The U.S. Army Armament Research, Development and Engineering Center (ARDEC) engineers from the Fire Control Systems and Technology Directorate at Picatinny Arsenal in New Jersey developed, tested, and placed into practical application the Bore Elevation and Azimuth Measurement System (BEAMS). The BEAMS provides a means to accurately measure the pointing ability of fire control for mortars, artillery, and other weapon platforms.

Heretofore, verifying weapon pointing accuracy in an engineering environment has been, and continues to be, a problem at many government test facilities.

Current methods employed at Government Proving Grounds for artillery and mortar weapon azimuth pointing measurements generally make use of a fixture inserted into the weapon tube. The fixture is composed of two disks, which engage the diameter of the weapon bore. The disks support a mechanical rod structure that extends the tube axis beyond the end of the tube where it may be observed. The long-rod incorporates two conical alignment points, the tips of which are machined to be on axis with the long-rod. The long-rod is machined to be coaxial with the two disks. In operation, the weapon tube is positioned on the azimuth of interest and the apparatus inserted into the bore. A theodolite is then positioned at a location such that the vertical line intersects the tips of both conical alignment points. At that time, the theodolite would be positioned in exactly the same vertical plane as both conical points and therefore along horizontal projection of the azimuth of the weapon tube.

This is a subjective process and highly dependent upon the skill of the theodolite operator. Shortcomings of such approaches are the inability to quantify or calibrate the mechanical apparatus and to establish or remove bias from the measurement. Additionally, these approaches may measure azimuth, but not the elevation angle.

The BEAMS device offers a low-cost technique to verify in a field test environment that the elevation and azimuth pointing accuracy requirement of a weapon’s fire control system is met. The BEAMS laser apparatus incorporates interchangeable lobes that allow for use with any weapon tube caliber. The lobes support two non-marring brass pads and a spring-loaded plunger, which allows the apparatus to self-center on the weapon tube axis. The apparatus incorporates an eye-safe laser that provides a projection of the tube axis. Mechanical adjustments allow the laser aperture to be positioned on-axis with the weapon bore, and optical adjustments within the laser housing permit the beam to be made concentric with the actual tube axis. These features facilitate measurement and/or removal of bias from the fixture.

The BEAMS uses a dual theodolite approach employing conventional geodetic survey procedures to make three-dimensional measurements of the laser’s position. From these measurements, the elevation and azimuth of the laser line and subsequently the weapon tube can be computed with exceptional accuracy. The computations may be performed in a spreadsheet or through the use of dedicated computer software. A fully automated system may be implemented through the use of digital theodolites operating under computer control.

This work was done by Robert P. Pinto for the Army Armament Research, Development and Engineering Center. For more information, download the Technical Support Package (free white paper) below. ARDEC-0007


This Brief includes a Technical Support Package (TSP).
Bore Elevation and Azimuth Measurement System (Beams)

(reference ARDEC-0007) is currently available for download from the TSP library.

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This article first appeared in the August, 2020 issue of Aerospace & Defense Technology Magazine.

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