What is a Crankshaft?

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  • Written By: Jessica Reed
  • Edited By: Heather Bailey
  • Last Modified Date: 03 August 2018
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The crankshaft is located in the engine of a vehicle and converts the force created by the engine's pistons moving up and down into a force that moves the wheels in a circular motion so the car can go forward. Located inside the car's engine, it is connected to all the pistons in the engine and to the flywheel. To understand this shaft, it is important to understand how the pistons and the flywheel work.

A car engine produces motion by creating explosions inside it. The pistons, which are attached to the crankshaft in an engine, are moved down by the explosions inside the cylinders. When the pistons move down, the crankshaft rotates. The pistons are connected to the crankshaft to ensure it moves with them and keeps their movements regulated.

To help smooth out the jerky motions created by the moving pistons, the flywheel is attached to the end of the crankshaft. As the shaft moves, it turns the flywheel in a circular motion. Notches in the flywheel help smooth its motions and connect it to other car parts that turn the wheels. This turns the up and down motion created by the engine into a circular motion needed to move the car's wheels.


For the pistons to work properly, a piece of the engine called the camshaft must rotate and open the intake and outtake valves. These valves open and close to allow the flow of air, which is necessary to create an explosion, into the cylinder. The crankshaft is connected to the camshaft and causes the camshaft to rotate along with it. This ensures the two engine parts work together and are never out of sync.

Problems occur when the crankshaft is too long because it needs extra support to deal with the pressure from the cylinders in the engine. To solve this problem, engines are often made in a V-shape, with short shafts instead of using the straight shape with long ones. A V-shaped engine has two sets of cylinders, one on each side, while the straight engine has only one set of cylinders all in a row. A V8 engine, for example, would have four cylinders on each side instead of trying to place eight cylinders in a straight line.


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Post 1

For 10 years my husband has been trying to explain a crank shaft to me and now, after reading this article, I think I finally get it! One thing I do remember from my "lessons" with him, however, that may help some people is that the flywheel isn't always necessarily called the flywheel.

In a manual transmission it's a flywheel, but some people call them flex plates in an automatic because of the way they are bolted on. It's still the same basic operating principal, but I thought that might help if someone ever heard the term and wondered what it was.

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