In the July 2010 issue of RET-Monitor, keyword: bearings, I wrote about lead-free bearings and possible engineering concerns surrounding their introduction. Extending the search for the reasons behind why the substitute for leaded bearing materials is not yet embraced by the race engineers led to a short interview with a leading supplier of competition bearing shells.
In addition to possible sensitivity issues concerning roundness (shape and steps in the circumference of the bearing bore) and the lower conformability and embedability of the unleaded, harder materials, the temperature inside the bearing is considered to be of major importance in the selection of the bearing material.
In another article in this issue of RET-Monitor, I have given what I hope is an insight into crankcase main bearing split design (keyword: heads-blocks). Background is the accuracy of the main bearing split line geometry, primarily focused on the roundness of a main bearing bore.
In most motorsport applications, bearings have had to cope with increasing loads as the requirements for higher performance of engine, gearbox and suspension components continues to increase.
Once problems with rolling element bearing reliability have been chased in NASCAR Sprint Cup Series competition, is it worth trying to gain performance improvements?
The terms rolling contact bearing, anti friction bearing and rolling element bearing are used to describe that class of bearing in which the main load is transferred through elements in rolling contact with each other. Friction in a rolling element bearing is present, but it is negligible when compared to the starting friction of a journal type bearing. The load, bearing speed and the viscosity of the lubrication all affect the friction within the bearing. Although it is not technically correct to refer to this type of bearing as anti friction, it is a name that is in constant use. 
Traditional main bearing construction is based on a three-layer bearing made of a steel backing, a hard mid layer and a thin overlay of a soft material.
Traditional journal bearings for internal combustion are of the tri-metal type. This type of bearing consists of a steel backing, a hard middle layer and a soft top layer. Typical soft bearing materials are: lead, tin, zinc, or alloys of these metals while typical hard bearing materials are: Aluminium-tin; lead-bronze; copper-lead. The soft top could comprise of three layers, providing five metal layers.
FATIGUE AND WEAR IN A JOURNAL BEARING (during start-up and boundary lubrication)
The purpose of a bearing is to support a load. Deflection of the journal within the bearing can adversely affect the load carrying ability of the bearing. This deflection can be greatly reduced by increasing the diameter of the journal and decreasing its length. This results in a short bearing with a consequential greater flow of oil out of the ends of the bearing. This outflow of oil transfers heat from the bearing and helps to reduce the bearing temperature.
For all of its engine bearing needs in NASCAR Camping World Truck Series (CWTS) engines, PME Engines of Mooresville, North Carolina has researched heavily to meet its main and rod end requirements.
