The Main Parts of a Piston and Their Functions

Pistons are common to countless reciprocating engines, compressors, cylinders, and other equipment that may be found in vehicles, aircraft, and more. In their most basic form, pistons serve to transfer force generated by expanding gas to a crankshaft through the use of a piston rod or connecting rod. As devices that have long been used in numerous settings and industries, having a general understanding of their makeup can help one better understand the benefits they provide to the systems that they are found in.

The piston ring is a split ring component that is commonly situated within the recessed area of the piston assembly. Ranging in number based on the application, piston rings are used to seal the combustion chamber and may manage the amount of lubrication oil that is used. The mounting grooves for the rings are specifically designed for securing the ring in place, and the surfaces between rings are known as piston ring lands. Placing such components within the assembly is often quite easy, and rings made from iron or steel are quite common. Piston rings may vary in type, the most common variations being compression, scraper/wiper, and oil control rings.

The piston skirt is the next common assembly component, coming in the form of a cylindrical element that is mounted onto the rounded section of the piston. These components are often constructed from cast iron for their advantageous properties, and grooves are implemented to accommodate the mounting of piston oil and compression rings. Skirts are useful for guiding the piston during its movement, ensuring that it can overcome any side forces that occur. If a piston is making slap noises after the engine has warmed up, the skirt may need to be tightened.

Piston pins, also known as wrist pins or gudgeon pins, are a component that make up the hollow or solid shaft of the piston skirt. With the use of the piston pin, the piston itself can also pivot. Such components are often constructed from alloy steel to achieve high tensile strength, and friction may be reduced through the use of holes that are made in the connecting rod. The piston pin is very useful for providing the piston bearing support, and they may come in the form of stationary or fixed pins, semi floating pins, and full floating pins.

The piston head is the top surface of the assembly, being the element that comes into contact with combustion gases. Constructed from steel alloy or other special alloys, the piston head is specifically designed to withstand the immense heat created by combustion. With the implementation of channels and cavities, swirls may be produced to enhance combustion. Depending upon the application, there are a few different head designs, each of which can determine the performance of the system in question.

The connecting rod is one of the most crucial elements of the entire assembly, serving as the link between the piston and the crankshaft so that the piston may shift back and forth out of the combustion chamber. Due to their role, connecting rods are often constructed from robust materials so that they may withstand the mechanical strains that they are typically faced with. In general, such components comprise a small end for lining the piston, a big end to connect the crankshaft, and a connecting rod beam that serves as the central section of the part.

Connecting rod bolts are the final major component for piston assemblies, serving as items that clamp onto the crankshaft rod. The bottom end is then secured with a nut, and a cotter pin ensures that loosening is prevented. Often constructed with steel, aluminum, or nickel, the connecting rod secures the crankshaft to the connecting rod and takes on strain. Due to their role, connecting rods should be well maintained for the safety of other components.


November 16, 2021

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