Sunday, April 19, 2020

Crosshead Bearing Construction Features. 
  •  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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