MIL-S-50725(MU)
the strap assembly in the position (b) of Figure 1. Locate a plumb line
precisely eight feet from the center of the pivot shaft of the bore sight
and in a vertical plane with the axis of the tube. By means of a peep
sight with a 1/8 inch aperture placed on the objective end of the tele-
scope, move the bore sight until the cross mark of the telescope coincides
with the plumb line when elevated 30 degrees above the horizontal. In
this position, check the level vial which shall meet the requirenmts of
3.6.3.
4.6.5 Elevation level vial.- Elevation level vial test is made by
checking the 45 degree angle of the tube of the device by means of a
commercial optical protractor. Mount the bare sight on the tube as illus-
trated in (a) of Figure 1, and cross level. In this position, the eleva-
tion level vial shall be central within the tolerance of 3.6,4.The same
test is repeated for checking the other "V" slide with the bore sight mount-
ed as illustrated in (c) of Figure 1.
4.6.6 Telescope travel.- Telescope travel is accomplished with the
bore sight and plumb line located as indicated in 4.6.4. Locate a mark
on a chart eight feet above the horizontal line of sight which will indi-
cate 45 degree elevation point, and another mark feet 7-1/2 inches below
the horizontal line of sight which will indicate the 30 degree depress-
ion point.The telescope shall travel from one point to the other to
meet requirements of 3.7.
4.6.7 Operating temperature.- Operating temperature test is made by
clamping the bore sight to a 4.50 inch outside diameter steel tube by
means of the strap assembly and exposing it to temperatures indicated
in 3.8 by means of a commercial cold chest and oven. When thermally
stabilized at these temperatures, the torque requirement of 3.9 shall be
made by means of a commercial spring scale attached to the end of the
telescope housing. The operability of the strap assembly is then checked
by releasing the clamp and moving the bore sight, and re-clamping at dif-
ferent positions.
4.6.8 Clamp screw.- Clamp screw check is a manual test made by revolv-
ing the screw from one end of the thread to the other end without binding
or other restrictions at all temperatures herein specified.
4.6.9 Torque.- Torque test shall be made by means of a spring scale
which can be hooked at one end of the telescope housing. The telescope
is then moved through its full travel by pulling the scale and observing
the indicator of the scale for requirements Of 3.9.
4.6.10 Strap assemblY.- Strap assembly test is performed by mounting
the bore sight on the tube of the device in (a) of Figure 1, and by means
of a torque wrench and adapter, apply a pressure of two pound inches to
the clamp screw. Sight the telescope on a target at the intersection of
the crosslines of the telescope. Hook a spring scale on the knurled por-
tion of the clamp screw and apply the pressure indicated in 3.10 in op-
posing directions parallel to the tube axis. Observe the target thru the
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