# Calculating Braking Torque for a Flywheel

• andycampbell1
In summary, the conversation is about calculating the braking torque required to bring a flywheel to rest from a speed of 12 rev/s in 8 seconds. The flywheel has a total mass of 300 kg and a radius of gyration of 900 mm. Friction in the bearing produces a torque of 70 Nm. The formula T = mαk² is used, which gives the answer of 2289 Nm. However, when subtracting the friction torque, the correct answer of 2221 Nm is obtained.
andycampbell1

## Homework Statement

A flywheel, together with its shaft, has a total mass of 300 kg with a radius of gyration of 900 mm. Friction in the bearing produces the equivalent of a torque 70 Nm. Calculate the braking Torque required to bring the the flywheel to rest from a speed of 12 rev/s in 8 seconds.

## Homework Equations

ΣF =ma
• F – Force (N)
• m –mass (kg)
• a=(v‐u)/t (m/s2)
• a=(v2‐u2)/2s

ΣT =Iα
• T‐ Torque (Nm)
• I =mk2(flywheel
moment)
• α=(ω2‐ω1)/t
• α=(ω2
2‐ ω1
2)/2Θ

F=T/r
m =I/k2
a=α r
v=ω r
s=Θ r

T = F x r
I = mk2

α = a/ r
ω = v / r
Θ = s / r

## The Attempt at a Solution

I have worked out the moment of inertia as I=mk^2 = 300x900^2= 243kgm^2
I also converted the rev/s to rad/s so that would be 12x2pi = 75.4 rad/s
I devided the rads/s by the time to get angular acceleration = 9.42
Then I used the formula T= m$$\alpha$$k^2 which gave me 300x9.42x900^2 this gave me the answer 2289. The solution to the answer gives me T=2221 Nm where have I went wrong?

hi andy!
andycampbell1 said:
A flywheel, together with its shaft, has a total mass of 300 kg with a radius of gyration of 900 mm. Friction in the bearing produces the equivalent of a torque 70 Nm. Calculate the braking Torque required to bring the the flywheel to rest from a speed of 12 rev/s in 8 seconds.

… this gave me the answer 2289. The solution to the answer gives me T=2221 Nm where have I went wrong?

if you subtract the friction torque, isn't that roughly correct?

Yep ha, it was right under my nose and I missed it, thanks for the help anyway.

## What is a flywheel torque problem?

A flywheel torque problem refers to a malfunction or issue with the rotational force or torque generated by a flywheel. This can occur in various mechanical systems that use flywheels, such as engines, generators, and industrial equipment.

## What are the common causes of flywheel torque problems?

Some common causes of flywheel torque problems include worn or damaged bearings, misalignment of the flywheel, and improper lubrication. Other factors such as excessive heat, vibrations, and contaminants can also contribute to these issues.

## How can flywheel torque problems be diagnosed?

Flywheel torque problems can be diagnosed through a variety of methods, such as visual inspection, measurement of torque and speed, and vibration analysis. It is important to identify the root cause of the problem in order to implement an effective solution.

## What are the potential consequences of ignoring a flywheel torque problem?

Ignoring a flywheel torque problem can lead to serious consequences, including increased wear and tear on other components, reduced efficiency and performance, and even complete failure of the system. It is important to address these issues as soon as they are identified to prevent further damage.

## How can flywheel torque problems be prevented?

Regular maintenance and inspection of flywheels can help prevent torque problems from occurring. This includes proper lubrication, alignment, and balancing of the flywheel. It is also important to address any potential issues or warning signs as soon as they are identified.

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