What is Horsepower?

[Poley4]

National Geographic Magazine

An archeological team, digging in
Washington DC, has uncovered
10,000 year old bones and fossil
remains of what is believed to be
the first Engineer.



They have determined that they

were just over 4’ tall.

 

[spacemule]

Hey Poley, I can't open that link. Can you post it in a jpeg or similar format? Thanks.

 

[THALL10326]

We'll deal with suckback after we've taken care of blowhard.

Space thats got to be the best one liner I've seen you toss out, I knew you had a sense of humor,

 

[Poley4]

National Geographic Magazine

An archeological team, digging in
Washington DC, has uncovered
10,000 year old bones and fossil
remains of what is believed to be
the first Engineer. They have determined that they
were just over 4’ tall.

See if this one works.

 

[spacemule]

Ha ha. Yup, that 'bout sums 'er up.

 

[Canyon Angler]

As I said:
Horsepower is a calculation of torque applied over time. Different formulae give different numbers.

The R part of RPM is irrelevant, the M part is what counts.

Not true.

I can put 20 foot-pounds of torque on one of the lug nuts on my truck for the next 10,000 years, but I will not have done a single lick of actual WORK unless I actually MOVE something (work is force applied OVER A DISTANCE).

This is why a fan or a vacuum cleaner SPEEDS UP when you plug up the hose or block the fan from moving air. If the fan is not moving any air, it's not doing any work, so it's not under load, so the fan speeds up.

So yes, the "R" part of RPM is very important. If there are no revolutions, there is no movement, and if there's no movement, there's no work, and if no work is done, no power was ever supplied (work over time).

 

[chowdozer]

With all do respect Woody, imo Chowdozer doesn't understand either.

so it appears we cannot get a unanimous understanding on this topic, I recommend we keep our own individual opinion. Next time you visit your dealer to buy a new saw, you certainly specify you want a torquey one and forget about the hp. Them manufacterers are all wrong you know, they must be using engineers to develop those saws ...

Hmmmm... I don't understand? It's really very simple. Torque defines the horsepower curve! If horsepower = (torque/time) then torque defines the horsepower curve every time! I understand perfectly!

 

[chowdozer]

Torque in this discussion is just derived from power and rpm.

And that is your error. Power is derived from torque and rpm.

Nice to see that there are some scientific people around here.

 

[Tzed250]

horsepower needs torque to exist

torque does not need horsepower to exist

 

[spacemule]

So, let me get this straight. Torque is a force, and horsepower is a force in relation to a rate of time? power = torque/time If this is the case, then can we not conclude that since power = torque/time, then power x time = (torque/<strike>time</strike>) x <strike>time</strike>, which means that power x time = torque?

 

[Mr.]

Debbie was never from Dallas.

You really need to find the movie to appreciate it.

Fred

 

[RiverRat2]

Please Please,,,,, Jeepers!!!!!!!!!

Can any one tell me why Husky has come out with Xtra torque saws lately? I must not be the only one that likes a torquey saw. Steve

You must not be from the scientific community,,,,,didn't you get the memo???? Torque has NOTHING to do with it!!!!!!!!

 

[RiverRat2]

Brahahahahahahahahah

So, let me get this straight. Torque is a force, and horsepower is a force in relation to a rate of time? power = torque/time If this is the case, then can we not conclude that since power = torque/time, then power x time = (torque/<strike>time</strike>) x <strike>time</strike>, which means that power x time = torque?

Good one,,,,,, on that one,,,,maybe a couple

 

[chowdozer]

So, let me get this straight. Torque is a force, and horsepower is a force in relation to a rate of time? power = torque/time If this is the case, then can we not conclude that since power = torque/time, then power x time = (torque/<strike>time</strike>) x <strike>time</strike>, which means that power x time = torque?

Yes, you can conclude that.

 

[Drive_1305]

In an early post I basically said the average engineer didn't know what they were talking about. Of course thats not true. I should of said- just because someone says they're an engineer doesn't mean they're always right about engineering topics.

Then Belgian who claims to be an engineer makes this post below about HP & Torque and he agrees with Bob and Peter on their therories- and he calls me stupid!

Bob, thanks for the reply, which explains it very well I think. HP is indeed the factor which determines the power of an engine. Torque is only a consequence of it ....and hence Peter is right IMO.

I've read post by these three guys who claim to be engineers and physicist. What they say about the relationship between HP & Torque make me think they don't have their facts straight.

They keep talking like HP & Torque are two different things and not related - they're not. Read their post they say it takes Torque to get the saw up to max speed, but then when you start cutting its about raw HP. Seems like your saying when you start cutting "Torque" stops doing its job and "HP" takes over. That just doesn't make good "engineering" sense to say that. When your cutting wood, something has to pull the chain through the wood- "The Chainsaw Fairy" doesn't jump in and do it - the Torque output of the engine does the job. Its all about Torque! You can't talk about HP like its not related to Torque. Torque comes first then you calculate HP from that.

I think Peter said in another thread ...two saws that have the same cutting speed the one with higher HP will win - thats true. Look at the formula- if the speeds are the same then the higher HP as to have more TORQUE.

I admit I don't undersand it all 100%, but after reading these guys post, I don't think they do either.

 

[ShoerFast]

In an early post I basically said the average engineer didn't know what they were talking about. Of course thats not true. I should of said- just because someone says they're an engineer doesn't mean they're always right about engineering topics.

Then Belgian who claims to be an engineer makes this post below about HP & Torque and he agrees with Bob and Peter on their therories- and he calls me stupid!



I've read post by these three guys who claim to be engineers and physicist. What they say about the relationship between HP & Torque make me think they don't have their facts straight.

They keep talking like HP & Torque are two different things and not related - they're not. Read their post they say it takes Torque to get the saw up to max speed, but then when you start cutting its about raw HP. Seems like your saying when you start cutting "Torque" stops doing its job and "HP" takes over. That just doesn't make good "engineering" sense to say that. When your cutting wood, something has to pull the chain through the wood- "The Chainsaw Fairy" doesn't jump in and do it - the Torque output of the engine does the job. Its all about Torque! You can't talk about HP like its not related to Torque. Torque comes first then you calculate HP from that.

I think Peter said in another thread ...two saws that have the same cutting speed the one with higher HP will win - thats true. Look at the formula- if the speeds are the same then the higher HP as to have more TORQUE.

I admit I don't undersand it all 100%, but after reading these guys post, I don't think they do either.

Like the old saying:
You can tell an engineer, but you can't tell them much!

 

[chowdozer]

Like the old saying:
You can tell an engineer, but you can't tell them much!

Hey buddy! Watch it!!! Grrr!

 

[ShoerFast]

Hey buddy! Watch it!!! Grrr!

Chowdozer, you know more about the "type" I'm talking about then I do!

H311, you probely have a longer list with names of people that you really wonder how they got were there at?

 

[peter399]

Let's hear you say again that torque doesn't matter.

I can say it again.

This is the LAST time I will try to explain it ok?

Power = Torque * angular velocity (since we are talking a rotating movements)

Now we have the famous formula:

M1*v1 = M2*v2 (that’s in a perfect world where you don’t have any mechanical losses on the way but that doesn’t matter here.)

Now let’s take the car example again:
M1 = torque on the engine’s crank shaft
V1 = speed of engines crank shaft
M2= torque on the rear wheels (where you want it! This torque will cause the acceleration)
V2= speed of rear wheels.

Since we are interested in M2 we have:

M2 = M1 * v1/v2 now use eq.1…… M1*v1 is ….. P! Engine power. Engine hp!

Hence M2 = P / v2

So where did the engine torque go? We lost is somewhere in the transmission!
Now what happens as the speed increases? The wheels will turn faster right?
V2 will increase. In order to continue the acceleration we need to keep our M2. So what do we need? More P, more hp.

So the fundamentals of all this is: The ability to cut more chips from a log or drive faster with a car is directly dependent on the power, raw kW.
(prefer kW over hp since hp is not unambiguous, depends for example on where on earth you live because of different g-constants)

A 600hp with 500Nm of torque will pull a heavy truck up the hill just as fast as the 600hp 2500Nm truck diesel engine. Engine torque as specified in car magazines only tells you what the characteristics of the engine look like. What the power vs. rpm looks like. It has nothing to do with the ability to accelerate fast or reaching high top speed.

 

[Drive_1305]

Keep it Simple!

Peter339 - Forget about Formula1 race cars, forget about Heavy Trucks, forget about gearing, keep it simple and use a chainsaw as your example. If you have to compare two saws don't use model numbers of different saws, don't throw in gearing changes. I would think if you use two saws to compare, each would have the same length bar, the same pins on the sprocket and the logs you saw would be very similar. Now keeping your examples simple, think it over and lets hear your "Torque Doesn't Matter Theory" one more time.