Flywheel sizing: Compared with a simple (single-expansion) steam engine of similar rating, does a compound steam engine require a heavier flywheel? Select the correct statement.

Introduction:
The purpose of a flywheel is to smooth cyclic fluctuations in torque and speed caused by the intermittent nature of piston work. The degree of fluctuation depends on how uniform the turning moment diagram is over a cycle.

Given Data / Assumptions:

• Simple steam engine: single expansion with one cylinder (or identical rating).
• Compound engine: multi-stage expansion (HP and LP) sharing load across phases.
• Comparable mean torque and operating speed.

Concept / Approach:
Compounding divides the expansion across cylinders timed to produce more uniform torque. The HP and LP cylinders contribute work at different crank positions, filling in low-torque portions of the cycle. Therefore, the turning moment is smoother, the coefficient of fluctuation of speed is reduced, and the energy that must be stored and released by the flywheel each cycle is smaller. Hence, for comparable conditions, a compound engine typically requires a lighter flywheel, not a heavier one.

Step-by-Step Solution:
1) Consider turning moment diagrams for single vs compound expansion.2) Observe increased uniformity in compound due to phase-shifted cylinder contributions.3) Lower fluctuation of energy → lower flywheel moment of inertia required.4) Conclude the statement “requires a heavier flywheel” is false.

Verification / Alternative check:
Empirical practice and design handbooks recommend smaller flywheel sizes for multicylinder and compounded engines versus single-cylinder counterparts at similar ratings.

Why Other Options Are Wrong:
“True” and conditional forms misinterpret the effect of compounding; unbalance affects vibration, not primarily energy fluctuation addressed by the flywheel.

Common Pitfalls:
Conflating counterweighting for reciprocating mass balance with flywheel energy storage requirements.

Final Answer:
False