What Is the Crankshaft and What Does It Do?

An engine can easily be considered one of the most important elements of any fuel powered vehicle, creating the power necessary to drive systems and create movement. Depending on the type of engine that one uses, there are various parts and components that work together to establish functionality. For a reciprocating engine such as those found on light, piston-powered aircraft, the crankshaft and piston are two essential parts that must be present for combustion and power generation to be possible. In this blog, we will discuss the crankshaft and piston of reciprocating engines in more detail, allowing you to better understand their role and importance.

Within the engine assembly, the piston and crankshaft are connected together through the use of a connecting rod. With the use of the crankshaft, the reciprocating motion produced by the upward and downward pivots of the piston can be transformed into rotary motion. As rotary motion is generated, it is used to drive the flywheel, allowing wheel assemblies, propeller assemblies, and other equipment to move. While motion is created through the use of the pistons and transferred through the connecting rod, it is useless unless there is a crankshaft present to transform motion into a usable force. In order to secure the crankshaft to the connecting rod and piston assembly, a series of crankpins and cranks are used.

While the crankpins and crank ensure that the connecting rod and crankshaft remain attached to one another, vibration dampers are also important for reducing the amount of thrust exerted on the crank. Additionally, the crank also takes advantage of a counterweight that ensures a lower amount of bending load on the crank. Alongside such components, the crankshaft itself will consist of a flywheel flung, balance holes, rod bearing journals, counterweight components, main journals, and oil passageways.

Reciprocating engines can often be classified based on the amount of strokes it takes to complete a full power cycle, common options being 2-stroke and 4-stroke engines. The power cycle of an engine is based on the number of turns that the crankshaft undertakes for a power cycle, 2-stroke engines requiring one full revolution while 4-stroke engines require two full revolutions. Depending on the engine and its particular needs, crankshaft assemblies may be a welded, one-piece, or semi-integral structure.

Connecting rods and their related components may be constructed from a variety of components, though the most common are cast iron, carbon steel, vanadium micro-alloyed steel, and forged steel. While many assemblies are made up of multiple pieces, some can be a one-piece design known as a monolithic type crankshaft. Monolithic type cranks are actually the most popular variation across the globe, though some larger and small internal combustion engines opt for assemblies. If price is of concern and one wants a more economically feasible option with reasonable load capabilities, welded assemblies are a good option.

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