Leading Edge Groove Technology in a Slimline Bearing

The LEG Slimline is a tilt-pad bearing that features Kingsbury’s Leading Edge Groove lubrication technology in a lower profile. This design reduces pad pivot temperatures, increases load-carrying capacity and enables a shallow envelope for installation.

It is important to note that trailer wheel bearing kits are sold in pairs, meaning the cup and cone are the same size. This is crucial because there are variations in the Ford and Holden trailer kit part numbers that could result in a mismatch.

Leading Edge Groove Lubrication Technology

Leading Edge Groove (LEG) lubrication technology is used in Kaydon's Slimline tilt pad journal bearings to reduce power loss, operating temperatures and friction. The LEG design uses the relative shear between the bearing pads and rotor to drag lubrication into the natural wedge-shaped gap between the pad faces.

Kingsbury tests have shown that a supply groove at the leading edge of the pad substantially improves running characteristics of large thrust bearings without increasing cold oil flow rate. Changing the groove depth, controlled by the parameter L3, also yields excellent results in terms of load capacity and maximum film temperature.

Unlike spray bar and other directed lubrication methods, the LEG provides an even distribution of cool inlet oil across the bearing surface. This helps to lubricate the entire surface and insulate the babbitt face from the hot oil carryover that adheres to the collar. The LEG also lowers pad temperature, increasing the bearing's load carrying capacity.

Leveling Plates

Most in metal fabrication know that plate leveling is critical. The processes that create sheet at the mill generate a plate full of trapped stresses, a virtual tug-of-war between compression and tension forces that must be brought into equilibrium to form flat metal for subsequent fabrication.

Industry plate flatness standards specify a tolerance of 0.25 in. over 8 ft., but heavy fabricators often require tighter tolerances that can save six-figures in scrap. It’s why fine-tuning at the plate leveler is so important.

A plate leveler’s operation bears a certain similarity to a roller leveler, but there are crucial differences. The extreme forces that a plate leveler applies, along with a wide range of material yield strengths throughout the plate, require a machine that can adjust in fine increments. The traditional method of adjusting a plate leveler is to use a flight of work rolls tied together in the same plane. This wouldn’t work for plate leveling because the varying conditions in the plate can vary the penetration of each roll, even in the same location.

Oil Feed Tubes

The LEG SlimLine’s oil feed tubes are positioned to deliver the direct flow of cool engine oil that’s critical for optimal bearing operation. This is a major difference between the LEG SlimLine and other tilt-pad bearings that rely on spray or mist lubrication. Kingsbury’s test data shows that this arrangement reduces operating temperatures and power loss, while providing a much higher load carrying capacity than flooded or spray fed bearings.

Passageways drilled in the back of the carrier ring deliver the fresh, clean oil that’s confined to each pad’s leading edge groove, where it’s then drawn down into an oil film wedge to cool the babbitt face. This direct lubrication technique eliminates the need for an internal grease seal, which limits oil exchange between the permanent grease and engine oil during operation.

TuneRS’ patent pending DOF kit features an adapted pressure fed oil line that runs from the positive oil pressure feed on the cylinder head to an opening in the custom Intermediate Shaft Bearing Flange, delivering a constant flow of filtered engine oil to the IMS bearing. This greatly reduces operating temperatures, while providing the constant lubrication and cooling the IMS Bearing needs.

Oil Film Wedge

Kaydon standard Slimline thin section bearings are designed for a particular direction of rotation. They are manufactured from low carbon steel with a high tin content babbitt face and use an offset center pivot design. The babbitt faces are supported by pads that can tilt to a degree. This allows the lubricant to reach all parts of the pad surfaces and reduce the frictional forces generated by the pad contacting surface.

The oil film wedge that forms between the two surfaces in relative motion is a result of the geometry wedge action combined with density and viscosity wedge actions. The pressure that the wedge generates creates fluid dynamic lubrication and prevents metal-to-metal contact. This is what is known as load-carrying lubrication. Normally, the center of the journal will ride in a stable eccentric position within this condition. This is dependent on the load, speed, clearance and oil viscosity. The LEG SlimLine lubrication groove and pad design provides the necessary conditions for this to occur.