Main bearings allow the crankshaft to rotate and are located at each end of the crankshaft. Engines can have more than two main bearings, but designers must weigh the benefit of additional bearings against the additional weight and cost. Main bearings are usually journal bearings, consisting of two surfaces that slide against each other under lubrication. The number of main bearings in an engine is influenced by the number of cylinders and their configuration. Bearing design and construction is an evolving field as new materials and alloys are developed to optimize performance and durability.
A component of all piston engines, a main bearing allows the crankshaft to rotate and is located, at a minimum, at each end of the crankshaft. Engines can have more than two main bearings, which improves the overall balance of the engine but adds weight to the engine. Designers must weigh the benefit of additional bearings against the additional weight and cost.
A main bearing is usually a journal bearing, also known as a journal bearing. This type of bearing is the simplest type and normally consists of two surfaces that slide against each other under lubrication and have no other moving parts or rolling elements. A shaft that rotates within a sleeve is a simple type of journal bearing. The newspaper is the part that moves. The bearing is the part that contains the journal.
In a piston engine, the main bearing usually consists of two semicircular pieces of metal that enclose the crankshaft, forming a ring. A groove runs the length of the center of the ring, and one or more holes are cut in the groove. These design elements allow engine oil to enter the main bearing and lubricate the crankshaft as it rotates. Piston engines depend on precision construction to be efficient and run smoothly, so the tolerances and clearances for a main bearing design are often extremely small, and these parts are made to exact specifications.
The number of cylinders in an engine and their configuration can influence the number of main bearings in the design. Longer crankshafts generally require additional main bearings as they benefit from the increased stability and balance. Diesel engines will often have more main bearings than a similar gasoline engine, to compensate for the increased stress on the crankshaft. Most modern engines have multiple main bearings, with inline configurations tending to have more than engines with the same number of cylinders arranged in a “V” configuration.
Engine and crankshaft designs are often described in terms of the number of main bearings present, and simply knowing the number of main bearings in a particular engine will allow an experienced mechanic to infer a great deal about the interior of an engine and his design. Bearing design and construction is an evolving field as new materials and alloys are developed to optimize performance and durability. Lead, for example, once a common component in bearing alloys, is becoming less common as manufacturers try to find substitutes due to environmental concerns.
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