| Author | Message | ||
     45_degrees |
Horsepower is work. Torque is a force. You don't feel work, but you do feel force. | ||
| Molly_hatchet |
like some im no engineer,,,but...ive been riding bikes for well over 25 years...i started out on 2 stroke dirt bikes....as soon as i was big enough i moved to the 500 class cause i was faster on a bigger bike....for me not nearly as much shifting i could take my KX 500 into a corner in 3 gear and blast out just by feathering the clutch a little...on the 125 it was all gear banging all the time....when i moved to street bikes it was all about the RD's it felt like my dirt bike.....my dad allways had harleys...so when again i was big enough i took that ole chopper fer a ride...the power felt like i could rape an ape through the corners if i could just harness that motor in a frame that was made for handling.....i can remember seeing the old harley cafe racer...i wanted one sooo bad...so for me its all about easy ,smooth ,useable power,,,,ive had big liter jap bikes and its kinda the same but not nearly as useable as the buell....im faster on the buell and not nearly as prone to OMG moments as i was on the R-1 .....im not a big fan of a smoking tire goin around a corner while gettin on the gas....if u watch supercross the smart guys keep low off the jumps cause all the show gets u nowhere its all about keeping the power to the ground...and once aaaagain...ive never met anybody that can actualy use a liter bike to its potential..sure its fun to say i have a busa...if u aint usin it ...ur a poser....and wasnt this buell rumors not buell horsepower bashing...we do this like every month in a new thread....if u want a duc...great u want a gixxer fantastic....want a ZX10 groovy...want an aprilla...go for it....i dont bash ur bike i love all motorcycles....hell id love to have a badass chopper....stay off my horsepower rating til u can come whoop me at the track aaaiiight. | ||
| Spike |
I'm aware of what torque is, it's rotational force. However, rotational force on its own doesn't do anything for us. It's how fast the rotational force gets something done that matters, and that's called power. I've already stated that the dyno measures work over time to give us power, and if the technical description of that is that it measures torque over time so be it. My statement about the dyno measuring horsepower and calculating torque was incorrect, or at least not specific enough. The correct statement would be that the dyno measures rear-wheel torque over time to determine the power output of the engine, but then needs to be told the engine rpm to calculate the actual torque output at the engine. The fact remains that the output it gives us is power, and it needs engine RPM to calculate the actual torque at the engine. The fact also remains that power output determines how fast we get down the road. The example of this is the engine with 50 more horsepower. I thought someone surely would have mentioned it, but the engine with 50 more power is producing more torque through the rpm range where the extra power is produced. Since we know that the engine with 50 more horsepower will accelerate faster, we know that power is what determines acceleration, not torque. We could try to rephrase it and say that torque at rpm is what determines acceleration, but there's a word for torque at rpm, and that word is power. | ||
| Spatten1 |
Wow! If you are talking physics, math and definitions, I have to give it to Spike and Reep. If you are talking slang, the other side is correct. One definition is technically derived. The other is not technically or mathmatically correct, but a common usage to describe low RPM power. Mathmatically, HP measures work performed, which is acceleration or forward movement against resistance. Torque measures static force, like a wrench on a stuck bolt. Until the bolt spins, there is no movement, no RPM, no accelereation, and technically no work performed. When on the bike you only feel the acceleration, which is work performed, measured by HP. If you had no tach and could not hear, you would only feel the HP in the form of acceleration. You would not know if it is (high torque X low rpm), or (low torque X high rpm). You only know how hard you accelerate, Horsepower. | ||
| Perry |
>>We could try to rephrase it and say that torque at rpm is what determines acceleration, but there's a word for torque at rpm, and that word is power. Spike is right on. Think of that beautiful FLAT torque curve. Imagine it was actually perfectly flat. Anyone thinking that the acceleration of the bike is the same at 1500 RPM as it is at 6500? No. On a perfectly flat torque curve you would experience exactly twice the accelerating force at twice the RPM. In other words, the HP curve would become a straight line as well, pointed up and to the right. Since the torque curve isn't really flat, it isn't a perfectly linear relationship between accelerative force and RPM. But the power is what accelerates you, and what you feel when you hit the throttle. A simplistic way to summarize is that torque measure force PER STROKE, while horsepower is measuring the total force being output by the engine. | ||
| Spatten1 |
In defense of the guys that "feel torque": At lower RPM, a Buell makes more power than a bike with lower torque at the same low RPM. I still think you are feeling the horsepower, not the torque. But... at that low RPM you will feel more acceleration if the torque rating is higher. | ||
| 45_degrees |
Wiseacres. | ||
| Molly_hatchet |
god i feel like im back in school...there isnt gonna be any homework on this is there....personaly..i think its all a bunch of crap its like listening to a bush speach....round and round we go while getting nowhere....ya'll can spout ur book learnin all ya want...it dosent take a genious to tell me that a gixxer is faster than my bike but off the line and through the corners il eat hs ass up....im glad ass hell im not as smart as some of u guys...too much thinkin not enough ridin fer me....have fun ladies when ya'll aarr done...lets ride. | ||
| Spatten1 |
Yeah, school sucks. Motorcycles are cool. Buells are cool. Riding is better than debating.  | ||
| 45_degrees |
Spatten and Perry... I can't see how you think Spike and Reepi are correct in their physics... They don't even understand basic physics! You don't either. Power is not a force. It is WORK done over a period of TIME. Torque is a force. Time is not part of the equation in torque. Acceleration is not torque. Acceleration is not horsepower. Debating is useless. I agree. Especially when there are wiseacres spewing out nonsense, calling perception reality. It then turns into misleading crap. | ||
| 45_degrees |
Probably will hear next that liquids can be compressed because they were able to "squeeze" a little more gas into their frame. | ||
| Spike |
I'm sure it's fun to just call people names and claim the opponent is wrong, but wouldn't it be more productive to leave the name-calling out of it and state facts that prove the other side is wrong? Which part of my last post disagrees with anything in your last post? | ||
| Ridrx |
45, This is useless, trying to explain physics to "the dyno guy told me" crowd is futile. Once again the masses are sucked in.  Wonder why diesels are so popular with all that pointless tq? My neighbor has an F350 SD Turbo diesel...on the almighty dyno it makes a whopping 328 hp and 621 lb/ft,yet somehow will still spank his own 400hp cobra...go figure? | ||
| 45_degrees |
"I've already stated that the dyno measures work over time to give us power, and if the technical description of that is that it measures torque over time so be it." This statement is confusing and incorrect. I never claimed to be a physicist. Torque is not power, but a force. Time is not part of the equation. I apologize if you are offended by the "name calling". However, it is more of a description than a title. | ||
| Spike |
How is it incorrect?
Time is not part of measuring torque, but it is a part of the equation when measuring power. A dyno gives us power output, therefore time is part of the equation.
Nice. Might as well say, "I'm not calling you an idiot because I think you're an idiot. I'm calling you an idiot because you actually are an idiot." How is that actually a defense to calling someone something? | ||
| Thepup |
45 degrees and Ridrx,a Japanese IL4 sportbike has a better 1/4 mile time and a better 60-80 and 80-100 times,all with less torque.I guess HP does count for something. | ||
| Spike |
Dyno both of them and lay the two charts on top of each other. If the F350 is faster, it has to be averaging more power over the whole RPM range. | ||
| Spike |
Here's a fun one, earlier you said this:
So torque can be measured without any movement, but power cannot. How then can we say that torque is what determines how fast something moves or accelerates? Would it not be possible to have 10,000ft-lbs of torque and zero horsepower so long as no movement took place? As soon as movement takes place, wouldn't we then have a measurable amount of power? How does that not prove that power output is the determining factor for movement? | ||
| Blake |
Spike is exactly correct. An inertial dynamometer does not measure torque. Besides, the torque reported by chassis dynamometers is the torque at the crank. The torque at the rear wheel is something else entirely. All an inertial dyno actually measures is the time interval between each rotation of the drum. Power = Force*Velocity Power = Force*(Displacement/Time Interval) For angular (rotational) systems the above translates to... Power = Torque*Angular Velocity Power = (Force*Distance)*(Angular Displacement/Time Interval) So how can a dyno report power without measuring Torque? A valid question. The answer is that there are other ways to calculate power than from torque. The inertial dyno software uses the known constant mass moment of inertia (M.O.M.) of the drum and it's angular acceleration (determined from the measured time intervals of each drum rotation) instead. How? Read on for a hint to this mind wrenching pun intended) ![: ]](http://www.badweatherbikers.com/buell/clipart/proud.gif) puzzle. Let's start by remembering that Force equals Mass times Acceleration (F=M*A), so we can rewrite the equations above without the "Force"; we can use "Mass * Acceleration" in its place. Cool! Power = Mass * Acceleration * Velocity Now we can rewrite the above equation by remembering that Acceleration = Change in Velocity/Time Interval... Power = Mass * (Change in Velocity/Time Interval) * (Displacement/Time Interval) And when we combine like terms we get... Power = Mass * Change in Velocity * Displacement / (Time Interval)2 In angular (rotating terms we have a slightly different set of equations, but in the same form... Power = M.O.M. * Angular Acceleration * Angular Velocity Power = M.O.M. * (Change in Angular Velocity/Time Interval) * (Angular Displacement/Time Interval) Power = M.O.M * Change in Angular Velocity * Angular Displacement / (Time Interval)2 Can we calculate the thrust force or the torque? Sure can. Torque = M.O.M. * Angular Acceleration So how does the dyno software know/figure the velocity and acceleration? Anyone? Really fun stuff!  (Message edited by Blake on March 07, 2007) | ||
| Spatten1 |
Nice engineering Blake. "So how does the dyno software know/figure the velocity and acceleration?"} Assuming you mean the Dynojet accelerometer type, is it just a sensor on the drum that gives the drum's RPM? The mass and Diameter of the drum are known variables in the equation, so doesn't the software just need to measure drum speed/ drum speed squared? With a load type dyno, the electrical current or water flow used to slow the drum would be used in addition to the calculation of drum mass, but still known variables that are quantifiable. Am I close? | ||
| Spike |
I might be missing the forest for the trees, but I don't think I understand the question. Isn't the dyno recording the RPM of the drum, and can't it determine velocity simply by knowing the RPM and the diameter of the drum? From there it only needs to monitor the change in velocity over time to figure the acceleration. . . . or did I miss the question entirely? | ||
| 45_degrees |
Spike... you are misunderstanding my point entirely... I never said that power was not important to create acceleration. I basically said torque is required to produce power in our bikes. Just my point about the zero rpm torque measurement. You claimed a dyno can produce power numbers without torque. But what causes the drum on the dyno to spin??? Horsepower? No. Again... horsepower is not a force. It is work. Ridrx pretty much nailed it on the head with the power formula. That should have been enough. | ||
| Terribletim |
WOW! Were there some rumors in here somewhere? This whole thread is WAY over my head! Can you measure the torque applied by my shoe? Do Nikes have more torque than Reeboks? And what about Vans? They're back in style all of a sudden. . .   Here is what I know from driving my racecar. . .Torque makes my tires spin instead of grab coming off the turns. Horsepower hauls my butt down the straights. Torque gets my trailer moving from the red lights on the way to the track. Does that help anyone?  When I was in high school I was known as my school's "burnout king". My secret was, my car made a ton more torque than everyone else and could sit there roasting tires until they blew. Don't ask how I know it could do that. . . It was a long walk home. . . Tip from me to you, Carry a spare, or two if you have posi. | ||
| Spike |
But you did say it was torque that was responsible for acceleration. Since an infinite amount of torque can exist without motion, torque cannot be the cause of motion.
I never stated such a thing. I stated the dyno can produce power numbers without knowing torque. Of course torque is being exerted while the rollers are spinning.
You already stated that torque can exist without motion. Power cannot. From that, we can logically deduce that power is required for motion, and thus more power is required for more motion.
I agree the formula is correct, but it doesn't prove anything about how an object moves. | ||
| Reepicheep |
If I don't understand physics, you don't understand the role of a transmission  A properly geared bike that makes more horsepower will accelerate faster, period. Acceleration is a result of work. If you have two bikes, one making more torque then the other, but both limited to the same maximum RPM, the bike with more torque is making more power. If you don't limit the RPM, and the bike that makes less torque makes more RPM, the bike with less torque could make more power if the RPMs are sufficiently higher. So the bike with less torque could indeed accelerate faster. All your arguments about torque seem to assume that there is no transmission involved. Here are a couple of simple exercises... 1) Say your bike makes 100 foot pounds of torque... Where does it make it? At the rear wheel? What torque does it make at the rear wheel? Now shift gears. What torque is it making at the rear wheel now? 2) Your engine makes the same torque (and power for that matter) regardless of gear. So how do your zero to 60mph times look if you only used 2nd gear? What about only using 5th gear? If you feel acceleration, you feel power. You "feel" torque, but only in the form of the work it does over time, which is directly proportional to the magnitude of your RPM's. I go back to my previous illustrative example. I could gear my dremel tool to make 70 foot pounds of torque (at say 1 revolution per hour). It's probably a .1 horsepower engine. My 9sx makes say 70 foot pounds of torque (at around 6000 revolutions per minute). It's probably a 75 horsepower engine. Both engines (with different transmissions) could produce the exact same torque. Are you really telling me you can't feel a difference between these two engines? Your argument only makes sense if you limit any two different engines to the same maximum RPM (which they never are) and force them to run through the exact same transmission (which they never would). And most Dyno's don't measure torque anyway. They measure the weight of acceleration of a known mass (their drum). Acceleration is determined by horsepower at the rear wheel. The torque (representing the static force on an imaginary one foot lever arm attached to your crank) is the imaginary number. Horsepower is as real as it gets. (Again, all this is independent of the definition error. When somebody tells me a bike has great low end torque, I don't argue with them, I understand that what they are telling me is that their engine is making a decent level of horsepower at lower RPM's, which is a good and noble thing). | ||
| Perry |
>>Power is not a force. It is WORK done over a period of TIME... They don't even understand basic physics! You don't either. Wrong, I actually know a substantial amount about physics. That goes far beyond the 8th grade knowledge you are describing, as well as knowing that "work" is force applied over a distance, as opposed to just applying a force. A force does not necessarily move anything AT ALL. Classic example is the upward force of the earth pushing against the downward force of gravity while you sit at a red light on your motionless bike. Does that force seem any more powerful whether you're sitting on a 1500 pound Harley or a 400 pound Buell? No. Yet the force is substantially different. Does that substantial force even move your bike? No. It is true that ultimately f=ma, so in the purest sense the accelerating force is a torque on the crank. However, the torque measurements we describe and discuss with regards to an engine are characterized in terms PER STROKE of the engine, not overall output. If you want to really get picky you can't neglect the fact that torque actually changes dramatically over the course of each piston stroke - only when the gas/air mixture is burned and expanding in the cylinder is there really any "torque" at all! On a four-stroke engine, that's actually less than half the time on a given cylinder! To believe that the acceleration you experience is measured more accurately via "torque" measurements is also to believe that you must accelerate most rapidly at "peak torque", which on a Buell XB12 is usually between 4500 and 5500 RPM depending on your setup (see dyno charts from muffler shootout). Let's experiment - hold your RPMs at "peak torque" and and then at "peak horsepower" and we'll see whether "peak torque" equals "peak acceleration". It does not. Peak acceleration occurs at peak horsepower - hence the accelerative force is best measured by horsepower numbers, not torque numbers. You are getting more force exerted PER STROKE at peak torque, but getting more total accelerating force at redline because of MANY more strokes, each of which is exerting approximately the same amount of torque (depending on the shape of the torque curve and current RPMs, etc.) That's why the repli-racers can smoke a Buell in a straight line despite much lower torque numbers - they rev so, so high and thus put out MORE total accelerating force in spite of LOWER torque measurements. Having said all that, I am happy that the Buell V-twin has a flat torque curve and thus you can actually ride and even accelerate reasonably at 3000 RPM. Buell doesn't have more peak power than repli-racers (it obviously has less), but it has more usable power because that power is spread more evenly over the rev-range. I don't want to have to hit 10,000 RPM to get any reasonable acceleration, even if I can get much more "peak acceleration" that way. I don't usually ride at redline... Now I'm done with this thread, and I'm off to ride. | ||
| Spike |
Just to be fair I have to point this out:
Reep is biased. He clearly has a vested interest in horsepower being the determining factor in acceleration. If it does turn out that torque is the determining factor, his bike is no faster than a dremel. | ||
| Terribletim |
LOL! Now I gotta figure out how to mount a Corbin Gunslinger on my dremel! | ||
| Triumph900 |
Anyone heard any good Buell rumors lately?  | ||
| Reepicheep |
Can you put nitrous on a dremel tool? I'm smelling a landspeed record... whats top speed for the .1 HP limited class? Now, how do I calibrate this calendar? |
