IBM Selectric I/O Manual Of Instruction page 18

FIGURE 28. Positive - Three Rotate! Operation
The left hand latch is attached directly to the end of the sec-
ond lever. When operated, the latch causes the left end of the.
second lever to move down. The right end of the lever cannot
rise so it acts as a pivot point. The second vertical link is
attached to the lever two-fifths of the distance from the pivot
point to the latch; therefore the link moves down two-fifthsas .
much as the latch.
Movement of the link is twice as much as when the rotate-one,
latch isoperatedalone. Therefore the movement obtained from,
the left hand latch is sufficient to rotate the type head two
Negative Rotation
Positive rotation of the typehead is achieved, by operating
the rotate bellcrank counterclockwise so as to create a pull on
the rotate tape. It follows then that operating the rotate bell-
crank clockwise wi II allow the rotate pulley spring to rotate
in a negative direction.
The rotate bellcrank is controlled by the balance lever in the
differential series. In order for the bellcrank to operate clock-
wise, the balance lever must be raised. The left end of the
lever cannot rise, because the stop lugs on the bracket prevent
any upward movement in the lever series. Therefore if the bell-
crank is to operate clockwise, the right end of the lever must
be raised.
The right end of the balance lever has a flat link connection
to the five-unit bai I assembly (Fig. 30). The bai I is a single
arm located under the cycle shaft and pivoted in front on the
bail shaft. When the five-unit bail is allowed to rise, the
right end of the balance lever rises to allow clockwise operation
of the rotate bellcrank.
5-Unit Drive Link
characters in the positive direction. Since the right hand latch
E--==--m:II-.--~
iscalledthe rotate-two latch, the left hand latch is referred to
as the rotate-2A latch.
The 2A latch is never used by itself. When its motion is added
to that of one or both the other latches, rotation of four or five
characters can be obtained. The rotate-one latch is used for
one-character rotation and the rotate-two latch for two-
character rotation. Both are operated together for three-
character rotation. The rotate-two and rotate-2A latches are
operated for a four-character rotation. The rotate -one, rotate-
two, and rotate-2A are operated for a five·-character rotation
(Fig. 29).
FIGURE 29. Positive - Five Rotate Operation
11
FIGURE 30. Five Unit Bail At Rest
The five-unit bail is prevented from rising by the five-unit
latch at the rear (Fig. 31). The latch is mounted to the di f-
ferential bracket and pivots front to rear. In the rest position the
latch is positioned above the head of an adjusting screw at the
Latch Prevents Bail From Rising
-
FIGURE 31. Five-Unit Bail During Positive Rotate Cycle