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722 HANDBOOK OF PROJECTION FOR
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The old type shoes are fitted with beveled edges which slide into a slotted groove in the film trap. To remove, first follow Instruction No. 2, then take out screws holding its upper end, one of which is shown at S-432-E, P.l. Remove guide rollers, as per Instruction No. 22. Remove entire intermittent unit as per Instruction No. 2. This latter is necessary because the part will not slide down past the intermittent sprocket. You may now slide the shoe down and out. The process of reassembling is merely a reversal of the foregoing.
Shoes of late design have four wearing edges. When worn they should shift from right to left, and vice versa. They may then be reversed and the back sides used in the same way. These shoes are released by taking out three small screws, S-432-E, P.l, the heads of which are on the film trap casting, under the heat shield, or cooling plate E-5, P.l.
CAUTION. — When installing a new shoe be sure the ends of the screws do not extend through the shoe or protrude on the wearing side. This is especially to be guarded against if the same screws removed from the old shoes are used. If they do, the end may be dressed down, using a very fine file, but great care must be exercised not to mar the guide rollers which protrude through the shoes near their top. It may even be well to, as a matter of precaution, remove the guide rollers, as per Instruction No. 22.
INSTRUCTION NO. 31.— INTERMITTENT SPROCKET IDLER SHOES.— The film is held to the intermittent sprocket by a cradle shoe, held in a steel apron attached to film trap gate, or door. This shoe performs the same office for the intermittent sprocket that the sprocket idlers perform for the other sprockets. The adjustment of the shoe or cradle is of great importance. Examine part C, P.2, and see exactly how it works. Note that the cradle held in the steel apron attached to lower end of gate, or door, is held in place by a flat spring which allows it to adjust itself to the surface of the sprocket, and to move back when a thick splice or a stiff splice goes through.
Note also that the adjustment must be made by observing the relation of the outer tracks of the shoe to the face of the sprocket. The adjustment should be such as will hold the film firmly to the sprocket, without undue friction, at the same time allowing sufficient movement to allow a stiff or