TM-9-2350-311-20-2
HOWITZER, MEDIUM, SELF-PROPELLED, 155MM; M109A2, M109A3, M109A4 AND M109A5
TECHNICAL MANUAL; UNIT MAINTENANCE MANUAL FOR CAB, ARMAMENT, SIGHTING AND FIRE CONTROL, ELEVATING AND TRAVERSING SYSTEMS AND ASSOCIATED COMPONENTS
DECEMBER 1993
TM-9-2350-311-20-2 - Page 692 of 828
TM 9–2350–311–20–2
18–22
Change 2
18–4 M145/M145A1 TELESCOPE MOUNT: SYNCHRONIZATION AND ADJUSTMENT
— CONTINUED
d.
Adjusting Synchronization of the M145/M145A1 Telescope Mount
NOTE
•
All movement of the cannon should be in elevation with no over travel.
•
All level vials should be brought to level from left to right with no over travel.
•
If muzzle is not equipped with flats, use gun tube leveling fixture.
1
Level the gun tube to zero at muzzle end of tube (2) by using M1A1 gunner’s quadrant (1) (end-for-end
correction applied).
2
Rotate the eccentric shaft (13) until the eccentric mark is in the 12 o’clock position.
3
Ensure 1 inch (25.4 mm) space between arm (14) of linkage assembly (15) and M145/M145A1 telescope
mount (5). Loosen four cap screws (16) and adjust as necessary.
4
Set the M1A1 gunner’s quadrant (1) to zero mils (end-for-end correction applied), (breech ring correction
factor removed) and place on M145/M145A1 telescope mount (5) quadrant seats (6). Ensure cross-level vial
bubble (7) is centered. Zero the M145/M145A1 telescope mount by loosening screws (16) and tap the
elevation counter box (17) up or down until bubble (4) is centered. Retighten screws. Recheck bubble.
5
Set M1A1 gunner’s quadrant (1) (end-for-end correction applied) (breech ring correction factor applied) to
400 mils and place on the breech ring quadrant seats (3). Elevate gun until bubble (4) is centered in the
M1A1 gunner’s quadrant.
6
Remove the M1A1 gunner’s quadrant (1) (end-for-end correction applied) (breech ring correction factor re-
moved) from the breech, set M1A1 gunner’s quadrant to 400 mils, place M1A1 gunner’s quadrant on the
M145/M145A1 telescope mount (5) quadrant seats (6) and ensure cross-level vial bubble (7) is centered.
7
If the bubble (4) on the M1A1 gunner’s quadrant (1) is not centered, turn micrometer knob (12) until the
bubble is centered. Remove M1A1 gunner’s quadrant, observe the offset reading. If the bubble is within
±
0.5 mils proceed to step 12. If bubble is not within the tolerance proceed to step 8.
8
If the offset is greater than 400 mils, add twice the offset to 400 mils. If offset is less than 400 mils, subtract
twice the offset from 400 mils. Set the results on the M1A1 gunner’s quadrant (1) (end-for-end correction
applied) and place the M1A1 gunner’s quadrant back on the M145/M145A1 telescope mount (5) quadrant
seats (6).
Example:
Offset reading
Offset
Results
Set results
400.8
.8 x 2
1.6
400 + 1.6 = 401.6
399.2
.8 x 2
1.6
400 – 1.6 = 398.4
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