As has been pointed out before, that's not really accurate. Its fun to say; to wrap it up in a sound bite. But it really just confuses the issue at this point.

Lets break it down:
How fast you hit the wall....
Well, your terminal velocity at the time you hit the wall tells us nothing at all about the HP of your vehicle. How heavy is the vehicle? What is its aerodynamic profile? How long of a run up did it take to reach that terminal velocity? You might be going 100MPH in 3hp Go-Kart or in a 400HP Tri axle dump truck. ( granted that one would probably not be geared to be able to go 100mph, but it could be)

Second, how far you take the wall with you....
Again, too many variables. The mass/density of the wall, for one thing. How was it anchored?
Now, we need to know the mass and velocity of the vehicle to know how much force it can apply to hit, destroy or drag the wall with it. Again, "crumple zones" and structural integrity of the vehicle notwithstanding, that go-kart, at a high enough speed, could have an equal amount of energy at impact, as a the dump truck at a much lower speed. So, in theory, they both have the ability to carry the wall the same distance, but at different speeds.

Wrong. Horsepower is. To have work, there needs to be a defined time. Torque DOES NOT HAVE A TIME FACTOR.

The 500 ft.lb. example is AT THE FASTENER. Ft. Lbs. Is measured at the center of rotation, not where I place my (at the time 130 lb. ) body. Leverage has nothing to do with this discussion.

See above. You completely missed the mark on your rebuttals.

Horsepower is "the rate at which work is done"... think "watts"!
https://en.wikipedia.org/wiki/Horsepower


Torque is "rotational force"... think "twist"!
https://en.wikipedia.org/wiki/Torque

Now the ? becomes is peak work time " HP " the same real world power output on a low torque engine that spins a lot of RPM compared to a high torque low RPM engine all things being equal peak HP wise.


Could a 450 HP small block Chevy that turns 6 or 7000 RPM drive 40 tons of semi down the road like 450 HP rig motor at 80 MPH being in it's peak spot of the power band ?


I don't think the small block could move the load over 50 MPH on flat land. I could be wrong but do not think so.


The rig engine is a 150 pound 200 watt Krell that can deliver it's load into a 1/2 OHM load and drive 8 woofers per channel to peak output.


The small block Chevy is a 200 watt 10 pound Kraco that can only run 1 woofer per channel into a 8 OHM load. It can never control the load of those drivers no matter what.


50 may be optimistic.


What they are saying is " Job to be Done " = HP, when in reality it is TORQUE and the HP rating is the rate you are laying down that torque.


When a motor is rated with a tag on it it should be stamped the MAX Torque # 1st at RPM # 2nd then = rated HP.

Actually.... this is not correct.

Horsepower is a measurement of work being done over a period of time. Engine RPM is a time factor.

Torque is a static measurement, it only measures the amount of available force at a given moment in time. When calculating torque, there is no time elapsed or anything moving. Moment in time = frozen time. What is the force applied at that particular instance.

For example, take a wrench and go try to break a rusted bolt loose that won't budge, even if it doesn't move there is torque applied because the force placed on the wrench exists. However there is precisely zero horsepower produced because nothing moved. So you applied force but did not create any work.

The most basic way to explain the differences without any math or physics whatsoever:
- Horsepower is a movie
- Torque is a single frame from a movie

Wow, I can't believe the amount of words being typed here.

Scientific facts based on proven mathematical formulas used by every engine builder known to man have now been turned into subjective banter.

Enjoy yourselves, I think I prefer Netflix.

Oh, and by the way, the title of this thread reveals the real motive. This was never meant to be an all inclusive discussion.

That darn Curtis and Cody seem to still be on the same page. Perhaps someone should ban them?

Oh, wait. One of the is a moderator. That or maybe they're onto something with their position.

This is almost as bad as arguing about how much air pressure is in the tire.

deltd 987654321

If you get the air pressure wrong I insta-ban you :-X19 :-X04 :-X04 :-X04

Curtis runs a "tight schip" LOL! :-drink

Thanks for all the posts, will take time to read through it in detail.


I am not called real slow for nothing but I think there is a lot of misdirection on purpose on this subject but I may just be real slow.


I am hoping I will find the answer without having to rig up a test, If I am correct which I probably am not a 400 HP turbo'ed crotch rocket motor spinning 12,000 cannot drive a 40 ton semi down the road at 80 MPH no matter what.


You can have all the HP in the world but if you do not have the torque coming off the crank you need to drive the load no matter what the gearing it ain't gonna happen.


Where as if you have the right amount of Torque coming off the crank to do the job but not enough HP from lack of RPM it will do the job but just not as fast as you like....

So... I hate to get in on a discussion like this, but there is a few points to be made:
1. When dealing with a constant speed, HP is what matters. It is all that matters. You can gear to whatever output speed you want, and it really doesn't matter how you make that HP or at what input(engine/shaft) RPM.
You can always gear around it any lack of torque, or go the other way if you have too much torque.

In an example of a gasser vs a diesel pulling a load at a fixed speed, if both engines make the same HP to the wheels at the same MPH, they will pull that same speed.

2. In the case of a variable speed situation(accelerating from a stop), it's not torque that matters. It's "area under the curve"(HP over MPH). Again, as long as everything is being measured at the wheels(after gearing losses), you are going to have a better time getting the load up to speed faster with more area under the curve...

Tesla vehicles are actually a good example of this - they produce a whole heck of a lot of HP, and lots of torque at the wheels... but the motor itself spins a lot faster than an IC engine(something like 18K RPM at max speed). They just use gearing to bring it down.
Heck, a lot of smaller electric motor applications do that - have motors spinning at 10-30K RPM and then bring the RPM down with a gear reduction, because it's easier(cheaper, smaller) to have a motor make more power(hp) at the higher RPM and then bring the torque up with a gear reduction than it is to build a motor to make that HP at a lower RPM.


Yes, you will.
Heck, I have in my possession a 50:1 gear reduction drive for a 3/4HP 1750RPM motor(something like 2.25ft/lbs of torque). After the gear reduction it will put out 112.5 ft-lbs of torque at 35RPM. A lot slower, but puts out a massive amount of torque for such a small amount of HP.
Why would you use something like this? To be able to drive just such a load. 2.25 ft-lbs isn't going to be able to move something like a big drum filled with coffee beans; 112.5ft-lbs of torque, however...
Now, this sort of deep reduction comes with a small cost in power lost doing the conversion, so perhaps it can only put out 100ft-lbs of torque at that 35RPM... but that's still a big big increase.

Back to the truck scale of things, dyno tests are interesting. As you well know, I've put my truck up on the dyno in various gears. I've found that going from 5th gear to 6th(GearVendor Overdrive) gear ends up losing 10HP or so, in the gearing losses and higher speeds of the entire drive train. That being said, that's only perhaps 4%.

I'll also want to point out that I could probably take one of my trucks, shove a small 8hp lawnmower engine in front of the manual transmission, stick it in 4lo and it would go. I could probably haul a big trailer with it, too... just at 2MPH or so in 4x4lo 1st. Because of the gear reduction factor. I'd be pushing 139 ft-lbs of torque at a whopping 375RPM out of the transmission.

edit:
I want to throw another anecdote out there, one you can do:
How much power does the starter in our IDIs put out? 2.5KW max? That's like 3HP more or less.
Put the truck in 1st, bypass the neutral safety switch and crank. The truck will /move/, at a couple MPH. And that's even with the load of the engine using up some of that power.
How much torque do you think that starter motor puts out by itself? Remember, the starter is already a gear reduction - from the motor to the bendix gear, and from there to the flywheel, you have two large reductions.
But, with enough gear reductions, it's possible to move even a 7,000lb truck with a starter. Just not very fast.

I'll add a serious post that is most important to this discussion.

Horsepower requires MOVEMENT, but Torque does not.

When you say "if you don't have enough horsepower" ... "to drive the load" it is an incorrect use of the term horsepower. If there was not movement, there was and is no horsepower...only torque.

Here's a page that goes into more detail with good examples to explain the difference.

Torque and Power

Hope this helps! :-drink

Yes, because the huge amount of time I, and others, have put into your previous thread (and to a lesser extent here) was only to misguide you and make you feel dumb.

Thanks for the appreciation.