If a belt drive's pulley diameter is doubled while belt tension and pulley width stay constant, what modifications are needed for the key____________________?
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Answer: C. increase key width
Explanation
Doubling pulley diameter while keeping tension constant doubles the torque transmitted through the shaft. Higher torque increases the shear force acting on the drive key connecting the pulley to the shaft. Increasing the key width provides greater shear area to safely handle the doubled torque load. Torque equals the product of belt tension difference and pulley radius. Drive keys are designed to fail as mechanical fuses if excessive torque jams the machinery. Standard key design formulas balance shear stress and crushing stress across the key dimensions.
Mechanical designers must recalculate shaft and key dimensions whenever pulley sizes are modified. Undersized keys can shear off under heavy loads, causing unexpected machine downtime in factories. Proper sizing ensures reliable power transmission in industrial belt drive and gearbox assemblies. Increase key length would also help but changing width directly accommodates the increased tangential force. Increase key depth addresses bending moments rather than primary torsional shear force requirements. Double all dimensions is excessive and unnecessary when only the torque proportional width needs adjustment.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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