Build Your Own Diving Helmet (Jun, 1933)
This is another one of those things that would never get by the liability lawyers today.
BUILDING a DIVING Helmet
Improvement follows improvement in the design of home made diving helmets as amateur divers become more and more acquainted with their use. This one of Hoag’s is the last word in helmets so far published by good old M-M.
ALL the thrills of exploring the lake bottom are yours with this simply constructed diving helmet; and, if you do not dive too deep, you are in no particular danger, either. Besides its use in recovering lost outboard motors at a substantial profit, the helmet will give you one of the most interesting experiences of your life; for until you have breathed and walked at leisure under water, you have missed something. It will take a good deal of nerve to go down the first time, but after that it will just be fun.
First, select a big tin can about 10 inches in diameter and 13 or 14 inches deep. Ask your grocer for a cookie can. Cut a hole in one side about 5 inches square and by means of tin channels soldered around this opening, set in a plate glass window, making it watertight by shifting around it with cotton dipped in thick shellac.
Let us refer hereafter to this window side of the helmet as the “front.”
Now split an automobile inner tube and wrap this sheet of rubber around the lower edge of the helmet (the open end), lapping it over in front, and bind it to the can with a couple loops of baling wire, using a little shellac between rubber and metal to insure a watertight junction.
The rubber should then be cut away over the shoulders.
Next, bolt a 24-inch length of eighth-inch strap iron (say 1-1/2 inches wide) to the back of the helmet to make the “rear bracket” in the drawing. A similar bracket should be bolted to each side of the helmet and bent out horizontally to rest on the shoulders. The bolts should be run through from the inside, with the heads soldered to the tin to prevent a leak.
On top of the helmet, near the front, solder in a valve stem out of an old inner tube and bind it onto your air hose, which can be ordinary rubber tubing fifty feet in length. Also on top of the helmet is an inlet valve for breath when above the surface, and is closed before diving. It consists of a piece of sponge rubber about 1 by 1 by 6 inches, backed with a piece of metal, and arranged to rotate on a bolt set in the center of the top surface of the helmet. Two , holes are punched through the top of the helmet. in such a position that the sponge rubber will completely cover them when you are ready to dive. Otherwise, the sponge rubber will be turned so that the holes are uncovered and air is admitted. The bolt has a thumb screw nut to clamp the rubber tight against the metal. A stop pin may be added to help you to tell when the valve is closed.
In addition, a ring should be bolted and soldered to the top of the helmet for a lifeline.
The exhaust valve, which lets the air stream out continuously, keeping it fresh, and equalizing the pressure between the air inside the helmet and the water outside, is located to one side of the window, below the level of your nose. On regulation helmets, the air supply comes in below and goes out above which makes for good circulation, that is true; but we don’t want the helmet to fill with water if the air supply is momentarily cut off, so we make this change. The valve consists of a 1/2 inch hole in the can with a leather tab covering it on the outside, which flaps down, closing the opening when you inhale and doing the opposite when you exhale.
A heavy elastic strap holds the can on; and it must be heavy because a can of this size when full of air has tremendous buoyancy. The strap should be about 36 inches long; try it before cutting to allow for differences in build. To each end should be securely bolted a 3-inch strip of iron. One of these metal tabs will have a quarter-inch hole bored through it, and the other will have a 3/16-inch bolt or rivet passed through it and protruding about half an inch. The two tabs fit over one another, the hole taking the peg, to form a quick-release buckle for the strap. The strap passes through slits in the back of the rubber sheathing, passing over the rear bracket at the mid point of the strap.
This strap must be just long enough to reach once around you, under the arms where it will not interfere too much with your breathing, cross in front, go back over the metal shoulder brackets, cross again in back, come around and buckle in front. The strap should be pulled quite tight so that the helmet is held down securely.
Your diving helmet is now completed. Connect a good big air pump to the rubber hose, the biggest pump you can find. An ordinary tire pump does not furnish enough air even when it is worked at top speed. Two or three used together will work, but of course this takes several men in your surface crew. With the pump you should use an inner tube with an extra valve stem for each pump, the air compressing in the tube and then going out to the helmet. Of course you must take the valve “insides” out of the exit stem so that the air will escape to the helmet. This inner tube must be mounted up in a casing and rim; otherwise the inner tube will only blow up from the pressure.
Now to dive. Use a sack full of rocks to anchor your boat or raft; and when you dive, climb down the anchor rope, holding yourself in a vertical position by keeping your feet around the rope. You must keep in an upright position all the time, never stooping over. If you do bend over, the water will fill your helmet, for it is kept from coming in only in the same way that a glass held inverted under water will remain full of air. If you must pick something up off the bottom, squat down, but keep your head up.
Don’t tie weights to yourself. Always go down the anchor rope and if necessary to walk around, carry the anchor with you. The rope will lead you right up to the boat, where you will have something to grab hold of when you reach the surface.
Don’t dive too deep. Stay under thirty feet for most of your dives, for at this depth you will not have to fear the “bends,” and you can come up just as fast as you wish. Only, don’t try to dive if you have a cold in your head. If you do, the pressure will not equalize between your nose and your ears, and you will feel a great pressure on your eardrums. If you have no cold you can swallow repeatedly as you dive and equalize this pressure.
Remember: don’t bend over, don’t tie any weights to yourself, and don’t go too deep.