The timing disk fits on the same shaft as the replacement hopper gear I built. The shaft also turns the cam that will move the picker knives which grab the bottom card in the hopper and push it into the rollers. The replacement hopper gear turns the rollers that will move the card into the pre-read station where it will sit waiting for a feed or read action.
A woodruff key on the shaft ensures that the timing disk is oriented in sync with the picker knife cam. The timing disk has a permanent magnet glued to it, with one pole at the rim of the disk. As the disk rotates, the magnet passes three coils that are arranged around the outside of the disk. These coils produce timing pulses, which IBM calls CB-1, CB-2 and CB-3.
A microswitch is deactivated by the weight of cards sitting in the hopper, but will turn on when no cards are placed there. This tells the controller logic when the hopper is empty. A card weight sits on the top of the card stack in the hopper, ensuring enough weight to keep the microswitch from activating as long as there is even one card in the stack.
A protective cover was reinstalled over the timing disk and gear train, finishing the reassembly of this area. When I hand crank the reader, everything turns smoothly in the hopper area and by manually tripping the trigger for picker knives, I see then completing one cycle to feed a single card. Normally a solenoid trips the trigger under control of the controller logic.
PARTIALLY REASSEMBLED STACKER SIDE MECHANISMS
I put most of the parts back together for the stacker mechanism, but may need to pull the top piece off when I am working on the new bumper. Cards are ejected at speed from the read station following an arc to convert horizontal to mostly upward motion. The card flies up to strike a foam bumper at the end of the top piece, arresting its motion and causing it to fall back down onto the nudger.
The nudger has arms that oscillate left and right, urging the card that just fell to move against the leftmost part of the stacker. An upright arm slides on a shaft, spring loaded to the right, so that as cards are added to the stack the arm will gradually move leftward as the size of the stack grows.
The nudger is driven by a second plastic gear I built as a replacement for the disintegrated original part. This turns a cam to cause the oscillation of the nudger arms. These now move freely left and right but the gear teeth are not engaging quite firmly enough; the gear turns most of a revolution but stops as the ramp on the cam is steepest.
The solution proposed by some genius restorers in Europe who have their own 2501 is to put a rubber band like sleeve on the teeth. This increases the effective diameter just enough to ensure good grab and the teeth don't have to mesh perfectly because the rubber squishes between the opposite teeth to generate enough friction.
When I receive the 3D printed part to replace the bumper inside the stacker and the rubber band for the stacker gear, I will complete the reassembly. Once they are installed then the rest of the stacker mechanism will be finished and working properly.
STILL TOO MUCH FRICTION ON SLIDER INSIDE STACKER
The spring loaded arm that holds the card stack towards the right, moving to the left as the number of cards increases, is attached to a shoe on the bottom that moves over a long metal rod. The shoe has sliding surfaces on its top that move under guide rails on the edges, plus it moves over the rod.
Due to corrosion from moisture and rodent exposure, both the rod and the surfaces of the shoe needed to be cleaned up and the bumpy surfaces removed. The parts are much better but the shoe is still a bit sticky. It should snap to the right under spring pressure and slide smoothly with minimum force as cards press against the arm. However, it has variable friction so that its movement is not even. Sometimes it will stop partially restored to the right rather than completing its movement. I need to work further on this to regain smooth operation.
WAITING ON 3D PRINTED PART FOR BUMPER INSIDE STACKER
The original bumper was a bit of rubber attached to a plastic part, which was screwed to the top lip of the stacker top piece. The plastic disintegrated, much like the two gears had, thus it needed replacement. A 3D printed holder will be arriving soon, to which I can attach some thick foam with a surface layer of Kapton tape. This is a solution also developed by the team in Europe to restore their own 2501. I have the foam and tape already.
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