The Moving picture world (November 1925-December 1925)

better Ppojection ^his Department llfasfoundjed in, 1910 bij its Snsent 6dibr^ ^.J{.3ilchardson Better Projection Pays As to Tension on The Picture SAMUEL F. Cooley, Projectionist, Lyric Theatre, Manchester, New Hampshire, and one of the Bluebook School students, hands us the following : Dear Friend and Brother: I have to ask for a bit of information, and as I am more than satisfied with the way the Department and Bluebook School are being^ carried on, therefore have no complaints or suggestions to make, I will get right down to business. On all motion picture projectors the film is held against the aperture plate tracks by tension shoes, the pressure upon which is supplied by springs. The Bluebook, pages 603 and 609, tells us how these springs should be adjusted to the minimum the projection speed permits. It is a well known fact that too much tension is harmful to the film sprocket hole edges, the intermittent sprocket teeth and to the entire projector intermittent mechanism, while too little tension also is bad, because it permits unsteadiness of the • 'r<jen Image. Presuming we set our projector tension in accordance with Bluebook instruction*, there is no way by which we may know whether the tension pressure is equalized. By this I mean that a certain, and presumably equal amount of pressure should be «xerted by each shoe — on either side of the film — and it seems to me there should be some method of making certain that the tension is thus exactly equalized. Assuming the projection speed to be 85 feet of film per minute, in order to get the best results — steady picture with a minimum of wear on the sprocket hole sides — sides of intermittent sprocket teeth, etc. — what should be the pressure, in ounces, on each side of the film at the aperture? In this I presume the pressure to be measured separately on each side — each tension shoe. It seems to me if tension were regulated along these lines, the wear upon film, sprockets nad everyhting else would be reduced, and that the condition would, in general, be improved. That is very true, Brother Cooley, but unfortunately we have not yet arrived at the sta^e where »uch a thing i« practicable. The Powers and the Simplex have an arrangement which automatically equalizes the pressure of the tension spring, so that each shoe receives the same amount of pressure. I am quite sure the Motiograph Deluxe has the same arrangement, though I cannot say positively from memory. Instruction No. 3, page 712 of the Bluebook, convinces me that I am not in error. These three projectors are the only ones in general use in the United States of America and Canadian America. What you say about applying a certain definite amount of pressure is correct, but it is not practical for the projectionist to apply in practice. How would be manage to measure such pressure accurately ? And it would have to be measured with a great degree of accuracy to be satisfactory in practical application. Even granting that a relatively few expert projectionists might be able to make such measurements accurately, for every one who could there are others who could not, and that is no slam at any one, either. Bluebook School Question No. 422 — Before connecting a wire to terminal binding of • switch or other thing, what should be done? Question No. 423 — What attention should terminal binding posts of twitches, rheostats, etc., have, and why is this attention of importance? Question No. 424 — Will power wasted in poor connections, burned wires, etc., be registered on the meter and have to be paid for? Name the possible source of waste of this sort. Question No. 425 — What do Underwriter's rules require as to the making of wire splices ? Question) No. 426 — Describe the proper method of making a wire splice, beginning with stripping the insulation. In a paper read before the S. M. P. E. some while ago, some on'^ proposed that the tension be such as would require a certain number of ounces of pull to start the film agairg'^t the breaking friction of the aperture tension. I did not take much interest in that, because I felt that while such a thing might be theroetically all right, it was one which the average man either could not or would not put into use. In the Bluebook I have given you what I then believed to be and do still believe to be a method which is more nearly practicable in application than anything I have yet seen advanced. If carefully done it will deliver the goods very well, too. As a matter of fact there will always be tension abuses, at least until we get to the point, if we ever do — (doubtful) — when projection speed is really fixed at one unchangeable value. I talked with Mr. E. S. Porter many times when he was the head of the Precision Machine Company, in an endeavor to get him to incorporate a tension adjustment on the The DUPLEX SPECIAL $52.50 worth of quality equipment for $41.50 DUPLEX MOTION PICTURE INDUSTRIES, INC. D<.Dt. w. inNG isiANn r.iTV. n. y. Simplex. Mr. Porter finally went to the length of having one made up — and an excellent one it was, too. But he finally balked on its actual incorporation in the projector, for this reason: "Richardson, said he, "while I grant you that there are a great many projectionists who would handle such an adjustment competently, and in whose hands it would really be an improvement, still there are very many who would not handle it intelligently, and in their hands it would be far from an improvement. They would jam the tension down as tight as they could get it, and let !t eo at that." And I am bound to admit that Porter was right in his contention, though I then held, and do still hold, that it is a mistake not to adopt all those things which are in themselves good, merely because in the hands of the careless or incompetent they will b« abused. I freely grant, however, that there are two viewpoints on such a matter as this, but anyhow that is the situation. It is that the manufacturer who does not incorporate a tension device must perforce set the tension of every projector to take care of the highest possible condition as to projection speed, whereas the projector with a tension adjustment may be set right, though it may also be set to "take care" of something much worse than the worst possible condition in the matter of projection speed. It may be used, for instance, to hold the slack out of a worn intermovement or a movement which needs adjustment. Personally, however, I hold the tension adjustment to be the better condition of the two, always provided it be so made that it is a really practicable device. How to Tell Positive Wire From Negative HARRY L. STEINBERGER, who writes from the "Roof of the World" from . Leadville, Colorado, where "pebbles" weighing fifty tons are common, asks : Is tliere any method of a.scertaining which is tiie positive and which the negative wire of a direct current circuit or of a batteryT There is. You have only to surround and capture an ordmary Irish potato, cut it in half and stick both wires into it, about threequarters of an inch apart if the current be 110. If it be a single cell battery the wires should be inserted into the potato less than half an inch apart. If the current be 220, then better get a big potato and stickum in at least an inch apart, or maybe more. With commercial current— 110 or 220 — bubbles will form around the negative almost immediately, and in a couple of minutes with a battery; also the potato will be stained green around the positive. The test is positive and simple in application.