Original Date: 07/13/1992
Revision Date: 01/18/2007
Information : Gun Tube Inspection
Watervliet Arsenal (WVA) defines gun tube straightness in terms of bend from a center line connecting the ends of the bore of the tube to be measured. Methods for measuring straightness in tube bores have progressed from "go -- no-go" plug gages to the use of laser technology. The current method used by WVA consists of a laser and photo position sensor or target.
The laser is mounted in the breech end of the bore of the tube to be checked and aimed at the muzzle end. A lateral-effect diode position sensor (target) is used to detect the laser beam position relative to the center line of the bore. The target is mounted on a gage head and positioned inside the muzzle end of the tube. The laser beam is positioned to the center of the target. Once in position, the target is moved through the bore of the tube toward the laser. A computer is used to control the down bore positioning of the target which is continually monitored through a linear encoder. The target is stopped at predetermined positions within the bore by the controlling computer programs. Horizontal and vertical measurements are recorded at each stop relative to the center line of the bore. The entire bore is checked at eight-inch intervals and then rotated 180 degrees to repeat the process in order to collect data for use in determining the effect of gravity -- or droop.
The collected data is then analyzed to determine straightness of the tube. Since WVA has determined straightness to be the bend from a center line connecting the ends of the bore, the two measured ends should have a zero deviation. This is ensured by baselining, a procedure that subtracts one end and the component of the slope line between the ends, from each measured position. After all data is baselined, the droop can be calculated and subtracted from the vertical bend profile of the first inspection pass.
Inspecting tube straightness in this manner has helped WVA reduce setup times when checking tubes and also provides a means for accurate checking in the field without having to remove the tube from the vehicle.
For more information see the
Point of Contact for this survey.