Abrams SC-1, Technical Manual

Page: 13 / 39

INSTALLATION
/. Shadow
Bar.—
The shadow bar (item 6)
is
a
straight,
narrow
bar pivoted on the shadow bar bearing on
the pivot
bolt.
It
determines where the shadow cast by the gnomon rod
should
fall
when
it
is
turned to the proper intersection
of
time
and
latitude lines
on
the
solar plate.
A
special shadow
bar
washer exerts
a
pressure
on
the shadow bar, tending to hold
it
in
the
position at which
it
is
set.
g.
Gnomon Rod.
—The
gnomon rod (item 8) is
a
straight
slender rod
6 inches long.
It
is
screwed into the head
of
the
pivot bolt.
Its
purpose
is
to cast
a
narrow
shadow
line
on
the
solar
plate.
It
is
equipped with
a
radium tip
to obtain bear
ings at night.
ft.
Sighting
Rod.
(Polaris)
—
The
sighting rod
used
when
sighting
on
Polaris (north star) is
a
slender rod,
3
inches long,
which screws into
the end
of the date bar opposite the
arrow
head.
It
also has
a
radium tip
for
use
at night.
It
is
shorter
than the gnomon rod
so
that
Polaris
can be
easily sighted
in
the
higher latitudes.
i.
Sighting
Rod.
(foresights)
—
The
sighting rod (item 9)
is
used
to obtain
a
foresight
on
n
distant object and
is
a
duplicate
of
the Gnomon rod.
It
is
screwed into
a
hole in
the
gimbal
arm near the level
vial.
/. Clamping Nut.
—
The clamping nut
is
a
large, star-shaped
nut which screws
on
the
lower
end
of
the pivot bolt.
It
is
used
to
clamp
the
solar plate and date bar
in
place
after all
settings
have
been
correctly
made.
k.
Carrying
Case.
—A
carrying
case
is
provided in which to
store and transport the sun compass when
it
is
not
in
use.
Only
the
gnomon and sighting rods
need be
disassembled from the
instrument
to
place
it
in
the case.
SECTION
III
INSTALLATION
1 .
MOUNTING.
a.
The
sun compass must
be
mounted away
from
shaded
por
tions
of
the
vehicle where
the1
sunlight will fall
on
it
at
all
times and
in
such a
position that the
driver
or
his
assistant
can
see
the shadow cast
on
the
solar
plate by the
gnomon rod.