CHAPTER IV.

THE CONSTRUCTION OF THE GENERATOR.

The construction of the generator is the first step in the mechanical part of the business, and to simplify this a complete set of reference drawings has been constructed and is herewith given. The assembling of the parts should be clear, with the assistance of the perspective drawing of the completed apparatus, and any mechanic of ordinary ability should be able to construct this generator without any trouble. The following bill of material should first be purchased:

One ⅞-inch whitewood board 10 inches wide and 8 feet 6 inches long.

One ½-inch whitewood board 12 inches wide and 4 feet 6 inches long.

One piece of 6-pound sheet lead 3 feet wide and 6 feet 6 inches long.

Three ⅛-inch female hose end gas cocks.

One piece of ⅛-inch brass tubing 2 feet long.

One foot of ¼-inch lead pipe.

One 4-inch charging screw.

One 1¼-inch cleaning screw.

Making the Charging and Cleaning Screws.

These goods can be readily purchased from dealers, with the exception of the charging and cleaning screws. They can be made in any brass foundry. The only difference between the charging and cleaning screws is the size. The charging screw, Fig. 5, should be at least 4 inches in diameter, or large enough to pass the hand through, while the cleaning screw should be 1¼ inches in diameter, or large enough to pass over a 1-inch pipe. A piece of sheet lead is fitted into the cover, as shown at _a_, to protect the metal from the acid. Soft putty is used for a packing, as shown in Fig. 5.

The best, although a more expensive, charging screw is shown in Fig. 6. As will be seen from the cut, it consists of a base, _k_; cover, _d_; clamp, _e_, and screw, _f_. The base is simply a plain iron or brass ring, 4 inches in diameter, ⅛ inch thick and 1 inch high. The bottom is to be faced smooth, while the top is recessed 3-16 inch deep to receive the sheet lead and packing of putty, as at _a_. Two nubs, _b_ and _b_, are cast on opposite sides, as shown, to act as grips for the clamp _c_. These nubs are ¾ inch long and project out from the body of the base ¼ inch, and are made sufficiently strong to stand the strain of the screw. The cover _d_ is made of the same material as the base, the center being raised, as shown, to give it strength. Cast directly in the center and on the top is the nub _e_, ⅝ inch high and ⅝ inch in diameter. This is drilled to receive the ⅜-inch screw _f_. A groove 1-16 inch wide and 1-16 inch deep is cut all around the bottom of the screw, as shown at _i_. A hole is then drilled through the side of the nub _e_, and in line with the slot _i_. A pin can then be driven through the hole and will pass through the slot _i_, making a swivel joint that will connect the cover and screw together. The screw _f_ is made of ⅜-inch round iron sufficiently long to give an action of about 1 inch. The top at _n_ is filed square to receive a wheel such as is used on a common gate valve. A long thread should then be cut on this screw. The clamp _c_ is made a half circle in shape, so as to clear the cover with ease. It should be ¾ inch wide, flat on the under side, while the top side should have a rib cast on it to prevent springing. The top at _g_ should be reinforced with metal and made heavy enough to stand drilling and tapping to receive the screw _f_. A wood pattern can be made for these parts, and they can then be molded in any brass or iron foundry. In making the patterns they should be cut down as much as possible, so as to make the finished article as light as is consistent with the strength required. The same directions will answer for the cleaning screw. The hole to receive the sheet lead over the cleaning screw should not be over 1½ inches in diameter, and the rest of the screw should be made in proportion to this hole. The advantage of this screw over others is that it does not wrench the sheet lead in making it up, and, owing to its construction, it is always sure to make a tight joint without straining the generator.

Building the Frame.

The frame can be made of galvanized iron, but wood is much superior, as it retains the heat generated in the gas chamber much better. To make the frame take the ⅞-inch board and cut off two pieces, 10 inches square, A and B in Fig. 8; 5 inches from one side and 2 inches from the back of one of these pieces bore a 1½-inch hole, C, and countersink it. This is for the acid supply pipe to pass through. These pieces are intended for shelves upon which to rest the acid and gas chambers. Cut the remaining board into two pieces 38 inches long. Lay these two boards together. Five inches from the side and 3 inches from the bottom bore a 1½-inch hole, _d_. Then saw out a V-shaped piece, Fig. 7. This will form the legs of the generator.

Take a square, and 12 inches from the top of these boards draw the lines _e_ and _e_. Twenty-two inches below these lines draw the lines _f_ and _f_. These lines represent the tops of the shelves. The shelves should be nailed or screwed into place. The shelf B should be placed on the top, keeping the hole C to the back. Take the ½-inch board and cut two pieces to measure 12 × 13 inches and two pieces 11 × 12 inches. These form the sides of the acid and gas chambers. The two 12 × 13 inch boards form the sides of the acid chamber and the 11 × 12 inch boards the sides of the gas chamber.

Directly in the center and 1¾ inches from the bottom of one of the 11 × 12 inch boards bore a 1½-inch hole. The remaining piece should be sawed out, leaving a hole at _g_. This is so that the board can be removed in case of a leak without disturbing the cleaning screw. These pieces should be fitted to their places with round head screws, and if properly done will form an acid chamber which will measure 10 × 10 × 12 inches, and the gas chamber will measure 10 × 10 × 10 inches. The acid chamber must be larger than the gas chamber, to allow the full charge of acid to be used without overflowing.

Now fit the sheet lead. Six-pound is plenty heavy for this generator and will last a lifetime. Cut it as shown in Fig. 8, A and B. Form the lead so that the seams when finished will come on the outside, as in case of a leak in a seam it can then be easily repaired by removing one of the boards. The projecting edges of lead should be dressed over the edges of the top to protect the wood from the acid, but do not fasten them, as the tanks will have to be removed and the seams burned.

Now cut the piece of lead C to form the top of the gas chamber. None is needed for the acid chamber, as it must be left open so that no resistance will be offered to the action of the gas on the acid. Five inches from the side and 2 inches from the back of this piece cut a hole, _d_, Fig. 8, 1¼ inches in diameter, and dress it up with the bending iron to 1½ inches in diameter, taking care to preserve the thickness of the metal. This is for the acid supply pipe to pass through.

Three inches from the side and 3 inches from the front cut a ⅛-inch hole, _e_. This is the gas outlet. Three and one-half inches from the opposite side and 4 inches from the front cut the hole _f_, 2¾ inches in diameter. Dress this up and over the flange of the charging screw _a_, Fig. 6. This may seem a difficult thing to do, but lead must be worked slowly. Heating the lead while dressing it will help wonderfully. If it is not possible to make a good job in this manner, then cut the hole 4 inches in diameter and burn in a collar sufficiently big to dress over and cover the flange of the screw. This is to prevent acid from coming into contact with the screw and destroying it. Treat the cleaning screw in the same manner. The location of this screw is in the center and as close as possible to the bottom of the gas chamber, as shown in Fig. 8 at _j_.

It is necessary to have a false perforated bottom in the gas chamber to rest the zinc upon and also to keep it above the solution. To make and support this bottom take a piece of sheet lead 14 inches square, as shown in Fig. 8, and form it in the shape of a pan, which will drop easily into the gas chamber _k_, Fig. 8½. A piece of 1½ or 2 inch lead pipe, 2 inches long, _n_, should be burned on the center of the false bottom, to prevent the center from sagging with the weight of zinc. Then punch the bottom O, Fig. 8, full of ¼-inch holes. A 1½-inch hole, _y_, should also be cut in line with the holes for the acid supply pipe.

Remove the tanks and burn the seams. Place the tanks back in place. Then take a piece of the ⅛-inch brass pipe, 1½ inches long. Cut a thread on one end, tin the other end, and burn it to the top of the gas chamber at _e_; also the collar for the charging screw. Then place the perforated bottom in the gas chamber, taking care to keep the holes for the acid supply pipe in line. Do not make any mistake in putting in this bottom. Its use is to act as a shelf to hold the zinc, and if put in properly it will hold the zinc about 2 inches above the real bottom. The top of the gas chamber _c_ should then be burned in. Now by measuring find the exact length of the acid supply pipe, Fig. 7, _i_. This pipe should extend from the bottom of the acid chamber _o_ to the bottom of the gas chamber _p_, as shown in Fig. 7. From one end of this pipe several V-shaped pieces should be cut, _p_, about 1 inch deep.

This is one of the most particular parts of the apparatus, as this is where the automatic action comes in, and great care must be taken in cutting these holes not to have any of them come closer to the perforated bottom than 1 inch. If this were not observed the acid would be constantly in contact with the zinc, and would rapidly get up pressure of gas sufficient to blow acid out of the upper tank, and the extra gas would escape through the acid supply pipe in blows. In fact, it would make the generator useless. This is the trouble with the French apparatus. The acid, having no place to expand in, is constantly coming into contact with the zinc, and unless the gas is being used as fast as generated it will blow acid out of the acid holder, making a bad mess, besides being very wasteful.

Now flange the other end of this pipe to fit the countersunk bottom of the acid chamber. Place the pipe in position and burn it to the bottom of the acid chamber and to the top of the gas chamber _n_, Fig. 7. One of the ⅛-inch gas cocks should be screwed on the brass nipple on top of the gas chamber. This will complete the gas generator. It will make a better job if the back of the generator be boarded tight and a door made to fit the space between the bottom of the acid chamber and the top of the gas chamber in front. It is very convenient to have it fixed in this manner, as in shipping it from one point to another the tubes and other incidentals can be placed in the space so made and shipped with safety. There is no objection to the acid and gas chambers being made in the shape of cylinders, instead of square, if so desired, but if made circular they should be made to fit the frame tightly to prevent jarring and eventually breaking the seams.