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MIL-M-70742 (AR)
cross level angle reading using the inspection aid, record this
reading.  Continue to rotate the cross leveling knob one revolution
beyond the index mark and return to the index mark. Exercise care
not to override this point of coincidence and record this reading
using the inspection aid.  The difference, if any, is considered
backlash and must conform to the limits outlined in 3.6.4.3.2.
4.6.2.5 Mount rigidity.  With the fixture positioned as
outlined in 4.5.2.3, position the mount as specified in 3.6.1 with
the level vial bubbles centered.  Check rigidity by gradually
applying and releasing the pressure specified in 3.6.3 at the top
left side of the telescope support as specified in 3.6.3. Take
the reading on the test target and record the movement.  Repeat
this procedure gradually applying and releasing the specified
pressure at the top right side of the telescope support. Take the
reading on the test target and record the movement.  The total
movement shall be within the allowable maximum deviation specified
in Table I of 3.6.3.  The same procedure shall be followed as the
simulated gun trunnion (cross leveling fixture) is moved from the
"O" position to the 1333 mil elevation position to conform to the
requirements of Table I.  The maximum movement at the various
settings shall not exceed the mil values specified in Table I.
4.6.2.6 Plumb travel.  With this mount and fixture set as
outlined in 4.6.2.1, this test is made by sighting through viewing
telescope F5549108 and observing coincidence between the
telescope's optical axis and the intersecting point of target
centerlines while simultaneously rotating the mount in elevation
and the test fixture an equal amount in the opposite direction.
The optical line of sight shall not deviate from the intersecting
point by more than the limits outlined in 3.6.4.1 as measured by
target mil blocks.  During this total travel the cross level vial
shall remain level within the limits of 3.6.4.1.
4.6.2.7 Elevation error and backlash. With the fixture and
mount positioned as outlined in 4.6.2.1, insert an elevation
reading into the mount.  Use the elevation counter as the recording
mechanism.  Insert this selected reading into the inspection aid
and position the inspection aid on the quadrant seat assembly and
by means of the fixture elevation handwheel relevel the quadrant
level vial, do not override this level position.  Observe
coincidence between both level vial bubbles.  Any non-compatibility
between level vial bubble positions shall be measured by means of
the quadrant:  This difference, if any, shall not exceed the limits
outlined in 3.6.4.2.  Note this reading.  Continue to rotate the
elevation knob approximately one revolution beyond this point of
coincidence.  Return the knob to reposition the elevation level
vial bubble to indicate level.  Note the elevation counter reading.
The difference, if any, in elevation reading is considered backlash
and must be within the limits outlined in 3.6.4.3.1.
14

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