The crankshaft is one of the most important components of any combustion engine.
Function and structure of a crankshaft
The crankshaft in an engine generates torque by converting the reciprocating motion of the pistons into rotational motion. Crankshafts are often subject to a high load.
Crankshafts are made from materials with extremely hard surfaces, such as nitriding steel or special tempering steel. Almost all crankshafts are still forged.
A crankshaft itself is made up of crank pins, crank webs, journal bearings, and counterweights. The crank pins are used to connect the connecting rods, the crank webs connect the journals, and the counterweights are also connected to the crank webs.
A crankshaft sensor monitors the movement of the crankshaft, and the crankshaft gear is responsible for the torque distribution.
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Types of crankshafts
Fully built crankshafts are commonly found in older engines and consist of a crank web, main journals, and a crank pin all joined together. The journals and crankpin are bored into the crank web.
Semi-built crankshafts are lighter than fully-built shafts and are able to carry high loads and withstand high bending stresses and shear. This type of crankshaft is found in some high-speed engines.
Welded shafts are created using the submerged arc welding process. They allow for significant savings in weight and the crank webs can be made thinner – providing longer bearing lengths.
Solid single piece shafts are made by forging or casting and are often used in both low-speed and high-speed engines.
Forged crankshafts are extremely strong and are typically found in high-stress engines. They are more durable than others and also give better dimensional stability.
Cast crankshafts are commonly found in a variety of engines. They are usually made from malleable iron and are popular because they are cheap, work well, and can withstand significant load from all directions.
Symptoms of a defective crankshaft
There are a number of key signs that a crankshaft may be defective. The most common ones are: clicking sounds, rumbling or grumbling noises, excessive vibration, oil leaks, and intermittent engine stalling.