Mainspring And Cords - IBM Selectric Manual

.010" to
Trigger Disengages
From Torque Bar When
Correct Pawl Clearance
Exists
Trigger Guide
Trigger Knock-Off
Eccentric
OLD STYLE
NEW STYLE
FIGURE 101. Escapement Trigger Guide Adjustment
1.
MAINSPRING-AND CORDS
Gear Mesh - The proper gear mesh between the escape-
ment cord drum and the carrier return pinion involves
two adjustments. Both must be considered together.
a. Adjust the operational shaft laterally so that the
crown surfaces of the escapement cord drum gear
and the carrier return pinion are even (Fig. 103).
On the 721, the position of the operational shaft is
controlled by the operational cam ratchet and the
shift clutch arbor. On long carriage machines the
position is controlled by a collar set screwed to the
shaftandthe shift clutch ratchet. Be sure to main-
tain .002" to .004" end play in the operational
sha ft.
b. The escapement cord drum gear should be adjusted
forward or back to obtain .002" to .004" backlash
at the point of tightest mesh with the carrier .return
pinion. Be sure that no binds exist throughout the
travel of the carrier.
38
/
.,./
FIGURE 102. Trigger Lever upstop
(Long Carriage Only)
These Two
Surfaces Even
.002" to .004"
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2.
FIGURE 103. Gear Mesh And Operational
Shaft Adjustment
CAUTION: The mainspring tension should be RE-
LAXE D before the escapement cord drum gear is
loosened. The cord tension should also be relaxed
by removing the cord from the pulley on the cord
tension arm. Be sure that no end play exists in the
escapement shaft before attempting the gear mesh
adjustment.
NOTE: No attempt should be made to adjust the
cord tension with the escapement cord drum because
the drum is set-screwed to a flat spot on the escape-
ment shaft.
Tab Governor Pinion - Adjust the tab governor pinion to
have .002" to .004" backlash at the point of closest
mesh with the escapement cord drum gear. Adjust the
pinion by moving both the tab governor hub and
c;J
lar
located on each side of the pinion. The pinion
~hcu!d
have a minimum of end play yet still rotute
ti2e:!