Swapped again to put new CR drum; fighting to reinstall a small spring

DISASSEMBLE THE CARRIER MOTION PART OF THE MACHINE, AGAIN

With the return drum holes partially stripped and not holding on the shaft, I had to disassemble the carrier motion mechanism to fix the issue. Cords hooked to both sides of the carrier wind around a pair of drums on a shaft which also attaches the main spring of the typewriter. 

During a carrier return operation, the shaft is rotated by motor power to pull the carrier all the way to the left margin. This also winds up the mainspring, whose energy will be released during each space or tab movement of the carrier to the right. 

I had to remove the circled parts, which in turn require removal of other parts to gain access including the motor start capacitor, its bracket, and linkages to the backspace operational latch.

STATE OF THE AXLE WHEN I PULLED IT APART

The front drum (escapement/tab) fits on the shaft with a setscrew tightened to a flatted section of the shaft. The rest of the mechanism pulls out the rear of the typewriter. The mainspring is carefully unwound and removed. The return drum is slid off the front of the shaft to remove it.

I found that the portion of the shaft where the return drum fastens (via two screws set 90 degrees apart around the hub) had some very sticky, gluey substance I had to clean off first. I suspect that a prior repair of the donor Selectric had added glue to help keep the drum from rotating. 

CLEANED THREADS ON DRUM SO SCREWS WORK WELL

The drum from the original mechanism had thread holes on the hub in decent condition. I carefully cleaned them out and worked the screws through them to ensure they would tighten down well on the shaft when I reinstalled everything. 

I slide the return drum onto the shaft and did a test with the two screws lightly tightened. The drum appeared to hold well, which is a good sign that it will work properly when I am applying full tension of the cords as my final adjustment. 

REASSEMBLING THE DRUM ASSEMBLY INTO THE MACHINE

Getting the parts back in place took some time, as I had to put the plate back in position with the return drum, add the mainspring, adjust the position of the escapement/tab drum to mesh properly with the operational shaft gears and tighten the setscrew. 

Next, the linkage to the backspace operational latch had to be put into place and the spring must be reattached that keeps it deactivated until the backspace function is triggered. This involves tedious manipulation with spring hooks through narrow openings. 

Spring around notches on the vertical lever, hooks to the rear

I have a set of tools that make it possible to attach and detach springs deep inside the machinery of the Selectric. There are hooks that grab one end of a spring and pull it into tension. These are useful when the far end is anchored and we just need to put the near end onto its holder. There are pushers that are used when the near end of a spring is attached and the far end must be pushed away into tension to fit over its holder. 

Finally there is a tool that fits through the body of the spring and clamps onto the far end. It allows a completely loose spring to be pushed into some cavity and then the far end hooked onto its holder, Before removing this tool, one would grab the near end with a spring hook and stretch it out to fit on the near end holder. 

The latch to the right of the backspace latch has its spring attached - hard to see in the picture but the spring fits around the vertical lever at the side notches and stretches directly backwards to a mounting point behind. Its role is to pull the lever backwards so that it is NOT pulled by the operational bail. The only way it is pulled down is if the activation of a backspace function forces the lever forward against its spring while triggering the operational clutch to take a cycle. Apologies for poor photo quality.

Far end attachment point circled

The surgery involves the tools inserted through every narrow openings, with limited opportunity to see what is going on or even to light it properly.

How I spend my hours at the shop

All too often, the spring pops loose and I have to start over. This is the kind of issue that arises which takes a process (reinstalling the drum, the cords and setting the tension) from what seems like a 30 minute task to a day or more of work. 

The area where I had to remove and replace the drum assembly is loaded with adjustments, quite a few of which are disturbed by the work and will need to be set properly once the cord attachment task is complete. 

The screw which wouldn't clear the horizontal bar until screwed way down