A 112-VOLT B ACCUMULATOR

Radio Record, Volume I, Issue 2, 29 July 1927, Page 14

A 112-VOLT B ACCUMULATOR

SIMPLE AND EASY TO CONSTRUCT

flere is a description of how to con@tract a B accumulator on the same fines as one that has been working without a hitch.for nearly two years. After success with a battery of the same ‘voitage but with smaller plates, this Was designed as an experiment im getting a fair capacity from lead plates ‘without pasting, which is a process that tiany would prefer not to tackle. It has been so successful and is compara-: tively easy to make that it is certain to le of great use to many a radio euthusiast who enjoys making his own accessories. Amn ideal way of using this accumulator would be to arrange a ‘trickle-charger that would operate durang the night, :o that a full supply of Hit current would always be ready for the tellowing day. It is not claimed that this battery has a very high capacity. ‘ut when forming of the’ plate is couplete, it will run a four or fivevalve set on loud speaker for at least five or six hours, even with power Weives in use. Smaller sets will, of corse, Tun proportionately longer, aud f+ iwo and three-valve‘sets and shortWave work it will be found particularly suizulle. Jt is convenient to use, givim tiiree voltages which can be altered b; plugging in as required, and each valve is protected by a reliable fuse attached to the positive leads as they dcuve the battery. For those who pre fer to go to the trouble of putting paste iti tlie plates in order to gain consider. aliy in capacity, with less frequent charging, the same size and shape otf fei] plates can be utilised in a manner tliet will be described at the end of this aticle, Everything clse is carried ont &s described, aud the only difierence is in the iinal treatment of the plates. The accumulator has an advantage over dry batteries, especialiy fer intermittent fine, as if charged up occasionally it will aimavs keep in good condition, whereas a cry battery is deteriorating whether used or not, and is comparatively costly te replace, whilst quieter reception will be assured with the accumulator. Frequent charginy is of course, necessary, but if convenient switching arrangemicuits ate provided, and a good chemical or other rectifier installed to chatge from 280-volt alternating current mains, there need be no inconvenience on that account, Very few public electric inStallationus utilise direct current, ut where this is the case, no rectifier is required, as the current from the mains may pass direct to the battery, regulated Iv a suitable number of lamps as resistances. Those who are still on 105volt supply must charge the battery in two halves simultaneously with a small additional switch attachment that will be described in due course The materials should not cost more than £2, and the cost of charging, even daily, will searcely show in the electric light bill. The diameter of the test-tubes used is nominally one inch, but there is usually some variation in size. even in the same batch, so the constructor would be wise to purchase the tubes before coimmening the woodwork, so that the size t» be provided for will be known. The fenoth of the tubes is six inches, and ewing to the way in which the lead jictes are folded and interlocked, a wuch greater capacity is provided than is the case when simple flat strips are used This shaping and placing of plates may seem difficult at first sight, Lut if the instructions are carried out correctly, it will be found = that the plates will drop together with a mini-

4 mum of trouble, and the assembling thus prove quite a quick and simple matter. Materials Required, 56 Test tubes, 6 x lin. Ebonite, }in., 6} x 3tin. 5 Terminals. 9 (or more) sockets. 4 pins for ditto. . 6 Brass bolts 4+ x 1-8in. with nuts and washers. Sheet lead 48 x 28in., about 82lb. Celluloid, 20 mils., 8 x 8 1-6in. Suitable timber and lathes. Hnamelled wire, brass screws, etc. The case is made of heart rimu or other good timber, and a smart finish is imparted by polishing with a rag dipped in a solution of shellac in methylater spirits. ‘This polishing may conveniently be done before the parts are screwed together. ‘The outside dimensions of the case are given on the perspective view, and it will be seen that at the back and frout an opening 2} inches high is left for inspection of the lower end of tubes and plates. A loose lid is provided, with a turnbutton at A which allows the lid to be kept slightly open whilst charging. ‘Timber used for the case should be 3-inch, with 3-8 battens under the bottom and inside the lid. One-ineh number 6 brass screws will be fownd suitable for putting the case together. At a distance of 1}in. from the top edge a 5in. slot-is cut in the front of case to allow the tap wires to reach the panel. The pane] stands away from the front on two side pieces of 3-8in. thickness, 4fin. by 14in. screwed to the case from inside, the top ends level with the top of the slot, the space at top being covered with a slip of thin wood projecting over the top edge of tlie panel and flush with its | front surface. Below the panel a strip of wood about an inch wide fills the remaining space and in this four holes are drilled to take the plugs when not in use The tubes are supported by a frame with 56 apertures each one-inch square, constructed of laths one inch wide by barely three-eighths thick. These are notched half-way through and interlocked as shown in the diagram. The outside of this frame must be a loose fit inside the case, and a Jath is screwed inside each end of the case to support tle frame so that its top surface is five inches above the bottom of the case. If. the constructor takes the sizes here given for the frame, he should make it first and make tlie case an easy fit for it, otherwise if the case is made first these sizes may not be quite correct, depending upon the exact. thickness of the wood used in making the case. Hight lathes are required, 103 inches long, and six of these must be marked j out and all notched hy making the corresponding saw-cut in each at the same j time, so that anv slight inaccuracy will not cause trouble in fitting the crosspieces. The notches must be of a width to take the laths snugly, and spaced out so that every division will be equal. Seven laths will be required of the short size, about 9 5-8in. and these will have six notches cut in each. Two laths will also be required for the ends of the frame, and tlic length of these will Le determined when the rest of the frame is assembled. The next operation will be the preparation of the lead plates. For these a piece of sheet lead 48 x 25 inches will be required, weighing about 32Ib. in the ordinary gauge usually procurable, about 1-16th inch thick. Heavy gauge (lead would be difficult to bead and cut. Before cutting up this sheet, lead must

be well flattened out and cleaned on both sides with kérosene and pumice powder, or other wet process that will make it fairly bright looking. No dry cleaning method must be used, as, the dust raised would be injurious to the health. Now scratch a line down the centre with a straight-edge as guide, giving two portions 11} by 48 inclies. Parallel to this central line two other lines two inches apart ar: to be marked down near the centre of each half, or in other words a line 4}in. from each edge and another line on each side of the centre line and 4jin. from it. Now f

with a pair of snips or strong shears cut down the central Jine and then proceed to cut each of the two pieces thus produce] into strips 114 by 1 5-Sin. as marked. Hach of these pieces will then, have two lines two inches apart marked across near the centre, Put eight of these aside for special treatment Fortyeight pieces are to have a piece cut out of the centre as shown by the two marks, but leaving a connecting strip on one side $-8in. wide, as diagram. The eight other strips are for the ends of each row of cells, and are to be cut into two pieces so that each has a 3-8in. Wide tag two inches long projecting at one side of the end, a small piece of waste coming out between the tags. Now the double plates can be bent to Shape over a strip of wood about 3-8in thick, with a rounded edge. All thr double plates are bent the same was and are put into the tubes alternate] as shown in the diagram. See that,th: tubes are clean, smear yaseline hal’ inch wide inside and outside*tops, an drop into place in frame. Now th double plates with the connectors vase lined may all be put in place, and i will be seen which way the end one must be bent so that the tag will com at the outside end of the row. ‘This tag on the end plates is to be bent a shown to prevent the plate from sink ing in the tube, and the tap wire is t he soldered to the extreme top of the tag, as by this means the jeint*is kept

clear of the acid. ‘he top of these plates also must be coated with vaseline, likewise the soldered joints when they are completed. ‘The tap wirés are also utilised to conuect one row of cells in series with the next, and these wires may be soldered to the negative end of each row, and then continue to tlie panel sockets. Each tap wire should tun just below the edge of the tubes, and to keep them in place they may be passed through holes drilled in a couple, of inch strips of celluloid about liin. long, running from side to side between the cells. The celluloid separators must now be made. They consist of strips 1 3-8in. by 1-3in. These are easily made, and a good supply is required, two for each cell, and some extra ones which may be needed. The celinloid should be 20 mils, thickness, and a piece 8 by 8 1-8in. will make a gross of separators. Divide the 8 inches into thirds of an inch, giving 24 and the 8 1-8in into six parts of 1 8-8in. each. Now take a straightedge and sharp steti point and_ rule deep scratches where the celluloid is to he divided When this marking is all done, the celluloid can be bent and broken where the scratches are, and a clean edge results. Warm the strips a | few at a time near a fire or over an electric radiator on a metal plate until they soften slightly, then bend to a V of the angle shown in diacram, which is about 70 degrees. but only needs to be approximate. ‘These separators are pushed down between the- plates as shown in the diagram, one at the bottom of one plate, and one at the top of the other plate. Jn odd places it may be necessary to put an extra one in, (lo be Concluded Next Issue.)