Ch 2. Torsion Multimedia Engineering Mechanics CircularBars Nonuniform &Indeterminate Thin-walledTubes Non-Circular Bars
 Chapter 1. Stress/Strain 2. Torsion 3. Beam Shr/Moment 4. Beam Stresses 5. Beam Deflections 6. Beam-Advanced 7. Stress Analysis 8. Strain Analysis 9. Columns Appendix Basic Math Units Basic Equations Sections Material Properties Structural Shapes Beam Equations Mechanics Tools Search eBooks Dynamics Fluids Math Mechanics Statics Thermodynamics Author(s): Kurt Gramoll ©Kurt Gramoll

 MECHANICS - CASE STUDY Introduction Motor Driving Two Gears It has been determined that a mechanical drive system needs to generate 900 N-m torque (clockwise) to turn two gears. Gears A and B have resisting moments of 500 N-m and 400 N-m respectively (counter-clockwise which is the opposite direction to the motor moment). The shaft needs to be sized to insure the safe operation of the system. What is known: The drive shaft is straight and continuous from the motor to the right support. The shaft material is an aluminum alloy with E = 69 GPa and ν = 0.33. The maximum shear stress of the shaft is 275 MPa. A factor of safety of 2.0 is required. The rpm of the motor is not known. Question Considering the factor of safety, what is the minimum radius so that the shear stress does not exceed the given stress limit? What is the total shaft rotation from one end to the other? Approach The motor torque must equal the moment loads applied to the shaft from the gears. The shaft internal moment needs to be determined (may not equal the gear loads). To determine the required radius, use the torsional shear stress equation,       After the radius is found, use the angle of twist equation to find the rotation angle,