Show form wound coils used by amateurs by 8 E WATSON every electrical worker hns has ocen slon nt various times to use form wound colla coils of special dimensions for the average job a form should bo be nindo made of exactly tho the same length ns as la desired for the finished finis lied coil making duo atio allo allowance for tho the necessary ichu antion to bo be added later inter each of the other two dimensions should bo be about ono on englith inai greater than the ilic corresponding dimensions of bf tho the cow core upon which tho the coll Is to bo be placed A block of wood planed pinned to the oversize indicated above and sawed to tho desired length Is the most convenient kind hind of core form A quarter inch hole la Is bored through tile tho longitudinal ax axis Is of this block and receives the lie t axle used in rotating tho the form tho the appearance of tho finished block Is shown in r fig ig i 1 FOR U DING JAPE fic 0 YF I 1 above illustrations show method of constructing form and moans means of winding coll coil two end pieces of suitable size are anro nindo from this board find and a quarter inch hole la Is bored in the center of cadi cacti ono one end piece Is screwed to fo each cacti end ortho of the core its center holo hole coinciding with that in tho the core the spool thus formed Js Is slipped onto a inch rod which has one end threaded for several inches and the other bent in tho the form of a crank A tap Is screwed up tightly to each ond end of tho the spool and tho the whole la Is mounted ns as shown in fig 2 tho the bearings anro simply wooden uprights with holo hole for tho the axle if all work has been dono done with reasonably reason maso ablo accuracy tho the spool should show no tendency to wobble when tile tho eflina Is turned the first stop step before winding the coll coil la is to be sure buro that it will slip off tho the core readily when it Is finished whid on the aro core a single layer of small hard twisted cord this layer must bo be wound perfectly smooth rind the ends should bo be brought out through small holes bales in tho the end pieces wrap upon this layer two or three of vila thin sun stiff paper just wide enough to come flush against both ends glue both tabs of the pa per slightly just enough to hold it in place on each side of tho the core and paral id to tho file axis glue eluo a strip of narrow cloth tape RS ns shown at A fig 2 allowing each end to COMO come up from tho the core along falonk tho the end pieces and fasten temporarily apon the outside the tape ends must bo be of df lelent length to tie over tho the coll coil when it Is wound thus providing a method of binding it tightly in the process of removal it if the coll coil Is to be a largo large one two or moro more pieces of tape should be placed on each side of tho the form after these binders are in place paint the coro core with shel shellac limN or insulating paint pass one end bend of tho the wire to be wound through a small holo hole drilled through one end piece draw several indies incites of wire through and fasten austen securely by wrapping around the shaft wini wind tho the required number of turns on tile tho spool laying each tu turn rn as closely as against tho the preceding one paint each layer as it Is wound with a liberal coat of insulating paint and allow it to partly dry before p putting ing on the next nest layer wire especially enameled wire may bo be placed much more satisfactorily ily if it Is wound on a bed of paint which has 1113 been allowed to iry dry just to the point of tackiness when all tho the winding Is in ill place paint the last layer release the tab ends enda and tie each piece of tape firmly boross the colt coil as shown in fig 8 3 allow time tim e for the paint to harden before removing rem the coll coil passing just sufficient current through the coll coil to warm up the wire will hasten the drying tave take the form from the axle remove one of the heads and n lid grasp the end of the layer of string by pulling in the direction parallel to the axis the 8 tring string may bo be removed thus leaving a free space between the coll coil and the core remove the coil from the core tape it and it Is jn in the final taping the binding tabs should he bo removed but it Is biot necessary to remove tho the paper narrow tape Is best ond and makes a much neater jot job on small colls coils each turn should overlap the preceding one ona by half its width going once around tile the coll coil tape in this wily way gives two nt at every point and tilts this Is usually sufficient lelent D science aad aid luv invention Invent eatton lon ani and radio N new |