International projectionist (Jan-Dec 1950)

it could drive the movement, while one frame was pulled down, without additional power from the crank. The location of the flywheel is important. If it is placed on the shutter shaft, for instance, all the gears, pins, and other parts between the shutter and the cam are subjected to the uneven torque. This causes undue wear on these parts and occasions considerable noise. The flywheel should be right on the camshaft; but this is inconvenient on the Simplex, so it is placed on the shaft which drives the camshaft. The uneven torque is thus transmitted through only two more gears. Simplex Working Parts Figure 16 shows the working parts in the Simplex movement. In the upper right corner is the flywheel shaft. In the intermittent case this shaft is in line with the intermittent shaft, the two gears are in mesh and the cam contacts the star. The longitudinal groove in the flywheel shaft is for oil distribution. The shaft runs in a long bearing, and portions of it may starve unless oil is disJributed throughout the entire bearing. End-play is adjusted at the flywheel. After loosening the lock screw, the knurled knob is held and the shaft is turned with a screwdriver until a just perceptible endwise movement of the shaft is present. With no end-play, there is danger of the shaft tightening up. Too much end-play results in clatter. Be sure to tighten the lock screw again. Eliminating Travel-Ghost Projectionists sometimes notice travelghost after making this adjustment, but fail to connect the two. When the adjustment is made the knurled knob is held, which also holds the shutter stationary. The flywheel shaft is then turned with a screwdriver, thus turning the gears and the cam in the intermittent case. Note that the shutter is stationary while the cam is turned — which amounts to holding the cam and moving the shutter. Immediately below the flywheel shaft is the camshaft. To adjust end-play loosen the lock screw, or screws (on some movements this requires removal of the flywheel). Then the flywheel (or FIGURE 16 the flywheel shaft, if the flywheel has been removed) is held while the nut on the camshaft is turned until the end-play is correct. In all cases the end-play should be tested again after tightening the lock screw. This holds true for many other adjustments about the mechanism. Locking the adjustment may throw it off, in which case it must be done over. PostAdjustment Procedure After adjusting end-play in either shaft the movement must turn perfectly free, if it has seen considerable service. On a new movement the bearings will bind enough so that this cannot be taken as a criterion, making attainment of proper end-play more difficult. In either event, the test should be made with the star in the locked position, because the pin may fit snugly in the star, or the intermittent shaft bearings may add a little drag, which throws one off. To adjust star-and-cam relationship the movement is turned so that the cam is directly under the star. The screws on the cover are then loosened and the weight of the cover and the parts carried by it forces the star down against the cam. Only a thin film of oil will then separate them. Tighten the screws again, and the job is done. Sprocket Change Procedure Next, in Fig. 16, we have the intermittent shaft with the star on the right end, and immediately to the left is a spiral groove, which also controls the oil; but this one keeps the oil from flowing to the right and out of the bearing, preventing loss of oil and a messy machine. The groove acts like a thread to "screw" the oil back into the case. In the center of the shaft are two holes for the taper pins which fasten the sprocket. Unless one has had considerable mechanical experience it is best not to touch these pins, nor to install a new sprocket. However, to help those who may have to change a sprocket, a few pointers will be given. The taper pins are forced in under considerable pressure, requiring strenuous effort to remove them. Unless certain precautions are taken, this pressure is enough to spring the shaft or damage the sprocket. A device is available to remove and to replace these pins with little chance of trouble. Lacking such a device, the shaft and sprocket are placed on some support so that the metal immediately surrounding the pin rests on it. If this be a block of hard wood, no hole is needed for the pin as it is driven through. However, if a metal support be used, a small hole must be drilled in it so the pin can fall out of the sprocket. A hammer and punch are used to remove the pin, placing the punch on the small end of the pin. The punch must not be much smaller than the pin, otherwise it will bury itself and expand the pin, wedging it in the hole tighter than ever. Adjustment of New Sprocket After removal of the pins the sprocket is slid off. The new sprocket should slide on easily. The holes in the sprocket are also tapered, and the large hole must be adjacent to the large end of the hole in the shaft. After the holes in the shaft and the sprocket are aligned, place the small end of the pin into the large end of the hole. Drive it in securely, but do not use extremely heavy hammer blows. The support must again be used under the central portion of the sprocket. Cut off the projecting portions of the pins flush with the sprocket. The shallow groove at the left end of the intermittent shaft is for the set screws holding the collar. This collar determines the end-play. After loosening the screws the sprocket and shaft are pulled firmly away from the machine, the collar is set up close against the bearing, and the set screws tightened. Do not pull too hard, as the sprocket is light and might bend. If the collar has been set up a trifle snug, loosen the set screws slightly, not enough so that they are completely free. Now tap the end of the shaft lightly until it just turns freely; then tighten the screws. Check the adjustment again after tightening the screws. The holes in the ends of the sprocket are to lighten it as much as possible and yet retain the required strength and rigidity. Remember that the sprocket and the shaft are started and stopped 24 times a second, and that the heavier the parts the harder it is to do this, throwing more strain on the rest of the machine and on these parts, too. Inside the intermittent case is an oil deflector which scoops up oil that is thrown by the star wheel and directs it into the holes to lubricate the bearings. It is a sort of circulating system: oil is INTERNATIONAL PROJECTIONIST May 1950