Page:Popular Mechanics 1928 01.pdf/123

 

an efficient A-battery and charger is not only an easy but an interesting task that many radio fans would have undertaken before except for the lack of definite details. The low cost, five dollars, appeals to those with limited pocketbooks, and the interest of the work to the experimenter who likes to do these things for himself. Ordinary quart fruit jars and auto storage-battery plates, easily obtained from the grocery and nearest battery station, respectively, are the main elements in the construction of both units. One, two or three cells can be made up to suit the needs of the builder, depending on the type of tubes he is using in his set. For instance, if the set employs tubes of the 199 type, two cells only will be required. The fruit jars cost about 10 cents each, and the plates from 15 to 20 cents apiece. Fifteen plates in all will be required for a 6-volt three-cell battery, five plates to each cell.



Select three 1-qt. fruit jars and discard the tops, clean them thoroughly and inspect them for cracks or flaws. Build a wooden case to contain the three jars comprising the A-battery, provided a 6-volt type is required, reducing the dimensions given so as to take two jars if a 4-volt type is to be built. The dimensions for the case will be found in sketches below and on page 122; 1-in. wood stock is used for the case and the outside measurements are 14 in. long, 6 in, high and 5 in. wide. The inside partitions are made of the same wood stock, are fitted across the inside at equal distances and reach from top to bottom. The three compartments thus formed are 4 in. square and 5$1/2$ in. deep, inside measurement, permitting the fruit jars to fit snugly, with the tops projecting about 1$1/2]$ in. above the top of the case. The completed case should then be painted inside and out with two coats of asphaltum; when thoroughly dry, screw the handles in position at each end, as shown in the illustration. These handles may be ordinary drawer pulls from the local 5 and 10-cent store, and rubber-headed tacks for feet 