Motion Picture Herald (Nov-Dec 1934)

52 MOTION PICTURE HERALD November 10, 1934 IK III! TECIiN€L€eiCAL The BLUEBOOK School By F. H. RICHARDSON QUESTION NO. 247. — (A) Describe the bearings of horizontal type motor-generators. (B) Nanne the reasons why cleanliness around a motor and generator is esential. (C) What precautions are necessary with regard to electrical connections? (D) Give your ideas as to necessity for ammeters and voltmeters, and their location. Answer to Question No. 241 Bhtebook School Question No. 241 was: (A) Name the various objections to using «. c. at the arc. (B) What is meant by "rectifying" the current? (C) Name the various means available for rectifying current. (D) Give your own views as to whether or not a current rectifying dezncc will return its co.<;t to the mmiageinent. The following made good : S. Evans and C. Rau ; D. Danielson ; G. E. Doe ; A. F. Sprafke (who also sent a correct belated answer to question 240); D. Ferguson; R. J. ArntsGii; D. Ferguson; J. Wentworth ; G. A. Atrley; C. E. Wainscott; H. Edwards ; J. T. Seller ; T. Van Vaulkenburg ; R. and K. Wells; M. and J. DeVoy; O. Allbright; N. L. Simms; T. Turk; L. R. O'Leary ; D. Lally and F. Ferguson ; L. M. and C. B. Traxler ; B. R. Walker; P. and L. Felt; D. Breaston and H. Haber; B. L. Patterson; L. N. Guiding; D. L. Sinklow; F. Simms and O. L. Daris; F. H. and L. Klar ; T. T. Davidson and R. G. Crews ; E. Hodson and S. Johnson ; F. L. Savior and G. N. Guidotti ; P. L. Mcintosh; M. F. Fallon; F. H., S. and P. Dalbey ; R. D. Oberleigh and J. Lansing ; S. Spooner and B. H. Thaller ; R. Geddings and L. Grant; D. Johnson; S. Spooner and B. H. Thaller; D. T. and L. B. Palmer; T. Turk ; T. R. Rosche ; A. Richardson and N. L. Haynes ; L. Thomas and N. N. Boyde; N. L. Tomlinson and G. Lathrop; H. Hughes and T. E. Mantol ; L. Grant and R. Geddings ; M. L. Spooner ; T. U. Grant; L. Thomas and D. D. Davis; H. N. Hoffman; R. and K. Wells; T. N. Onby ; F. Harlor and G. Harrison ; K. L. Knight, L. Henderson and B. I. Henderson; W. R. Greiver and L. Howell; D. L. Patterson; T. Morris and D. L. Danielson; F. L. Dodson and F. L. Benton ; C. Umphrey; C. B. Burray, D. T. Bennett, R. Crawford and G. E. Osborn. While several made most excellent answers to Section A, I believe you will all agree the one selected for publication (that of G. E. Doe) could not be much improved upon. He says: "I take it the question is not intended to include the new type a.c. arc that still is building its reputation, which I understand to be excellent where only a limited screen illumination is necessary. "Starting with that premise, the a. c. arc is quite unstable as compared with the d. c. arc. Second, it is much less efficient because of the fact that half the light producing power is wasted, the crater of one carbon facing away from the collector lens or mirror. Third, the a. c. arc is not as silent in operation as is the d. c. arc, and some of the transformers used with it also are more or less noisy. Fourth, there is not the steadiness of illumination provided because at each cycle the light from the source of available light drops off heavily in brilliancy, which has the effect, if not of visible flicker, of reducing the brilliancy of screen illumination as a whole. Fifth, the a. c. arc produces a harsh light tone as compared with d. c. light." The fourth subdivision of Doe's answei' brought up a question. He says the drop in brilliancy once each cycle reduces screen illumination as a whole, and while that point has never, so far as I know, been brought up, I hold he is correct. It seems to me it just must be so. Evans and Rau and almost every one else answers Section B as follows : "Rectifying the current means changing alternating current into direct current — current that flow continuously in one direction only. It is not of constant voltage, however." (C) P. and L. Felt answer thus: "There are many devices that may be used to rectify alternating current into direct current. Those available for serving an a. c. arc are the motor-generator, the mercury arc rectifier, the rotary converter and the chemical rectifier — the latter doubtful, meaning that while it can be used, its reliability and efficiency are doubtful. "For other purposes there are the vacuum tube, the synchronized commutator, the electrolytic rectifier, the vibratory method and the copper oxide rectifier. (D) H. Edwards says, "The exhibitor or manager who has a. c. supply and installs proper means for rectifying the current into d. c. will be well repaid. The a. c. arc is very wasteful because of the fact that only half its light production can be used. As a matter of fact, the same wattage used in a d. c. arc would, or at least should, more than double the available illumination. "Of course, there are losses in rectification, hence the cost would not be cut in two, but nevertheless the superior excellence of illumination and reduction of eye strain to theatre patrons would fully justify the expense of rectification." J. Wentworth answers thus : "With the understanding that in this answer I am not considering the new type of a. c. arc, about which I as yet am possessed of no very satisfying information (I am waiting for the new Bluebook, expecting it will be contained therein) I would answer with an emphatic yes. My reasons would be ( 1 ) that the d. c. light produces better results upon the screen than the a. c. light, (2) that while it is true it costs money to rectify current, it is a wise expense for the reason that it improves screen results and anything that does that increases the box office income, and (3) that it is debatable whether the increase in income will be sufficient to justify the additional outlay incurred by current rectification, but exhibitors should believe that anything that will improve the show to any considerable extent will be in the nature of justifiable expense, provided, of course, the expense is not unreasonable. "The expense of current rectification is considerable, true, but after all it must be remembered that we get at least twice as much light per watt from d. c. that we can use for projection than we can get from a. c, because with a. c. exactly half the light goes in exactly the wrong direction — away from the lens or mirror. "Repeating myself, therefore, my answer is an emphatic yes. In the end the whole cost will come back to the box office, with a lot of profit money tagging along behind it." Toronto Auditoriunn Wired The total of available seats for motion pictures in Toronto has been increased by 2,770, with the wiring for sound films of the civic concert auditorium, operated by a board of trustees, on a non-profit basis. No regular film schedule is planned, merely occasional film to fill concert program gaps.