International projectionist (Jan-Dec 1935)

May 1935 INTERNATIONAL PROJECTIONIST 23 NOT TOUCHING XT / CORNER Figure 3 good condition, they do not require much attention. The brushes should be worked up and down in their holders occasionally to see if they are free and are not sticking. At the same time notice the tension. As the brushes wear, the tension becomes less. The tension cannot be judged if the brush is sticking, thus the first thing is to free the brush. If doubtful as to whether the brush is free, remove the spring while the brush is worked up and down in the holder. Sticking is nearly always due to a gummy deposit on the brush or in the holder. After cleaning the brushes and the holders, the brushes should be put back in their respective holders, because it is almost impossible to have all the holders adjusted exactly alike. When the brush is put back so that it strikes the commutator at a new angle, it will not fit properly. The tension can now be adjusted. Too much tension is undesirable because of excess wear, also because the commutator runs at a higher temperature due to increased friction. Not enough tension causes the brush to vibrate, and the contact between it and the commutator will be poor, causing sparking and also heating and wear of the copper. Probably the best indication of the brush tension is sparking or absence of sparking. There are, of course, other things that cause sparking; nearly all armature troubles show up in this way, I as does overloading of the machine. When the machine is running perfectly and is delivering a normal load, there should be only the very faintest trace of a spark at the brushes. It usually is visible only when getting in a position so that one can look almost right between the brush and the commutator. The sparks will be very small and extend clear across the width of the brush, and all the brushes will have the same amount of sparking. When pressing the brush against the commutator lightly results in considerable decrease in sparking, the tension should be increased. If this does not cause much change, the tension is probably sufficient. Try decreasing the tension a bit, and if this results in increased sparking the tension has been too light. The idea is to get just enough tension to reduce sparking to a minimum and then increase it a trifle in the interest of safety. PROPER fitting requires that the brush be lifted and sandpaper placed between it and the commutator, with the back of the paper next to the. commutator. The brush then is dropped, and the paper is drawn past it in the direction that the commutator turns. This latter instruction is extremely important because if the paper be drawn through in the opposite direction, the brush will be improperly fitted. This is repeated until the brush is fitted. At A in Figure 3 is shown the correct way to accomplish this. There is a slight amount of play between the brush and its holder, which is necessary so that it will not stick. The arrow within the curved line shows the direction of rotation of the armature, the curved line representing the commutator. The brush touches the lower part of the holder at the right, while at the upper end it touches the holder at the left. XX represents the strip of sandpaper. When the sandpaper is drawn in the direction shown by the arrow above it, the brush is pulled into the same position as it occupies during normal operation of the machine, and this fit will be right. If the paper be drawn the other way, as shown at B, the brush is tipped the opposite way in the holder, consequently changing the angle it makes with the commutator. If the brush would stay in this position when in normal operation, everything would be in order; but when the machine starts, the brush assumes the position as at A (Fig. 3) with the result that the face of the brush does not fit the commutator. This is shown at C. Not only will this cause overloading of the brush, as a small area has to carry the current that the entire brush is supposed to carry, but also sparking and improper commutation. It is important that the sandpaper be (Continued on page 43) NOT TOUCHING. AT CORNER Show Business By WALLACE G. CROWLEY DINNER on a tray in my room and not alone — that's luxury in some countries, but not to me on matinee days . . . it's actual necessity . . . the room I referred to is the projection room . . . the company, another projectionist . . . did you ever try making a change-over while balancing a piece of pie in one hand? ... A real projectionist is one who in an emergency will sacrifice the pie . . . That's a tough yardstick to measure up with . . . Saturdays and Sundays are our week-days wherein we work longer hours. It's great getting to watch the happy crowd making their ways to seats during a Sunday night intermission . . . You sort of realize that we are not one of the happy majority . . . We lead a life far apart from that of the butcher, plumber, clerk, or business man . . . While they play we work . . . Their amusement is our toil . . .Their idlydropped fifty-cent piece is the source of our very existence . . . Ever count two rows of heads in a balcony and remark that there sits my week's pay? Have you ever regretted the necessity for being away from home Sundays, holidays and evenings? . . . No idle chatting over the back fence with your neighor on Saturday afternoon . . . No Sunday stroll through the park with the wife and kids, watching the array of happy humanity on parade . . . When the Thanksgiving turkey is only half eaten, you apologize hastily to the guests and hurry away . . . While the kids are happy with their new toys playing around the Christmas tree . . . One of them pauses and shouts, "Ma; where's Daddy?" The answer comes with just a touch of sadness in the tone, "He's gone to work at the show, dear" . . . If all this could apply to you — and you have no regrets or self-reproach, then you'll be a real success in this show business . . . you heartless wooden Indian. Sitting at the bedside of a dying projectionist who said that he was glad he had been able to bring happiness to so many people ... in the strained mock hospital gaiety the remark went unnoticed . . . days later, after it was all over, it dawned on me what he really meant ... he couldn't have lived in vain; his daily work was to cause lights and shadows to lull thousands of restless world-weary minds into forgetfulness — oblivion for a time — gained by staring at his handiwork on the screen. They lived for a time with kings and queens — returned to reality only when the curtain closed and the lights came up. They go their various ways better beings because of their brief respite from reality. *From I. P., Dec, 1931