Your truck, SUV, or performance car’s torque and power come from the powertrain they have.
The powertrain consists of the engine and the drivetrain. The drivetrain consists of the front and rear differentials, axles, transfer case, driveshaft, wheels, and transmission.
These components serve the purpose of providing the torque and power for your performance car, SUV, or truck to go forward or backward.
One essential component of the powertrain that we left out is the flywheel. If a flywheel fails, it will negatively affect other powertrain components.
Now, you are probably asking: “What does a flywheel do? What the heck is it?” The article will explain three functions of a flywheel and the signs of a bad flywheel.
What Is A Flywheel?
A flywheel is a heavy disc attached to the end of a rotating shaft that helps smooth out the engine’s power pulses and store energy through rotational momentum.
Although a flywheel can take other forms, such as a cylinder or an outside ring with spokes like a wagon wheel, in automotive uses, it’s usually a solid, metal disc that’s about an inch thick, a foot in diameter, and around 10 to 40 pounds (depending largely on material, from lightweight aluminium to heavy cast iron).
It is attached to the end of the engine’s crankshaft, where it bolts to the transmission.
Why Is It Important?
Nearly all automotive engines of recent years, and for most of the last century, have a four-stroke design, with each “stroke” being 180 degrees or one-half turn of the crankshaft. Of those four strokes (intake, compression, power, and exhaust), only one, the power stroke, encourages the crankshaft to turn.
The compression stroke coming right before it (where the rising piston compresses the air-fuel mixture) adds a load, or resistance to turning, to the crankshaft, while the crankshaft kind of coasts through the exhaust and intake strokes.
Thus, without a flywheel to smooth things out, the crankshaft would slow down during the compression stroke; then accelerate rapidly during the power stroke, coast through exhaust and intake strokes; then repeat the process. This would result in an uneven flow of power and a decent amount of vibration.
Think of it this way: If you were turning a rotating shaft with a crank handle, you’d likely be able to apply more muscle at some points during a full revolution than at others.
But if there were a heavy flywheel at the end of the shaft, the rotating momentum of the flywheel would help you rotate the shaft at a more consistent speed. Its momentum would also keep the shaft turning even after you let go of the handle.
How a Flywheel Works
At its core, a flywheel is a mechanical device specifically designed to store rotational energy. It works on the principle of inertia, meaning it resists changes in rotational speed. Here’s how it functions in a car:
- Storing Energy: During the engine’s power stroke, the flywheel stores energy as the piston moves down, and the engine generates power.
- Releasing Energy: The stored energy is then released to smooth out the power delivery during the other strokes of the engine cycle (intake, compression, and exhaust), ensuring consistent performance.
- Assisting in Starting the Engine: When you turn the ignition key, the starter motor engages the flywheel to crank the engine. Starting the engine would be much more difficult without a properly functioning flywheel.
What Does The Flywheel Do?
StartingTheEngine
In vehicles with manual transmissions, the flywheel plays a crucial role in starting the engine. The flywheel is connected to the engine’s crankshaft and provides the necessary momentum for the engine to begin rotating when the starter motor engages.
The flywheel’s weight and rotational energy help overcome the engine’s initial inertia and kickstart the combustion process.
Reducing Vibrations
Another essential function of the flywheel is to reduce variations caused by each power stroke during combustion. The rotational mass of the flywheel evens out these fluctuations, resulting in smoother power delivery and preventing stalling or jerky movements of the vehicle.
The flywheel also serves as a vibration damper, reducing engine vibrations caused by the reciprocating motion of the pistons. By absorbing and dissipating these vibrations, the flywheel helps maintain engine stability, reduces stress on engine components, and enhances overall comfort and durability.
Contains The Clutch Assembly
For vehicles with manual transmissions, the flywheel houses the clutch assembly. The clutch disc is pressed against the flywheel’s surface to engage or disengage the transmission from the engine.
The flywheel’s smooth and flat surface provides the necessary friction for the clutch to engage securely, allowing for seamless gear shifting.
Parts of the Flywheel
The following are the parts of a flywheel:
#1. Flywheel Housing.
The flywheel housing is solid and sits outside of the flywheel. The flywheel is the part of the engine that rotates and delivers power to the alternator.
#2. Springs.
The flywheel is consists of two-phase bent springs in parallel. The outer arc is adjusted to raise the spring when the engine is operating. The soft outer arc spring only serves to improve the uncertain resonance frequency range.
#3. Planetary Wheel.
A planetary wheel consists of many planetary gears fixed on a flywheel bracket. When the flywheel bracket is operated by a screw and rotates, the meshing with the outer ring gear produces a compound motion composed of each planetary gear revolution and rotation.
#4. Axial and Radial Sliding Bearing.
While the axially acting bearing serves only for weight compensation, the imbalance or parasitic radial forces initiated by the motor or generator unit must be compensated by
radial Bearings.
#5. Ring Gear.
A ring gear is fitted to the outer diameter of the flywheel. It is usually fixed to the flywheel with the help of an interference fit, which is produced by heating the ring gear. So, the thermal expansion enables it to be placed around the flywheel.
#6. Support Disc.
As the name suggests, the support disc is attached inside the flywheel to support the two-phase bent springs and other components of the flywheel.
#7. Flywheel Sliding Shoe.
Sliding shoes preferably have a convex radial outer portion bearing on the inner wall of the flywheel. In this area, they are preferably manufactured to promote slip and suffer minimal wear and tear.
#8. Flywheel Cover.
The flywheel cover is commonly made of chrome. This chrome-plated flywheel cover will prevent dust from getting into the internal functions of the flywheel, which it is causing it to run poorly.
Functions of the Flywheel
To understand how a flywheel works in a better way, take the example of a four-stroke, single-cylinder engine. There are occasions when more power is produced than at other times. This tends to make the crankshaft speed up and then slow down.
The engine delivers power only during the power stroke. It absorbs power during the other three strokes to eject exhaust gases, take a fresh charge into the cylinder, and compress this charge.
Thus, during the power stroke, the engine tends to speed up, and during the other three strokes, it tends to slow down. The inertia of the flywheel tends to keep it running at a constant speed. When the engine tends to speed up, the flywheel resists it.
The flywheel resists when the engine tends to slow down. Thus, the flywheel absorbs energy as the engine tries to accelerate and gives back as the engine tries to slow down, keeping the engine speed almost constant.
In a multi-cylinder engine, the flywheel acts, in the same way, to smooth out still more the peaks and valleys of power flow from the engine.
The flywheel is also used as a part of the clutch mechanism and fluid drive unit. The outer edge of the flywheel has forged teeth to mesh with the electric cranking motor-driven pinion when the engine is being cranked to start it.
Types of Flywheel
The following are the types of flywheels used in vehicles:
- Solid disc flywheel
- Rimmed flywheel
- High-velocity flywheel
- Low-velocity flywheel
#1. Solid Disc Flywheel.
A solid disc flywheel is crafted from cast iron material, imparting robustness and durability. Its solid cross-section design ensures enhanced strength and stability, making it a reliable component within the system.
By utilising cast iron, the solid disc flywheel offers a sturdy construction that can withstand the demanding forces and pressures encountered during operation, contributing to its overall performance and longevity.
#2. Rimmed Flywheel.
In comparison to a solid disc of the same dimensions, a rimmed flywheel exhibits wear at lower RPM levels. This characteristic makes it well-suited for low-capacity engines that operate at high torque but low velocity.
Due to its design, the rimmed flywheel is optimised to effectively handle the specific demands of such engines, ensuring reliable performance and longevity while operating within the desired RPM range.
Its construction allows for efficient energy transfer and enhanced durability, making it an ideal choice for engines characterised by high torque and lower rotational speeds.
#3. High Velocity Flywheel.
High-velocity ranges typically span from 30,000 RPM to 80,000 RPM. These components are designed to be lighter in weight, enabling them to rotate at elevated speeds. The emphasis on reduced weight facilitates the ability of these high-velocity components to attain and sustain the desired rotational velocities.
By optimising their design for lighter construction, they are engineered to operate efficiently and safely within the specified high RPM range, meeting the demands of applications that require rapid rotational motion.
#4. Low Velocity Flywheel.
The angular velocity of these types of Flywheels comes up to 10000 rpm. They are bulky and heavy compared to high-velocity Flywheels. They need periodic maintenance and do not use magnetic levitation bearings
Their installation needs special concrete construction to support its weight. They are cheaper in comparison to high-velocity Flywheels.
Materials Used to Make a Flywheel
The flywheel is made from many different materials depending on its applications. Cast iron flywheel is used in older steam locomotives. The flywheels used in the car’s engine are usually built of cast or nodular iron, steel, or aluminum.
Flywheels are also made of high-strength steel. The composite flywheel is meant for use in vehicle energy storage and braking systems. The power of a flywheel is determined by the maximum amount of energy that it can store per unit load.
Symptoms of a bad flywheel
A problem with your flywheel can be very dangerous. Because your flywheel transmits the power from your engine to your transmission, your ability to control your vehicle’s power can be affected.
A bad flywheel could potentially cause a loss of power to the wheels and result in an accident. Many factors can cause wear to and deterioration of your flywheel. Here are some of the warning signs of a bad flywheel:
- Pulsation felt through the brake pedal.
- Abnormal noise when the starter motor is engaged.
- Rattling noise when depressing or releasing the clutch.
- The clutch “grabs” when engaging.
- The car slips out of gear, going into neutral or another gear.
- Shaking or vibration felt through the clutch pedal or the floor of the vehicle.
- Burning smell from the clutch.
- Clutch chatters when engaged.
- Clutch drags, will not release completely.
- Inability to change gears.
Advantages of the flywheel
- Less overall cost
- High energy storage capacity
- High power output
- They are safe, reliable, energy efficient, and durable
- It is independent of working temperatures
- Low and inexpensive maintenance
- High energy density
Limitations of the flywheel
- They can take up a lot of space
- They are expensive to manufacture
- Building material is always a limitation for it
Uses of the flywheel
- In reciprocating internal combustion engines
- In wind turbines
- In a locomotive propulsion system
- In satellites to control directions
- In the mechanical workshops
- In punching machines
FAQs.
Q: What are the signs of a bad flywheel?
The flywheel is one of those things you do not want to give up without signs on your car. If you do that, it means you are parking your vehicle in a garage until you can replace it. Fortunately, some signs will show before the flywheel goes out. They are:
- Rattling noise when you press or release the clutch pedal.
- The gear goes into neutral or slips out when shifting gears.
- Burning smell from the clutch.
- Regular vibration while driving.
- The car makes a strange noise when turning the starter motor.
Q: Does the flywheel constantly spin?
We previously mentioned that the flywheel continuously transfers power from the engine to the transmission once the engine is started.
From this, you may conclude that the flywheel spins all the time, which is false. The flywheel won’t spin if the engine isn’t in gear or is in neutral.
This is because the input that connects to the clutch plate, connected to the pressure plate connected to the flywheel, is free-spinning when the vehicle is in neutral.
Q: Can you drive with a bad flywheel?
It appears to be possible to drive with a failed flywheel. It just depends on the severity of the damage. In some instances, a flywheel can leave you stranded in the middle of nowhere.
Additionally, you should note that while you may have the option of continuing to drive with a broken flywheel, when a flywheel goes out, there is a possibility of causing failure or damage to other powertrain components in that area, as the flywheel acts as a balancer between the engine and transmission as the crankshaft rotates.
When the flywheel fails to act as a balancer, there will be vibrations as you drive. You will also notice rough idling, which will contribute to the engine not being able to produce peak performance.
Q: Why is a flywheel so expensive?
There are two types of flywheels, fixed and dual flywheels. The fixed flywheels are generally affordable for all car owners.
On the contrary, dual flywheels can increase in price more than a fixed flywheel because of the material used to make the part. A standard style of flywheel lasts a lot longer and is very tough to replace.
Q: What happens if the flywheel breaks?
If the flywheel breaks, the function of transferring horsepower from the engine to your tranny, you can expect to do some irreparable damage.
Additional symptoms include vibrations, rattling noise, gear slippage, hard shifting gear or strange noise when turning over the starting motor, etc. In the worst-case scenario, your engine may underperform and lose torque and power altogether.
Q: How much does it cost to resurface a flywheel?
Discoloration or glazing on the flywheel is a sign of wear and can interfere with how well the flywheel meets the clutch. If it is experiencing wear, the flywheel must be resurfaced.
Resurfacing your flywheel should be approximately $20 to $50, but it will not include the mechanic’s service fee.
Q: Does the flywheel need to be replaced with a clutch?
In the case of gear slippage or any indication of a bad clutch – assuming you have a worn clutch disc or something similar, you don’t always need to replace the clutch together with a flywheel.
If you are at high mileage, my recommendation is to simply cut it again whenever you remove the clutch.
Q: How long does it take to machine a flywheel?
There are two methods of resurfacing a flywheel: grinding or cutting. No matter which method is used, resurfacing a flywheel should not take any longer than about 3-5 minutes.
The goal of resurfacing a flywheel is to remove the harder surface and leave a homogeneous and smooth surface.
Q: How many times can you resurface a flywheel?
There is no recommended number of times to resurface a flywheel, but 1 overall time or 2 is recommended, and no more than that.
In general, machine operators are able to determine the need (or no longer need) of resurfacing a flywheel with just a glance. After all, it is what they do and are trained to do.
Final Word
At this point, you are not wondering what a flywheel is, what it does, and what symptoms to look for when it starts to fail.
Not only do you now have enough information to answer the question “what does a flywheel do”, but you also know what happens if you drive with a bad flywheel. If at any point you notice any of the symptoms above, make sure you go to a mechanic to have them inspect and repair it.