richlew55
main bearings,thrust bearings& main bearing caps.

garthlocklin
Hi. The crankshaft is generally mounted in the engine block with main bearings on each end. The bearings are sealed, and in grease usually so they reduce friction and can't be penetrated by dirt or water. The bearings are pressed by a machine into place. The crankshaft drives the pistons. The pistons are connected via connecting rods, which also have bearings so the crankshaft can turn. When a motor is "over revved" or worn out, this is the part that starts to knock. Usually the bearing is going bad on the connecting rod where it is attached to the crankshaft. Good Luck!!

ssg/emt
One half of the bearing the crankshaft rides in is part of the block casting. The other half of the bearing is in a cap, bolted to the block. The crankshaft is sandwiched in between them. The bearing surfaces are lined by bearing shells that are inserted in between the shaft and the block to prevent wear. They are made from metals designed to reduce friction, and embed small particles if they get into the bearing. They are drilled, and oil is force fed through the bearing and other holes and channels let the oil get up to the connecting rod. The bearings aren't sealed, and what oil they use drips back into the oil pan. At one end, or sometimes in the middle, one of the bearings has an extra surface to hold the crank from moving lengthwise, that is the thrust bearing. This page shows several good diagrams and pictures of a crankshaft being insatalled.