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two methods. Early 12" and 16" tapes used a hook fastener
which was secured in a hole in the carriage bed with a rubber
plug (Fig. 21). Currently all tension tapes are screwed to the
right end of the escapement rack.
An improved main spring and holder assembly was introduced
ahead of the present centrifugal· governor mechanism. It was
designed to provide a more constand carriage tension by the
use of a cross curve spring. This spring replaced the former
style and was designed to minimize failures during repeat space
bar operations and also to provide for a less critacal tab friction
governor adjustment. Early main spring and holder assembl ies
were mounted to the power frame with two screws which pre-
vented the holder from turning (Fig. 21). The improved as-
sembly mounts to the power frame by the main spring drum
mounting stud.
An ear on the holder contacts the power frame
and prevents rotation of the holder. By employing a special
disc in the drum assembly, this type of assembly may be used
as a replacement for the former style.
The improved main spring and holder assembly has been further
improved for safety on machines above Serial number 553017.
The centrifugal governor drum gear and main spring are now
held together by a retainer clip (Fig.
22).
This prevents the
main spring from accidentally jumping out of the holder when
it is being installed or removed. The power frame has been
countersunk to provide clearance for the retainer clip.
Installation and removal of all main springs and drums should
continue to be made with extreme caution.
Figure 21. Early Main Spring and Holder Assembly
Two types of trip links have been used on the Model Bl. One
is the solid link with pin clevis, the other uses a clevis contain-
ing a compression spring. The spring clevis was designed to
improve impression by equalizing the tripping force at various
typing speeds. This spring clevis is not used presently and may
be replaced by-the conventional link and clevis if desired (Fig.
18) •
Two types of escapementpawl\:lracket assemblies are used on
the Model Bl. Machines of 62/5 and 14 pitch, and all deci-
9
mal tabulation models use an escapement pawl with
.038"
of
left to right motion. This assembly bears no identification
mark. Machines of 8, 9, 10, and 12 pitch use an escapement
pawl with
.058"
of motion and can be identified by a round
groove in the front edge of the pawl tai I and spacer. The
spacer .used with this pawl has the upright lug positioned .010"
to the right. This arrangement is referred to as the "floating
pawl" and permits increased typing speed without type piling.
Increasing the length of the elongated slot in the escapement
pawl allows the pawl to snap further to the right after being
tripped. Consequently, the carriage begins to move the pawl
back to the left sooner. The pawl spacer lug, being further
to the right will pick up the pawl tail earlier and be ready for
the next operation.
The floating type escapement pawl is also used on the Model B
lift platen typewriter above Serial number
358277.
The toll
bi Iler and decimal tab machines use the former non floating
style pawl.
Main
Figure 22.
Main Spring Holder
MARG1N SET
The term "margin" denotes the distance between the edge of
the paper and the typewritten material. Left and right margins
are determined by the position of the margin stops on the mar-
gin rack. Carriage travel is limited when the stops strike the
Mar{lin Set Bracket
Figure 23. Margin Set Mechanism
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