A main bearing is a bearing in a piston engine which holds the crankshaft in place and allows it to rotate within the engine block.
The number of main bearings per engine varies between engines, often in accordance with the forces produced by the operation of the engine. Main bearings are usually plain bearings or journal bearings, held in place by the engine block and bearing caps.
The number of main bearings is primarily determined by the overall load factor and maximum engine speed. [1] Increasing the number of bearings in an engine will generally increase the size and cost of the engine, but also reduces bending stress and deflection caused by the distance from the crank pins to the nearest bearings.
Most engines have at least two main bearings— one at each end of the crankshaft. Additional bearings may be located along the crankshaft, sometimes as many as one bearing per crank pin, as used on many modern diesel engines and petrol engines designed for high RPM. [1]
Some small single-cylinder engines have only one main bearing,[ citation needed ] in which case it must withstand the bending moment created by the offset distance from the connecting rod to the main bearing.
When describing a crankshaft design, the number of main bearings is generally quoted, as the number of crank pins is determined by the cylinder layout. For example, the Toyota VZ V6 engine is described as having a "four bearing crankshaft" and the Jaguar XK6 straight-six engine has a "seven bearing crankshaft". [2] [3]
The lower half of the main bearings are typically held in place by 'bearing caps' which are secured to the engine block using bolts. The basic arrangement is for each bearing cap to have two bolts, but some engines may have four or six bolts per bearing cap (often referred to as "four-bolt mains" or "six-bolt mains" engines). The additional bolts result in increased strength, allowing the engine to withstand higher power output or RPM. [4]
The first car engine to use four-bolt main bearings was the V12 Maybach Zeppelin of 1928, that used them on three of its eight main bearings. [5]
The typical design for a six-bolt main bearing is four vertical bolts (two on each side of the crankshaft) from the bottom extending into the block and two lateral cross-bolts coming from the left and right side pan rails into the side of the main caps to provide additional lateral strength.
A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting rods.
A V6 engine is a six-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V configuration.
The inline-six engine is a piston engine with six cylinders arranged in a straight line along the crankshaft. A straight-six engine has perfect primary and secondary engine balance, resulting in fewer vibrations than other designs of six or fewer cylinders.
A connecting rod, also called a 'con rod', is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the crankshaft. The connecting rod is required to transmit the compressive and tensile forces from the piston. In its most common form, in an internal combustion engine, it allows pivoting on the piston end and rotation on the shaft end.
The Ford small-block is a series of 90° overhead valve small-block V8 automobile engines manufactured by the Ford Motor Company from July 1961 to December 2000.
The Slant-Six is the popular name for a Chrysler inline-6 internal combustion engine with an overhead valve reverse-flow cylinder head and cylinder bank inclined at a 30-degree angle from vertical. Introduced in 1959 for the 1960 models, it was known within Chrysler as the G-engine. It was a clean-sheet design that began production in 1959 at 170 cubic inches (2.8 L) and ended in 2000 at 225 cubic inches (3.7 L). It was a direct replacement for the flathead Chrysler straight six that the company started business with in 1925 until the old design was discontinued in the 1960s.
The Chrysler 1.8, 2.0, and 2.4 are inline-4 engines designed originally for the Dodge and Plymouth Neon compact car. These engines were loosely based on their predecessors, the Chrysler 2.2 & 2.5 engine, sharing the same 87.5 mm (3.44 in) bore. The engine was developed by Chrysler with input from the Chrysler-Lamborghini team that developed the Chrysler/Lamborghini Formula 1 V12 engine in the early 1990s.
The KA engines were a series of four-stroke inline-four gasoline piston engines manufactured by Nissan, which were offered in 2.0 and 2.4 L. The engines blocks were made of cast-iron, while the cylinder heads were made of aluminum.
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The Toyota VZ engine family is a series of V6 gasoline piston engines ranging from 2.0 to 3.4 L in displacement and both SOHC and DOHC configurations. It was Toyota's first V6 engine, being made as a response to Nissan’s VG engine, one of Japan’s first mass-produced V6 engines.
A crankpin or crank pin, also known as a rod bearing journal, is a mechanical device in an engine which connects the crankshaft to the connecting rod for each cylinder. It has a cylindrical surface, to allow the crankpin to rotate relative to the "big end" of the connecting rod.
The Lotus-Ford Twin Cam is an inline-four petrol engine developed by Lotus for the 1962 Lotus Elan. A few early examples displaced 1.5 litres, but the majority were 1.55-litre (1557ml) engines. It used a Ford 116E iron cylinder block and a new aluminium cylinder head with dual overhead camshafts. The Twin Cam was used in a variety of vehicles until Lotus stopped production in 1973. It was succeeded by the Lotus 907 engine.
The Chevrolet 90° V6 family of V6 engines began in 1978 with the Chevrolet 200 cu in (3.3 L) as the base engine for the all new 1978 Chevrolet Malibu. The original engine family was phased out in early 2014, with its final use as the 4.3 L (262 cu in) V6 engine used in Chevrolet and GMC trucks and vans. Its phaseout marks the end of an era of Chevrolet small-block engine designs dating back to the 1955 model year. A new Generation V 4.3 L (262 cu in) V6 variant entered production in late 2013, based on the LT1 small block V8 and first used in the 2014 Chevrolet Silverado 1500.
The Ferrari flat-12 engine family is a series of flat-12 DOHC petrol engines produced by Ferrari from 1964 to 1996. The first racing Ferrari flat-12, the Mauro Forghieri-designed Tipo 207, was introduced in the Ferrari 1512 F1 car in 1964. Later flat-12 racing engines were used in Ferrari Formula One and sports racing cars from 1968 until 1980, including the 212 E Montagna, 312 B series, 312 PB and 312 T series. The roadgoing flat-12 engines were introduced with the 365 GT4 BB and were produced in various versions until the end of F512M production in 1996.
The Mercedes-Benz OM 138 is a diesel engine manufactured by Daimler-Benz. In total, 5,719 units were produced between 1935 and 1940. It was the first diesel engine especially developed and made for a passenger car. The first vehicle powered by the OM 138 was the Mercedes-Benz W 138. The light Mercedes-Benz trucks L 1100 and L 1500 as well as the bus O 1500 were also offered with the OM 138 as an alternative to the standard Otto engine.
The De Dion-Bouton 130 hp aircraft engine, also referred to as De Dion-Bouton 12B, was a twelve-cylinder, air cooled vee aircraft engine that has been built by De Dion-Bouton.
The Volkswagen-Audi V8 engine family is a series of mechanically similar, gasoline-powered and diesel-powered, V-8, internal combustion piston engines, developed and produced by the Volkswagen Group, in partnership with Audi, since 1988. They have been used in various Volkswagen Group models, and by numerous Volkswagen-owned companies. The first spark-ignition gasoline V-8 engine configuration was used in the 1988 Audi V8 model; and the first compression-ignition diesel V8 engine configuration was used in the 1999 Audi A8 3.3 TDI Quattro. The V8 gasoline and diesel engines have been used in most Audi, Volkswagen, Porsche, Bentley, and Lamborghini models ever since. The larger-displacement diesel V8 engine configuration has also been used in various Scania commercial vehicles; such as in trucks, buses, and marine (boat) applications.