International projectionist (Jan-Dec 1950)

To the Editor of IP: It seems that some of our boys are losing their eyesight, judging by the punch-marks and other markings used as changeover cues — yes, and this extends even to some new prints. Some of the screens in this area look like cancelled postage stamps. Another annoyance here are the Penna. state censor strips which are not removed when prints are sent from Philadelphia exchanges into New Jersey. Here in New Jersey we run no censor seal, yet the exchanges will not eliminate the Penna. seal. It seems that they always have to place them between the end of the feature and the repeat cast following. Our only alternative is to remove these seals, or waste our time patching them on the very end of the print. A good idea, I think, is for every projectionist to mark the first band of each feature with the actual running time. I do this on all my prints, and I feel that in this way we can help each other all along the line. John J. Dwyer Member, Local 359, Trenton, N. J. Marking print footages is a good idea which will help the craft generally. Print mutilation is something else again, because the "butchers" will evidently always be with us and most exchanges are indifferent due, IP thinks, to the fact that exchange workers are vastly underpaid and grossly overworked. Concerted action by Southern New Jersey and other non-Penna. Local Unions served from Philadelphia exchanges might eliminate the censor seal nuisance, particularly on an "or else" basis. — Ed. To the Editor of IP: I was most interested in the symposium on cooling means for high-intensity arc projection which appeared in IP recently.* Considering the status of the contributors thereto, I was somewhat surprised at the conflict of views on the matter. Some years back I worked in two theaters on the German water-cooled Ernemann V projectors. In both cases the projectors were connected to the main water supply through a regulating valve, and the merest trickle of water served to keep the gate and film really cool. The arcs pulled about 80 amperes. Dual Cooling Setup In addition to the water-cooled gate, the Erneman V was fitted for air-cooling, and in the case of the latter the manufacturer utilized an interesting little plant. This consisted of a small compressor which blew the air through a water-filled vessel (somewhat like the Turkish Hookah pipe) , thus delivering perfectly clean air to the gate and also, by reason of the moisture in the air, helping to rehumidify the film. I never worked on this equipment myself, but I understand that it was quite efficient. In my view, however, no air-cooling system can be so effective as a circulating water system, as the latter actually removes the heat from the projector and does not depend upon dissipating the heat into the atmosphere surrounding the projector. While a water-cooled gate seems to be the answer to projector cooling, it does not completely solve the problem, as it still leaves open the question of the impact effect of the arc spot on the film, which in a really powerful arc is considerable. It would seem that an optical heat filter of moderate power is needed. The complete and simple answer would seem to be for all projectors to use waterjacketed gates, and all arc lamps to use heat-absorbing optical filters. Incidentally, the British-made Walturdaw V projector is fitted for both water and air-cooling. H. C. Bromley London, England Many IP readers other than Mr. Bromley were surprised at the sharply conflicting views expressed by the contributors to the aforementioned symposium. IP expressed its own opinion of the symposium's content in the Monthly Chat column for October. There is much food for thought by equipment manufacturers in Mr. Bromley's letter, if they can ever reconcile their opposing viewpoints.— Ed. Sapphire Inserts to Reduce Projector Wear; IP's Views * "Cooling Means for H-I Arc Projection"; IP for September, 1949, p. 22. SPECIAL sapphire inserts at points of concentrated wear are claimed to eliminate difficulties caused by uneven rates of wear on various parts of motion picture projectors, according to a statement by the Elgin National Watch Co., which developed these inserts for the DeVry Corp. of Chicago. The "wear parity" thus achieved, it is said, solves a series of problems common to almost all precision machines. Other portions of the Elgin statement are appended hereto within quotes; and thereafter there appears an exposition of IP's views on this topic. "Tests have shown the normal wear life of a projector to be increased approximately 400%. In addition, the sapphire inserts minimize film damage and produce outstanding increases in normal expected film life. Greatly Reduced Wear Cited "The sapphire is applied in two locations, the contact finger of the film shuttle and the film side guides in the film channel. The cam-activated shuttle engages the sprocket holes in the film to place a new frame before the projection aperture 24 times each second. Due to the highly abrasive nature of film, ordinary shuttles with contact fingers of hardened steel wear sufficiently to interfere with smooth operation and cause film damage in about 250 hours of running time. Sapphire shuttle contact fingers show no appreciable wear after 1200 hours of running, more than 100 million cycles. "Film side guides of chromium plated steel, subjected to continual sawing action as they bear on the edge of the film under spring pressure, normally wear out in approximately 500 hours. Sapphire side guides continue to function effi ciently, showing no wear, after as much as 2000 hours. "As wear progresses on ordinary steel shuttles and film guides, the tendency to film damage is increased. A 'hook' worn into the shuttle contact finger tends to rip out sprocket holes and grooves side guides seize and rip the film. These film hazards are reduced by the sapphire inserts. Among the properties of sapphire contributing to superior performance in this application are extreme resistance to wear and low friction values." Commentary By IP In the opinion of IP, the application of sapphire inserts, in places where hardened steel shows too much wear, may be necessary in certain projector designs. The parts shown are useful only on Top: on the film shuttle the sapphire insert acts as the actual contact finger. Bottom: the film side guides against the film edges. INTERNATIONAL PROJECTIONIST January 1950 21