Page:Popular Science Monthly Volume 90.djvu/963

 �Q Amateur - Electrician

��^p^d Wireless Operator

��The Construction of a Fifty- Volt Storage- Battery

THE increasing use of the audion bulb for wireless work brings up a power problem that is by no means easy of solu- tion. The necessity for using 40 or more volts for the amplifying circuit has troubled many of the experimenters who would like to use this efficient form of detector. The small flashlight batteries are in common use more particularly for the portable sets, but while they serve their purpose very well, their first cost and subsequent replace- ment make them out of the question in many instances. The cost of these dry cells is about 30 cents and it is necessary to use 8 or more. Although the audion draws but a small fraction of an ampere, the cells must be discarded before any reasonable returns are made on the invest- ment, as the dry cells deteriorate regardless of whether they are used or not. The fact that the audion requires such a small amount of current suggested that it is possible to construct a storage-battery that will require no replacements and that can be quickly charged at a small cost.

Two general forms of a storage-battery are given, one for charging from the electric mains having a current in excess of 60 volts and the other for charging from a Bunsen, sal ammoniac or bichromate cell. Each battery consists of 24 cells made of test tubes having an outside diameter of i in. and a wall 3/64 in. thick, the length being about 6 in. The fillers for the test tubes are made of lead tubing ^ in. outside diameter with a wall 3/32 in. thick. The lead tubing is standard stock in assayers or chemical supplies and the test tubes are standard stock. After procuring the 24 test tubes, proceed to make a frame A, Fig. I. This style of battery is for use on the ordinary direct current electric main. Lay out and mark the places for the holes

��and bore them with an expansive bit to make a sliding fit for the test tubes. The flared end of the tubes will keep them from slipping through. It will require some care in boring the holes to prevent the board from splitting, and it may be neces- sary to first bore a small hole, say with a 3/16-in. bit, for the lead screw of the ex- pansive bit. If the cells are to be charged from primary batteries the construction, of course, is as shown in Fig. 2.

To make the elements for the battery as shown in Fig. i, cut 23 pieces of the lead tubing, each 12 in. long, as shown in Fig. 3,

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��Test tubes used for cells in making a storage battery

��and two pieces, each 6-5/8 in. long, as shown in Fig, 4. The 23 pieces are perforated with a ^in. drill, numerous holes being made for a distance of 5 in. from each end. Then the pieces are bent into a U-shaf>e as shown. The two short pieces are drilled for 5 in. of their length in the same manner and the undrilled end is bent over in the shap>e of an L. Use a sharp drill running

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