ADVANCED CUTTER DEVELOPMENT FOR EGRESS BORING MACHINES

CURRENT EGRESS BORING MACHINES, UTILIZING CONVENTIONAL 17-INCH DISC CUTTERS, ARE CAPABLE OF ACHIEVING MAXIMUM ADVANCE RATES OF 80 FEET PER HOUR, BECAUSE OF CUTTER LIMITATIONS. THE AIR FORCE HAS DETERMINED THAT NATIONAL NEEDS REQUIRE SUBSTANTIALLY FASTER BORING RATES. ALSO, IT IS CRUCIAL THAT THE CUTTERS BE CAPABLE OF COMPLETING THE EGRESS SHAFT, WITHOUT ANY MAINTENANCE/REPLACEMENT OF THE CUTTERS. CURRENT CUTTERS, THAT HAVE EVOLVED ESSENTIALLY AS A RESULT OF TRIALAND-ERROR EXPERIMENTS, DESIGN COMPROMISES, AND MANUFACTURING LIMITATIONS, FALL FAR SHORT OF THE AIR FORCE'S GOAL. EXISTING DESIGNS ARE OFTEN SUBJECT TO BOTH BEARING AND CUTTER FAILURES, EVEN WHEN OPERATED BELOW RATED THRUST LEVELS. PROPOSED HEREIN IS AN INNOVATIVE ANALYTICAL-CUM-EXPERIMENTAL STUDY, CENTERED AROUND THE CONCEPT OF A ONE-PIECE HUB/CUTTER RING STRUCTURE. MATERIALS BETTER SUITED FOR THE CUTTER STRUCTURE AND BEARING ELEMENTS HAVE BEEN SELECTED AND DESIGNS PROPOSED FOR EVALUATION IN PHASE I. THE BEST OF THESE WILL BE INCORPORATED TO DEVELOP BASIC CRITERIA TO BE APPLIED FOR DETAILED DESIGN/DEVELOPMENT OF THE CUTTERS IN PHASE II.