KyleF

Yea... that is simplifying a cutting operation. Which is a lot different than just pushing a car.

If you have a granny gear like an old truck, you can dump the clutch an not bog.

If you didn't read the entire thing, I said HP tells you how much gear multiplication you can use to multiply torque. I never said it wasn't important or useful.

You can't seperate the two.

Is you saw direct drive or is geared through a set of pulleys? Our industrial equipment utilizing electric motors is never direct drive.

KyleF

Again, don't know much about your saw... but I know my Nakamura Lathe. It has a 15hp main spindle... and a hp curve posted right on the machine.

So, when I am setting up a cut, I know how much power is available. Excellent.

You know what the cutting tool guy want's to know... how much torque is transmitted. This is because it takes force not power to sheer the material at the cutting tools tip. If the force is not high enough, it will bog the spindle down and start to slow down. Until it reaches the point where the forces equalize. This also has to take into account not the chuck size but the workpiece diameter... or in the case of milling, the cutting tool diameter.

Now, you know the force to cut, surface speed of the cut and you can calculate the required power consumption utilized to make that cut... but not every cut will be done at the engines peak hp point either. Ideally we would because as I said before, peak Hp is where you can get the greatest mechanical advantage through gearing. The lathe doesn't have but a 2 speed gear box.

MatthewMiller

You told me that what I wrote was making your point. But that is not true.

I'm not angry. I am, however, getting tired of going in circles with you, and I'm not going to keep doing it. I've asked you questions that prove my point exactly (that crankshaft torque doesn't predict performance). I've repeated, ad nasuem, the very definition of power. I've given examples of the ways in which chassis dynos can accurately measure power without knowing crankshaft torque. And today I provided an extremely simple formula that tells you exactly how much force is available to accelerate a car, based on power and road speed and not any torque value. If I know the power the engine is making, and all the resistive forces of the car, then I can tell you how fast the car can go at that power output. You can't tell me that with just crankshaft torque. If I know the mass of the car and the power the engine is making, I can tell you how fast it can accelerate. Again, you can't tell me that with just crankshaft torque. There really is nothing else to say.

Yes, this is correct.

I don't even know what the hell you're talking about here, and neither do you. The tractive force that accelerates the car is determined by the power the engine puts out. There's no marrying of words. It's just super-basic physics. No wedding, no snapshots, no other goobledygock that you like to write.

If the car makes 400hp at 180mph, then it is creating 833lb of tractive force. If the car's total resistive force at 180mph is also 833lbs, then the car has reached its max speed. If the car has less resistive force than that, then it can keep accelerating. If the car has more resistive force than that, then it will not reach 180mph with 400hp.

It's. That. Simple.

Yeah, anybody who says "horsepower is a man-made number" and uses that to justify the notion that torque is all-important is an idiot. I've got news for you: all units of measure are just man-made numbers. Lb/ft is a man-made number, just like miles and hours. OTOH, the things those man-made numbers measure are most definitely NOT man-made. Power is not man-made or imaginary. Neither is force, distance, or time. I can measure power in lots of man-made units, like horsepower or watts. But power is very, very real.

I know we're on the same side, but I do want to make a correction here for clarity. In electricity: force(torque)=volts, rpm=amps, and power=Watts. Also, I understand exactly what you were trying to point out to Kyle. But the problem is that he can't focus on what's important, and he keeps trying to make things way more complicated than they really are. I've learned the hard way that every time we try to introduce a new example to him, it just compounds his confusion.

jayjones

The concepts in this thread aren't simple, and become extra confusing when terms like power an torque are used loosely in some posts and rigorously in others. People with years of experience and great hot-rodding knowledge still throw around sayings like "horsepower is what you read about and torque is what you feel". I think this thread and others like it are very good for the community to learn and dispel fallacies. Newton had to develop an entire new type of math to describe the relationship of applying forces (torque) on objects in motion. Analogies are helpful to a degree but can also lead to bad assumptions.

MM regularly makes very informative posts here and is fighting the good fight, but the frustration starts to show after a while. All I can offer is don't give up, we are all here to learn and share and we wouldn't be here without having the same interests. Someone can be wrong and smart at the same time.