H. F. Shepherd.

The accompanying sketches and description apply to a small storage cell which has been found to give excellent results in practice. One of these cells, built by the writer, has been used for igniting the charge of a gas engine, and had a capacity of a trifle over 2 volts and about 12 amperes. For the construction of the cell there are required about l1/2 sq. ft. of sheet lead 1/16" thick; 1 lb. of red lead; 1 lb. of yellow lead or litharge; 1 lb. of sulphuric acid; 6" of lead wire \" in diameter; two brass nuts, and a binding post.

The outside shell of the cell is of sheet lead, and forms part of the negative electrode. This is made by cutting out of the lead sheet a piece 95/8" wide in one direction, and 6" wide in the other, with a lug or ear at one corner 2" long and V wide, as shown by Fig. 1. This is rolled into the form of a cylinder 3" in external diameter, which will give a lap of about 3/16". The edge that is 6" wide should lap on the outside of the edge 8" wide, and the joint should be soldered, taking care not to fuse the lead any more than is absolutely necessary.

The bottom of the cell consists of a disc 3" in diameter, to which the edges of one end of the cylinder should be fitted rather carefully and soldered. Next cut out a sheet of lead 51/2" by 8", and punch this full of holes not larger than 1/4" in diameter, and as close together as possible without making the lead so weak that it cannot be safely handled. The holes can be cut with an ordinary belt punch. This perforated sheet should be rolled into a cylinder 21/2" in outside diameter and 5" long, the lap being soldered in three or four places, but not necessarily throughout its length.

This cylinder should be set inside the first cylinder so as to leave an annular space of 3/16" uniform width between it and the interior wall of the main cup. This annular space should be filled with a paste made of litharge or yellow lead and dilute sulphuric acid, the acid being diluted by mixing it with ten times its weight of water. After packing the paste into position, let it dry thoroughly.

The struoture thus far obtained constitutes the negative plate of the cell.

Next take the piece of \" lead wire, thread it through a countersunk hole in the center of a wooden disc 25/16" in diameter and 1/2" thick, beating a burr on the end of the lead wire which will fill the countersink in the wooden disc, as indicated in Fig. 2. This disc must be thoroughly boiled in paraffin. Then cut out ten lead discs, 21/4" in diameter, and drill a hole 1/4" in diameter in the center of each disc. Flute the edges of each disc with a pair of pincers, so as to convert each one into a very shallow dish, as indicated by Fig. 3, and punch the bottoms of these dishes full of holes not over 3/16" in diameter. Thread the first dish on the wire, letting it rest on the shoulder of the wooden disc, and fill it with a paste made of red lead and dilute sulphuric acid. Next thread another dish on the lead wire, taking care not to push it entirely down on top of the first dish, and fill it also with red lead paste.

Fig. 2.

Fig. 1.

It will be found a good plan to set two strips rubber or thoroughly dry wood across the top of the first dish for the second dish to rest on until its paste has hardened. The holes in the center of the dishes should be a tight fit on the lead wire, so that the friction there will tend to prevent the dishes from slipping down. The succeeding dishes are slipped on the wire and filled with paste one by one, until the whole ten are in position, and the cell may then be assembled, as shown by the cross-sectional view (Fig. 4), the electrolyte being put in before the cover is put on, of course. The electrolyte consists of dilute sulphuric acid, exactly like that used in mixing the paste, and the level should be well above the topmost dish.

Fig. 4. - Cross Sectional View of Storage Cell.

Fig. 3. - Lead Dishes Punched with 3-16 ths in. Holes.

Fig. 5. - Cover.

Fig. 6. - Storage Cell Complete.

The cover of the cell may be made of hard wood or of rubber, preferably the latter, and should be of the shape shown by Figs. 4 and 5, the lower part of the cover fitting snugly the interior diameter of the outer lead shell. If the cover is made of hard wood it must be boiled in paraffin. The hole in the center of the cover, through which the lead wire passes, should be tapered, as indicated in Fig. 5, and filled with coal tar or pitch, so as to prevent the acid fumes from passing up through the hole and attacking the brass nuts on the outside.

The binding post should be of the wood-screw variety, and its screw should not be long enough to go entirely through the cover. The ear, 1" by 2"', shown in Fig. 1, is bent over on top of the cover, and the binding post passed through the hole in the ear, the post being screwed down hard on the ear to form connection with the outer shell. The cover must have a venthole about 1/16" in diameter, in order to allow the escape of liberated gases. Fig. 6 shows the cell with the outer shell and the litharge paste cut away to reveal the perforated inner shell.- American Electrician.