Crosshead Bearing Construction Features.
Crosshead Bearing Working Condition
High sudden load – Effect of combustion is directly on bearing
High bearing pressure – Bearing is placed high in engine. - Space limitations. – Assembly reciprocating.
Diameter & length – Diameter & length of bearing are low. – Bearing area limitations. –High specific loading
Possibility of bearing distortion – Bending moment & deflection are maximum at center. Pin bored at center (earlier model engines). Less stiffness & high stress concentration. – Bearing
surface deflection. – Alignment difficulty.
Lubrication – Unsatisfactory or difficult oscillating moment. – Con rod swings over 25° -30°.
Oil supply disturbed – Difficult smooth & uninterrupted oil flow.
2 stroke engine – Unidirectional load.
- Thin shell bearings are used and bearing on either end of crosshead pin.
- No shim used with thin shell bearing
- Oil grooves or gutter used on bottom half to distribute oil.
- Grooves do not extend to end and grooves are small because of loaded half.
- Grooves to be limited otherwise reduce bearing surface.
- Lubricating oil is directly supplied to crosshead bearing
- Bearing material usually Sn-Al with Pb-Sn overlay.
Crosshead Bearing Working Condition
High sudden load – Effect of combustion is directly on bearing
High bearing pressure – Bearing is placed high in engine. - Space limitations. – Assembly reciprocating.
Diameter & length – Diameter & length of bearing are low. – Bearing area limitations. –High specific loading
Possibility of bearing distortion – Bending moment & deflection are maximum at center. Pin bored at center (earlier model engines). Less stiffness & high stress concentration. – Bearing
surface deflection. – Alignment difficulty.
Lubrication – Unsatisfactory or difficult oscillating moment. – Con rod swings over 25° -30°.
Oil supply disturbed – Difficult smooth & uninterrupted oil flow.
2 stroke engine – Unidirectional load.
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