drill two 3/32 inch holes in one end of it, to correspond to the two holes in the middle of the base plate, and thread these to fit a couple of 6-32 machine screws.
Next drill a ⅛-inch hole clear through the top of the bar, or standard, as it is now called, 3/16 inch from the top. This must be very accurately done, in fact, it ought to be done with a drill press, for if it is not precisely at right angles to the base, the spindle will not run true, and besides there will be a great loss of power.
Drill a hole through the top of the standard until it meets the hole through which the spindle is to pass, and by means of this top hole keep the spindle well oiled. The pillow block is shown complete in Fig. 15 and 17.
To make the spindle, get a piece of soft steel rod ⅛ inch in diameter and 4½ inches long. Thread it from one end to within 1⅜ inches of the other end, and screw on a nut as far as it will go. Push the smooth end through the hole in the pillow block; slip a collar over the end close up to the standard, and screw it fast. To make the pusher mechanism complete put a grooved pulley 1½ inches in diameter on the end of the spindle up close to the collar and screw it fast.[13]
The last part of the pusher control is the pusher itself. It is simply a round brass rod ¼ inch in diameter and ¾ inch long, with a hole drilled through it lengthwise and threaded to fit the spindle. Solder a bit of brass near one end, to make it heavier on one side than on the other.
Now, when the motor is set in place in the hull and its small pulley is belted to the large pulley on the spindle and the current is turned on, the spindle revolves, but the weight on the pusher will keep it from turning with the spindle. Instead, the curious result is that it screws itself toward the free end of the spindle, and when it reaches the end, the hollow pusher goes over the stem of the piston. When it strikes the piston it pushes on it until it presses the other end of the stem against the pin of the bicycle valve and this opens it.
If you will keep the piston, the pusher, and the bearings well lubricated with sewing-machine oil, there will be little power lost through undue friction. But you must be careful not to get any oil on the commutator of the motor, for this will keep it from running properly.
The Propeller-Shaft.—Before you install the motor you must put the propeller-shaft through its bearing in the tail block.
To make the propeller-shaft, get a piece of soft steel rod ⅛ inch in diameter and 5¼ inches long and thread it at both ends. Slip it through the tube which forms the bearing. Soak some cotton-waste in machine oil and pack it in the stuffing box in the tail block. Now screw the circular plate to the face of the tail block to keep the packing in place.
Installing the Motor.—While we have given you the height to make the pillow block, it will, of course, depend on (1) the height of the motor, and (2) the height of the center of the piston when both are measured from the floor of the hull; this is because the pusher spindle and the piston stem must be exactly in a line with each other.
Another thing: The motor we have shown is 3 inches high from its base to the center of its armature shaft; but the motor you get may not be of this height. While it can’t be any higher than 3 inches unless you change the design of the boat, it can be shorter if you mount it on a block of the right thickness.
Before installing the motor in the boat, see that both pulleys are in a line with each other, and put on a belt. Thread the end of the motor-shaft and fit a coupling to it so that the propeller-shaft can be screwed into the other end. To make the coupling take a piece of brass rod ¼ inch in diameter, 5/16 inch long; drill a 3/32-inch hole in it, and thread it to fit the motor- and propeller-shafts.
Screw the coupling on the motor-shaft. Mount the motor on a board of the right thickness, and set it in position in the hull. Screw the propeller-shaft into the coupling, and be sure to have the motor set so that the shafts are in perfect alignment—that is, in a line with each other—as shown in Fig. 15.
Unless this is done the propeller-shaft will bind in its bearing and it will take a large part of the power of your motor to overcome it. When the motor, the pusher spindle, and the propeller-shaft all spin freely on closing the battery circuit, you can then secure the motor to the floor of the hull with a couple of machine screws as shown in Fig. 15.
Ballasting the Boat.—The next thing to do is to ballast the boat by pouring melted lead into her hull to make her sink deep enough in the water to balance her and to make her submerge entirely when water is let into her ballast tank.
The way to do this is to cork up the hole in the pipe in the bottom that leads to the ballast tank and then set the boat in a tub full of water. Now lay the battery cells in the positions they are to occupy in the boat, as shown at B and C in Fig. 11, and see how far up the water-line comes on the hull—or, in other words, how deep the hull sinks into the water.
Next pour melted lead in between the sides of the ballast tank and the hull while the boat is still in the tub of water and distribute it so that the boat floats on a perfectly even keel. When you have poured enough lead into the hull to make her sink to within an inch or so of her gunwales (the upper edge of the boat’s sides) and she is nicely balanced, let the lead cool, take the boat out of the tub and put her back on her stocks on your bench.
And now a couple of parting hints: (1) You can melt the lead in an iron ladle over a kitchen fire, and (2) put a little water in the ballast tank so that the hot lead will not open the soldered seams.
Making the Superstructure.—This consists of the top, or deck, and the conning tower, which in this model serves for the compressed air tank.
To make the deck, cut out a sheet of heavy tin the exact shape of and dimensions given in Fig. 18. Cut a ½-inch hole half way between the ends, and in the middle, for the air-valve pipe to pass through and which is screwed to the conning tower as shown in Fig. 15.
Cut out a 2½-inch hole in the aft end of the deck for a hatch, and make a cover, or hatch, for it 3½ inches in diameter; this hatch will allow you to get your hand through the deck and into the hull to reset the pusher device when your submarine is to make another trip.
Cut out a rectangular hole ½ inch wide and 2 inches long in the for’ard end of the deck, for the screws and the wires of the switch to pass through. Screw the porcelain block of the switch to a board of the same size, with the tin deck in between them; this insulates the screws of the switch from the tin, which would otherwise short circuit the battery and run it down. Run sealing-wax in and around the edges of both the porcelain and wood blocks to make a watertight joint, for water must not get into the boat.
This done, connect up the batteries and these with the motor, with heavy rubber-covered copper wire, and connect the battery and the motor with the switch with flexible electric-light cord. Set the deck on the hull; and if you are sure everything is in first-class working order, solder it on tight. If, though, you are not quite certain, you can do a temporary job by putting it on with sealing-wax.
Supposing you are young enough to have imagination or old enough to have dim vision, the switch mounted on the deck will look very much like a gun that is just coming through the hatch and getting ready for action.
And Now the Conning Tower.—The conning tower is an airtight vessel—as far as your model goes—having a conical shape.
To make it, scribe two circles, using the same center, on a sheet of heavy tin, making one of them 4 inches in diameter and the other 5 inches in diameter, and cut it out around the larger circle.
Cut a ½-inch hole in the center of the disk. Put the ½-inch length of threaded pipe we told you about under the caption of The Air Control Mechanism in the hole, and solder it fast. Cut the edge of the disk radially with your shears, from its edge to the smaller scribed circle, and then you can bend up the edge all the way round.
Next cut out an arc of tin of the size marked and the shape shown in Fig. 19. Make a lap seam and solder it.
Scribe a 3-inch and a 4-inch circle on a piece of tin and cut it out. Cut the edge radially as before, and bend it up all the way round. Cut a ½-inch hole near the edge of the intake air-valve pipe. Solder the two disks to the cone and be sure the ½-inch threaded pipe is inside.
To complete the conning tower, get a 5- or a 7-inch length of pipe; bend over one end a little; thread it and screw in a bicycle valve. Finally stick the other end of the pipe through the hole in the top of the conning tower and solder it there, as shown in Fig. 20, which also shows the conning tower complete. The purpose of this pipe is so that you can pump air into the tank with a bicycle, or an auto pump.
Screw the conning tower on the end of the pipe of the air-valve mechanism which projects through the top of the deck, and then you are ready to do something else.
Setting the Propeller.—A 2½-inch brass propeller with three blades can be bought for about 40 cents of Luther H. Wightman and Co., 132 Milk Street, Boston, Mass.
This little propeller has a hub diameter of 5/16-inch, as shown in Fig. 21. When you get it, drill a 3/32-inch hole through the hub and thread it; screw it on to the end of the propeller-shaft, and then screw on a nut to hold it on tight. (See Fig. 22.)
Putting on the Rudder.—And last of all comes the rudder. Cut off two pieces of ⅛-inch brass rod 4 inches long; thread one end of each rod down 1 inch, and sharpen the end a bit; thread the other end of each one down ⅝ inch and screw a nut on it.
Drill two 3/32-inch holes in the tail block in a vertical line with each other 4⅜ inches apart, and screw in the brass rods as shown in Fig. 22. Cut the rudder out of heavy tin—or, better, 1/32-inch-thick sheet brass—the size and shape shown also in Fig. 22.
Bend the end of each tongue of the rudder to make a knuckle, and slip the knuckles over the pins. Screw a nut on the end of each pin, and by tightening them up you can make the rudder stay at any angle you put it.
Painting Your Craft.—You can buy a good marine paint of almost any color you want at paint stores generally.[14]
Gray is the most appropriate color to paint your model craft with; but whatever color you choose, lay it on the long way of the boat so as not to streak it but make a good smooth job of it. Put on three coats and let each coat dry thoroughly before you apply the next one. And now your submarine is done, and if you have made a good job of it, it will look like the half-tone cut shown here.
How to Work Your Submarine.—Having everything in readiness, take your terrible little U-boat under your arm to the nearest lake or river.
Pump the conning tower full of compressed air and then gently put her in the water. Throw on the switch, and it will do the rest. By this, I mean that the moment you turn on the current the motor will drive the propeller at a goodly clip and the craft will travel over the surface of the water awash—that is, with the water washing over her deck.
At the same time, the ballast tank begins to fill with water, and the added weight makes the boat go deeper and deeper until only the bridge[15] of her conning tower can be seen; and after a few moments more her periscope (or air supply tube) sinks out of sight.
While she is going down the weighted pusher is moving slowly but surely over the threaded spindle; when it reaches the piston it pushes it against the pin in the air-valve and so opens it and keeps it open.
The instant the air-valve opens, the compressed air from the air tank (conning tower) rushes into the ballast tank, and because it is under a high pressure it forces the water out of the tank through the hole whence it came in.
When the water has been blown out of the ballast tank the boat is, of course, lighter, and naturally she rises to the surface again. This is your cue to be right there with a rowboat and get her and to pump more air into the compressed air tank before she makes another trip.
If you don’t do this and she ever goes down with her ballast tank full of water and there is no compressed air left to blow it out with, you can send a censored report to the daily papers that another U-boat has been sunk and that there was no time to save the crew.
But, anyway, you will have oceans of fun with your model, and your head will brim over with submarine lore.