# How do I calculate flywheel torque for a single cylinder diesel engine?

• //Preeti//
In summary, the flywheel will experience hoop and radial stresses which can be analysed by standard means. However, the flywheel will also experience stress due to speed variations. This stress can affect the flywheel, depending on the stroke the speed may vary.
//Preeti//
Hey,
I am doing a small project on improving the performance of a flywheel in a single cylinder diesel engine. I am stuck at a point where I have to calculate torque on the flywheel. Information that I have is power of the engine is 5bhp, and rpm of the engine is 2600, I do not have any other information. Can anybody please help

Try looking up the formula to calculate horsepower. There are 3 three terms in it (and a constant); RPM, Torque, Horsepower. Given any two, the third can be found.

Tom.G said:
Try looking up the formula to calculate horsepower. There are 3 three terms in it (and a constant); RPM, Torque, Horsepower. Given any two, the third can be found.
My doubt, is it OK to use the power of the engine directly to calculate the torque on flywheel. Actually I am supposed to do an FEA analysis of that flywheel.

//Preeti// said:
My doubt, is it OK to use the power of the engine directly to calculate the torque on flywheel. Actually I am supposed to do an FEA analysis of that flywheel.
Well, an FEA analysis of the flywheel will not give you the torque produced by the motor.

SteamKing said:
Well, an FEA analysis of the flywheel will not give you the torque produced by the motor.
Since I want to do FEA analysis I need to put in the load conditions. Tats y I need the torque

Flywheel will experience hoop and radial stresses which can be analysed by standard means .

(2) Flywheel experiences additional loads when speed is changing as a result of :

(a) cyclic variation within one rotation of engine or load .
(b) more general load variation .
(c) scheduled changes under user control .

(3) During periods of speed change the flywheel experiences angular acceleration . Consider the flywheel as a notional nest of concentric rings with each ring driving the next outer (or inner dependent on +/- acceleration ) . This gives rise to shear stresses between the notional rings . Not too difficult to evaluate stresses analytically for constant value accelerations but needs a numerical procedure for non constant acceleration and in particular for in cycle accelerations which are commonly rapidly varying .

The basic hoop and radial stresses will additionally change as speed changes

(4) When speeding up or slowing down the flywheel is effectively either storing energy or giving it back to the crankshaft .

(5) The torque between crankshaft and flywheel always acts in such a way as to oppose speed variations . Thus the flywheel acts effectively to make a smoother running engine .

(6) Single cylinder slow running engines need the flywheel also to maintain running speed during the dead parts of the engine cycle .

Nidum said:
Flywheel will experience hoop and radial stresses which can be analysed by standard means .

(2) Flywheel experiences additional loads when speed is changing as a result of :

(a) cyclic variation within one rotation of engine or load .
(b) more general load variation .
(c) scheduled changes under user control .

(3) During periods of speed change the flywheel experiences angular acceleration . Consider the flywheel as a notional nest of concentric rings with each ring driving the next outer (or inner dependent on +/- acceleration ) . This gives rise to shear stresses between the notional rings . Not too difficult to evaluate stresses analytically for constant value accelerations but needs a numerical procedure for non constant acceleration and in particular for in cycle accelerations which are commonly rapidly varying .

The basic hoop and radial stresses will additionally change as speed changes

(4) When speeding up or slowing down the flywheel is effectively either storing energy or giving it back to the crankshaft .

(5) The torque between crankshaft and flywheel always acts in such a way as to oppose speed variations . Thus the flywheel acts effectively to make a smoother running engine .

(6) Single cylinder slow running engines need the flywheel also to maintain running speed during the dead parts of the engine cycle .
Thanks for the elaborate explanation nidum... Clearly in my case the flywheel will not be rotating in steady speed, depending on the stroke the speed may vary and hence there will be angular speed variations. But I am curious to know how much of this stress due to speed variations can affect the flywheel. I mean can I not just assume an average speed for stress calculations.

//Preeti// said:
But I am curious to know how much of this stress due to speed variations can affect the flywheel. I mean can I not just assume an average speed for stress calculations.

Depends on the application . For your present purpose stresses calculated from average running speed will be probably be perfectly adequate .

Just note that some flywheels have things like shaft couplings , clutch faces and drive gears built in . If you have any of these then further analysis is needed .

Nidum said:
Just note that some flywheels have things like shaft couplings , clutch faces and drive gears built in . If you have any of these then further analysis is needed .
But then I am not changing anything in those. My motto is to analyze the present flywheel then change its dimensions and again analyze it for improved inertia.

## What is a flywheel?

A flywheel is a mechanical device that stores rotational energy. It is typically a heavy disc or wheel that is attached to a rotating shaft and used to smooth out fluctuations in rotational speed.

## How do you calculate flywheel torque?

Flywheel torque can be calculated by multiplying the moment of inertia of the flywheel by its angular acceleration. This can be represented by the equation T = I * α, where T is torque, I is moment of inertia, and α is angular acceleration.

## What is the purpose of calculating flywheel torque?

Calculating flywheel torque is important in understanding the performance of a flywheel in a system. It can help determine how much energy the flywheel can store and how efficiently it can transfer that energy.

## What factors affect flywheel torque?

The two main factors that affect flywheel torque are the moment of inertia and angular acceleration. Other factors that can impact flywheel torque include the mass and shape of the flywheel, as well as any external forces acting on it.

## How is flywheel torque used in real-world applications?

Flywheel torque is used in various applications that require energy storage or stabilization of rotational speed. Some examples include flywheels in engines, energy storage systems for renewable energy, and gyroscopes in navigational systems.

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