IBM Selectric I/O Reference Manual page 16

ADJUSTMENT THEORY
MOTOR AND DRIVE
1. Drive Belt - Adjust the motor mounting brackets forward
or back to obtain a minimum amount of belt noise.
Both ends of the motor must be adjusted the same in order
to maintain the rotor shaft perpendicular to the drive belt.
The belt must never be so loose that jumping cogs on the
motor pulley is a possibi lity. Check by operating the
shift mechanism while holding the carrier with the car-
rier return in operation. This loads the motor to a point
where fai lure wi
\I
be most probable.
2. Motor Pulley - Adjust the motor pulley left or right so
that the drive belt rides fully on the teeth of both pul-
leys without rubbing the flange of either. Position the
retaining clip for .005 11 to .015
11
end play.
3. Motor Clutch Pawl Stops (Fig. 1) - Form for a ctearance
of .010
11
to .020" between the clutch pawl tip and pul-
ley ratchet when the pu Iley is manua lIy rotated.
Form This Tip
FIGURE
1.
Motor Clutch Pawls
4. Idler Gears - Adjust the idler gear studs so that minimum
backlash is present between mating gears. The mechan-
ism must be free of binds throughout 360
0
rotation of the
gears.
Minimum backlash is necessary to prevent erratic opera-
tion of the drive train and to insure minimum overthrow
of the driven shafts.
The lower idler gear must be adjusted first because the
upper idler gear is adjusted to the final position of the
lower gear.
CAUTION: After any removal and replacement of the
left hand cycle shaft bearing, the mesh of the lower id-
ler gear must be checked. The lower idler gear stud is
mounted to the bearing plate; therefore any slight rota-
tion of the plate wi II affect the gear mesh.
Selection Mechanism
5. Latch Bai I Shaft - Adjust the plate that supports the right
end of the bail shaft so that the bail shaft is paraiiei to
the cycle shaft.
2-1
This adjustment is extremeiy important because the rollers
on the latch bail MUST contact their respective selector
cams at the same point and with the same pressure in ord-
er to insure that both cams operate the bai I together.
The bai I shaft is set at the factory and shou Id not requi re
a readjustment unless the piate becomes ioosened or
parts replacement is necessary. This is a difficult ad-
justment to make and should not be loosened unless ab-
solutely necessary.
The bail shaft plate must be adjusted both vertically and
horizontally in order to make the rollers of the latch bai I
ride their respective cams equally. Changing either the
vertical or horizontal position will affect the other;
therefore both adjustments must be consi dered together
and adjusted alternately unti I both are correct. If a re-
adjustment is necessary, the following procedure may be
used.
a. The correct vertical position is obtained by raising
or lowering the bai I shaft mounting plate until both
bail rollers have equal pressure against their re-
spective cams. Check by testing the drag on strips
of paper inserted between the rollers and the cams.
b. The front to rear positi on of the bai I shaft plate can
be set relative to the cycle shaft. Set the Hoover-
ometer to span the distance between the cycle shaft
and the left end of the bai I shaft as illustrated in
Fig. 2. Move the Hooverometer to the right and
adjust the bai I shaft plate forward or back to the
same clearance as at the left side. With the bail
shaft parallel to the cycle shaft, the bail rollers
should be contacting their respective cams at the
same point.
NOTE: As a final check for the adjustment of the latch
bail plate, hand cycle the machine using a zero rotate,
zero tilt character (all latches removed from the bail).
Both latch bail rollers should maintain contact with their
respective cams throughout the cycle.
CAUTION: On early level machines the cycle bail stop
and the character interrupter must be readjusted after any
change in the position of the bail shaft plate, because
both of these parts are mounted on the plate.
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FIGURE
2,
latch Bai I Shaft Plate Adjustment