Carriage return adjusted and works perfectly

WORKING THROUGH THE ADJUSTMENTS STEP BY STEP

With complicated mechanisms in the Selectric, there are interactions so that one change can throw off other adjustments that were previously okay. The Field Engineering Maintenance Manual for the 1053 covers step by step checks and adjustments for each area of the machine's functioning 

All told it took about four and a half hours to work through all of these, partly because I fought with a spring for well over an hour and a half. Once or twice I had to backtrack but overall it was pretty straightforward. 

Quite a few adjustments or checks involve clearances, which you test with thickness gages. A few places had very limited clearance and needed special wrenches or other tools. IBM provided a spring scale to their engineers and I am fortunate enough to have one so that I could verify some forces were within spec. 

FIRST ADJUSTMENT - TORQUE LIMITER

During a carrier return, the motor is clutched to the escapement drums and cords to pull the carrier to the left margin. If something blocked the movement of the carrier or the mechanism got jammed the motor power could cause damage to the typewriter parts. To protect against this, IBM installed a torque limiter in the Selectric which limits the force with which the motor can pull on the carrier and cords. 

One side of the limiter is hooked to the motor driven operational shaft which constantly rotates whenever the motor is switched on. That side has a coil spring which is turning all the time with a regular spring pulling the other end of the coil spring to a particular tightness. 

Inside the coil spring is a disconnected shaft that is hooked to the gears that turn the escapement and return drums. The coil spring is not tight enough on its own to force the disconnected shaft to turn; the coil spring slips around the disconnected shaft. 

To activate a carrier return, a nylon shoe pressed down on the far end of the coil spring, which causes it to tighten further and thus drag the disconnected shaft into rotation. The design is such that if the resistance from the disconnected shaft gets too high, the coil spring slips again, thus it limits the torque delivered to the cords and carrier. 

My first check was to use the spring scale to measure the force needed to stop the carrier from moving leftward during a manually cranked carrier return. It should begin slipping around 1.5 pounds of force. On this machine, it didn't slip at all so that the force quickly zoomed beyond the limits of my spring scale. 

I looked closer and saw that the coil spring was spread beyond its normal position and all the adjustments seemed really far off. I disassembled the limiter and got it squared away, then made the appropriate adjustments until it slipped at exactly the correct torque level. 

I had removed the rather strong spring which pulls the far end of the coil spring so that it is slipping when not activated and able to to drive the escapement cords when the shoe presses on the coil. What I discovered was that the spring end was barely larger than the diameter of the stud it fits on, such that it was very very difficult to pull against a strong spring and wrestle it over the stud. 

Spring on the right has to fit on the stud at the left

Ninety minutes later, after trying every spring hook and tool I had, somehow I got the spring reattached. Finishing the adjustments for the torque limiter was a snap once the spring was on. 

Finally attached and the torque limiter is back together

ESCAPEMENT PAWL ADJUSTMENT

When the carrier is returned to the left margin, it could ratchet all the way back with the escapement pawls bouncing out of each tooth of the escapement rack, but that adds resistance and slows the process of a return. Therefore, part of the return mechanism will move the escapement pawl out of the way so that the carrier can move freely while it is being pulled to the left. 

The activation of carrier return twists the escapement torque bar to cause the pawl to move out of the rack teeth. The next adjustments verify that the pawl is far enough from the rack that the carrier moves freely, but that the pawl is full seated when return is not active. 

Red is the lever and green is the escapement torque bar

To adjust this, I had to put a wrench on the eccentric bolt you can see in the diagram, loosen the nut on the rear of the bolt and turn it until the pawl moved to the proper position relative to the escapement rack. It had a tendency to shift its adjustment as the nut was tightened but with persistence I got it set properly.

CARRIER RETURN LEVER ADJUSTMENTS

The operational clutch triggered to start a carrier return will pull down on a lever which activates a number of linkages. Most importantly, it has to latch into place so that the return continues long after the clutch cycle completed. 

circled latch end pointed to by red has to fit in notch (see green arrow)

Latched condition shown

A Keeper Latch Arm Adjusting Screw sets the distance that the latch moves down when the operational clutch activates the return function. It has to move low enough that the lever with the notch will snap under the tab and hold the return function until it is complete when the carrier reaches the left margin. 

I had to hand cycle the return activation until the operational clutch had the activation lever at its furthest low point. Then I turned the adjustment screw until the tab on the latch was .01 to .025" below the top of the notch. 

During the process of setting the adjustment screw

The lever that is pulled down by the operational clutch dangles down so that its lip would fit under the bail that the operational latch drives down and up. When that clutch was triggered for a return, the interposer also pushes the lever under the bail so it will be pulled down. 

Another screw adjustment sets the height of the lever so that it will activate the return function by fitting under the bail. I set this, which was also far off on this typewriter. 

x

Latch Arm Height adjustment scr3ew

Lever peeking out under the edge of the bail

CARRIER RETURN SHOE ADJUSTMENTS

So far we have seen the mechanisms to limit torque, pull the escapement pawl out of the way and to lock in the return operation. The next part of the return mechanism is the nylon shoe which in a sense activates the clutch to turn the return drum to move the carrier itself. 

It must be positioned so that it clamps on the final three turns of the coil spring - this is one adjustment that was already correct unlike so many I encountered with this 1053. 

shoe in proper position

The next adjustment sets the shoe so that it is not dragging on the coil spring at normal times, only grabbing the coils during a return. There must be at least .01" clearance between the coil spring and the shoe face. 

Shoe before proper adjustment - dragging

The adjustment was made by turning the screw just above and to the left of the shoe 

MARGIN BANK OVERBANK ADJUSTMENTS

A bar across the front of the typewriter has sliding margin levers to set the leftmost and rightmost columns. The left margin lever has a projection that is struck by a matching projection on the carrier. It pushes the margin bar to the left as the carrier reaches the left extent of its travel. 

The first adjustment sets a .001 to .005" gap between the two projections after the carrier has come to a stop. This is important to ensure that the carrier locks to the correct column when it stops. 

Escapement pawl pops in correct column as return stops

As the margin bar is pushed leftwards by the stopping carrier, it pulls on a pushrod which will unlatch the carrier return function by pulling the notch away from the tab. 

The margin bar is initially latched to the right at the start of a carrier return function so that it can be moved leftward when the carrier reaches the left column. The pushrod above is pulled as the margin bar moves leftward, but first the bar has to be released to pop to the right - armed so that it will trip when the carrier reaches its left margin. There is a second pushrod that releases the margin bar to move rightward. 

latched to the left after the prior return ended

unlatched to move to the left at the start of a return function

Another adjustment verifies that when the left margin is set to the furthest left column, the return function can unlatch correctly and stop.

CLUTCH UNLATCHING ADJUSTMENTS

The pushrod had to be adjusted so that it leaves the tab latched in the notch until the margin bar pulls on the rod, at which time it has to reliably unlatch the return function. Using the measurements and adjustments from the manual, I set this up to work properly. 

CARRIER RETURN INTERLOCK SWITCH

This switch has a pair of contacts, one of which is opened when the return latches on, the other closes when the return is active. This was properly adjusted already.

CR CLUTCH UNLATCHING FOR HIGH SPEED RETURN

MARGIN RACK LATCH BELLCRANK ADJUSTMENTS

The bellcrank is pushed when the operational clutch is first activating the return function. It pulls on a pushrod which releases the margin bar to move to the right. This has to be positioned in two dimensions simultaneously - one to leave a gap before the activation begins, the other to ensure that the crank does turn when needed. 

After setting this correctly I had the pushrod activating and the margin bar releasing every time the return function switches on. With the other pushrod adjusted properly, at the time the margin bar is pushed leftward it releases the latch to stop the return. 

CLUTCH LATCH KEEPER STOP

A stop plate is the last thing to adjust. It limits how far the tab moves into the notch so that the function can be released reliably by the pull of the pushrod. 

SUCCESS

Having completed all the adjustments, the return function worked perfectly. I alternated tabs and returns, satisfied that the machine was now performing as it should. 

The only adjustments left to complete are the character selection and type ball homing adjustments, in particular the rotate ones. I will take this on when I am next in the shop.