Clutch design — What do cushioning (torsion) springs primarily reduce? In a single-plate clutch, the cushioning or torsional damper springs in the hub primarily reduce which undesirable effect during engagement and power transfer?

Introduction / Context:
Clutch hubs often include torsion springs to moderate the transmission of oscillatory torque from the engine to the drivetrain. This protects gear teeth, reduces noise, and smooths engagement.

Given Data / Assumptions:

• Dry single-plate clutch with a sprung hub.
• Engine produces cyclic torque fluctuations (firing pulses).
• Driver engages clutch during take-off and shifts.

Concept / Approach:
Engine torque is not perfectly steady. Torsional damper springs act as a compliant element, reducing amplitude of torque oscillations and driveline lash impacts. While this also results in smoother take-off (less jerk), the primary engineering intent is to mitigate torsional vibration transmission and gear rattle.

Step-by-Step Solution:
Identify disturbance: cyclic engine torque and engagement shock.Insert compliance: springs in hub twist under load, storing and releasing energy gradually.Outcome: reduced torsional vibration, less NVH, smoother engagement.

Verification / Alternative check:
NVH testing shows reduced gear rattle and driveline clunk with sprung hubs compared to solid hubs.

Why Other Options Are Wrong:
Vehicle speed: not controlled by clutch springs.Jerky starts: improved as a consequence, but root function is torsional damping.None of these/brake fade: unrelated.

Common Pitfalls:
Assuming springs exist only for engagement softness; they also work during steady driving to reduce gear rattle.

Final Answer:
torsional vibrations