Exhibitors Herald (1925)

March 28, 1925 EXHIBITORS HERALD 35 rollers with the intermittent sprocket, otherwise damaged perforations will result. (See Fig. 5 and Kig 6.) If these rollers bind, the face of the rollers will develop ridges which will roughen the edge of the film, as shown in Fig. 7. It is also well to examine new rollers closely as in some cases they are received from the factory in a semi-finished condition, and have rough faces against which the edge of the film comes in contact. F riction T ake II p The take-up adjustment should be checked up closely from time to time. An excessive pull can always be detected by the film making a “singing” sound at the take-up sprocket. The sprocket, of course, acts as a hold-back or brake and puts a strain on the film, when starting on a small hubbed reel. This is sometimes enough to cause very severe damage to the upper side of the perforation. Fig. 8 shows the sprocket damage resulting from a tight take-up. Proper setting of the spring is a simple matter and care should always be taken to keep the friction disc, whether leather, cork or fiber, absolutely free from oil. Contrary to some opinions oil will, not cause smoother operations in a case of this kind, but will really create a certain amount of suction which in turn results in an uneven, e.xcessive pull. Tension on Upper Magazine Shaft or Spindle Some widely used makes of projectors have an adjustable spring tension on the upper magazine shaft or spindle. Proper adjustment of this spring is important. If set too loosely the film will come from the feed roll with a jerky motion. This is especially noticeable if used with a bent reel, which is bad for any film, particularly film which is in a dried-out condition or badly worn. If the tension is too tight the effect would not be noticeable on a full reel of film, but the tension on the last SO or 75 feet would be sufficient to cause serious perforation damage when a small hubbed reel is used. It is not uncommon for the film to break under this strain. Sprocket Idlers All Sprocket idlers must be properly adjusted. If set too 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. Intermittent Film Guide The intermittent film guide is 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. Fig. 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. There is a right and a wrong way to install this film guide in the holder. Fig. 10 shows proper installation — pointed end down. If in the reverse position as in Fig. 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 picture unsteadiness is an excessive amount of play between the moving parts of the intermittent movement, 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 perforations off-center. {Continued on page 36) We Invite Comparison Before You Buy Your Records Are Being Watched USE A MOONEY THEATRE RECORD BOOK Tahe a Chance Courtesy of Leslie s Sample Pages Will Be Mailed on Request Copyrighted Finch & McCullouch AURORA, ILLINOIS MODEL C (PATENTS APPIABD FOK) Try One in Your Own Theatre Upon the request of any responsible exhibitor in the United States we will arrange to have our equipment installed in his theatre on trial for thirty days free of charge. Stereopticon with Automatic Slide Changer is the Last Word in Projection Equipment American Reflecting Arc Corporation BOSTON 24 MILK STREET Made in 17. S. A. MASSACHUSETTS HILLGREEN, LANE & CO. ORGANS will be found in theatres, churches, residences and concert halls through' out the United States and Canada. Correspondence Solicited Factories: Alliance, Ohio