The Moving picture world (November 1926-December 1926)

November 27, 1926 MOVING PICTURE WORLD 245 Bluebook School Answers 532 and 533 Note : — This "School" is designed to arouse interest in the study of those many problems which constantly arise in motion picture projection, AND to cause men to really study the Bluebook and assimilate the vast amount of knowledge contained within its covers. Question No. 532 — At what temperatiire is the resistance of wires, as given in tables, calculated, and what is the effect of a higher or a lower temperature? E. Fergodo, Livermore, Calif. ; G. L., Bill, John and (a new one) Charles Doe, Chicago, 111.; W. C. Budge, Springfield Gardens, N. Y. ; C. H. Hanover, Burlington, Iowa; Thomas Allerton, Topeka, Kansas ; S. F. ■Cooley, Manchester, N. H. ; G. V. Rumley, Des Moines, Iowa; Charles F. Curie, Chattanooga, Tenn. ; Frank Dudiak, Fairmont, W. Va. ; Allan Gengenbeck, New Orleans, La.; ■Charles C. Colby, Santa Fe, New Mexico; John Peters, Allentown, Pa. ; Ty R. Donaldson, Pottsville, Indiana; Wm. T. Smith, New York City; T. D. Boyd, Springfield, Mass.; T. M. Dodd, Hendersonville, Ky., "and Albert Johnson, Akron, Ohio, all replied correctly. I think, however, Brother Hanover puts the thing in the best form as to words. He says : "The resistance of wires as given in the various tables, is calculated on the basis ot the temperature of the wire itself being at what is termed 'normal,' which means To degrees Fahr. or 24 degrees Cent. "The effect of a temperature greater or less would be, as set forth in the Bluebook, that as temperature is increased above normal the resistance of the wire is increased in proportion, which increase may be accurately calculated by the use of what is known as the temperature co-efficient — see page 66 of the Bluebook. The resistance decreases in the same proportion as the temperature drops below normal, though the possible range there is so small that in projection practice it amounts to nothing. It only counts where very great accuracy is demanded." The foregoing was very nearly the same as Cooley, G. L. Doe, Gengenbeck, Curie and Dudiak said. In fact, Curie's reply was, I think upon second reading, perhaps a bit better, but not sufficiently so to justify making a change now. Question No. 533. — Describe some of the properties of some metals used for resistance. To the before named list of correct an■swers must be added the following : B. Mc■Clung, Spencer, W. Va., and T. R. Boyle, Richmond, Va. Also some of the ones namsa in the first list fell down on this one, but I'll not tell tales as to who they were. Let 'em get away with it, says I, due to the excellence of their answer to the first one. The question was only asked to direct attention to the subject, and to get yon to scrutinize what data the Bluebook and such •other works as you might have available contained. The answer of Curie is correct and good, but that of Brother Fergodo serve s the purpose of publication very well on such a subject, and it is brief. He says : "Among the metals used for rheostatic resistance, cast iron and various grades or alloys of nickle steel are most common and seem to serve the purpose best. ''Little is known of the properties of cast iron with respect to its resistance characteristics, except that where a considerable difference between the resistance offered at normal and at higher temperatures is not important, it forms a cheap and fairly satisfactory resistance element. " "iClimax' resistance wire is a high-grade, high resistance nickle steel alloy, well suited for use in rheostats. 'Advance' wire is a copper-nickle alloy containing no zinc. It is uniform in its composition and its lesistance remains practically constant at all temperatures. The temperature co-efficient cannot therefore be applied to it. The same is true of 'Ideal.' " 'C^rlido' is a high percentage nickle chromium alloy containing a small percentage of iron. It has an extremely high melting point. 'Nichrome' also has an extremely high melting point, and is practically noncorrosive. The same applies to 'Nickel.' " Powerlight and Other Things RECENTLY from some mysterious source a rumor came that "Powerlight," the reflector type lamp marketed by the International Projector Corporation, was to be taken ofif the market. I went immediately to that corporation and asked if this was true. The "No" which greeted the query almost blew me out through three solid doors and down two flights of stairs. I think after that experience I may say as positively as anything may be said that the rumor not only has absolutely no foundation in fact, but also never did have any. So that's that, and "Powtrlite" will proceed to supply the excellent screen illumination as in the past, and bring smiles of joy to those using them. While I was at 90 Gold street, the lair of the International Projector Corporation, this remark was made by one of the officials : "You ought to drive home to projection SPECIAL ROLL and MACHINE TICKETS Your own special Ticket, any colors, accmrately numbered; every roll guaranteed. Coupon Tickets for Prize Drawing: for t7.M. Prompt shipments. Cash with the order. Get the samples. Send dngram for Reserved Seat Coupon Tickets, serial or dated. ROLL AND MACHINE TICKETS In Five Thousand Lots and Upward Ten Thousand $iJt Fifteen Thousand 7.00 Twenty. five Thousand 9.00 Fifty Thousand 12.S0 One Hundred Thousand 18.00 National Ticket Co. Shamokin, Pa. ists and exhibitors, who, after all are, in the last analysis, our customers, even though they may not deal directly with us, the fact that they can only place reliance on statements made by responsible manufacturing and selling organizations. There are a large number of fly-by-night concerns in the business, some of whom think nothing of ma'Kiii.j wild statements. The statements of such irresponsible parties are often trusted to the ultimate damage of all except the one making them. They were made, primarily, for the advantage of that one, and no one else. "In this matter of the Powerlite, for instance, you have done exactly the right thing in coming to us direct for information. I believe it would be well that you point out to your readers the advisability of following the same course. They should either consult the manufacturer, or some one directly affected, or write direct to >ourself for authentic information." Best to Write Direct Correct, but I would amend that by saying that it is best to write direct, rather than to me. I am very busy, and while I am always willing to help, still, the manufacturer knows Ihe facts, and is the logical one to give them to you. On the other hand, manufacturers are often remiss and cause much unnecessary trouble for themselves, and misunderstanding on the part of others, by failure to advise this department when changes in equipment, etc., are made. Through this department they can immediately reach at least nine-tenths of the projectionists of this country and Canada, and also a large percentage of the exhibitors and many of both in other lands. This department is very willing to render this service, but it is not either able or willing to chase around and get the information in addition to giving it space free of charge. Blame Unfairly Placed I would also add to the statement of the International Projector official by saying that the exhibitor or projectionist vvho liurchases a spurious part for a projector— a part not made by the manufacturer of the projector— is being hugely unfair to the manufacturer, to the projector and to himself. The projector manufacturer is the one w'lo has a direct, abiding interest in seeing his projector give perfect service in screen results. The parts manufacturer is, very naturally, only concerned in the performance of the single part sold to the exhibitor, and if It performs badly, nine times in ten it 's not the maker of the part who gets blamed, but the projector itself, because it gives punk results as a whole by reason of the "cheap" (?????) punk part. But does the exhibitor, or the average projectionist, blame the part? Not so! He blames the projector. Stick to the statements of responsible manufacturers and their responsible agents, and to the things made by responsible manufacturers, IS my advice— and it's solid gold diamond-trimmed ad vice, too, mark you well.