Clutch design practice — a road vehicle clutch is usually sized to transmit a design torque equal to which proportion of the maximum engine torque, to ensure reliability and avoid slip under transient loads?

Introduction / Context:
The clutch must transmit engine torque without slip during launches, gear changes, and transient load spikes. Designers include a safety margin above the quoted peak engine torque to account for manufacturing tolerances, friction coefficient variation, heat, wear, and dynamic factors. The question asks for the typical design proportion relative to maximum engine torque.

Given Data / Assumptions:

• Conventional dry friction clutch in a passenger vehicle or light commercial vehicle.
• Variable friction coefficient with temperature and wear is expected in service.
• Transient torque spikes can exceed rated engine torque momentarily.

Concept / Approach:

Clutch torque capacity T is proportional to normal load, mean radius, number of friction surfaces, and friction coefficient. To prevent slip under worst-case conditions and to provide service life, a margin of about 1.25 to 1.5 times the maximum engine torque is common. Among the given options, 150 percent is the recognized textbook value that captures this safety factor succinctly, ensuring that even with reduced friction due to fade or contamination the clutch still holds torque.

Step-by-Step Solution:

Verification / Alternative check:

Engineering handbooks cite design targets in the range of 1.25 to 1.5, with 1.5 widely used for robust service, corroborating the selection.

Why Other Options Are Wrong:

Equal to maximum torque leaves no margin and risks slip. Eighty percent is clearly inadequate. “None of these” is not applicable since 150 percent is a standard guideline.

Common Pitfalls:

Ignoring friction coefficient drop at elevated temperature; forgetting that clutch wear reduces clamp load over time, which the design margin counters.

Final Answer:

150 per cent of the maximum engine torque