The characteristic of the multilobe bearing, is the non-cylindrical bearing bore. This deviates from conventional, cylindrical, hydrodynamic bearings by having two or more lobes. The lobe radius (R) is larger than the shaft radius (r) by a specific amount. This difference in the radius of the shaft and the lobe results in the formation of a wedge gap in each arc. This gap begins at the oil inlet groove, "a" axially positioned at the widest point of the respective arc. As a rule, the narrowest point of the gap lies in the center of the lobe. When the shaft begins rotating, basic theory dictates that the lubricant's adhesive effect on the shaft and lobes acts to pull the lubricant into this gap, which narrows in the direction of rotation. Peak pressure develops between the shaft and the bearing. Once this pressure reaches a certain level, it lifts the shaft off the bearing. Thus, the shaft and the bearing are separated by the lubricant gap. In other words, the shaft operates hydrodynamicly with no metal to metal contact.
