1. 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.

2. Drill Depth up to 48” Bit Isolator Chuck Isolator

3. 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

5. FULLY BONDED: 1 3/8”” 53/14/2016 1 3/8" DBI, R. Michael, PE 1 3/8” Drill Bit Isolator – Design Review: Chuck isolator: Drill Bit isolator:

6. 63/14/2016 1 3/8" DBI, R. Michael, PE Look at metal components: Where would you expect max stress to occur? Critical Area!!

7. 3/14/20161 3/8" DBI, R. Michael, PE7

8. Results: FE Analysis 1 3/8” DBI All cases, thurst load = 8,000 lb, torque = 300 lb-ft (3,600 lb-in) 83/14/2016 1 3/8" DBI, R. Michael, PE

9. Max Principal,  1 Min Principal,  1

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

11. From Axial Load From Torque Principal Stresses: =11.95 +/- 35.8 ksi HAND CALCS: How do these values compare with FEA results? Next: use Mohr’s circle to resolve