We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
THE PROJECTOR 321
of device to supply tension to the reel in the upper magazine (110) to hold it in retard. This brakes the momentum of the reel, which otherwise would continue to run rapidly after the projector is stopped. Should that occur, when the projector is again started and the slack is taken up, the reel will start with a hard jerk, which is likely to pull the film apart. The necessary tension may be determined by experiment outside of show hours, starting and stopping the projector several times, meanwhile adjusting the tension until the braking effect is sufficient.
Take-Up Tension
The reel in the lower magazine must take up (rewind) 90 feet of film per minute. At the beginning, when the film roll is small, the reel rotates at high speed, gradually slowing down as the diameter of the roll increases. (Ill) To provide for this continuous change in speed, slippage is provided for between the driving pulley and take-up reel spindle. In one simple form this slippage consists of two metal discs, several inches in diameter, between which is a plate of fibre friction material. These two discs are held together by spring pressure sufficient to provide friction to drive the take-up spindle, at the same time allowing slippage to compensate for the continuous change in speed. (112) The spring pressure should be as low as is necessary to keep a slow moving film-laden reel in rotation until the end of the run. Adjust the tension so that when the reel is full its rotation may be stopped by a slight touch of the finger at the rim of the reel. (113) Too much tension is bad. It is hard on the film sprocket holes ; it wears the lower or "hold back" sprocket teeth unnecessarily. There must be just enough to drive the reel without danger of it stopping.
Magazine Rollers and Fire Trap
The rollers are presumed to make it impossible for fire to get through the fire trap. They are spaced exactly right by the manufacturer, the maximum distance being