Fixed backspace, fine tuned carrier return operation, verified solenoids will trigger functions

DONOR SELECTRIC ALLOWS EASY ACCESS TO VISUALIZE PARTS LOCATIONS

The IBM 1130 version of the typewriter has quite a bit bolted on to allow for computer operation and support the front panel pushbuttons. Sadly all the additions tend to block the view and access to the primary areas that implement the five movement functions - tab, space, backspace, return and index (line feed). 

The donor selectric typewriter I have been using does not have any of the additions and thus we can use it to look at and understand the mechanical functions we have to work on. First we look at the underside of the machine with the rear at the bottom of this picture. We can see the five long plates, which IBM calls interposers, that trigger tab, space, backspace, return and index movement functions (left to right of the picture. 

In the picture above you can see the five springs that will pull the interposers to the rear (down in the picture) when they are tripped. The two horizontal bars across the middle are the two clutch release mechanisms. The left bar is pushed by any of the first three interposers when it moves rearward; this causes the left operational clutch to take one half-rotation cycle. The right bar is pushed by either of the right two interposers moving rearward, and it causes the right operational clutch to take a full rotation cycle. 

The next picture is shot from the rear, showing the operational bracket which is what helps translate the rotary motion of the operational clutches into an down-up movement of various linkages to perform the actual movement function.  In this picture we see one of the levers dangling down and having a spring hold it forward so that the bottom lip is not under the entire bracket which is a bail that moves down and up. 

However, the interposer which has been pulled rearward after it was tripped will push its lever lip under the bail and thus as the cam on the operational clutch turns the bail cycles down to pull the lever. I have disassembled part of this machine so that we only see one of the levers in place, but another would dangle in the opening to the right of our one lever. 

Just visible at the bottom of the picture above are the springs we saw in the first picture, the ones that act to pull interposers to the rear if they are not latched forward in their idle state. 

This is another picture, taken from the side in the rear, showing the same bail that pivots down and up as the left operational clutch rotates. You can see that the one dangling lever does not have a lip projecting out to the left under the edge of the bail. If you follow the small spring fastened to the middle of the lever, the other end is the back of the interposer and it has a projection below that pushes the lever back under the bail when the interposer is pulled to the back. 

BACKSPACE ISSUE WAS A BAD SETTING, NOT A MISSING SPRING

My first guess for why backspace did not trigger a clutch cycle or function was that the spring was missing that should pull the backspace interposer to the rear. When I looked, however, it was attached and working. Instead, the problem was that the lip of the dangling lever was too high and when the interposer tried to push it rearwards, the lip jammed into the side of the bail instead of under it. 

That not only kept the lever from fitting under the bail to be actuated, it also kept the interposer from moving far enough back to trip the horizontal bar for the left operational clutch that we see in the first picture of this post. 

The mechanism that transfers the levers downward motion into moving the carrier back a column involves a couple of pivoting levers with screw adjustments. The vertical screw adjustment determines where the lever lip dangles and was set too high when I checked it. I adjusted it so that tripping the backspace interposer allowed it to move fully rearward, pushing the lever lip under the bail and pushing the horizontal bar to release the clutch for a cycle. 

The lower screw and nut control the backspace lever

As this pivoting linkage moves downward from its initial point we determined with the screw above, it pushes a second smaller pivoting linkage that will shove the backspace rack sideways. That has its own screw/nut adjustment which determines how far the backspace rack is moved when the bail pulls down on the lever. 

The adjustment instructions for this are a bit odd, as the backspace function will not successfully move the carrier back when the machine is hand cranked. It only works due to the tiny bit of additional momentum from full motor power operation. Thus one has to adjust the backspace rack so that the escapement pawl is right on the edge of falling into the prior column's tooth on the escapement rack, but not achieve it. 

Escapement pawl holding the carrier at a column position

I wasn't able to capture a good picture of the pawl at the point where it is just shy of engaging the next column back, but imagine the pawl (triangular object projecting upward in this picture) sitting on the left edge of the tooth just to the left of where it is engaged in this picture. I successfully completed the adjustment and the backspace function is now ready to go. 

CARRIER RETURN MECHANISMS CONTROLLING THE MARGIN BAR

The way that carrier return works is tied into the margin bar, on the front of the typewriter, which is used to detect when the carrier reaches the column set as the left margin. As the right operational clutch pulls down on a lever to rotate some linkages for starting the carrier return, it also pulls on a rod that releases the margin bar to pop rightward; it is normally latched to the left. 

When the carrier strikes the left margin, it drives the bar leftward. An air piston is used to decelerate the carrier rapidly. The left movement of the margin bar pulls on a second rod, releasing the carrier return function. 

I had to adjust both so that they worked reliably, as otherwise the carrier will jam to the left edge of the machine instead of disengaging correctly at the chosen left margin column. This was done and return is now ready to go. 

TWEAKED ALIGNMENT OF PUSHBUTTON MECHANISM FOR RELIABLE OPERATION

I tested the pushbuttons and slide the parts around to ensure that it would reliably trigger tab, space or return when the associated pushbutton on the front of the typewriter was pressed. 

PULLED ON EACH SOLENOID ARMATURE TO VERIFY IT TRIGGERS ITS FUNCTION

The solenoids of the operational magnets are underneath the machine. When energized, the pull down on a link which trips the associated interpose. Thus the interposer can be tripped either by a pushbutton, if one is assigned to that function, or by a computer command. I checked that each armature would reliably trip its interposer and drive the movement function. 

View from underneath of operational magnet assembly

side view underneath showing solenoids and armatures

CHECKING ADJUSTMENT OF TWO MICROSWITCHES ON OPERATIONAL MECHANISM

On the sides of the operational magnet assembly are two microswitches and pivoting levers. These are activated by the interposers for tab and carrier return, respectively. Both of these are relatively long movement functions, compared to space and backspace which last the same time as printing one character, or index which takes exactly twice the time to print a character. 

A tabulate will move the carrier rightward until it reaches a column that has tab set, or the right margin whichever comes first. That is a variable number of columns from the current position of the carrier, thus a variable time delay. Similarly, a carrier return moves the carrier leftward until it reaches the left margin. The time it takes depend upon the current position when return is triggered and the distance to the left margin setting. 

These two microswitches are part of a circuit that is used to feed back to the computer times when the machinery is busy on one of these long functions. The computer will hold off on triggering the printing of the next character or any other movement commands until the long function has completed.

The time that the operational clutch is busy is usually shorter than the total time of the long function, so the 1053 uses a pair of switches per function to block the computer from initiation up to the completion of the long movement function. When the movement is first commanded by the computer, through energizing one of the operational magnets, the interpose slides to the rear to start off a clutch cycle. 

The interposer closes the switch on the operational magnet assembly and the pivoting bar holds the switch closed until the end of the clutch cycle. This is because the interposer is forced forward and relatched in the midst of the clutch cycle thus the switch otherwise would open only partway through the cycle. The pivoting bar swings out of the way when the clutch check pawl engages to hold the clutch idle at the end of a cycle. Thus the microswitches on the operational magnet assembly are active from initiation through the end of a clutch cycle. 

A second set of microswitches are placed on the linkages which are latched while the long movement is underway, so they stay closed long after the operational clutch completes its cycle that started the movement. A switch on the left side near the rear latches when the tab torque bar is twisted and is released when the carrier hits a tab or right margin. A switch on the right side near the rear is closed when the carrier return is latched on and opens when the margin bar is struck by the carrier reaching the left margin and pulling a rod. 

The combination of the two microswitches in each pair ensure that the computer is blocked from the time that the interposer is first released rearward until the long function ends at a margin or tab stop. I verified that the switches for the tab were working properly but the switch for carrier return on the operational magnet assembly is not releasing properly when the clutch cycle ends. 

RIGHT HAND OPERATIONAL CLUTCH CHECK PAWL IS NOT FALLING INTO SLOT

I determined that the pivoting bar which holds the carrier return switch closed during a clutch cycle is not releasing because the check pawl on the right operational clutch is not snapping into the slot as it should. The pivoting bar is blocked from releasing until the pawl falls into place. 

the right operational clutch, whose right side is show here, has a disk that contains the slot which is adjusted relative to the rest of the clutch. An eccentric screw, visible in the picture above, is turned until the check pawl falls into the slot as the clutch ends its cycle. The smaller bolt in the picture, and a counterpart 180 degrees around the disk thus hidden in this picture, must be tightened once the eccentric adjustment is complete.

My initial difficulty is the thinness of the bolt heads. When I put a 5/32 wrench on the eccentric, I can't get a 1/4 wrench to grip on the tightening bolt. This requires special very thin wrenches. I have several thin wrenches for use with Selectric but I do not have these sizes in a very thin format. I will have to figure out a method to turn and hold the eccentric while tightening the outer bolt. 

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