The Moving picture world (November 1925-December 1925)

90 MOVING PICTURE WORLD November 7, 1925 may be concerning things which seem quite simple. The editor would set the framing lever central, for the reasons set forth by various ones, and if the projector did not operate well with the lever there he would most emphatically want to know WHY. Question No. 374 — Another practical question, this time by T. R. Guimond, Mobile, Alabama. Using carbons well within their rated capacity, either positive or negative pencil — bum to a long, slim point. What is the probable cause, or what various things might be the cause? I forgot to say that in addition to those named, W. C. Budge, Springfield Gardens, Long Island; T. R. Guimond, Mobile, Alabama; C. H. Hanover, Burlington, Iowa, and Chas. C. Colby, Santa Fe, New Mexico, also answered question No. 373 more or less acceptably. And now to proceed. All those before named, except Wineki, who only answered two of the set, made good answers to 374; also William L. Barton, Houston, Texas. Hanover replies thus: Penciling in carbons may be due to any one of the several causes, or to a combination of one or more of them. Usually it is due to current overload — current in excess of the capacity of the carbon, but by the terms of the question this is '"out," so we must look elsewhere. A carbon which is considerably too soft in its shell composition, or which offers abnormal resistance to the current, will have a tendency to pencil below its capacity as judged by its diameter. Why the soft carbon pencils J am not sure, but believe it to be because of fault in its binding material — the material which is used as .i binder for the carbon itself, and which is presumed to be transformed into carbon of a sort in the leaking proce&s, is of very poor quality, and disintegrates in the heat of the arc, thus permitting the carbon particles to fall away before they are volatilized. This, mind you, is only a sort of guess, so if I am in error don't laugh. (Don't think your "guess" is such a bad one, though the further fact that a very soft carbon naturally has not the adhesion of particles a hard one has, due, in part at least, I think, to less applied pressure in the process of manufacture, may have something to do with it. Also I am not sure, but soft carbon has a higher resistance. Don't laugh if I'm wrong, for I, too, am making a more or less intelligent guess. It is impossible to know, or at least to remember, all of such details as this, and there is not time to ask a manufacturer for the absolute low down on it. — Editor). Abnormal resistance will cause a carbon to pencil, because it sets up abnormal heat, and abnormal heat in a carbon always has tendency to cause penciling. Anything which sets up abnormal (unnecessary) heat in the carbon will tend to cause it to pencil, therefore if my carbons, or either of them penciled under the conditions named I would first examine the' contacts, to see if they were of ample area and in good condition, because poor contact sets up heat; also I would be very sure the lamphouse ventilation was free and open, for the same reason, and I would test to find out if the amperage was not really higher than I thought it was, because if the carbons were only working a little below rated capacity— as carbons are supposed to do in projection work — a comparatively small boost in amperage, which if it came gradually might not be noticed, would do the trick. This set of answers is getting lengthy, due to my action with regard to the first one, and Hanover's reply is, I think, so excellent that we need not publish any more, except to just list the causes set forth by Messrs. Thoreau, Clark and Richards. They are : "Dirty contact jaws. Badly pitted jaws. Jaws made of metal having a too-high resistance. Faulty carbon, or badly mixed . composition in manufacture. Faulty line-up (don't get you there. — Ed.) Soft carbons. Poor lamphouse ventilation, caused most likely by lack of attention on part of man or men in charge. Ammeter out of order, showing less amperage than is really being used. Damp carbons." Question No. 375 — Describe a cartridge fuse, in detail. Brother Gnaegy replies -thus : .\ cartridge fuse consists of two metallic terminals joined by a "barrel" of insulating material, which also is fireproof. Inside the barrel is an electrical conductor made of fuse metal which connects the metallic terminals; also the terminals are connected by a "pilot wire," which is a small wire of fuse material parsing to the side of the barrel and just under a small hole in the same, over which is placed a paper label. This pilot wire is presumed to fuse when the main wire does, and in so doing discolor the paper label so one may tell by glancing at it whether or not the fuse is "dead." The pilot is not present in refillable fuses. In non-refillable fuses the barrel is filled with a powered, non-conducting material which serves the purpose of instantly breaking the arc when the fuse blows. In some fuses there is an air chamber, its purpose being that, the heat conduction through insulating material being slow, the temperature of the fuse wire will rise rapidly, and always in the same proportion, regard CI_ASS1FIED ADVERTISEMENTS Help and Situations Wantwi Only 3c per word per insertion Mir.imum charge 60c Ttniu. Strictly Cash with Order Copy must reach ufc bj Tutiday dood to Iniwr* publication In that week's itaue. SITUATIONS WANTED PROJECTIONIST desires permanent connection reputable house. Ten years' active work large theatres. Have managed. Mechanic and electrician. Go anywhere immediately. 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SPECIAL TICKET PRICES Five Thouiand $3.50 Ten Thousaiid 6.M Fifteen Thousand 7.00 Twenty -five Thousand 9.00 Fifty Thousand 12J0 One Hundred Thousand 18.00 National Ticket Co. Shamokin, Pa. le^:s of what the temperature of the outside air may be. which is presumed to establish a practically constant point of fuse capacity at point of blowing. 'LI right, brother Gnaegy, go up to the head of the class, though several of the Kang gave you a narrow squeak for that distinguish tonnor. Question No. 376 — Name and describe two types of cartridge fuses. Everybody made good on this, of course. Hurlbutt says : There are two types of cartridge fuse, the difference being in the kind of terminal used. One of what is called a "ferrule' contact, which consists of a metallic "ferruleplaced around and engaeingr the barrel at either end. This ferrule is slipped into what amounts to a spring contact, the same beine two metallic clips engaging with t.\\f fuse block terminals at their lower end, and terminating in up-standing prongs, shaped to fit the contour of the fuse ferrule, which sorins' apart to receive the ferrule when It is shoved between the clips under pressure. The other type is the same, except that in either end of the fuse is a short bar of copper, to which the fuse wire is attached at its inner end. This bar is of width and thickness varying with the amperage capacity of the fuse. These copper contact bars are designed to slip between two copper contacts on the fuse block. The contacts are made precisely the same as are the contacts of an ordinary knife switch. All right, all right! Shut up I You've told the story, and told it well, so let's hie us a step forward and tackle Question No. 377 — Suppose you took charge of a new installation and found there would be a maximum current consumption, at times, of 150 amperes of current in tbe projection room.. The projection room supply circuit you found to be fused with 200 ampere cartridge type fuses, with ferrule contact in good condition and tight.. Would you accept the layout? Brothers Budge, Thoreau, Clark and Richards, Wallace, Hanover and Doe saw the fly in this one and — swatted it. Gnaegy did it neatly and expeditiously, as follows : I would NOT! The layout is neither safe nor correct. Cartridge fuses with ferrule contact? are used only on circuits carrying sixty amperes or les.*^. Moreover I believe that fusing at 200 amperes for a 150 ampere consumption is allowing a too-wide margin of safety. Gnaegy is the only one who, in my judgment, made an absolutely 100 per cent correct reply, though Wallace came pretty close to it. You will note that the question distinctly states that the MAXIMUM current consuniption would be 150 amperes. True the wires would carry 200 amperes, but it does not follow that the motors or lamps would stand such an inrush of current as a rise in voltage which would run the amperage up to about 220 amperes, which would be required to blow tliese fuses, and though the separate circuits are all fused, I hold it is good practice to fuse quite a bit more closely than that, remembering that fuses are designed to carry ten per cent, over and above their rated capacity. As to the ferrule contact, I refer you to pages 112-113 of the Bluebook. Examine wording on diagrams at top of pages. TYPHOON COOLING QYSTEM ^ I TYPHOON FAN CO. 345W.39"ST. NEW YORK ^ , L_ ■ _^iJ