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This case study explores the design and performance of combined drill bit isolators specifically engineered for underground mining applications. These isolators are crafted to handle a thrust load of 8,000 lbs and 300 lb-ft torque, ensuring maximum safety during operation. Results indicate that the integration of bit and chuck isolators yielded a significant 7 dB(A) reduction in sound pressure levels at the operator’s position. Detailed design reviews highlight the critical stress points in metal components, supported by finite element analysis (FEA) and hand calculations to validate performance metrics. ###
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CASE STUDY – Combined Loading • Drill bit isolators for underground mining – all metal components and elastomer must be safe! • Design requirement: 8,000 lb thrust load and 300 lb-ft (3,600 lb-in) torque – these are basically the cutting forces.
Bit Isolator Drill Depth up to 48” Chuck Isolator
Results showed that in combination, the bit isolator and the drill chuck isolator provided a 7 dB(A) reduction in sound pressure level at the operator position. Ref: Noise controls for roof bolting machines, P. Kovalchik, A. Smith, R. Matetic and J. Peterson
FULLY BONDED: 1 3/8”” 1 3/8” Drill Bit Isolator – Design Review: Drill Bit isolator: Chuck isolator: 1 3/8" DBI, R. Michael, PE
Critical Area!! Look at metal components: Where would you expect max stress to occur? 1 3/8" DBI, R. Michael, PE
Results: FE Analysis 1 3/8” DBI All cases, thurst load = 8,000 lb, torque = 300 lb-ft (3,600 lb-in) 1 3/8" DBI, R. Michael, PE
Max Principal, s1 Min Principal, s1
Max shear stress, tmax VERIFY FEA RESULTS WITH HAND CALCS!!!!
HAND CALCS: From Axial Load From Torque Principal Stresses: =11.95 +/- 35.8 ksi How do these values compare with FEA results? Next: use Mohr’s circle to resolve