Engine Mechanisms — Primary function of the connecting rod In a reciprocating engine, what is the principal function of the connecting rod?

Introduction / Context:
The slider-crank mechanism converts linear motion of the piston into rotary motion at the crankshaft. The connecting rod is the vital link between piston pin (gudgeon pin) and crank pin.

Given Data / Assumptions:

• Piston, connecting rod, and crankshaft form a classic slider-crank.
• Four-stroke cycle assumed.

Concept / Approach:
The connecting rod transmits force and motion bidirectionally: expanding gases push the piston, forces travel through the rod to the crank, producing torque; during other strokes, the crank pulls/pushes the piston through the rod. It must resist compressive and tensile loads, bending due to side thrust, and fatigue over millions of cycles.

Step-by-Step Solution:
Identify kinematic role: link between piston and crank.Identify load path: gas pressure → piston → pin → rod → crank pin → crankshaft.Therefore choose “transmit motion of the piston to the crankshaft.”

Verification / Alternative check:
Free-body diagrams show axial forces in the rod and torque at the crank proportional to gas pressure and geometry.

Why Other Options Are Wrong:
Turning the flywheel: done by the crankshaft with torque delivered through the rod, but not the rod’s independent function.Driving a drive plate or fuel pump: ancillary tasks via other mechanisms.Synchronizing valve timing: handled by the timing drive and camshaft, not the rod.

Common Pitfalls:
Attributing accessory functions to the connecting rod; its core role is motion/force transmission.

Final Answer:
to transmit motion of the piston to the crankshaft