8 inc Howitzer manual.pdf - Replica Plans and Blueprints

49
elevating gear of the carriage. Set site clinometer and range drum
at zero. The bubble of the Rite clinometer should now be in the
center of its run; if it is not, adjust as follows:
Adjustment.-Bring the bubble of the site clinometer to the center
of its run by working the milled head. Slacken the screw seeming
the indicator of the mil scale and the nut securing the micrometer
scales shift indicator and micrometer scales to zero and reclamp.
4. To VERIFY PARALLELISU OF Lh'I"ES OF SIGHT A..'\'D AXIS OF BORE.
The sights are correctly adjusted when, at zero elevation and deflection,
the lines of sight are parallel to the axis of the bore.
When the carriage is placed with wheels on a level platform, the
howitzer with axis of bore horizontal, and the sights at zero elevation
and deflection, the points in which the lines of sight and the axis of
the bore prolonged pierce a distant plane perpendicular to the latter
should be located with refereuce to each other as indicated on Plate
XVIII.
A target made according to the dimensions on Plate XVIII should
be placed in a vertical position perpendicular to the line of sight at a
distance of not less than 100 yards from the howitzer, and at such a
height that the point B is at the same height as the axis of the bore of
the howitzer. The verticality of the target should be assured by a
plumb line attached at X and coinciding with the vertical line
through B .
The carriage should be rested on carefully leveled solid supports;
the howitzer should then be directed so that the axis of the bore, prolonged,
pierces the target at the proper point. The lines of sight of
the open and panoramic sights, if adjustment is true, should pierce
the target in the points marked Sand D, respectively.
In order to train the bore of the howitzer accw·ately on B, secure two
threads or hairs at the muzzle, fastening them perpendicular to each
other with the point of intersect-ion coincident with the axis of the
bore and sight through the axial vent of the breech mechanism.
In the field, where from lack of time or proper facilities the method
just given can not be followed, the adjustment of the sights may be
verified by bringing the lines of sight at zero elevation and dellection
to bear upon some sharply defined point of a distant object. At such
a range (for instance, 2,000 yards or more) the parallax may be neglected,
and if the sights are correctly adjusted the lines of sight and the
prolongation of the axis of the bore will sensibly pass through the
selected aiming point.