Some success with tab and carrier return cord installation

USING THE NEW METHOD OF ROTATING THE CARRIER RETURN DRUM A BIT

With the carrier return function engaged so that the drum shaft won't turn on its own, the two screws holding the CR drum to the shaft are loosened and the drum rotated enough to add a bit less than a half an inch to the net cord length. The cord would then fit over the spring loaded pulley (transport pulley) and the pulley sits at the scribed line  on the assembly to indicate proper tension. 

LOOSENED AND THEN REMOVED SCREWS BUT COULDN'T BUDGE DRUM

I loosened the two screws but the drum wouldn't turn on the shaft with hand pressure. I backed out the screws further and eventually they came fully out of the drum yet it wouldn't budge. 

Drum with screws removed

Removed screws

TOOK APART DONOR MACHINE TO CHECK THE SHAFT FOR FLAT SPOTS

The from (tab) drum uses a single setscrew that tightens against a flat spot on the common shaft, but the presence of two screws on the CR drum suggested it did not have a flat spot. However, with no movement of the drum, I considered the possibility that my speculation was wrong. 

I therefore removed the entire shaft and drum assembly from the parts donor Selectric I had acquired and got the drum off to examine the shaft. The drum didn't slide off but when I used vise grips to turn it relative to the shaft, I began to turn. Apparently it was just grime that had hardened to stop the drum from turning. 

Studying shaft from donor typewriter

USING TOOLS TO START THE CR DRUM ROTATING

Once I was comfortable that this should and would rotate freely around the shaft, I carefully applied some tools to the metal hub of the CR drum and worked on moving the drum. I did get it to move, slowly at first and then with less pressure as I increased the distance it had moved. 

This allowed me to move the carrier and even up the pressure on the tab and CR cords. The cord could then be pulled over the transport (spring loaded) pulley with the assembly just about at the scribed line. I tried moving the carrier in both carrier return and tab directions with hand cranking and it appeared to be working correctly. Clearly this method is the key to getting everything perfect.

LENGTH OF CORDS AND TENSION IS NOT PERFECT YET

Because I hadn't replaced and tightened the screws while I was checking the cord tension and positioning, the force of movement rotated the CR drum a bit more resulting in the transport pulley sitting too far out from the frame. There is not quite enough tension now.

Cord is a bit too loose

All this means, however, is that I have to move the CR drum back in the other direction, tighten down the screws and then verify the tension. It may need a bit of iteration but I am certain to get the tension just right using the new method. That will be my next task when I return to the workshop, then I can move on to setting the rotate spring to its proper tension.