Crosshead bearing Lubrication

[Nithin kumar]

Generally lubricant enters at the unloaded part of the bearing. In a crosshead bearing why is the lubricant introduced at the bottom of the bearing?

[Ramalingam]

The load on the crosshead bearing is on the top portion, so the luboil is introduced into the bottom portion......am i right?

[Nithin kumar]

Your right but what happens when the piston is going for the compression stroke?

[pravinvignan]

THe cross head brg is only oscillating and the lower shell is always loaded, the cooling oil must be injected between shaft (crosshd pin) and lower brg.
the load is constantly downwards and bcoz the conrod swings abt the pin, changin direction each stroke, true hydrodynamic lub cannot take place.Instead the lub starts as boundry, and as rubbing speed increases, hydrodynamic film is built up. As the rubbing speed decs the lub becomes boundry once again

[seasriram]

hi guys... salute to the administrators of the forum...
my answer is
1. refer manuals for xhead diagrams.. it will show the strut of the con rod is designed as a xhead brg at top and bottom end brg at bottom.. the design is such that the lubrication happens all the time right from tdc to bdc and vice-versa..note that the xhead lubrication happens only at the top half and the oil which enters the bottom half of xhead is passing through the con rod for bottom end brg lubrication..pls note that right from tdc to bdc and bdc to tdc the bottom half of xhead is comparitively not in contact with the brg pin. always top shell is in contact..i think that the l/o holes are to be well noticed that \" the main xhead brg lubrication is thro the top holes, which doesn\'t have elongated elliptical slots in the bearing shell.\" \" but the bottom shell of xhead brg has 3 to 4 elongated elliptical slots thro which oil passes to bottom end brg...\"
2. i appreciate that everybody say that xhead lubrication is neither boundary nor hydrodynamic...but then pls note it is \"elasto-hydrodynamic lubrication\"...

[hemant goyal]

in bottomhalf gutter for oil passage are provided to remain always oil in bottom half...as bpttom half is alwas under load ...no lubrication in top half of bearing..