Still battling print escapement adjustments

PRINT ESCAPEMENT FINAL ADJUSTMENT

The filter cam with its one setscrew is nearly inaccessible as it sits at the idle position of a print cycle. 

Filter cam with setscrew under heavy aluminum block

Filter cam buried under all this hardware

Once the torque bar was upright, the eccentric was set up right and the cam on the filter shaft was turned to its proper position, the major remaining step for adjustment was to play with the length of the pull rod until it reliably triggered a one column movement after each print cycle. 

The goal was to have about .008" clearance from the claw to the torque bar tab when the filter shaft cam is at its low point between print cycles. The pull of the rod should move the claw down enough to trip the escapement torque rod. There is a limited range of movement of the pull rod thus this has to be very carefully set up to work properly. 

Pull rod from filter cam at top to lever arm at bottom

pitted main lever across bottom of view

Escapement trigger (claw) at torque bar tab

ADJUSTMENT OF PULL ROD HAS HIDDEN ADJUSTABILITY

The manuals all say to adjust the length of the pull rod. The obvious method is to remove the clevis where it attaches to the filter shaft cam lever, turn the clevis half turns to lengthen or shorten the rod and reattach. 

However, the range of correct operation is very narrow and sometimes one side of the half turn is too short and the other side is too long. It was while looking at my parts from the donor machine that I noticed that IBM very cleverly used two different thread pitches on the two sides of the pull rod. 

That is, the clevis on the cam side is coarser pitched and moves more per turn than the clevis that hooks to the escapement lever in the rear. By turning the rear clevis one can get finer control over the length! 

Never mentioned in any of the many IBM service manuals nor in any YouTube video, but an important capability. I used it to set up the pushrod for the maximum movement of the claw (escapement trigger) while still restoring over the torque bar tab when print cycles are at idle. 

ESCAPEMENT TRIGGER ECCENTRIC ADJUSTMENT IS THE KILLER

The escapement trigger (claw) moves on a stud that is eccentric - by turning the position of the stud, the latch sits higher or lower and pivots away from the tab torque bar tab differently. It too is an adjustment with a narrow range of settings that work. 

Eccentric stud on the donor typewriter claw

The challenge is in adjusting this part. The screw head for the stud is buried inside the frame and only visible through a small opening when the escapement lever is held twisted downward pulling the claw downward. The other end of the stud is a nut which is a bit more accessible but wrenches can only move a few degrees at a time because of other parts blocking their swing. 

Claw and eccentric stud nut

From the picture above, you can see a few things. IBM went with a double claw on the 1053 compared to the part in the picture above it. Presumably the wider contact area allowed the 1053 to rack up many more hours of operation without wear than a regular Selectric typewriter. You may also see that the other side of the eccentric stud is up against the inside of the power frame and surrounded by many parts for indexing, carrier return and other operations. 

This again introduces the classic problem - not enough hands - when making the adjustment. The escapement lever has to be held down in order to pivot the escapement trigger and its stud low enough to be (barely) visible through a small opening in the side of the machine. The lever and the eccentric nut are accessed from the rear, while the stud screw head is accessed from the side. 

Turning the nut to loosen or tighten it also rotates the escapement lever, thus one has to hold it twisted for access to the screw but also hold it from moving up or down as you tighten or loosen the nut. The screw must be turned with a screwdriver through the narrow side slot. 

Once you believe you have the stud rotated to a good candidate position, you have to tighten the nut to lock it down. That means continuing to hold the escapement lever down, holding the screwdriver on the screw head, turning the nut with a wrench, stopping the stud screw from rotating the screwdriver, and blocking the escapement lever from moving up or down from the wrench torque. 

I wedged the escapement lever down with a big screwdriver, which relieved me of one hand's activity, but that doesn't hold it when torquing the nut so that still needs a hand or finger. Screwdrivers that can fit into the small opening and the slot on the stud are tiny and very hard to stop from rotating. 

This is where I kept failing before I ran out of shop time. I could not get the stud to any setting other than its lowest point because of all the rotations involved with the screw head, screwdriver and escapement lever as I fought to lock down the nut. 

UPSTOP ADJUSTMENT

There is an upstop that keeps the mechanism from bouncing too far upwards after activation, but that adjustment is super easy to make once the escapement mechanism works well.