Crankshaft bearings are generally what type?

Crankshaft bearings are generally what type?

• A. Ball bearings
• B. Roller bearings
• C. Plain bearings
• D. Needle bearings

Answer: (C)

Crankshaft bearings are plain bearings (journal bearings). They provide a large, smooth sliding surface around the crankshaft journals and rely on a thin film of oil to carry the load between the journal and the bearing surface. This hydrodynamic lubrication lets the crankshaft rotate with minimal friction while handling the heavy radial loads and occasional slight misalignment common in engines. The bearing shells are typically lined with a soft alloy (like babbitt) to improve conformability and oil retention. Rolling-element bearings such as ball, roller, or needle bearings would use discrete rolling parts to carry the load. A crankshaft’s large-diameter journals and the engine’s lubrication environment make rolling elements impractical, because they’d concentrate loads, demand tighter tolerances, and be more sensitive to alignment and oiling issues. Plain bearings, by contrast, are well suited to the size, load, and lubrication conditions of crankshaft operation.

Crankshaft bearings are plain bearings (journal bearings). They provide a large, smooth sliding surface around the crankshaft journals and rely on a thin film of oil to carry the load between the journal and the bearing surface. This hydrodynamic lubrication lets the crankshaft rotate with minimal friction while handling the heavy radial loads and occasional slight misalignment common in engines. The bearing shells are typically lined with a soft alloy (like babbitt) to improve conformability and oil retention.

Rolling-element bearings such as ball, roller, or needle bearings would use discrete rolling parts to carry the load. A crankshaft’s large-diameter journals and the engine’s lubrication environment make rolling elements impractical, because they’d concentrate loads, demand tighter tolerances, and be more sensitive to alignment and oiling issues. Plain bearings, by contrast, are well suited to the size, load, and lubrication conditions of crankshaft operation.