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CHAPTER XII. THE MOTION PICTURE PROJECTOR
(1) A motion picture projector consists basically of four parts: (a) a pedestal or support; (b) a lamphouse, or source of the projection light; (c) a soundhead, the function of which is discussed elsewhere in this book, and (d) a projector head, also called the projector mechanism, which is subject of the present chapter.
(2) A word, however, is needed concerning the pedestal on which the other thee parts are mounted. This must be of sufficient strength and rigidity to hold them without vibration. Its contact with the floor must have sufficient area to assure this condition, assuming the floor itself to be without movement or vibration. In considering the projector support it must be remembered that any vibration of the mechanism backward and forward upon its base will be magnified many times upon the screen, the magnification being proportionate to the distance between lens and screen.
(3) Because absolute rigidity is required, the floor itself must be without vibration and the projector supporting stand must contact it securely by means of anchor bolts.
(4) When building a new floor, the kind and model of projector should be decided upon in advance, a template made and the anchor bolts suspended therein, with heads not less than four inches below the floor surface. The concrete is then carefully and solidly packed around them, forming an ideal anchorage for the projectors.
(5) It is possible to embed anchor bolts in a cement floor that is already laid. Drill holes four inches deep and of sufficient diameter just to admit the heads of the anchor bolts, which need only be one-eighth inch larger than the bolts themselves. Then, with a small, round
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