How is torque measured?

[RomanV]

The one thing that confuses the issue of torque vs. Horsepower for me, is... the definition of 'torque'.

My understanding is that 'torque' is merely the force applied to the flywheel; whereas horsepower is the amount of work done in a set period of time. (one minute)


However, how is torque actually measured?
Since an engine delivers its power in 'pulses', it would make sense that they meausre the highest amount of torque produced by one of the pulses... However if this was the case, a V10 wouldnt necessarily make more torque than a single cylinder engine, as the maximum force exerted at one point in time is the same, assuming that there arent two pistons firing at the same time.

The only other way you could measure torque that makes sense, and seems more in line with reality, is to measure torque over a period of time, in which case the force of all 10 pistons in the V10 firing could be measured, as a force applied to the flywheel.

However if the measurement of torque happens over a period of time, (even if it is a very small period of time!) as opposed to instantly, how is horsepower relevant?
Since horsepower is merely a measurement of torque over a period of time... when torque is already measured over a period of time anyway.

'Horsepower' makes sense to me, if 'torque' is measured instantaneously, but this doesnt seem to be the case.

[strx7]

(HP x 5252) divided by RPM = Torque in lb/ft

[Silent Knight]

http://www.4x4abc.com/jeep101/torque.html

I haven't read through the whole thing yet but does that have the info you seek?

This one explains what torque exactly is...

http://www.physics.uoguelph.ca/tutorials/torque/Q.torque.intro.html

[Punter]

I thought torque was measured as the force required (placed on the flywheel) to stop the engine gaining rev when at full throttle. this would obviusly change at different revs.

[RomanV]

Punter, if that is the case, then measuring 'torque', as described in this context, must occur over a period of time.


If 'torque' already describes an amount of work done over time...

Then HP must be work, done over time, over time.......

[Punter]

Punter, if that is the case, then measuring 'torque', as described in this context, must occur over a period of time.

Well i suppose it is measured over time, but the value would not change. It will always be the same for a given rpm.

[Punter]

If 'torque' already describes an amount of work done over time...

Torque has no relation to time, it is simply a force at a distance from a fulcrum.

*edit:sp*

[RomanV]

Torque has no relation to time, it is simply a force at a distance from a fulcrum.

Well i suppose it is measured over time,

Got contradiction?
Actually, you just described incredibly well what I have been trying to say.
Torque, as measured in an automotive sense, doesnt seem to match the 'classical' definition of torque.... as it has to be applied over a period of time, as the power is delivered in 'pulses'. In which case, from what I can gather, HP ceases to be relevant...

Or at the least, it ceases to describe: 'work done over a period of time, as compared to a horse'.

[Punter]

Torque has no relation to time, it is simply a force at a distance from a fulcrum.

Well i suppose it is measured over time,[/b]

Got contradiction?
Actually, you just described incredibly well what I have been trying to say.
Torque, as measured in an automotive sense, doesnt seem to match the 'classical' definition of torque.... as it has to be applied over a period of time, as the power is delivered in 'pulses'. In which case, HP ceases to be relevant...

Yea i know what you mean, but in terms of a motor my understanding is that once the torque applied to a motor stops the motor from gaining speed, then the motor must be by definition applying the same force in the oppiste direction.

Once this torque value is found it has no relation to time.

[fivebob]

Torque is only measured over ime when using a rolling road dyno and deriving the value from the rate of acceleration of the drum. When using a dyno like the Dynapak the force is measured directly.

Either way the value of derived has no time component.

[Caveman]

Torque has no relavence to time.

Energy, or horse power is measured in watts, whichs is Joules per second.

One of the ways I understand the difference in power and torque, you can have a torque, but no power.

If I push against a wall and it doesn't move, im applying a torque, but no power is being exerted as no work is being done i.e. no movement.

Just like a chair sitting on the ground. A torque is being applied, but no work is being done.

I shouldnt actually use the word torque, more the word force. Torque is simply a moment or force couple about a fulcrum.

So the only way you can have power is if work is happening i.e. movement in the case of a car.

The engine has to spin something to create power.

A dyno will measure an equal and opposite force needed to stop the car. Power is derived from the torque and RPM.

grrrr too hard to explain. off to eat food.

[vvega]

its hard to wplain because you completely off the rails
yoube got the right idea
the right words but they are no portayed in any know lanquage

Torque – The measure of the force applied to a member to produce rotational motion usually measured in foot-pounds. Torque is determined by multiplying the applied force by the distance from the pivot point to the point where the force is applied.

the pure definition of torque is a rotational movement

pushing on a wall does not exibit torque
sittign on a chair does not exibit torque

torque is the ROTAIONAL eqivalent of force

to be honest i dont understand how so many people can have no idea about somthing that is taught in 5th form.......

v

[Jazza]

Torque in general is turning force.

[vvega]

Torque in general is turning force.

ffs
......
i give up

[Jazza]

It is

[Caveman]

its hard to wplain because you completely off the rails
yoube got the right idea
the right words but they are no portayed in any know lanquage

Torque – The measure of the force applied to a member to produce rotational motion usually measured in foot-pounds. Torque is determined by multiplying the applied force by the distance from the pivot point to the point where the force is applied.

the pure definition of torque is a rotational movement

pushing on a wall does not exibit torque
sittign on a chair does not exibit torque

torque is the ROTAIONAL eqivalent of force

to be honest i dont understand how so many people can have no idea about somthing that is taught in 5th form.......

v

Pushing on a wall will cause a force couple. It will cause a force x distance in the wall creating moments at each fixing point. It may also cause a resultant force in a particular direction.

A seat sitting on a floor will create bending moments across the surface. These can be represented as torques.

My english may be pretty crap at best. Hence why I stated I shouldnt actually use the word torque, more the word force. Torque is simply a moment or force couple about a fulcrum.

However if you get into the details you'll see there are moments in most equations.

oh and FYI im second year mechanical BE

[RomanV]

Torque – The measure of the force applied to a member to produce rotational motion usually measured in foot-pounds. Torque is determined by multiplying the applied force by the distance from the pivot point to the point where the force is applied.

I already knew this, even before the start of this thread.
That wasnt the nature of the question.

Perhaps I need to clarify myself.
As an example.
A single cylinder 4 stroke engine is spinning at 2000rpm.
A split second before combustion is to occur, how much torque is this engine producing, at this specific point in time?

And how much torque is it producing, at the instant point in time, just after combustion?

Are these two numbers different? yes.

If these two numbers are different, how can you say that the engine is producing xxx amount of torque at 2000rpm?
If you have a 10 cylinder engine that only fires one cylinder at a time, (and you take a measurement of torque at one instant in time) how can all 10 cylinders affect the torque output?

I suppose I could have restated my question as:

How is torque measured, when it isnt applied as a constant force?

[vvega]

A seat sitting on a floor will create bending moments across the surface. These can be represented as torques.



oh and FYI im second year mechanical BE

good for you
but flasshing a dgree your not even half way though does not impress me whatsoever

like i said this is 5th form stuff


ill put it simple
if its not a rotational movement it CANNOT be represented as torque

if you wish to argue that the please give me a book title and referance that will back up this

think of it as a paper where you have to give referance for all facts
been at uni and in your 2nd year you will be no stranger to this

http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/RotationalDynamics/DefinitionOfTorque.html

there is my referance
ill give you a online one because you wont have the books i have till you get to your 4th year

v

[RomanV]

Vvega, do you have an answer relating to the example above?

[sergei]

Well to say it bluntly they take value before and after and divide by 2 to get an average.
Say you apply 10 Nm for 10s then 20Nm for another 10s,here is the equation to get Torque out ofthat:
(10Nm * 10s + 20Nm * 10s) / ( 20s) = 15 Nm ! no time componet in result (20s is total time when torque was measured)