Abrams SC-1 User manual

T
RDEPARTMENT TECHNICAL MANUAL
u
COMPASS, SUN
UNIVERSAL TYPE,
MODEL SC-1
This is a reprint of TM 5-9422, Compass, Sun, Universal
Type, Abrams, Model SC-1. No distribution will be made
to personnel possessing the original publication.
.. DEPARTMENT ,1NOVEMBER 1943

WAR DEPARTMENT TECHNICAL MANUAL
TM 5-9422
COMPASS, SUN
UNIVERSAL TYPE,
ABRAMS MODEL SC-1
WAR DEPARTMENT •1NOVEMBER 1943

WAR DEPARTMENT,
Washington 25, D. C, 1November 1943
TM 5-9422, Compass, Sun, Universal Type, Abrams Model SC-1,
is published for the information and guidance of all concerned.
/A.G. 300.7 (1 Nov. 43)./
By order of the Secretary of War:
G. C. MARSHALL,
Chief of Staff.
OFFICIAL:
J. A. ULIO,
Major General,
The Adjutant General.
II

TABLE OF CONTENTS
Title Page
SECTION I. Introduction 1
II. Description 1
III. Installation 5
IV. Operation 8
\. Inspection and Maintenance 21
VI. Disassembly, Inspection, Repair, Reassembly .21
Group Assembly Parts List 24
M558501

FIGURE 1.—The Universal Sun Compass.
Gimbal mounting
Level vial
Protractor plate
Date bar
Solar plate
G. Shadow bar
7. Pivot bolt
8. Gnomon rod
9. Sighting rod
IV

INTRODUCTION AND DESCRIPTION
SECTION I
INTRODUCTION
1. This manual is aHandbook of Instructions with aparts
list for the Universal Sun Compass Model SC-1, adirection
instrument for land navigation.
a. This Handbook contains descriptive data and instructions
for the installation, operation, maintenance, and disassembly
and assembly of the Sun Compass.
6. The Parts List contains agroup assembly parts list ar
ranged and intended to show the relationship of single parts
to sub-assemblies and of the sub-assemblies to the main as
sembly. Column 1contains alist of key numbers by which
each part is designated on the accompanying exploded view of
the instrument. Column 2is the manufacturers part number
by which each part and sub-assemblies may be procured. Col
umn Sis the part name with descriptive information on stand
ard commercial parts. Column 4indicates the number of parts
in asub-assembly, and the number of sub-assemblies in the
main assembly. When. apart number is preceded by an aster
isk ('*), this indicates that the part is procurable in the as^
sembly only.
SECTION II
DESCRIPTION
1. GENERAL DESCRIPTION.
a. The Universal Sun Compass is amechanical device which
utilizes the azimuth of the sun to obtain true direction. The
instrument is ruggedly built and can be used on any type of
vehicle on which it can be mounted properly.
6. The sun compass has many definite advantages over the
magnetic compass. It is more rugged than the magnetic com
pass. The sun compass is not affected by any local magnetic
attraction such as electrical circuits or metal as is the case
with the magnetic compass. -It is avery accurate direction
instrument and has long been used to correct errors due to
deviation of magnetic compasses. The sun compass can only
be used when the sun is shining, or by sighting on the north

MAINTENANCE MANUAL
star at night when it is not cloudy. So it is the complement of,
and does not replace the magnetic compass. The land navi
gator must be equipped with both, using the sun compass
whenever possible, and reserving the magnetic compass for
cloudy periods.
c. The sun compass is attached to the vehicle by means of a
universal gimbal mounting (figure 1, item 1) which allows tip
ping the instrument in any direction to make it level. Alevel
vial (item 2) attached to the extended arm of the gimbal
mounting indicates when the instrument is level. Acircular
protractor plate (item 3) is secured to the gimbal mounting.
Adate bar (item 4), an oval shaped solar plate (item 5), and
ashadow bar (item 6) are mounted successively on top of the
protractor plate. Apivot bolt (item 7) acts as apivot for
these parts. The date bar can be rotated afull 360 degrees to
any desired setting on the protractor. The solar plate can be
slid along the date bar to the proper date mark. The shadow
bar can be rotated afull 360 degrees over the surface of the
solar plate to the proper time-latitude setting. The solar plate
and the date bar are clamped at the desired settings by astar-
shaped clamping nut on the lower end of the pivot bolt. A
vertical gnomon rod (item 8) is mounted in the center of the
pivot bolt. It casts ashadow which falls on the shadow bar
when the proper adjustments have been made. This gnomon
rod is used in conjunction with asighting rod (item 9) on the
gimbal mounting arm, to obtain aforesight or to sight on astar.
2. DETAILED DESCRIPTION.
a. Oimbal Mounting. —The gimbal mounting (figure 1, item
1) frictionally prevents the compass from tilting, but allows it
to be readily leveled. The holes provided for the mounting
bolts in the bottom support of the gimbal mounting are made
slightly oversize to provide an adjustment in aligning the com
pass parallel to the centerline of the vehicle. Wing nuts on
the pivot bolts of the support can be tightened to rigidly secure
mounting after it has been leveled.
6. Level Vial.—The level vial (item 2) is around, heat re
sistant glass vial, enclosed in ametal cap and mounted on the
Gimbal arm. It provides aready means for leveling the com-