The motion picture projectionist (Oct 1927-Sept 1928)

October, 1927 The Motion Picture Projectionist 33 far from the sprockets, the film is liable to jump out of place and ride over the teeth, whereas, if they are set too close they will ride the film, causing creasing, especially on the lower sprocket which acts as a brake on the friction take-up. The small lock nuts on all idler adjusting screws should always be kept tight. Failure to observe this rule will allow the idlers to drop, not only causing creasing but otherwise weakening and permanently marking the film. It has been found that the safest distance to set an idler from a sprocket is the thickness of two pieces of film. Some manufacturers recommend the thickness of one piece of film but this is insufficient as the distance between the sprocket and idler is too small to allow the average splice free passage. When the idlers are properly **£ adjusted, it should be possible to move any idler from side to side without danger of touching the sprocket teeth. Badly worn idlers mark the film and should be replaced immediately. Fig. 9. The arrow shows where Intermittent Film Guide the teeth have been grooved to a knife-hke sh»pneSS by coming The intermittent film guide, is m contact with the wall or the o ' film guide. This will ruin film, for the purpose of holding the film snugly against the intermittent sprocket but otherwise has nothing to do with the steadiness of the picture. Filing the openings in the film guide holders is sometimes necessary to insure the proper amount of side clearance for the sprocket teeth. Moving the film guide from side to side while the projector is running will determine whether or not the teeth have sufficient clearance. Figure 9 shows the results of the wearing of the teeth against the wall of the guide, thereby developing sharp edges which cut into the film. This is the correct position for the film guide. Arrow 1 shows the guide holder and 2 is the film guide. There is a right and a wrong way to install this film guide in the holder. Figure 10 shows proper installation — pointed end down. If in the reverse position as in Figure 11 the pointed end will present a shoulder to the film against which all splices must strike. This strain is so great as to cause torn perforations or even a break in the film especially if the splices are stiff, thick or buckled. Many Projectionists have found it advisable to substitute a slightly lighter film guide holder spring for the stiff one now furnished by the manufacturers. By this small change, less strain is put on the film at this point, with absolutely no change in screen results, wide and stiff splices, especially, going through with greatly decreased resistance thereby lessening the chance of film breakage due to the yielding of the film guide. One of the main reasons for pic Fig. 11. Here the film ... r. guide is upside down, ture unsteadiness is an excessive strfhe 'shared of amount of play between the moving the guide, stiff splices parts of the intermittent movement, won't last under these * , -r-, ■. • . • ■. conditions. due to wear. Readjustment is made by means of an eccentric bearing but care must be taken to see that it is not set too tightly, otherwise the parts will bind. Projector models using an eccentric bearing at each end of the intermittent shaft should be checked carefully after an adjustment has been made, to see that both bearings are lined up correctly, otherwise the intermittent sprocket will run out of true, resulting in the breaking out of the perforation on one side of the film. Some Projectors provide for a side adjustment of the intermittent shaft by means of a collar and set-screw. Proper alignment is necessary to insure against the intermittent sprocket striking the film perforation off-center. Excessive wear of the pin-cross type of intermittent movement results in flat sides on the pins, thereby causing a slightly quickened pull — down which gives an added strain on the film perforations. On newer models these pins are equipped with rollers insuring smoother operation. Proper Alignment of Upper Magazine One widely used projection machine has an adjustment on the top magazine which allows for its proper alignment. Unless great care is taken to see that the magazine is in line, the film coming from the valve rollers will not feed squarely under the idle roller. This generally causes fractured film to crack from the perforations to the edge of the film. This improper alignment also causes film breaks resulting from film with nicked edges and from loose splices coming in direct contact with the side of the valve. Size of Idler Rollers The idler roller on the same machine mentioned above is Yz' diameter and causes the film to make a sharp turn on itself. On a roller of this size film which has been dried out and thus has become brittle may break especially if there is an improper amount of tension on the feed roll. Fig. 1 2. Shows I feed sprocket and small roller 2. the the If trouble of this nature is encountered the substitution of a larger roller, preferably the diameter of a sprocket namely, 15/16" is a practical remedy. This means but a small amount of work, as only a simple extension is necessary to allow the proper amount of clearance and it will be found to be well worth while. Figures 12 and 13 illustrate the J4" roller and how the large idler roller can be installed in its place. I Reels Bent reels and reels with loose and sharp edged flanges should be discarded immediately. Figure 7, on page 32, plainly shows what happens to the film when such reels are used. Fig. 13. Here a 15/16" idler replaced the smaller one shown in Fig. 12. The bar. 2, is the only other alteration necessary. The larger idler makes the film last longer. is common practice to move the framing lever very quickly. Figure 14 shows Framing In framing a picture, it