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Very well written Ash, with the correct description of all the quantities. I, however, think that your paragraph: "Putting this into an easier example, think of it in terms of turning a crank to lift a water pail from a well. You have two people perform the task of turning the crank to raise the water pail. They both have equal strength; however, one of them can turn it faster. It should be clear that although they are exerting the same force, one of them will actually do more work than the other." When you say they both have the same strength and exert the same force, yet one can turn it faster, that means the person that is turning it slower is fighting some resistance or has a heavier pail. Otherwise, if they exert the same force on the pail, it's not possible for one to do it faster than the other because work is a function of force. Therefore, they must be exerting different amounts of force to be doing different amounts of work. For example:
If the pail requires 10 Newtons to be lifted, when they apply 10N of force, the pail will accelerate upwards at the same rate. The second person necessarily needs to apply more force to get the pail to accelerate upwards at a higher rate. So, I would think that torque is independent of the hp characteristics and considering the amount of force exerted compared to velocity achieved resulting in energy (work); are important to the equations.
:I know this has been a big debate not only on this forum, but on almost every car forum out there. I've been doing a bit of thinking about this over the months and think I have a reasonable answer to it.
:Simply defining: Torque is a measure of the twisting force produced by the crankshaft. It is not based on time or distance, and in common automotive terms its unit is foot-pounds, or ftlbs for short. If you were to attach a 1-foot long bar to a 21mm socket and attach it to the crank pulley bolt of a locked up engine (perhaps a rod failure, such that it wont turn) andd at the end of that rod you were to hang a 450 pound weight from it, you would be exerting 450 foot-pounds of force. Since the engine is locked up, nothing will move, nothing will turn, and no 'work' will have been done, but you still have a value of 'torque' exerted. In this case, nothing is happening, nothing is being done, and you just wasted your time and effort of rigging all this up to see 450ftlbs of torque doing nothing.
:Horsepower is a function of torque, meaning that in order to know how much horsepower you are making, you have to know the force used (in this case it is torque), what distance it went and for how long. When you apply a force to mass and move it a distance over a period of time, you have performed 'work'. Kindof like waking up in the morning, hauling your butt to work, doing your job, and then going home. Work is actually never over because you are continually moving your mass around over time. But if you move yourself around further or for longer, you would say that you have worked 'more', and you would be correct in saying so. On the contrary, if you just sit there, your butt is producing a force on your chair, but no work is actually done. You wouldn't get away with telling the boss that because you are sitting there on your chair and exerting a force on it that you are actually working, because you wouldn't literally be working by definition since you aren't moving over time. You could be fired on grounds of "employee produced a lot of torque with his fat ass, but produced no work.".. and you would go on your unemployed way, working your butt off hauling it likely to the nearest bar.
:So you order your favorite liquor shot and fire up your cig, shoot it down and request a second one. Your bartender has seen this behaviour before and sympathetically asks, "Too much torque?" You confirm, slam the second shot, and state that you dont understand why you can posess so much torque and not do anything.
:But the bartender is a smart cookie and tells you to watch as he walks over to the rack to grab the 750ml, walks back to the bar, and begins to pour another shot for you. "You see, I'm actually doing work by using force to move things around over time" he says.
:And then it becomes apparent to you. If you use force to actually move something over distance for a period of time, you have done work.
:Work is the transfer of energy from one physical system to another, especially the transfer of energy to a body by the application of a force that moves the body in the direction of the force. It is calculated as the product of the force and the distance through which the body moves and is expressed in joules, ergs, and foot-pounds.
:The dynomometer is an interesting piece of equipment: a large heavy roller that you accelerate with your wheels and the computer monitors the speed of the drum. You are performing work which transfers the energy produced at the wheels (which came from the engine) into the heavy drum. A dyno doesn't actually measure torque and only by monitoring the engine RPM can it backward calculate it from horsepower.
:TQ = HP*5252/RPM
:Accelerating your heavy Z down the track requires work as you are moving mass over distance and time. Torque is the root of power since it takes force to do work, but the car accelerates down the track at a rate consistent with the horsepower your car generates over its range of RPM you are operating in. It does not accelerate according to the torque curve.
:In an example I have personally witnessed, a Datsun 510 equipped with a B13 rotary engine that produced 500RWHP over the operating RPM of the engine when it is going down the track. Its torque peak was only 180ft/lbs at one RPM range and it fell as RPM increased. That car ran 8's in the 1/4 mile.
:There is always the group of old musclecar V8's at the track and they produce some sick torque numbers and launch out of the hole like slingshots, but they all tend to 'lay down' at the top end of the track and have lower MPH than a lot of Z's. Although they have a lot of torque, their HP #'s are usually lower and as I said before, the HP curve defines how the car will accelerate down the track.
:So which is better? Torque or horsepower? Its actually a very simple question to answer based on what they define, but it seemingly gets the best of people when they try and put all the other variables like traction, weight distribution, suspension, etc. into the equation. Power is the defining element of what you can actually do.
:Putting this into an easier example, think of it in terms of turning a crank to lift a water pail from a well. You have two people perform the task of turning the crank to raise the water pail. They both have equal strength, however, one of them can turn it faster. It should be clear that although they are exerting the same force, one of them will actually do more work than the other.
:Setting all the other variables aside, it seems pretty clear to me that in terms of building a powerplant for a drag car, in order to get the car to the other end quicker will require more horsepower over the range of RPM the engine is running within during the race as horsepower defines quantitatively how much work you can do.
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00:44:21 01/20/04
