| Author | Message | ||
| Geronimo S. Realzola (Geronimo)
New member Username: Geronimo Post Number: 26 Registered: 1-2003 |
Anyone know a good Neuro surgeon? Great post Todd! | ||
| rich (Dino2400)
Member Username: Dino2400 Post Number: 428 Registered: 10-2001 |
I can't believe I read that whole thing! It was good though so thanks for posting it. Just remember to rev those cars high if you are interested in max acceleration! You have to be pretty far lower than your peak torque before it makes sense to shift. It seems in many cars that the factory marked redline is pretty darn close to the shift point in 1st and 2nd and then somewhat lower from that point on since the ratios are getting closer. (as an example, i calculated for the dino 2400 and while torque peak is at 4600, shift points were 8000, 7500, 7500, and 7000) | ||
| Rob Schermerhorn (Rexrcr)
Member Username: Rexrcr Post Number: 748 Registered: 11-2002 |
I wish I could take credit for the following, it is very well written and concise. Excellent examples. I have tried to contact the author, he has not returned my inquiries yet. I personally have not written any of the following text, though I agree will the entire contents. Best regards, Rob Torque and Horsepower - A Primer From Bruce Augenstein, [email protected] [Before I let Bruce explains the stuff, here's a quick summary. Remember that the magic number 5252 works only with torque in ft-lbs units. Torque in other units such as Newton Meters or kg-m require a different number. - Maximum acceleration at any speed occurs at the HP peak. - Maximum acceleration in any gear occurs at the torque peak - HP = torque * RPM / 5252 - torque = HP * 5252 / RPM - torque = HP at 5252 RPM HP is not measured directly, it is simply calculated from torque. However the HP to torque formula is useful to figure out how much torque the engine is making at peak HP. I wish when the car magazines do a road test they would include the torque and HP graph, gear ratios vs speed, 0 to top speed table in every 10 miles with G (acceleration) values... etc. - Frank] There's been a certain amount of discussion, in this and other files, about the concepts of horsepower and torque, how they relate to each other, and how they apply in terms of automobile performance. I have observed that, although nearly everyone participating has a passion for automobiles, there is a huge variance in knowledge. It's clear that a bunch of folks have strong opinions (about this topic, and other things), but that has generally led to more heat than light, if you get my drift  . I've posted a subset of this note in another string, but felt it deserved to be dealt with as a separate topic. This is meant to be a primer on the subject, which may lead to serious discussion that fleshes out this and other sub-topics that will inevitably need to be addressed. [Bruce hit it dead on. Anyone who's read UseNet for a period of time knows how much crap is on it. There are many knowledgeable folks posting quality discussions (in all newsgroups) but they are easily overshadowed by stupid posts. - Frank] OK. Here's the deal, in moderately plain English. Force, Work and Time If you have a one-pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done. If you unbolt the weight, and apply a force sufficient to lift the weight one foot, then one foot pound of work will have been done. If that event takes a minute to accomplish, then you will be doing work at the rate of one foot pound per minute. If it takes one second to accomplish the task, then work will be done at the rate of 60 foot pounds per minute, and so on. In order to apply these measurements to automobiles and their performance (whether you're speaking of torque, horsepower, newton meters, watts, or any other terms), you need to address the three variables of force, work and time. Awhile back, a gentleman by the name of Watt (the same gent who did all that neat stuff with steam engines) made some observations, and concluded that the average horse of the time could lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 foot pounds per second, or 33,000 foot pounds per minute, for an eight hour shift, more or less. He then published those observations, and stated that 33,000 foot pounds per minute of work was equivalent to the power of one horse, or, one horsepower. Everybody else said OK. For purposes of this discussion, we need to measure units of force from rotating objects such as crankshafts, so we'll use terms which define a *twisting* force, such as foot-pounds of torque. A foot-pound of torque is the twisting force necessary to support a one-pound weight on a weightless horizontal bar, one foot from the fulcrum. Now, it's important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynamometer) is torque, expressed in foot-pounds (in the U.S.), and then we *calculate* actual horsepower by converting the twisting force of torque into the work units of horsepower. Visualize that one pound weight we mentioned, one foot from the fulcrum on its weightless bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (Pi * a two foot circle), and, incidentally, we have done 6.2832 foot-pounds of work. OK. Remember Watt? He said that 33,000 foot-pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per revolution of that weight into 33,000 foot pounds, we come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 foot pounds per minute of work, and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it's the equivalent of 1/2 horsepower (16,500 foot pounds per minute), and so on. Therefore, the following formula applies for calculating horsepower from a torque measurement: Horsepower = (Torque * RPM)/(5252) This is not a debatable item. It's the way it's done. Period. The Case For Torque Now, what does all this mean in car land? First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same. In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*. You don't believe all this? Fine. Take your non-turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? The Case For Horsepower OK. If torque is so all-fired important, why do we care about horsepower? Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*. For an extreme example of this, I'll leave car land for a moment, and describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which was connected to the works inside a flourmill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2600(!) foot pounds of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drive wheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice . On the other hand, twelve rpm of the drive wheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us: 6 HP. Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited. At The Dragstrip OK. Back to carland, and some examples of how horsepower makes a major difference in how fast a car can accelerate, in spite of what torque on your backside tells you . A very good example would be to compare the current LT1 Corvette with the last of the L98 Vettes, built in 1991. Figures as follows: Engine Peak HP @ RPM Peak Torque @ RPM ------ ------------- ----------------- L98 250 @ 4000 340 @ 3200 LT1 300 @ 5000 340 @ 3600 [Numbers for 94 Integra LS/RS and GS-R Engine Peak HP @ RPM Peak Torque @ RPM ------ ------------- ----------------- B18B 142 @ 6300 127 @ 5200 B18C 170 @ 7600 128 @ 6200 If you overlap the torque curve for B18B and B18C, you'll see that B18C's maximum torque (127 vs. 128 ft-lbs) is about the same as B18B, except B18C's torque curve just keeps on climbing, thus the much higher HP. B18B and B18C are quite similar, but not identical. Mostly notably the B18B has slightly longer stroke, which gives it the displacement of 1835 cc vs. B18C's 1797 cc. The stroke explains why the B18B has better low end, and it is also a factor why it revs slower and has lower redline than B18C. [Monitor YAHP for an article that will talk about the basic relationship between bore and stroke. - Frank] The cars are geared identically, and car weights are within a few pounds, so it's a good comparison. First, each car will push you back in the seat (the fun factor) with the same authority - at least at or near peak torque in each gear. One will tend to *feel* about as fast as the other to the driver, but the LT1 will actually be significantly faster than the L98, even though it won't pull any harder. If we mess about with the formula, we can begin to discover exactly *why* the LT1 is faster. Here's another slice at that formula: Torque =(Horsepower * 5252)/(RPM) If we plug some numbers in, we can see that the L98 is making 328 foot pounds of torque at its power peak (250 hp @ 4000), and we can infer that it cannot be making any more than 263 pound feet of torque at 5000 rpm, or it would be making more than 250 hp at that engine speed, and would be so rated. In actuality, the L98 is probably making no more than around 210 pound feet or so at 5000 rpm, and anybody who owns one would shift it at around 46-4700 rpm, because more torque is available at the drive wheels in the next gear at that point. On the other hand, the LT1 is fairly happy making 315 pound feet at 5000 rpm, and is happy right up to its mid 5s redline. So, in a drag race, the cars would launch more or less together. The L98 might have a slight advantage due to its peak torque occurring a little earlier in the rev range, but that is debatable, since the LT1 has a wider, flatter curve (again pretty much by definition, looking at the figures). From somewhere in the mid range and up, however, the LT1 would begin to pull away. Where the L98 has to shift to second (and throw away torque multiplication for speed), the LT1 still has around another 1000 rpm to go in first, and thus begins to widen its lead, more and more as the speeds climb. As long as the revs are high, the LT1, by definition, has an advantage. Another example would be the LT1 against the ZR-1. Same deal, only in reverse. The ZR-1 actually pulls a little harder than the LT1, although its torque advantage is softened somewhat by its extra weight. The real advantage, however, is that the ZR-1 has another 1500 rpm in hand at the point where the LT1 has to shift. There are numerous examples of this phenomenon. The Integra GS-R, for instance, is faster than the garden variety Integra, not because it pulls particularly harder (it doesn't), but because it pulls *longer*. It doesn't feel particularly faster, but it is. A final example of this requires your imagination. Figure that we can tweak an LT1 engine so that it still makes peak torque of 340 foot pounds at 3600 rpm, but, instead of the curve dropping off to 315 pound feet at 5000, we extend the torque curve so much that it doesn't fall off to 315 pound feet until 15000 rpm. OK, so we'd need to have virtually all the moving parts made out of unobtanium :-), and some sort of turbocharging on demand that would make enough high-rpm boost to keep the curve from falling, but hey, bear with me. If you raced a stock LT1 with this car, they would launch together, but, somewhere around the 60 foot point, the stocker would begin to fade, and would have to grab second gear shortly thereafter. Not long after that, you'd see in your mirror that the stocker has grabbed third, and not too long after that, it would get fourth, but you'd wouldn't be able to see that due to the distance between you as you crossed the line, *still in first gear*, and pulling like crazy. I've got a computer simulation that models an LT1 Vette in a quarter mile pass, and it predicts a 13.38 second ET, at 104.5 mph. That's pretty close (actually a tiny bit conservative) to what a stock LT1 can do at 100% air density at a high traction drag strip, being power shifted. However, our modified car, while belting the driver in the back no harder than the stocker (at peak torque) does an 11.96, at 135.1 mph, all in first gear, of course. It doesn't pull any harder, but it sure as hell pulls longer . It's also making *900* hp, at 15,000 rpm. Of course, folks who are knowledgeable about drag racing are now openly snickering, because they've read the preceding paragraph, and it occurs to them that any self respecting car that can get to 135 mph in a quarter mile will just naturally be doing this in less than ten seconds. Of course that's true, but I remind these same folks that any self-respecting engine that propels a Vette into the nines is also making a whole bunch more than 340 foot pounds of torque. That does bring up another point, though. Essentially, a more "real" Corvette running 135 mph in a quarter mile (maybe a mega big block) might be making 700-800 foot pounds of torque, and thus it would pull a whole bunch harder than my paper tiger would. It would need slicks and other modifications in order to turn that torque into forward motion, but it would also get from here to way over there a bunch quicker. On the other hand, as long as we're making quarter mile passes with fantasy engines, if we put a 10.35:1 final-drive gear (3.45 is stock) in our fantasy LT1, with slicks and other chassis mods, we'd be in the nines just as easily as the big block would, and thus save face . The mechanical advantage of such a nonsensical rear gear would allow our combination to pull just as hard as the big block, plus we'd get to do all that gear banging and such that real racers do, and finish in fourth gear, as God intends. :-) The only modification to the preceding paragraph would be the polar moments of inertia (flywheel effect) argument brought about by such a stiff rear gear, and that argument is outside of the scope of this already massive document. Another time, maybe, if you can stand it . At The Bonneville Salt Flats Looking at top speed, horsepower wins again, in the sense that making more torque at high rpm means you can use a stiffer gear for any given car speed, and thus have more effective torque *at the drive wheels*. Finally, operating at the power peak means you are doing the absolute best you can at any given car speed, measuring torque at the drive wheels. I know I said that acceleration follows the torque curve in any given gear, but if you factor in gearing vs. car speed, the power peak is *it*. An example, yet again, of the LT1 Vette will illustrate this. If you take it up to its torque peak (3600 rpm) in a gear, it will generate some level of torque (340 foot pounds times whatever overall gearing) at the drive wheels, which is the best it will do in that gear (meaning, that's where it is pulling hardest in that gear). However, if you re-gear the car so it is operating at the power peak (5000 rpm) *at the same car speed*, it will deliver more torque to the drive wheels, because you'll need to gear it up by nearly 39% (5000/3600), while engine torque has only dropped by a little over 7% (315/340). You'll net a 29% gain in drive wheel torque at the power peak vs the torque peak, at a given car speed. Any other rpm (other than the power peak) at a given car speed will net you a lower torque value at the drive wheels. This would be true of any car on the planet, so, theoretical "best" top speed will always occur when a given vehicle is operating at its power peak. "Modernizing" The 18th Century OK. For the final-final point (Really. I Promise.), what if we ditched that water wheel, and bolted an LT1 in its place? Now, no LT1 is going to be making over 2600 foot pounds of torque (except possibly for a single, glorious instant, running on nitromethane), but, assuming we needed 12 rpm for an input to the mill, we could run the LT1 at 5000 rpm (where it's making 315 foot pounds of torque), and gear it down to a 12 rpm output. Result? We'd have over *131,000* foot pounds of torque to play with. We could probably twist the whole flour mill around the input shaft, if we needed to . The Only Thing You Really Need to Know Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*." Thanks for your time. Bruce | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 909 Registered: 4-2002 |
"So why does the HP curve and Torque curve look completely different?" Because HP = TQ * RPMs / 5252 And the horizontal scale is RPMs So if TQ if flat; then HP is rising linearly "if its true that you could plot the HP curve as a function of Torque, then how come the published curves dont match?" HP = TQ * RPMs / 5252 of TQ = HP / RPMs * 5252 So it is as easy to get one from the other as vice versa. Simple math, surprising implications. But in response to Chris: one CAN measure HP directly with a bolometer (a device that measures the amount of heat produced). But it is vastly easier to measure a force and do the simple calculations than to use a bolometer in a thermally isolated environment. | ||
| Chris Tanner (Ctanner)
Junior Member Username: Ctanner Post Number: 62 Registered: 5-2001 |
You can only measure torque. It is measured on a dynometer. Horsepower cannot be measured. It can only be calculated, by using the formula shown at the beginning of the thread. All torque/horsepower curves cross at 5250 rpm, check the math. Both torque and horsepower are important components in evaluating an engine. As mentioned previously, torque is the rotational force that moves the car. High torque that comes on at low rpms is what gives you that kick in the pants feel when you accelerate. Because of the formula, horsepower is low at low rpms. However, horsepower climbs with rpm, even as the torque is decreasing. Horsepower is a function that lets us take advantage of gearing. As the rpms go up, horsepower goes up, more work is being performed. Ideally, a car would have one gear and constant torque, you could run the rpms to infinity, and work would still be done. No shifting would keep the horsepower from dropping with every gear change, which is what happens when rpms drop. Now this is unreasonable on earth, but essentially, the goal of a high rpm engine is to taking advantage of gearing to produce more work. In real life, as the rpms go up, we can tell there is a point that the car isn't pulling as hard when we accelerate. Torque is falling off so fast that rpms cannot compensate, so we shift to the next gear. The rpms will be lower, but the torque will be higher, therefore, more horsepower is available to propel us down the street. In terms of which is most important for a car, it depends on what you are doing with the car.....road racing, drag racing, towing. In road racing, higher revving engines seem more common because a smaller engine can be used that revs high, produces horsepower even though torque is decreasing, has light weight, can be packaged easier in the car. Drag racing stop lights, I'll take a high torque engine. The kick the high torque engine gives feels great. Think big V-8, or even better, a Viper. Big torque at low rpms gives the initial jump to get your car out in front. Towing your race car home from the track, you want a truck that has lots of torque at low rpm. You don't want to rev the engine up to 5000 rmp just to get the trailer moving off the line. In summary, (1) you can't have horsepower without torque (2) Torque gets your car moving (3) Horsepower lets you take advantage of gearing. | ||
| William Henderson (Billh)
Junior Member Username: Billh Post Number: 68 Registered: 5-2002 |
So why does the HP curve and Torque curve look completely different? if its true that you could plot the HP curve as a function of Torque, then how come the published curves dont match? | ||
| DES (Sickspeed)
Senior Member Username: Sickspeed Post Number: 5452 Registered: 8-2002 |
i emailed this thread to a friend; he didn't have time to reply here, but gave me a quick thingie to post: "Torque = Rotational Force in Newton-meters. Work = Torque * Distance, (radians/sec which is translated into Rotations/minute or RPM), and the ability to do work as a function of time is Power, expressed as Horsepower by means of James Watt's equation. Therefore, T*D/Time= Power." Flat12, i'll see if i can get him to dress it up in a non-auto, non-math equation... | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 632 Registered: 5-2002 |
Todd, Steven, I don't think either of you got it. Torque is the twisting FORCE, thrust is a pushing FORCE. They are basically equivalent and only tell you � the story. You need HP too, so car, airplane and space shuttle engines are rated for both. In the case of and airplane, you can have 2 engines that both have 100 lbs of thrust, both blows the air at 100 mph, the other at 200 mph, the 200 mph engine has twice the hp and the plane will fly twice as fast. hmmmm a simple example in. A child�s teeter-totter is a good example. You sit on one end, a child on the other and adjust lengths until it is balance, you both pick up your feet and it doesn�t move. Say you are sitting 5 feet from the pivot, the child 10 feet. You weight 200 lbs, the child 100 lbs. The torque for you is 5 times 200 or 1000 ft-lbs, and the child�s is 100 times 10 or 1000 ft-lbs. The torques are equal, so it balances. The difference comes when you start it moving. Because the child is twice the distance from the pivot, they will move twice the speed you will. You are making the child move twice as fast as the child is moving you. You have twice the hp the child does. That�s as simple as I can make it. | ||
| stephen r chong (Ethans_dad)
Member Username: Ethans_dad Post Number: 347 Registered: 3-2002 |
Art, Wouldn't the Shuttle be producing 'thrust' in lbs/ft of lift? All you flyers out there can chime in; are aircraft engines rated in HP or some other more useful aviation unit? I know... OT warning coming this way. | ||
| todd (Flat12)
New member Username: Flat12 Post Number: 6 Registered: 7-2003 |
I now understand torque is the rotational energy and horsepower is , well the power. but I'm still confused. Can someone turn this into a non-auto non-math equation? ie story problem using vegetables or the turtle and hare. I need some more analogies I guess. | ||
| arthur chambers (Art355)
Intermediate Member Username: Art355 Post Number: 2128 Registered: 6-2001 |
Torque is what moves the car. It's the force produced each RPM. HP is the power caused by Torque and RMP. More torgue equals more power, same torque, higher RPM equals more power. It used to be that engines made their torque at low RPM, and thus they had high torque. Nowadays, the engines turn a lot of RMPs and the torque is less. We have smaller cubic inches than we did, but because the engines turn higher RPMs, the cars accelerate as well, if not better. Art | ||
| Lawrence Coppari (Lawrence)
Member Username: Lawrence Post Number: 717 Registered: 4-2002 |
I'm starting to feel physical and mathy again. | ||
| Robert McNair (Rrm)
Member Username: Rrm Post Number: 547 Registered: 5-2002 |
Uh Oh this could be trouble............. | ||
| steve coleby (Ferraridriver)
Junior Member Username: Ferraridriver Post Number: 101 Registered: 6-2003 |
Hi BHP sells cars. Torque wins races! Steve | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 890 Registered: 4-2002 |
I will borrow a couple of equations from "Tell me about driving around at High RPMs" f = M * a p/v = M * a Power divided by velocity is a force. When the velocity is zero the P/V term is "nonsensical" but implies taht power must have gone to zero also. This is why TQ dominates the bottom end--the P/V term is nonsensical. Another way to look at it, is that HP represents TQ at high RPMs in a way that is independent of gearing. Force causes the acceleration, acceleration causes speed, speed causes distance. | ||
| Dave (Dave)
Member Username: Dave Post Number: 545 Registered: 4-2001 |
An old gentleman once said H.P. makes you go fast... Torque wins races... | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 622 Registered: 5-2002 |
Todd' If it's spinnig it's torque. If it is pushing in a direction, it's force. So all the flames coming out the shuttle result in a force, that does the work of moving the shuttle. The hp part is how fast the work gets done. | ||
| Ben Cannon (Artherd)
Member Username: Artherd Post Number: 577 Registered: 6-2002 |
Here's a thought on torque... http://www.caranddriver.com/article.asp?section_id=4&article_id=1919 | ||
| Tim N (Timn88)
Advanced Member Username: Timn88 Post Number: 3279 Registered: 6-2001 |
Todd, all that energy coming out of the back of the shuttle is doing work on the shuttle. a good way to think of work is to think work is when the momentum of something is changed. Power is just the rate at which the change happens. this threa is going to drag on forever. | ||
| todd (Flat12)
New member Username: Flat12 Post Number: 5 Registered: 7-2003 |
So torque could be all the flames/heat/energy coming from the space shuttle launcher( I know it's in joules sp?)), and horsepower would be when it actually leaves the ground. | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 620 Registered: 5-2002 |
Steve, I have a couple German freinds that are always giving me Power and torque in kw and kN-m. BTW, 1 rpm = 2(3.14)radians/60 sec = .104, or divide by the reciprocal = 9.550 The torque is generally quoted in kN-m, so divide be 1000 = 9550 | ||
| Lawrence Coppari (Lawrence)
Member Username: Lawrence Post Number: 714 Registered: 4-2002 |
Holy merde,here we go again. | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1961 Registered: 1-2001 |
The equation that Mark posted is only valid for the following units: power (horsepower) torque (foot-pounds) RPM or rotational speed (rev/min) but you could also use the equation: Torque x Rotational Speed / 9550 = Power if the units are: power (kiloWatts) torque (Newton-meter) rotational speed (rev/min) So my question (for the non-US based FCers) is: Is engine "power" usually/typically/sometimes/never referred to as HP or kW? And the same for "torque" -- is it ft-lbs or N-m? Kind of interesting that RPM is universal (and it's not radians/second somewhere) for rotational speed... | ||
| John B (John_b)
New member Username: John_b Post Number: 35 Registered: 5-2003 |
Torque is tortional (twisting) force but is not "work". "Work" happens when mass is moved. i.e. when you put a wrench on a really tight bolt and push really hard on it but it is not moving you are generating torque, perhaps 250 ft/lbs, but are actually acomplishing no "work" and consequently no HP as you are not moving the nut. Once the nut begins to move you are generating HP as you are moving it. Mark is correct in that HP=Tourque*RPM / 5250. Observe that if RPM = 0, HP = 0. Consequently you dont "feel" Torque, only HP. There are lots of misconceptions about this, I hope this helps. | ||
| Oldslow308 (Djparks)
Member Username: Djparks Post Number: 405 Registered: 2-2003 |
I was told that torque is the POTENTIAL twisting force available to do the work. There was great discussion in the previous thread on how these values change character and value as soon as motion occurs. | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 884 Registered: 4-2002 |
Torque does the work, HP takes the credit! | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 1968 Registered: 11-2002 |
Here's some Torque figures to mull over. :-) ************************************************* From 0 to 300 km/h in under 14 seconds To blink even once, for a fraction of a second, could mean missing part of the excitement: the Bugatti EB 16-4 Veyron all-wheel-drive sports car needs scarcely 14 seconds to reach a speed of 300 kilometers an hour - an unsurpassed figure, though admittedly a largely theoretical one. What determines the Bugatti's character even more convincingly is the engine's unbelievable flow of torque. When exposed to the full 1,250 Newton-meters (922 lbs-ft of torque), the resistance of the air and even the force of gravity itself seem to have no chance: the EB 16-4 Veyron eats up the road as if these physical laws had just been abolished.;-) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 616 Registered: 5-2002 |
Torque is the force you have to turn the or do work. HP is the rate the torque is available at. For example, say it takes 10 ft-lbs of torqure to turn your wheels and push the car and the wheel. If you have a 1 hp, it can turn the wheel at 1x5250/10 = 525 rpm. If you have a 10 hp engine you can turn the wheel 5250 rpm and go 10 times faster. Or if you want to accelerate, you can send 10 times more torque to the wheel and accelerate 10 times faster. TOrque does the work, hp tells you how fast. | ||
| Hubert Otlik (Hugh)
Intermediate Member Username: Hugh Post Number: 1083 Registered: 1-2002 |
so, there's this thread, by the name of "tell me about driving at high rpm's" there's about 400 + posts on the topic. look it up. a good read. | ||
| Mark (Markpdx)
Junior Member Username: Markpdx Post Number: 77 Registered: 4-2003 |
Torque x RPM / 5250 = Horsepower | ||
| Tom Bakowsky (Tbakowsky)
Member Username: Tbakowsky Post Number: 482 Registered: 9-2002 |
OOOhhhh boy another 400 posts | ||
| todd (Flat12)
New member Username: Flat12 Post Number: 4 Registered: 7-2003 |
Would someone explain the difference in these to me. I know there is rotational power, flywheel power, rear wheel power but am confused as horsepoweer vs torque. |