Regarding crankshaft end play, which statement is correct?

Regarding crankshaft end play, which statement is correct?

• A. The end play is controlled by the fillet radius of the crankshaft journals
• B. The end play is limited by the main bearings
• C. Both statements are correct
• D. Neither statement is correct

Answer: (D)

End play refers to the small amount of axial (front-to-back) movement the crankshaft can have in the engine. This movement is controlled by the thrust clearance between the crankshaft’s end faces and the opposing thrust surfaces, which are provided by thrust bearings or the thrust faces on the main bearing caps. The fillet radius of the crank journals affects strength and oil flow around the journals, not how far the crankshaft can slide axially. While some designs use main bearings with thrust surfaces, others use a separate thrust bearing, so saying end play is limited by the main bearings alone isn’t universally true. Because of these design variations, neither statement captures the universal way end play is controlled.

End play refers to the small amount of axial (front-to-back) movement the crankshaft can have in the engine. This movement is controlled by the thrust clearance between the crankshaft’s end faces and the opposing thrust surfaces, which are provided by thrust bearings or the thrust faces on the main bearing caps. The fillet radius of the crank journals affects strength and oil flow around the journals, not how far the crankshaft can slide axially. While some designs use main bearings with thrust surfaces, others use a separate thrust bearing, so saying end play is limited by the main bearings alone isn’t universally true. Because of these design variations, neither statement captures the universal way end play is controlled.