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An overhead valve engine, abbreviated (OHV) and sometimes called a pushrod engine, is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with flathead (or "sidevalve") engines , where the valves were located below the combustion chamber in the engine block .
The cam can be seen as a device that converts rotational motion to reciprocating (or sometimes oscillating) motion. [clarification needed] [3] A common example is the camshaft of an automobile, which takes the rotary motion of the engine and converts it into the reciprocating motion necessary to operate the intake and exhaust valves of the cylinders.
Pushrods are long, slender metal rods that are used in overhead valve engines to transfer motion from the camshaft (located in the engine block) to the valves (located in the cylinder head). The bottom end of a pushrod is mated to a lifter, upon which the camshaft makes contact. The camshaft lobe moves the lifter upwards, which moves the pushrod.
A camshaft operating two valves. A camshaft is a shaft that contains a row of pointed cams in order to convert rotational motion to reciprocating motion.Camshafts are used in piston engines (to operate the intake and exhaust valves), [1] [2] mechanically controlled ignition systems and early electric motor speed controllers.
In September 1948, Kraus & Naimer (of Vienna) produced C15 (15 A), the first company-owned cam switch. In 1949, the company also presented the world's first cam-designed cam switch. At the beginning of 1950, Kraus & Naimer cam switches C30 (30A) were followed with the same design. The Kraus & Naimer cam switches C16 to C200, which came into the ...
In an overhead valve engine the tappets (on right) are sandwiched between pushrods and the camshaft. In an internal combustion engine, a tappet (also called a 'valve lifter' or 'cam follower') [3] [4] [5] is the component which converts the rotation of the camshaft into vertical motion to open and close an intake or exhaust valve.
SOHC design (for a 1973 Triumph Dolomite Sprint) . The oldest configuration of overhead camshaft engine is the single overhead camshaft (SOHC) design. [1] A SOHC engine has one camshaft per bank of cylinders, therefore a straight engine has a total of one camshaft and a V engine or flat engine has a total of two camshafts (one for each cylinder bank).
The top of the pushrod presses upwards on one side of the rocker arm located at the top of the cylinder head, which causes the rocker arm to pivot downward on the top of the valve, opening it. To reduce friction, uneven wear and "bell-mouthing" of the valve guide , [ 1 ] a roller rocker uses needle bearings (or a single bearing ball in older ...