Bearings

Section 3 General Construction

Section 3
General Construction

It is important to have a familiarity of the engine bearing construction, when trying to determine the primary cause of bearing damage. There are three basic constructions for the connecting rod and crankshaft bearings. They are trimetal (see Figure "Trimetal Bearing Construction" ), rillenlager (see Figure "Rillenlager Bearing Construction" ), and sputtered (see Figure "Sputtered Bearing Construction " ). ‪

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1. Flashing‪

4. Lining‪

2. Overlay‪

5. Backing‪

3. Barrier‪

Figure 1. Trimetal Bearing Construction

  • Flashing - Tin plating covering the entire bearing for the protection prior to installation.
  • Overlay - Alloy mainly of lead with tin to provide embedability, conformability, and protection against marginal lubrication.
  • Barrier - Nickel layer plated over the lining to prevent chemical reaction between the lining and overlay.
  • Lining - Alloy mainly of copper and lead for maximum fatigue strength.
  • Backing - Made of steel to provide support for the bearing lining.
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1. Overlay‪

3. Aluminum Alloy‪

2. Barrier‪

4. Backing‪

Figure 2. Rillenlager Bearing Construction

  • Overlay - Provides embedability and lubricity (approximately 75% of surface area).
  • Barrier - Nickel layer plated over the lining to prevent chemical reaction between the lining and overlay (maximum 5% of surface area).
  • Aluminum Alloy - Bearing material with excellent strength and durability used as a substrate for the overlay (approximately 25% of surface area).
  • Backing - Made of steel to provide support for the bearing.
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1. Sputtered Overlay‪

3. Lining‪

2. Barrier‪

4. Backing‪

Figure 3. Sputtered Bearing Construction

  • Sputtered Overlay - Made of an aluminum-tin alloy.
  • Barrier - Nickel layer plated over the lining to prevent chemical reaction.
  • Lining - Alloy mainly of copper and lead for maximum fatigue strength.
  • Backing - Made of steel to provide support for the bearing.

The main bearings have an upper and lower shell. The lower shell, which fits in the removable cap, supports the crankshaft. For maximum load capacity, the lower shell has no oil hole or grooves. The upper shell fits into the engine block saddle bores. The upper main shell is grooved or slotted. Oil is directed though the grooves and holes from the crankshaft main journals.‪

Upper and lower main bearing must not be reversed in their position in the engine. To prevent an incorrect installation from happening, the locating tang on the upper and lower shells are normally in different positions.‪

The connecting rod bearings have an upper and lower shell. As with main bearings, the lower connecting rod shell fits into a removable rod cap. The upper shell may or may not have a means of supplying lubricating oil to further lubricate the piston pin/bushings and cool the underside of the piston. The locating tangs are provided in order to assist in installing the shells correctly in the bore of the connecting rod.‪


Bearings Technician's Guide - 7SE448
Generated on 10-13-2008

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