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.

Drill Depth up to 48” Bit Isolator 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”” 53/14/ /8" DBI, R. Michael, PE 1 3/8” Drill Bit Isolator – Design Review: Chuck isolator: Drill Bit isolator:

63/14/ /8" DBI, R. Michael, PE Look at metal components: Where would you expect max stress to occur? Critical Area!!

3/14/ /8" DBI, R. Michael, PE7

Results: FE Analysis 1 3/8” DBI All cases, thurst load = 8,000 lb, torque = 300 lb-ft (3,600 lb-in) 83/14/ /8" DBI, R. Michael, PE

Max Principal,  1 Min Principal,  1

Max shear stress,  max VERIFY FEA RESULTS WITH HAND CALCS!!!!

From Axial Load From Torque Principal Stresses: = / ksi HAND CALCS: How do these values compare with FEA results? Next: use Mohr’s circle to resolve