What is a Crankshaft and Its Function

Did you know that a crankshaft is the heart of an engine? 

It is one of the most crucial components of a reciprocating engine, also called a piston engine. This mechanical component is responsible for the proper operation of an engine, besides converting linear motion to rotational motion.

Know more about crankshafts in automobiles, how they are manufactured, types and functions.

A crankshaft is an essential mechanical part that converts the piston's to-and-fro motion into rotational motion. The rotational motion is then transferred to the flywheel, thus helping achieve the torque required for the engine to function.

The crankshaft is an important component in any automobile, demanding meticulous design and utmost precision. Any mistake in creating the crankshaft can significantly increase the chance of engine failure.

The construction of crankshafts often relies on cast iron because of its excellent durability and ability to withstand the demand of engine operation. In certain cases, crankshafts are also manufactured using forged steel to withstand the heavy load involved.

Cast iron crankshafts are created through a casting process, while forged one involves heating a block of steel until it gets red hot. Subsequently, the forged steel is kept under high pressure to shape it in any desired form. 

The manufacturing process of crankshafts also includes surface hardening and heat treatment techniques like carburising, nitriding etc., in order to enhance durability. Lastly, the choice of materials used for crankshaft construction depends on various factors such as operating conditions, the engine’s power output, and more.

Here’s a step-by-step explanation of how the crankshaft works.

• Step 1: The crankshaft pushes the piston from the top centre to the bottom centre in a downward motion via the connecting rod.
• Step 2: Thereafter, the crankshaft undergoes the task of converting the piston’s linear motion into a rotary motion which is then transmitted by the crankshaft to the camshaft.
• Step 3: The camshaft, upon receiving the rotary motion from the camshaft, allows the entry of the air-fuel mixture. And as the piston moves upward, the camshaft closes the exhaust marking the completion of the compression process.
• Step 4: Next is the ignition phase, wherein the compressed mixture ignites, forcing the piston to move downward and transferring motion to the crankshaft.
• Step 5: The crank has two ends where one end is connected to the engine and the other to the flywheel. As the crankshaft receives the linear motion of the piston, it converts it into the rotary motion.
• Step 6: As a next step, the rotary motion is transferred to the flywheel, which stores the motion to power vehicular wheel movement.

There are various types of crankshafts, each serving different purposes. Some of the notable ones are as follows:

1. Cast Crankshaft: These types of crankshafts are made by casting process using cast iron. They are commonly used in diesel and petrol engines.
2. Forged Crankshaft: Stronger than cast cranks, they are commonly used in high-stress engines. It is formed by shaping a single block of metal into the shape of your choice.
3. Single Piece Crankshaft: It is made up of a single and solid piece of material.
4. Semi-built Crankshaft: Mostly used in high-speed vehicle engines, in semi-built crankshafts, some of the parts are manufactured and assembled separately.
5. Built-up Crankshaft: Buil-up crankshaft is one where all the parts are manufactured separately and assembled using the shrink fit technique. This technique ensures all parts fit together to form a tight fit.

The crankshaft plays a crucial role in the operation of an engine, performing a range of essential functions, which are listed below:

1. Power Conversion: The primary function of the crankshaft is to convert the pistons’ linear motion into rotational motion, and this is what drives the output shaft of an engine.
2. Lubrication Regulation: The crankshafts help regulate the distribution of oil required for lubrication in an engine.
3. Power Delivery: The counterweights on the crankshaft transfer power to the pistons as and when required. The controlled power delivery ensures the overall efficiency of the internal combustion engine.

To summarise, the crankshaft is capable of performing a range of functions, all of which are essential for the smooth operation of the engine!

The advantages of a crankshaft can be summarised as follows:

1. Improved efficiency
2. Smooth engine operation
3. Better torque for improved performance
4. Increased engine power

Now let’s examine the disadvantages of crankshafts:

1. High manufacturing costs
2. Bearing failure risk
3. Increased friction which results in heating

While the crankshaft rarely experiences malfunctions, here are a few common failures that can occur:

1. Fatigue Failure: Fatigue failure is the common type of crankshaft failure that can occur due to insufficient quality of the crankshaft material.
2. Worn Journals: This type of failure mostly happens due to insufficient oil pressure and may lead to serious damage if not addressed promptly.
3. Lack of Maintenance: Neglecting regular check-ups of components like engine oil or oil cooler can lead to failure in the crankshaft.

Undoubtedly, the crankshaft serves as the building block of the combustion engine. A balanced and correct type of crankshaft plays a crucial role in maintaining smooth engine operation and minimising energy wastage.

 

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