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Discussion Starter · #1 ·
I been a little bored latetly on the forum, so I thought I would like to start a little conversation about torque versus horsepower. Hopefully we can keep this civil. I will start with a statement that is fact. Torque is measurement of force( in the U.S commenly given in ft-lbs). Horesepower is the amount of work a engine can do,it is calculated by torque x rpm/5252. Assuming these statements are true(or close enough for our use) I am going to say 90ft-lbs is 90ft-lbs whether applied for 1 second or 1 year. 90ft-lbs is 90ft-lbs. So I ask to the people who stands behind the idea that torque is what accelerates your bike,why cant I take the engine off my bike place a torque wrench on the transmission shaft and make my bike quicker by cranking transmission by hand? I can easily deliver 110ft-lbs with 18 inch wrench.
 

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First Bike Bliss
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Well, by quicker, do you mean faster off the line, i.e., greater acceleration?

Given your numbers, you probably CAN accelerate the back wheel from 0 to .01 MPH in less time than the engine can. But acceleration is a change in velocity with respect to time. So, you will reach maximum velocity in a very short time and will no longer be able to maintain 110 ft/lbs of torque. So your acceleration will drop to 0, very quickly. On the other hand, the engine can continue to apply the same amount of torque over a much greater velocity, and continue to accelerate.

Now, as far as HP are concerned, you will never be able to turn that wrench anywhere near even the idle speed (~1000 RPMs). The best you could hope for is maybe 1 RPM. I don't think you were implying that you could generate more horsepower than the engine could, anyway.

Cheers,
 

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Discussion Starter · #5 ·
Well, by quicker, do you mean faster off the line, i.e., greater acceleration?

Given your numbers, you probably CAN accelerate the back wheel from 0 to .01 MPH in less time than the engine can. But acceleration is a change in velocity with respect to time. So, you will reach maximum velocity in a very short time and will no longer be able to maintain 110 ft/lbs of torque. So your acceleration will drop to 0, very quickly. On the other hand, the engine can continue to apply the same amount of torque over a much greater velocity, and continue to accelerate.

Now, as far as HP are concerned, you will never be able to turn that wrench anywhere near even the idle speed (~1000 RPMs). The best you could hope for is maybe 1 RPM. I don't think you were implying that you could generate more horsepower than the engine could, anyway.

Cheers,
Thanks for the reply.You are correct that I was not implying that I could produce more horsepower than the engine. I hear so many people say that torque is king and horsepower doesnt matter. That just isnt true when talking about performance. Both replys I have had have mention basically rpm and time which by definition is horsepower or wattage or work potential however you want to look at it.
 

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I'm your Huckleberry
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It all stems from people who have taken a basic physics course, and mis-apply the laws. They know just enough to be dangerous...not enough to get the answer correct.

Power is the rate at which work can be done. Max acceleration will always occur at max HP. A CVT (in a performance car...don't believe there is such a thing yet) will be set to this RPM for max acceleration runs.




Oh, also fun:

Your parking brake is applying a torque when you park on a hill ;)
 

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Oh, also fun:

Your parking brake is applying a torque when you park on a hill ;)[/QUOTE]

I think your parking brake is having a torque applied to it since it has no way of converting anything into power. The car on the hill however is using gravity to create motion which the brake is simply allowing to be stored as potential energy. maybe I'm wrong but I think that is what is happening.
 

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I'm your Huckleberry
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I think your parking brake is having a torque applied to it since it has no way of converting anything into power. The car on the hill however is using gravity to create motion which the brake is simply allowing to be stored as potential energy. maybe I'm wrong but I think that is what is happening.
You misunderstand...the car isn't moving (its parked). The brake is holding the car on a hill from moving. The brake is applying torque to the wheels to prevent the car from moving under the gravitational force trying to pull it down the hill. There is no power...none what so ever...but there is still a torque being applied.

To think about it in another way: grab a torque wrench, apply 30 ft-lbs to your axle nut. The nut won't rotate (hopefully :eek: ) but you are still applying a torque of 30 ft-lbs.

Point being: Applying torque does not mean anything moves. Torque is just a force multiplied by a radius ('moment arm'). Power, by definition, requires movement (force * distance / time or torque * angular velocity).
 

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Discussion Starter · #13 ·
You misunderstand...the car isn't moving (its parked). The brake is holding the car on a hill from moving. The brake is applying torque to the wheels to prevent the car from moving under the gravitational force trying to pull it down the hill. There is no power...none what so ever...but there is still a torque being applied.

To think about it in another way: grab a torque wrench, apply 30 ft-lbs to your axle nut. The nut won't rotate (hopefully :eek: ) but you are still applying a torque of 30 ft-lbs.

Point being: Applying torque does not mean anything moves. Torque is just a force multiplied by a radius ('moment arm'). Power, by definition, requires movement (force * distance / time or torque * angular velocity).
Does that go both ways? would the axle nut be applying force on me as well
 

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2x the bike for 1/2 the $
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I think your parking brake is having a torque applied to it since it has no way of converting anything into power. The car on the hill however is using gravity to create motion which the brake is simply allowing to be stored as potential energy. maybe I'm wrong but I think that is what is happening.
You are correct. By means of gravity, the weight of the vehicle is applying torque on the brake. not the other way around. The brake is inanimate. The force is the weight of the car, which would be set into motion against the inanimate brake, due to gravity.
 

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But isn't the wheel applying the rotational force since it is the moving part or the part trying to move like the torque wrench and the brake is the fixed object like the axle nut it can't move.
I understand the concept torque being a rotation force even in a stalled condition applied to an object that will rotate even if it snaps like a rusty nut if sufficient torque is applied
In your example if enough torque was applied the brake would yield.
and I guess to make matters worse the brake is using friction to hold back the torque applied by the wheel.

Anyway there's gravity,torque and friction at work in there somehow
 

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So, since we're just talking here .... how about this for an overly simplified view - since I have no scientific knowledge on the subject -

Torque is what speeds you up and horse power is what gets top speed.

or

I feel max torque in my butt and max horsepower makes my lips go wacka wacka while the bugs hit my teeth.


:biggrin:
 

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Discussion Starter · #18 ·
So, since we're just talking here .... how about this for an overly simplified view - since I have no scientific knowledge on the subject -

Torque is what speeds you up and horse power is what gets top speed.

or

I feel max torque in my butt and max horsepower makes my lips go wacka wacka while the bugs hit my teeth.


:biggrin:
Thanks for your input. A lot of riders I hang with say similar type things,but my stance is this.Torque is the force the engine puts on the crankshaft. Just that force.Much like my scenerio with the wrench on the transmission. I can generate more torque than your engine can so by your line of thinking I should be able to out accelerate you.I cant because while I can generate more torque than the engine my body cant spin the transmission fast enough to accelerate to a very high speed. Key word is work which is what horsepower is a measurment of. Torque with increasing rpm is what you feel in the seat of your pants. Which again is basically horsepower. Thats my view anyways. Like you said just talking, thanks for the conversation
 

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Anyone ever read on the transport ship engines? They make monsterous HP and torque, at like 600 RPM direct drive to the screw.

I think Kawa makes those too.
 
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