# What is Flywheel: Definition and 262 Discussions

A flywheel is a mechanical device specifically designed to use the conservation of angular momentum so as to efficiently store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, if we assume the flywheel's moment of inertia to be constant (i.e., a flywheel with fixed mass and second moment of area revolving about some fixed axis) then the stored (rotational) energy is directly associated with the square of its rotational speed.
Since a flywheel serves to store mechanical energy for later use, it is natural to consider it as a kinetic energy analogue of an electrical inductor. Once suitably abstracted, this shared principle of energy storage is described in the generalized concept of an accumulator. As with other types of accumulators, a flywheel inherently smoothes sufficiently small deviations in the power output of a system, thereby effectively playing the role of a low-pass filter with respect to the mechanical velocity (angular, or otherwise) of the system. More precisely, a flywheel's stored energy will donate a surge in power output upon a drop in power input and will conversely absorb any excess power input (system-generated power) in the form of rotational energy.
Common uses of a flywheel include:

Smoothing the power output of an energy source. For example, flywheels are used in reciprocating engines because the active torque from the individual pistons is intermittent.
Energy storage systems
Delivering energy at rates beyond the ability of an energy source. This is achieved by collecting energy in a flywheel over time and then releasing it quickly, at rates that exceed the abilities of the energy source.
Controlling the orientation of a mechanical system, gyroscope and reaction wheelFlywheels are typically made of steel and rotate on conventional bearings; these are generally limited to a maximum revolution rate of a few thousand RPM. High energy density flywheels can be made of carbon fiber composites and employ magnetic bearings, enabling them to revolve at speeds up to 60,000 RPM (1 kHz).Carbon-composite flywheel batteries have recently been manufactured and are proving to be viable in real-world tests on mainstream cars. Additionally, their disposal is more eco-friendly than traditional lithium ion batteries.

View More On Wikipedia.org
1. ### Use of flywheel to enhance human powered drivetrain

Hey , I’m participating in a sailboat race that forbids gas or electric engines. Paddles and oars are popular with smaller boats while racers over 25 feet rely on peddle drives. As we are poor substitutes for engines these devices work but not very well ! My thought is to add a flywheel, as...
2. ### Calculating Flywheel Inertia Using Conservation of Energy Equations?

I am stuck on what to do to calculate the inertia of a flywheel using the method described. I am supposed to use conservation of energy equations to calculate the inertia. I have a picture of the experiment and also the measurements I have taken. It seems each method I try I get a different...
3. ### Friction between motor and flywheel

For a model, I am making I need to know the friction between a motor and a flywheel. The electric motor is on the side of the flywheel and the idea is when this motor turns the flywheel will start to rotate due to the friction between them. I however can not find a good way to calculate this...
4. ### Stress in a spinning flywheel

I'm wonder how one could calculate the total mega pascals total mega pascals that can be applied to a spinning flywheel before it exceeds its tensile strength example: a cast iron flywheel is spinning at 10,000rpm(Tangential velocity = 104.72) it has a radius of 100mm and a weight of 500g...
5. ### I How to transfer angular momentum between two flywheels?

I am trying to build a simulation of a car engine and wheels for a game project. My model is currently this: Engine outputs a torque -> this spins up a flywheel over time (the physics step of 1/60s) -> the flywheel is coupled with the clutch and thus transmission -> the transmission multiplies...
6. ### Interested in flywheel mechanical batteries

Can someone point me to advanced engineering/ physics based literature / textbooks on the subject?
7. ### B Calculating Flywheel Mass and Diameter for Efficient Generator Drive

Hi guys! I have a real life physical problem. I need to calculate the mass and diameter of a flywheel made of steel to run generator with parameters: 123 kVA - 98 kWe; Frequency 50 Hz, 400 V, Class F M8 - 674 nM. The better question is, how much (kinetic) energy do I have to input into the...
8. ### Help please with power calculations to turn a large flywheel at 1rpm

How did you find PF?: Trying to find answers Hi I’m trying to solve this problem .hope someone can find the answers, I need to find the hp needed to run a flying wheel ring shape. 42 ft in diameter weight 200.000 lbs the wheel is Suport by bearing inside and out of the edge of the rim, the...
9. ### Help with flywheel / clutch calculations

Hey everyone, I have a problem with sizing a clutch for my machine. My problem is, I don't know how to calculate the needed value (Nm) for the clutch to withstand the torque affected by the flywheel. I have a flywheel that weighs 90kg and is 600mm in diameter. It is rotating at 500rpm...
10. ### Spinning up a flywheel with a motor

i'm simulating a small dc motor that is driven by volt = 1.54v, current = 250 milli amps, so that gives me 0.385 watts supplied to the motor next i attached a 4mm thick circular acrylic disc as a flywheel. so in this simulation i spin up the acrylic disc as a flywheel my acrylic disc is 12cm...
11. ### Finding the angular acceleration of a flywheel

I have solved part a using the conservation of energy, getting a (correct) answer of 47.9 km/h, but I am unable to make headway with part b. Based on the flywheel rotating at 237rev/s when the car is moving at 86.5 km/h, I obtained omega = (237*2pi)v/24=62v. Differentiating both sides should...
12. ### Automotive Motorcycle: Flywheel mass and rear wheel torque

Hello, I made this account to ask this question that I’ve been loosing sleep over. My question is say you have 2 identical motorcycles the engine the exact same and everything the only difference is the mass of the flywheel one bikes engine has a flywheel twice the mass as the other will the...
13. ### Rotational motion: Number of revolutions before a flywheel comes to rest

Hi there I have been having a go at this question and I'm uncertain if my answer to part b) is valid? The problem is when I plug this into the calculator I get 6.379... revs however this doesn't make sense to me. 2*pi is roughly 6.28 radians so doing 4.061... rads / 6.28 rads = 0.647 revs...
14. ### Rotating Flywheel: Tips & Tricks for Beginners

Hey everyone! Was trying to answer this question and was wondering if this was the right way to go about it? Any help would be really appreciated!
15. ### Calculating the initial frequency of a decelerating flywheel

I converted 5 minutes to 300 seconds, and movement angle per second as shown on the picture. From here on I am lost, as the angular velocity can't be calculated, as the time given isn't the one in which the flywheel does one rotation. I apologise if I used any expressions wrong, english is not...
16. ### How to Calculate This Horsepower from a flywheel?

I have a flywheel (150 Kg, Diameter-18", RPM) How I Calculate Horsepower from These information. I am working on a project Thank you physicsforums
17. ### Show that the flywheel inside the train counteracts lean in a curve

Summary: Consider a train carriage rolling along a curve that forms a left turn on the track. The carriage speed is directed along the y-axis (into the plane of the paper) in the figure. The trolley will have a tendency to curl in the curve in the specified direction. A flywheel is inserted...
18. ### Turning Moment of Single Cylinder 4-Stroke Engine | Explanation

Figure 1 shows the Turning Moment diagram of Single Cylinder four stroke Engine. Can anyone tell me, how the turning moment becomes positive at the end of suction and exhaust stroke. Net force F = Force due to gas pressure - Inertia Force - Reaction Force due to friction If the net force...
19. ### I need to know the power of a flywheel

hi sir i have 1100 watt motor and i want to rotat the fly wheel from rest to 1450 rpm.i want to know how big should be the flywheel to rotate at the motor 1100 watt and to get extra energy 700 joule or more than if possiable best regard thnx
20. ### What would happen if the flywheel is not used in an IC Engine?

What would happen if flywheel is not installed to IC Engine? Does it have serious consequences?
21. ### Calculate the speed of the flywheel for my drone motor

I have drone motor with propellers attached to the top of ring flywheels rim at the edge and the flywheel is 18 inches in diameter and weigh's 2kg. The drone motor with propellers rpm 5200 and thrust 900 grams. What rpm will the flywheel be rotating at.
22. ### Auto/Motor Can a 5 HP Gas Motor and a Flywheel Revolutionize City Driving?

Hello Team, Had a shower thought, and thought I spend a few minutes online with people much smarter than I to throw an idea at... So, I have a light weight truck. Say a little dodge dakota pickup that weighs +/- 3000lbs. I want to take out the motor and replace it with a little baby 20hp...
23. ### Automotive Dual mass flywheel clutch - How does it make a difference?

I was going through these two documents: https://www.schaeffler.com/remotemedien/media/_shared_media/08_media_library/01_publications/schaeffler_2/symposia_1/downloads_11/4_DMFW_1.pdf http://www.partinfo.co.uk/docs/140 My primary interest was to understand why and how Dual Mass Flywheel (DMF)...
24. ### I need to maximize my RPMs in a single cylinder flywheel

I am working on a flywheel single-cylinder engine powered by a 40 psi air compressor. My task is to achieve as many RPMs as I can. I have already bored two exhaust ports in the frame as shown in the pictures attached. I've done some 600grit sanding on points of contact, am using lubricant prior...
25. ### What is the torque exerted by the flywheel on the machine?

Homework Statement Flywheels are large, massive wheels used to store energy. They can be spun up slowly, then the wheel's energy can be released quickly to accomplish a task that demands high power. An industrial flywheel has a 2.0 m diameter and a mass of 260 kg . Its maximum angular velocity...
26. ### Flywheel Inverted pendulum torque calculation

Hey all, I started building my own flywheel inverted pendulum (i'm using a standard PID controller for the balancing). I came across many articles regarding the differential equation of the pendulum. Most article develop the motion equation using the Euler–Lagrange, few chose the Newtonian way...
27. ### Calculating Work Supplied by a Flywheel for Forming Machine Operations

Homework Statement A motor which drives a forming machine runs at an average angular velocity of 100−1. The machine forms steel shapes from flat sheet steel. The work done per operation is 7kJ. It takes one second to form each shape and four seconds to change over the next sheet of steel. If...
28. ### Automotive The effect of a flywheel on a car's launch

Hello,I have been searching for a good answer but I couldn't find any. Let's say a car's engine is producing 200 Nm of torque throughout its entire range.since gear ratios and tire radius are fixed,it must provide the same amount of wheel force in a gear.So,theoretically,whatever RPM you launch...
29. ### Exploring Energy Storage Combinations & Optimal Control Schemes

I'm currently working on combining energy storage systems like flywheels and batteries to balance consumption/regeneration. I've been looking at using an optimal control scheme so that a cost function can be tailored to our wishes. I'm curious about what other people in this field have been...
30. ### Ways to Spin a Flywheel using linear motion

I am to try to find simple way to spin a spinning flywheel. What linear motion device acting on the outside edge of a spinning flywheel can be used to increase the speed of the flywheel. Need to use a repeating pattern such as pushing your hand down over and over on the edge of the wheel to...
31. ### How to calculate torque and power for self starter and flywheel

How to calculate following input and output parameters- 1. Input at starter motor - Drive torque and power as shown below 2. Output at flywheel axle - torque, power, Kinetic energy, centrifugal force as shown below Input parameters: starter motor rpm -3600, Gear ratio- 18: 1 if any parameter...
32. ### Calculate hydraulic motor for a Flywheel

Gentlemen: I got stuck in this problem and I really need your help: I have an hydraulic line of 23Mpa ( 3.300 psi) 10 gallon/min I built a flywheel weight 58,000 grams with the following Inertial properties Principal moments I1= 2.5 , and I2= 2.3 and I3= 632170437 grams mm3 Flywheel will...
33. O

### Calculate Horsepower from a flywheel

I have a flywheel (not connected to an engine, just on a shaft and bearings, so assuming zero resistance), that weights 60 lbs, 18" wide, at 3200 RPM's. How can I calculate horsepower, brake, or torque? Working on a project, Thank you, Larry
34. D

### Input Power against time graph - Flywheel from rest to 300rpm

Homework Statement gearbox and flywheel are as shown in FIGURE 4. The output shaft rotates in the opposite direction to the input shaft at 5 times its speed. The gearbox has an efficiency of 92%. If the flywheel is solid, has a mass of 50 kg, a diameter of 1.5 m and is to accelerate from rest...
35. D

### Gearbox and flywheel question, How to calculate input torque

Homework Statement A flywheel is attached on the output of the gearbox. The output shaft rotates in the opposite direction to the input shaft at 5 times its speed. The gearbox has an efficiency of 92%. If the flywheel is solid, has a mass of 50kg, a diameter of 1.5m and is to accelerate from...
36. ### Determine torque required to accelerate the flywheel

Homework Statement A solid disk of diameter equal to 500 mm and a mass of 60 kg is to be used as a flywheel in an energy recovery device. Determine the torque required to accelerate the rotation of the flywheel, about its axis, from rest to 250 rpm in 6 revolutions. Homework Equations [/B]...
37. ### Maximizing Power and Efficiency: Flywheel Torque vs. Horsepower

Dear friends, i want to know if flywheel (30inch) 96kg weight running on 1400rpm then how much power can save in hp or tarque? and how much power required to drive this wheel? regards kashif
38. ### Calculate how many revolutions the flywheel turns

Homework Statement [/B] Homework Equations I have calculated the kinetic energy and the total moment of inertia. https://www.physicsforums.com/file:///C:/Users/javad/AppData/Local/Temp/msohtmlclip1/01/clip_image002.png The Attempt at a Solution I really don't know how to solve the problem...
39. ### How large of a flywheel can my motor spin?

Hi All, I'm hoping you all can help me with what I think should be some relatively simple calculations. I'm looking to determine how large (diameter / weight) of a flywheel a particular AC motor can spin from a stop to full RPM given the torque / HP of the motor. For instance, if I have a 1/3...
40. ### Calculating Flywheel Rotations in Angular Speed and Constant Acceleration

Homework Statement [/B] A flywheel with a D=1.2m is rotating at an angular speed of 200 rev/min (a) Whats the angular speed in rad/s ? (b)Whats v=? in the point on the rim ? (c)What const. ∝ ( in rev/min^2) will increase its angular speed to 1000 rev/min in 60 sec ? (d)How many...
41. ### Flywheel Rotation Question

Homework Statement A flywheel turns through 40 rev as it slows from an angular speed of 1.5 rad/s to a stop.Assuming a constant acceleration,find the tme for it to come to rest. Homework Equations ##w-w_0=∝t## The Attempt at a Solution In Δt secon the change in w...
42. ### Flywheel Inertia: Calculating Mass & Radius

Hi, I couldn't find how to calculate this flywheel inertia , any help please?! I know that I=1/2(mass*radius²) but it seams more complex then that!
43. ### Controlled Energy Release Mechanism

I am working on a mechanism which controls the release of energy while remaining energy efficient. An image of the concept is shown below. (The image is meant simply to get an idea of how it would work- it is by no means perfect). A source of energy (from a spring being released, for example)...
44. ### Angular Acceleration of a Flywheel Lab

Homework Statement Assume no friction for 1 - 6 1. Draw a free body diagram of the fly wheel (from above), and a free body diagram of the weight (from side). 2. What force appears in both diagrams? 3. What is the relationship between the torque on the flywheel and the tension in the string...
45. ### Automotive Twin engine vs inline flywheel supercharger idea?

Had this idea today in my garage when I was setting up timing marks on the crankshafts and flexplate,the front engines flexplate would not be spinning the transmission.The flexplate is 14 inch diameter could you weld a series of fan blades to the flywheel face, get a modified bellhousing create...
46. ### Automotive How to calculate how much power required to turn a flywheel?

How to calculate how much power required to turn a flywheel at constant velosity ? Suppose I have a flywheel of 24 inch diameter, width 5 inches,50kg and constant angular velosity is 1500 rpm. How do I calculate the required power (HP) to turn this or any other with different values?
47. ### How Does a Flywheel Begin to Move with Constant Speed After Adding a Mass?

For this problem, I don't understand how can the system be at rest and immediately after placing the mass, to move with constant speed. But anyways, can you tell me please how to proceed? On the hanging mass, there is mg acting and T the tension of the rope. On the flywheel, the tension of the...
48. ### Mean Radius of Annulus with Bolt Hole Pattern

Hello all, I am trying to remember (I did it in Uni) how to calculate the effective mean radius of an annulus that contains a pattern of holes on a PCD. Consider the following image (pinched from: https://www.solenoid-valves.com/ ): If one was to vary the value of PCD, then the effective...
49. ### Working out the angular acceleration of a flywheel

I am trying to work out the angular acceleration of a small flywheel (with axle running through) when an attached piston (by means of a pin) with an outstroke force acts on it. I assumed I would need to work out the torque using the formula torque = force x radius, and find out the flywheel’s...
50. ### Calculating torque required to operate a flywheel

So basically, I'm making a vehicle that should regenerate energy from braking. the car will start at rest at a ramp between 30 to 50 degrees slope. a flywheel will be connected to the front wheels of the vehicle I want to determine what kind of a flywheel will be sufficient to store the...