Moving Picture World (Nov-Dec 1923)

Better^ Equipment CONDUCTED T. KEYSER The Independent Generating Plant For Motion Picture Theatre Service IN a recent issue, we made some observation regarding the value of independent lighting plants as an item of motion picture theatre equipment. We also rashly offered to advise our readers regarding suitable plants for their individual requirements if the3r would advise us just what these requirements were: We use the word “rashly” advisedly, because many of those who wrote us for information either skipped entirely the requests for requirement data or had failed to acquire any knowledge regarding same. As a sample of what we were up against, here are two communications on the subject which were received in the same mail : * * * " Enclosed we are sending you a self-addressed stamped envolope for information regarding a theatre lighting plant. We are interested in a plant of 4-5 KW capacity, direct connected, no batteries, 110 volts, and if possible one that can be operated on kerosene. Gas is so expensive down this part of the world, now forty cents per . gallon — at one time as high as fifty cents per gallon. * * * Read your article in the September 15 issue of the World about the installation of the independent lighting plants. We would like to get full information in regard to theatre lighting plants. * * * The first was from the manager of a small house who knew just exactly what he wanted and we were able to supply him at once with the information requested. Letter number two was from the managing director of a big theatrical chain and it required correspondence on our part to extract the information that the projection requirements alone called practically for a 10 KW outfit. Data Was Vague While the interest manifested was greater than we had anticipated, the information which the average exhibitor seemed to have on tap regarding his requirements was so vague that, being of a restful disposition and somewhat averse to unnecessary exertion and duplication of labor, we are going to make a few general remarks regarding the independent lighting plant as a means of saving future unnecessary correspondence, on the same principle as employed by the pious but time-saving farmer who said grace over the entire barrel of pork instead of over the individual meals at which it was afterward served. To Which Class Do You Belong? There are several reasons why an exhibitor may require an independent, or as technically termed, an isolated lighting plant. He may be in a section, such as recently developed oil fields, where current is unobtainable. He may be in a territory where the current supply is poor or unreliable, subjecting him to taking a chance on a dark screen and a gloomy house just when he needs the illumination most; so that he is willing, even should his current be more expensive in actual dollars and cents, to install his own lighting plant and be absolutely independent. He may, for good and sufficient reasons, wish to feel absolutely secure from interruption of his show, even though his electric service be normally good, and, in this latter case, the requirements may be divided into two general classes — a plant sufficient to take care of his projection and a moderate amount of interior lighting, or a plant of sufficient capacity to carry on and provide the full current requirements of his house, such as projection, interior lighting, the power for fans and ventilating apparatus and the exterior lighting and signs. Qutfit Depends Upon Requirements Now, the outfit to be selected depends upon into just which one of these classes each individual exhibitor, contemplating the installation of an independent lighting plant may fall. For the house which intends to manufacture its own current absolutely independent of outside sources of supply, apparatus generating a voltage of less than 110 is quite practical, particularly if Mazda or mirror lamp projection be used. Even with the ordinary low intensity arc projection, 60 volts will give admirable service, and, as this lower voltage is to be used continuously, all motors and lighting ILLUSTRATION ONE A compact 2 kw. independent generating plant particularly adapted for service in connection with Mazda or mirror reflecting arc projectors appliances adapted to the lower voltage may be installed. On the other hand, if the independent generating plant is to be utilized as a substitute during a breakdown of service from the local electrical company, a plant generating current of the same voltage as that of the public service company is more desirable, as it eliminates the necessity for duplication of lighting fixtures and additional transformers. Determining Wattage Capacity Required In determining the wattage capacity required of the plant, the factors to be considered are whether the plant in question is, in case of emergency, to take care of the entire requirements of the house, in the way of projection, interior, exterior and sign lighting, and also the operation of fans and the ventilating system; or whether what is desired is an outfit which will simply keep the screen from going dark and keep the exits and a few other necessarj interior lights illuminated. If the former, an outfit of moderate wattage capacity will fill the bill. If the latter, increased capacity may be provided by either one of two methods. The generating plant may either be of sufficient capacity to care for the maximum requirements of the house at peak, or a plant of more moderate capacity may be utilized in connection with a series of storage batteries, which may be called upon to take care of the lighting requirements for a moderate length of time. The objection to the latter method lies in the fact that storage batteries, except when actually in use, tend to deteriorate and they are generally a source of anxiety to all but those skilled in their management. If a battery system be utilized in connection with the generating plant, it should be kept charged. The best method of doing this is, at stated intervals, to cut out the current from the public service station and run the show on the independent generating set, in which the storage batteries are, what is technically termed, floated on the line. And, after the show is over, continue the operation of the generating lighting plant until the batteries are again fully charged. With a generating plant of sufficient capacity to take care of one's requirements without a storage battery attachment, no such method of procedure is necessary, and the plant may remain idle, except for a turning over test once in a while, until the actual necessity for its use arises. When the cost of a storage battery equipment is considered and the amount of care that it must be given, it will be found, in the majority of cases, that it is true economy to install a generating plant, the output of which is sufficient to care for the requirements of the house. * * * As an illustration of plants suitable for the various requirements of the exhibitor, (.Continued on page 174)