Bearing clearance 1

[wr180561]

Can some tell me what is the formula used to determine the clearances of bearings of diesel engines based on their diameters. The bearings I'm talking about are the main bearings for crankshaft, conrod bigend bearings, piston pin bearings etc... Regards WR

 

[CESSNA1]

WR180561: It depends somewhat on the journal diameter for sleeve bearings. I have never seen a formula or equation only rules of thumb. I am a little rusry and may be off a little but for journals in the area of 1 - 6 inches in diameter it runs about .0005" to .001" per inch of journal diameter. The clearance increases slightly as the journal diameter increases. I would not go beyond about.003" - .004" inch on a six inch journal. Oil viscosity also enters into it. For thicker oil open the clearnace a little.

Regards
Dave

 

[ivymike]

for bushed small-end bearings (rod eye), about 0.8 to 1.25 microns per millimeter of pin diameter. For non-profiled bushed piston bosses, clearances run 0.8 to 2.0 microns per millimeter. For bushingless pin bosses in steel pistons, they run towards the high end of that range. For pin bosses in aluminum pistons, the clearances run tighter than that, and depend on piston temps, pin ovalisation, and peak cylinder pressure (perhaps other parameters as well).