Crankshaft terminology in engine design: The statement ‘‘The portion of a crankshaft that rests in (and is supported by) the cylinder block or crankcase bearings is called the main journal’’ is — select the correct evaluation.

Introduction / Context:

An automotive crankshaft has distinct journal types that serve different functions and see different loads. Clear terminology helps during inspection, machining, and assembly. This item verifies the correct naming of the journals supported by the crankcase.

Given Data / Assumptions:

• The crankshaft is supported in the crankcase by bearings located in saddles (caps).
• Connecting rods attach at offset throws that convert reciprocating to rotary motion.
• Standard nomenclature from engine handbooks is assumed.

Concept / Approach:

The main journals are the cylindrical surfaces that ride in the engine's main bearings within the block or crankcase. The crankpins (or rod journals) are the offset journals to which connecting rods attach. Therefore, the portion ‘‘resting on the cylinder block’’—more precisely, supported by the block's main bearings—is indeed the main journal.

Step-by-Step Solution:

Verification / Alternative check:

Overhaul manuals specify main journal diameters, clearances, and bearing shell sizes separately from crankpin dimensions, confirming the terminology.

Why Other Options Are Wrong:

• No and conditional options contradict standard definitions; journal naming does not depend on engine cycle or fuel type.
• Plain vs. rolling bearings: regardless of bearing type, the supported journal remains the main journal.

Common Pitfalls:

• Calling crankpins ‘‘main journals’’ or vice versa when measuring wear or grinding undersizes.

Final Answer:

Yes