Steam engine compounding layouts: cross-compounding In cross compounding (two-cylinder compound engine), the high-pressure and low-pressure cylinders are arranged ________, each having a separate piston, connecting rod, and crank.

Introduction / Context:
Compounding expands steam over multiple cylinders to improve efficiency and reduce cyclic torque variation. Two common arrangements are tandem compound and cross compound. Correctly identifying the geometry helps in understanding balance, torque smoothness, and mechanical layout.

Given Data / Assumptions:

• Two-cylinder compound engine (HP and LP).
• Standard crankshaft practice for smoother torque delivery.
• Goal is improved efficiency and reduced peak forces.

Concept / Approach:
In cross compounding, the HP and LP cylinders are on separate cylinder centerlines and use separate pistons, connecting rods, and cranks mounted on the same shaft but set at about 90 degrees to one another. This phasing evens out the turning moment and reduces dead-center problems. In contrast, tandem compounding places HP and LP in line on the same piston rod with a common crank.

Step-by-Step Solution:
Identify cross-compound: two separate cylinder lines, two separate cranks.Set cranks ≈ 90° apart to smooth torque and improve starting.Steam exhausts from HP to an intermediate receiver, then to LP, completing compounding.

Verification / Alternative check:
Historic marine and stationary engines used 90° phase to avoid simultaneous dead centers; drawings show distinct connecting rods and cranks for HP and LP in cross-compound layouts.

Why Other Options Are Wrong:
“Common piston/rod/crank” describes tandem compound, not cross-compound. “Side by side with separate cranks” omits the 90° phasing that defines standard practice for smoothness.

Common Pitfalls:
Confusing the terms “cross” and “tandem”; assuming phase angle is arbitrary—90° is conventional for two-cylinder arrangements.

Final Answer:
at 90° and each cylinder has separate piston, connecting rod and crank