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Show (EdUed y - DouSlas Eardrop. Edltor ot Radio Merchandising.) Layout loyou orr edero Ccadersen for Sandard Condenser Diagram of the Universal Vernier That Locates Holes for Condenser A Useful Kink for Builders of Radio Sets. By R. J. ROBBINS Since tlie inception of the new tunable transformers for R. F. circuits It has been found desirable to devise some method of mounting the various units so that the angle from the vertical ver-tical may be readily varied without dismantling and redrilling panel several sev-eral times. It is, of course, possible to construct the Neutroformer in such a way that it can be mounted to the panel -by a single bushing in the center. This is quite obviously the most practical prac-tical method of getting around the difficulty, and the writer" has noted one or two such makes offered for sale. For the benefit of those who have to contend with mounting screws and other attendant evils the following idea may be of some benefit. There are probably as many different dif-ferent makes of variable condensers as there are breeds of dogs, so the writer will make no attempt to make this into a catalogue of all the ones which may be used. We will assume as a starter that an angle of 45 degrees will be the medium angle, and that the direction in which the unit will revolve may be an equal distance either to right or left of this point. This enables us to place the Neutroformer either in a position nearly near-ly vertical or nearly horizontal as desired. de-sired. We will consider but two common types of condenser and leave the rest to the ingenuity of the reader if he happens to have a condenser which does not come within the specifications specifica-tions mentioned. The first is relative to any type of condenser which mounts by means of three or more screws, all of winch are located on a circle and spaced equidistantly. This is exemplified exempli-fied by the well known Federal, which mounts with three screws, Or the Malone-Lemmon, which uses four. In each case these are all located symmetrically sym-metrically as regards the center, which opens up the possibility of changing the angle of the whole by a very simple sim-ple expedient. This consists of cutting slots along the circle on which the holes are laid out in which the screws may slide smoothly. These slots are to be made 3-10 of an inch wide and are all of the same exact length. It Is necessary that these be laid out very carefully with dividers and a steel square. How to Proceed. The procedure will be roughly as follows: 1. Strike lightly the circle 'on which the various holes are located. 2. Strike two more, one of a radius smaller by 3-82 of un inch, the other larger by the same distance. The two latter circles form the main outline of the slots. 3. Divide the circle into quadrants and bisect one of the angles to obtain a 45-dogive angle. 4.. Working from the point on the circle, set the dividers so as to trisect tri-sect the circle. (Or divide in four if there are four mounting screws). 5. Lay aside the large dividers and get a small pair, which set at about one-half or five-eighths of an inch, according ac-cording to desired length or slot. Set dividers at each of the throe (or four) points previously located and step off distances each side of the center points. 0. I'ricU punch thfs points care-full'v. care-full'v. Drill a 3-10 of an in -h hole at each of these points, taking care that drill does not creep in the least. These holes form the round, d ends of the slots, and the roniaiu'.iig material ma-terial between each pair of holes should now be carefully removed by drilling out and tiling until the (unshod , slots are perfectly smooth and the serous will ride in them as the Neutroformer Neutro-former is U.rn.d. A t :i2 of an inch hole is drilled In the center to accommodate accom-modate the shaft as usual. All that is ece-sarv now to finish the Job w.ll be to substitute round bead Jo- machine screws for the usual Hat heads. A small washer on each will help to preserve the edcos of the slots. It will now be found lo be a simp.e matter to turn the unit in the direction l '''-and '''-and after locating the correct an-.o to tighten the mounting screw securely m place. Other Type of Condenser. The other type of ce-.iden-er is the standard zed form as exemplified hy ,he Sleeper. V. S. Tool. Signal, etc. These ali .,int ' ,u" screws local. .1 on a lino one-quarter of an inch offset from the center l.r.e. The method of appljin-' this . a to su.h condensers is very sine! -,r that out: in.-! above for ti.o 1.1 t:.I. , In this cao the vcrthai an-! -Ul cent, r lines are ,!r;,T r.r; ;.!.. I tb- location of the ).-: gree ',,? point found roughly by bisecting 'one of the angles. This will be made clear by a study of the diagram (Figure (Fig-ure 2). Another line is now drawn parallel to it, the bisecting line, and one-quarter of an Inch to the left, as shown. If this line, in turn, is now bisected and a distance of one inch Is spaced each way from the point of section sec-tion we shall have located the exact center points for the two mounting screws for the condenser. The next step will be to set the compasses or dividers for a radius which will pass a circle directly through both these points. The rest of the procedure will be similar to that already outlined for the Federal condenser. In this case, however, the slots may be laid out somewhat longer if desired, owing to the increased latitude permitted by the small number of holes. The same idea may be applied to any condenser employing the same or similar methods of mounti, and it is hoped that the above may he of some use to the vast army of experimenters who now make radio research their pastime. New York Globe. |