What is a Flywheel? Working, Functions, Selection Criteria, Advantages [PDF]

What is a Flywheel?

A flywheel is a heavy disk-like structure used in the machinery which acts as a storage device to store energy when energy input exceeds demand and releases energy when energy demand exceeds supply. In steam engines, internal combustion engines, reciprocating compressors, and pumps, energy is produced during one stroke, and the engine is designed to run the entire cycle with the energy produced during that one stroke.

What is a flywheel?

For example, in an Internal Combustion engine, energy is produced only during the power stroke, which is much higher than the engine load. For a 4-stroke engine, no energy is produced during the intake, compression, and exhaust strokes, and for a 2-stroke engine, during compression. The extra energy generated during the power stroke is absorbed by the flywheel and released to the crankshaft during other strokes where no energy is generated, causing the crankshaft to rotate at a steady speed.

How does a Flywheel Work?

The basic working principle of a flywheel is to absorb rotational energy during the power stroke and release that energy during the other strokes (Suction stroke, Compression stroke, Exhaust Stroke). First of all, power is given to the flywheel in the early stages. It moves the crankshaft & thereby moves the piston in the cylinder. Fuel burns out in the combustion chamber during the compression stroke. When the Power stroke is activated, the flywheel draws power from the Power stroke, which is used in three other strokes. In this way, it helps stabilize the rotary motion of the transmission system.

Energy equation

The energy equation for the flywheel depends on the angular velocity and moment of inertia of the flywheel. It is therefore clear that the energy stored in the flywheel increases with increasing weight, size, and angular velocity.

How is Energy Stored in a Flywheel?

Well, you can compare it with the mechanics of a mechanical battery. A battery stores energy in chemical form, whereas a flywheel stores power in the form of motion or kinetic energy, to be exact. A little consideration shows that when the flywheel absorbs energy it speeds up and when it releases it slows down. So instead of maintaining a constant speed, the flywheel only reduces speed fluctuations.


A flywheel can store more energy if it spins faster or has a higher moment of inertia. But spinning faster than adding mass always works best. In machines that operate intermittently, such as punch presses, shears, riveters, and crushers, flywheels store energy from the power source for most of the operating cycle and release energy only for short periods of the cycle. Thus, energy from the power source is supplied to the machine throughout the operation at a constant rate.

What are the Functions of Flywheel?

Flywheel has numerous applications. Following are some common ones:

  • Smooth Running: A flywheel helps the vehicle run smoothly.
  • Avoiding Short Term overloads: A flywheel makes it easier to overcome short-term overloads, such as when starting the engine from the rest condition.
  • Large Energy Storage: It stores large amounts of energy and releases it again when needed.
  • Delivers Energy: Flywheels are sometimes used to deliver intermittent pulses of energy.
  • Higher Energy Capacity: By absorbing energy into the flywheel over time and releasing it quickly, it delivers energy beyond the capabilities of the machine. Example: riveting machine.
  • Smooth Operation: It suppresses torque fluctuations and makes the rotation of the crankshaft smoother.
  • Stability: It balances the crankshaft of the engine.
  • No Limitations beyond dead centre: A flywheel allows the mechanism to continue past the dead center.
  • Works as a Charger: It also helps charge the battery.

Types of Flywheel

There are different types of flywheels available in the market, and each type has its own unique characteristics and advantages. In this article, we will discuss the four most common types of flywheels:

  • Solid Disc Flywheel
  • Rimmed Flywheel
  • High-Velocity Flywheel
  • Low-Velocity Flywheel

Solid Disc Flywheel

The Solid Disc Flywheel is the most basic type of flywheel. It is made up of a solid disc of metal that is attached to the engine’s crankshaft. This type of flywheel is commonly used in small engines, such as those found in lawn mowers and chainsaws. The Solid Disc Flywheel is relatively inexpensive and easy to manufacture, but it has a low energy storage capacity.

Rimmed Flywheel

The Rimmed Flywheel is a more advanced type of flywheel. It is similar to the Solid Disc Flywheel, but it has a metal rim attached to the outer edge of the disc. This rim increases the energy storage capacity of the flywheel, making it suitable for use in larger machines, such as generators and industrial machinery. The Rimmed Flywheel is more expensive than the Solid Disc Flywheel, but it is also more efficient.

High Velocity Flywheel

The High-Velocity Flywheel is a type of flywheel that is designed to store energy at high speeds. It is made up of a lightweight disc that rotates at a high speed. This type of flywheel is commonly used in racing cars and other high-performance vehicles. The High-Velocity Flywheel is expensive and difficult to manufacture, but it has a high energy storage capacity and can deliver a burst of power in a short amount of time.

Low Velocity Flywheel

The Low-Velocity Flywheel is a type of flywheel that is designed to store energy at low speeds. It is made up of a heavy disc that rotates at a slow speed. This type of flywheel is commonly used in large machines, such as wind turbines and hydroelectric generators. The Low-Velocity Flywheel is less expensive than the High-Velocity Flywheel, but it is also less efficient.

Common Problems of flywheel

Like any other mechanical component, flywheels can face problems over time. Here are some common problems of flywheel that you should be aware of.

Clutch Dragging

One of the most common problems of flywheel is clutch dragging. This occurs when the clutch fails to disengage fully, resulting in a situation where the engine and transmission are still connected even when the clutch pedal is fully depressed. Clutch dragging can cause excessive wear on the clutch, flywheel, and other components, and can lead to a variety of other problems down the line.

Clutch Slipping

Another issue that can arise with flywheels is clutch slipping. This occurs when the clutch fails to engage fully, causing the engine to rev higher than usual without any corresponding increase in vehicle speed. Clutch slipping is often caused by worn out friction plates or a damaged pressure plate, and can lead to reduced vehicle performance and fuel efficiency.

Burning Smell

A burning smell is another common problem that can occur with flywheels. This can be caused by a variety of factors, including overheating due to excessive use, worn out friction plates, or a damaged clutch assembly. If you notice a burning smell coming from your vehicle, it is important to have it checked out by a qualified mechanic as soon as possible.

Clutch Chatter

Clutch chatter is another issue that can arise with flywheels. This occurs when the clutch vibrates excessively during engagement, causing a chattering or rattling noise. Clutch chatter can be caused by a variety of factors, including a misaligned clutch, worn out components, or a damaged flywheel. If left unchecked, clutch chatter can cause excessive wear on the clutch and other components, and can lead to more serious problems down the line.

How to Choose the Correct Flywheel for Your Engine?

Flywheel selection depends on many factors, including engine torque, vehicle weight, transmission, and intended use. Choosing the right weight is critical to enhance your driving experience. Weight depends on flywheel diameter. Therefore, the fewer cylinders an engine has, the lighter the flywheel will be. A standard weight flywheel can store more energy. As a result, it has proven to be suitable for moving stock transmission vehicles as well as heavier vehicles such as trucks, drag cars, and rock crawlers.

how to choose the correct flywheel for your engine?

In addition, heavy flywheels slow throttle response and reduce engine RPM when decelerating. A lighter flywheel can provide the inertia of a heavier flywheel. However, as the RPM increases, a slightly modified driving style is required to accommodate the clutch slipping to keep the vehicle moving. In general, the lighter the flywheel, the heavier the vehicle will feel. Of course, there are exceptions that depend on the model of the flywheel.


Why does the flywheel rotate clockwise in an engine?

The flywheel is of little help in determining the direction of rotation of the engine. It’s easy to see which direction the engine is spinning by looking at the engine flywheel. This is because the flywheel does not have its own direction of rotation. However, please follow the direction of the installed engine and see it from the flywheel side. If it rotates clockwise, the engine is clockwise. Similarly, if the engine’s flywheel rotates counterclockwise, it is of the left-handed type.

Heavy multi-cylinder engines such as industrial and marine. These flywheels can also be used to determine the piston position within the cylinder. You can see which cylinder has the piston at TDC by looking at the cylinder markings on the flywheel. This can be used to determine the firing order of the engine. If the engine has been stopped for a long time and needs flushing. These flywheels are really useful. To bleed air from the engine, you must turn the flywheel through the engine either manually or with the indicator valve open.

Engines can rotate both clockwise and counterclockwise, but in general, most engines rotate counterclockwise. However, it is not a hard and fast rule as which one to choose is a matter of the designer’s decision. Therefore, it is always necessary to know the correct direction of rotation of the engine. Either by the engine manual or by visual inspection of the flywheel.

Why are flywheels having teeth?

Not all flywheels have teeth, but most flywheels on cars, motorcycles, heavy generators, and ships do. but why? As you know, flywheels help maintain constant power output. But how can you get that power if you don’t start the engine? If you own or have a vehicle, you should know that you have to press the pedal or start it yourself to keep the engine running. It is to rotate a flywheel through a small gear attached to the teeth of a large diesel engine. These flywheel teeth are used for high-pressure fuel in large diesel engines where compressed air is used to start the engine.

Is flywheel & governor the same?

Both the flywheel and the governor are used to regulate engine speed but in another way. On the one hand, the flywheel regulates the speed of the engine with different strokes. This is to keep the average speed constant.

However, governors are used to regulating the average speed of an engine with variable loads. This is achieved by regulating fuel injection to meet the power demand. If the load increases sharply; the engine begins to slow down. The governor increases the fuel injected into the cylinder to produce more torque, thereby increasing its RPM to keep the speed constant. Although flywheels & governors appear to do the same thing in actuality, they are different.

Flywheel what is it?

In a manual transmission system, the flywheel plays a critical role. It is a disc-shaped component that is mounted on the engine’s crankshaft and is responsible for transmitting power to the gearbox. The flywheel is a heavy component that stores rotational energy, which helps to maintain the engine’s momentum and keep it running smoothly. When the clutch pedal is disengaged, the flywheel continues to spin, providing the engine with the energy it needs to restart quickly. The flywheel’s weight and size also affect how the engine performs, with a heavier flywheel providing more rotational energy and a smoother driving experience.

What Does a Flywheel Do?

The purpose of a flywheel is to smooth out the fluctuations in the speed of a machine’s engine or motor. When a machine is running, there are often times when the engine or motor speeds up or slows down slightly. This can cause vibrations and other problems that can damage the machine over time. A flywheel helps to smooth out these fluctuations by storing energy when the machine is running faster than its desired speed and releasing that energy when the machine slows down. This helps to keep the machine running at a consistent speed, which can improve its efficiency and lifespan.

Flywheel Cost

Flywheel cost can vary depending on several factors, such as the type of flywheel, the materials used in manufacturing, and the supplier. They are generally in the range of $100-$500 and above. The cost of materials used in manufacturing flywheels, such as steel, aluminum, or composite materials, also affects the overall cost. Moreover, the supplier’s pricing strategy, quality, and delivery time can impact the cost of flywheels. To get an accurate estimate of flywheel cost, it is essential to consider all these factors and compare prices from different suppliers. Investing in high-quality flywheels can save money in the long run by reducing maintenance costs and increasing efficiency.

Flywheel parts

Following are the main parts of a flywheel:

Flywheel Housing
Planetary Wheel
Axial and Radial Sliding Bearing
Ring Gear
Support Disc
Flywheel Sliding Shoe
Flywheel Cover

Read more : Flywheel

Video on Working of Flywheel

Credits : Velkes


In conclusion, understanding the flywheel of a car is essential for every driver to know. The flywheel is a vital component in the transmission system that helps in balancing the power output and torque generated by the engine. It is responsible for storing rotational energy and transferring it to the transmission system, enabling the car to move smoothly. Without a flywheel, the engine would struggle to maintain consistent RPMs and would lead to a bumpy ride. Overall, the flywheel plays a critical role in the efficient operation of a car.

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