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A rocker arm is a valvetrain component that typically transfers the motion of a pushrod in an overhead valve internal combustion engine to the corresponding intake/exhaust valve. Rocker arms in automobiles are typically made from stamped steel, or aluminum in higher-revving applications.
The rocker cover has been removed, so the pushrods, rocker arms, valve springs, and valves are visible. A valvetrain is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine. [1]
The 1894 prototype Diesel engine used overhead poppet valves actuated by a camshaft, pushrods and rocker arms, [3] [4] therefore becoming the first OHV engines. In 1896, U.S. patent 563,140 was taken out by William F. Davis for an OHV engine with liquid coolant used to cool the cylinder head, [ 5 ] [ 6 ] but no working model was built.
through a pushrod which actuates the valve via a rocker mechanism (in an overhead valve (OHV) engine); via direct contact with the valve stem or rocker arm (in an overhead camshaft (OHC) configuration). Oil under constant pressure is supplied to the lifter via an oil channel, through a small hole in the lifter body.
However, a desmodromic system must deal with the inertia of the two rocker arms per valve, so this advantage depends greatly on the skill of the designer. Another disadvantage is the contact point between the cams and rocker arms. It is relatively easy to use roller tappets in conventional valvetrains, although it does add considerable moving mass.
On most overhead valve (OHV) engines, proper clearance between the camshaft and tappet is achieved by turning a set screw in the end of the rocker arm that contacts the end of the pushrod until a desired gap is achieved using a feeler gauge. Too large a gap results in wear from misaligned parts and compromised engine performance, and too small ...
The primary exhaust rocker arm contacts a low-profile camshaft lobe during low-RPM engine operation. Once VTEC engagement occurs, the oil pressure flowing from the exhaust rocker shaft into the primary exhaust rocker arm forces the VTEC switching piston into the secondary exhaust rocker arm, thereby locking both exhaust rocker arms together.
For pull-rod suspension systems, the only difference is the orientation of the rocker arms. In a push-rod system, the rocker arms are placed at the highest point in the assembly. As such, the rod is under pressure as it transfers compression forces upwards into the rocker arms. In a pull-rod system however, the rocker arms are located between ...