The film advance mechanism of a Realist stereo camera has five main parts:
Function: The knurled knob turns the axle, which turns the spool, which pulls the film. The spring and washer serve as a lock and release mechanism. The spring grips the axle and prevents it from turning except during film advance and rewind, when the spring's prongs are moved slightly in the direction that tends to unwind the spring, thus freeing the drive axle. The method of loosening the clutch is different for advance and rewind. To advance the film, it is necessary to press the film release button on the back edge of the top camera plate near the rewind knob. The button moves a lever to the left. This clutch lever has a small hole into which the tooth on the outer rim of the clutch release washer has been inserted. The lever pulls on the tooth, causing the washer to rotate slightly. One prong of the clutch spring is lying in the recessed groove of the washer, and as the washer rotates, the prong, caught in the groove, moves with the washer. Since the other end of the clutch spring is resting firmly against another lever, the spring unwinds slightly and allows the axle to turn. As the film advances during the winding, its sprockets pull a sprocket gear through one revolution. Partway into the revolution a cam holds the clutch lever in its leftward position, allowing the operator to release the button. As the revolution ends, the sprocket gear locks in place and the cam releases the lever, allowing the clutch spring to grip the drive axle again. To rewind the film, the advance/rewind disk on the top of the camera must be moved from A to R. This action frees the sprocket gear and allows the film to be pulled backward through the camera into the film cartridge. When the disk is turned to the R position, a rewind lever is also moved slightly to the left. Since the second prong of the clutch spring is resting against the rewind lever, the spring is slightly unwound and the axle is released for the rewind operation. Moving the disk to the A position allows the clutch spring to grip the axle tightly again.
Clutch Spring Replacement: When the clutch spring breaks (usually, one of the prongs breaks off), obtain a replacement spring. Remove the camera back. Remove the knurled winding knob by removing the machine screw that serves as its axle. Remove the Allen set screw in the slotted spool. Pull the steel axle out of the camera by lifting the gear with a small tool, gripping the gear and pulling upward, or by removing the bottom of the camera and pushing the bottom end of the axle out of its bearing hole. Removal of the axle frees the winding spool, the clutch spring and the clutch release washer. Save the broken clutch spring for bragging. Hold the camera upside down. Using tweezers, put the clutch spring in place by putting the longer, hooked prong between the rewind lever and the small cylindrical post on the left. The spring should be centered on the axle hole. Next, put the clutch release washer against the spring, with the second, shorter prong resting in the radial groove. The raised boss should be nestled against the body of the spring. Don't try to put the tooth of the washer into the film advance lever yet. Carefully insert the slotted winding spool, with its flange against the clutch release washer. Now, insert the steel axle up through the hole in the inverted camera, through the spring, washer and spool, and toward the bearing hole in the bottom. At some point, the clutch spring will meet the thick part of the axle, and some force will be needed to push the axle farther. At this point it may be helpful to use tweezers to put the tooth of the clutch release washer into the hole in the film advance lever. If this is done, then turning the advance/rewind disk to R will force the spring slightly open and allow the axle to move into final position. If the axle can be put into position without engaging the tooth and lever, then put the tooth into the lever's hole next. Replace the knurled winding knob. Finally, turn the knob until the flat spot on the axle is aligned with the key hole and replace the Allen set screw in the film advance spool.
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