Horsepower: Do you really use yours?

[KrisZ]

Originally Posted By: CR94
Originally Posted By: ZeeOSix
Originally Posted By: KrisZ
HP is an antiquated measurnment just like mouthfuls, cubits, etc. ...
Not if you understand what HP is measuring. It's a pretty simple relationship consisting of only torque and RPM.
No, it's not. It's an antiquated unit of measure equal by definition to exactly 33,000 foot-pounds per minute. Conventionally (but not necessarily) it's used in connection with mechanical power production or transfer. It can be linear speed times force, just as easily as torque times rotational speed.


He's confusing the measurement of power with a unit of power, further proving my earlier point.

 

[Nyogtha]

Agreed CR94, that's a fundamental plank of science & engineering based education. In high school physics class, we were sent one at a time to run up & down the stairs by the gym (so no classes would be disturbed) 5 times, then come back and calculate how many HP were involved. No wheels, no torque, just legs like the original horse except 2 human ones instead of 4 animal ones.

I seriously doubt such a fundamental demonstration would be allowed in a high school physics environment today though, without hemets, pads, an officer watching the students to ensure they only went up & down the stairs and then directly back to class, etc.

 

[KrisZ]

Originally Posted By: KrisZ
HP is an antiquated measurnment just like mouthfuls, cubits, etc. ...


Re-reading my earlier post, looks like I also got confused with the HP being a measurement of power. I should've said, it's an antiquated unit of power.

 

[dailydriver]

Originally Posted By: Nyogtha
I seriously doubt such a fundamental demonstration would be allowed in a high school physics environment today though, without hemets, pads, an officer watching the students to ensure they only went up & down the stairs and then directly back to class, etc.


Was that really pertinent to, and necessary for this discussion?

I think by now everyone knows where you, and the overwhelming majority on this site, stand as far as general worldviews go.
WHY the compulsive need to constantly reiterate it over and over again, every and ANY chance you get?
WHO are you trying to convince, or get confirmation from, when everyone is already 'on your side'??

 

[Nyogtha]

I think my doubts have validity. My point is lacking such fundamentals leads some to think an engineering mindset is a matter of plug & chug, or memorizing formulae, which is far from the truth.

Do you have a pertinent example of what exactly is substitued these days for such an exercise in the world of secondary education, or anything to show lack of validity for my doubts?

 

[Silk]

At my technical college we measured HP on a pony brake. We noted the rpm of the single cyl engine, read the pounds on the spring gauge, and calculated the HP by using the often repeated formula. Real world physical physics...reading torque and HP on a computer screen while the vehicle is on a dyno is very nice...but how did those figures appear there ? The dyno certainly doesn't measure HP...but to the observer it does appear to....

 

[Nick1994]

I drove the Camry to work toda after it's been sitting for 14 months.

My god, yes I do use all the power that car has to offer LOL, it's gutless.

 

[Nyogtha]

Originally Posted By: Silk
At my technical college we measured HP on a pony brake. We noted the rpm of the single cyl engine, read the pounds on the spring gauge, and calculated the HP by using the often repeated formula. Real world physical physics...reading torque and HP on a computer screen while the vehicle is on a dyno is very nice...but how did those figures appear there ? The dyno certainly doesn't measure HP...but to the observer it does appear to....


Exactly - an honest grasp of the fundamentals is really necessary for a useful discussion on such topics.

 

[ZeeOSix]

Originally Posted By: CR94
Originally Posted By: ZeeOSix
Originally Posted By: KrisZ
HP is an antiquated measurnment just like mouthfuls, cubits, etc. ...
Not if you understand what HP is measuring. It's a pretty simple relationship consisting of only torque and RPM.
No, it's not. It's an antiquated unit of measure equal by definition to exactly 33,000 foot-pounds per minute. Conventionally (but not necessarily) it's used in connection with mechanical power production or transfer. It can be linear speed times force, just as easily as torque times rotational speed.


Who implied it isn't describing mechanical power production or that it couldn't be linear? HP is the "rate at which work is done", and it can certainly be translated into other units, some not even mechanical.

When I said it's a "relationship consisting of only torque and RPM" I mean in terms of HP output of an engine (rotational torque x RPM) ... that is what we're discussing here. Of course there are other kinds of ways to describe the "rate at which work is done" ... so what?

Units of mechanical HP is (lbs-ft)/min ... which could also be used to describe raising X lbs over Y ft in Z min, or by someone running up stairs to climb Y vertical feet in Z minutes, etc. Many ways to cause a "rate at which work is done".

Originally Posted By: Silk
The dyno certainly doesn't measure HP...but to the observer it does appear to....


Pretty obvious the HP is calculated from the torque and RPM measurements by the dyno in order to make the calculation. Semantics and hair splitting.

 

[ZeeOSix]

Originally Posted By: CR94
It's an antiquated unit of measure equal by definition to exactly 33,000 foot-pounds per minute.


What makes it "antiquated" in your mind? It's a man-made definition of mechanical HP by Mr. Watt. Anyone could have come up with a definition of Power (the rate of doing work) - more below on that.

The German DIN 66036 defines one metric horsepower as the power to raise a mass of 75 kilograms against the Earth's gravitational force over a distance of one meter in one second - again it's in units of (force x distance)/time. So the Euro guys came up with their own definition of mechanical power related to the rate of doing work.

Someone could say a "Squirrel Power" (SP) is equal to raising 1 lbf over a distance of 3 feet in one second or 3 lbf-ft/sec = 180 lbf-ft/min. In that case, 183.33 SP would equal 1 HP of the Mr Watt variety.

Maybe some guys here should be expressing their car's power in SP instead of HP.

Would be cool to say "hey, my Honda Civic has 27,500 SP.

 

[Shannow]

"metric horsepower" is an abomination that should not have been born.

Metric, I can measure the volts and amps at the Generator terminals, and come up with a number of 747.16MW, or (less likely) measure the torque and the RPM (they CAN measure the torque these days with shaft twist)...the units are interchangable without having to come up with a "nearly 3/4" conversion factor.

As previously mentioned, a horse can do multiple horsepower, certainly over 10...stupid unit of measurement...wasn't even valid when Mr Watt invented it, as it "averaged" the output of a horse over an entire working day.

 

[ZeeOSix]

Originally Posted By: Shannow
As previously mentioned, a horse can do multiple horsepower, certainly over 10...stupid unit of measurement...wasn't even valid when Mr Watt invented it, as it "averaged" the output of a horse over an entire working day.


It's just an invented definition of mechanical power - mankind defines everything in this world, and those definitions become standards. Mechanical power could be defined a hundred different ways. Someone had to come up with it, so what Mr. Watt defined as "HP" has stuck to this day, and I doubt it will change anytime soon. What would be a better definition of the mechanical "rate of doing work" in your mind?

 

[Shannow]

Originally Posted By: ZeeOSix
What would be a better definition of the mechanical "rate of doing work" in your mind?


Watt...

named after the inventor of the horsepower.

 

[Shannow]

Lets you accumulate them in units called "Joules", and convert between electrical and mechanical power without

5252 making disparate units "equal"
1 hp second "equalling" 178.11 calories.

Does a horse making 17 "horsepower" make any sense to you ???

 

[ZeeOSix]

Originally Posted By: Shannow
Originally Posted By: ZeeOSix
What would be a better definition of the mechanical "rate of doing work" in your mind?

Watt...

named after the inventor of the horsepower.

Lets you accumulate them in units called "Joules", and convert between electrical and mechanical power without

5252 making disparate units "equal"
1 hp second "equalling" 178.11 calories.


You can certainly express an engine's power output in Watts or Kilowatts ... it's done in other countries using the SI unit system. But in the USA it will most likely stay the unit of HP.

Originally Posted By: Shannow
Does a horse making 17 "horsepower" make any sense to you ???


Watt defined the HP based on the continuous average sustained rate of work a horse could do - not it's maximum peak output.

Cherry picked:
In 1993, R. D. Stevenson and R. J. Wassersug published correspondence in 'Nature Magazine' summarizing measurements and calculations of peak and sustained work rates of a horse.[13] Citing measurements made at the 1926 Iowa State Fair, they reported that the peak power over a few seconds has been measured to be as high as 14.9 hp (11.1 kW)[14] and also observed that for sustained activity, a work rate of about 1 hp (0.7457 kW) per horse is consistent with agricultural advice from both the 19th and 20th centuries"

[13] Stevenson, R. D.; Wassersug, R. J. (1993). "Horsepower from a horse". Nature. 364 (6434): 195. Bibcode:1993Natur.364..195S. doi:10.1038/364195a0.

 

[Shannow]

Originally Posted By: ZeeOSix
Watt defined the HP based on the continuous average rate of work a horse could do - not it's maximum peak output.


Yeah, I said that it was the average over a working shift a few posts back.

Originally Posted By: ZeeOSix
The German DIN 66036 defines one metric horsepower as the power to raise a mass of 75 kilograms against the Earth's gravitational force over a distance of one meter in one second - again it's in units of (force x distance)/time. So the Euro guys came up with their own definition of mechanical power related to the rate of doing work.


That's over a second...doesn't make it "modern", nor "non obsolete". So the "modern" "metric horsepower" took a shift's worth of effort, and applied it to a second..making it "modern" ???

If the US wants to report their latest in mousepower as it's a bigger number, doesn't make the unit useful for the rest of the engineering world.

You asked me what unit would make more sense, and I answered...the Watt...

 

[Shannow]

And the "Euro guys" were using the watt before they defined the "metric horsepower" abomination.

edit...which was rendered obsolete in 1972, and replaced with the Kilowatt, although HP could be used for advertising.

 

[Shannow]

And the "Euro Guys", who build things like the "Baby Durmax" VM Motori 2.8.

http://www.vmmotori.com/images/data_sheet/A428_DOHC-NEW.pdf

Note the use of "mm", in the engine's construction, the "KW" in it's output and the conversions into CV (cheval) and PS...for the purposes of advertising.

I can almost guarantee that the US car manufacturers are doing their development work in S.I. and converting it across for the market.

 

[Nyogtha]

Why be squirrely or mousey inventing units of squirrelpower and mousepower? Just quote power in ergs, an existing CGS unit of work over time if you want a larger numerical value. Already set and done.

Besides, hamsters would be more appropriate for imports, since Kia Soul comes from Hamsterdam.

 

[ZeeOSix]

Originally Posted By: Shannow
Originally Posted By: ZeeOSix
The German DIN 66036 defines one metric horsepower as the power to raise a mass of 75 kilograms against the Earth's gravitational force over a distance of one meter in one second - again it's in units of (force x distance)/time. So the Euro guys came up with their own definition of mechanical power related to the rate of doing work.

That's over a second...doesn't make it "modern", nor "non obsolete". So the "modern" "metric horsepower" took a shift's worth of effort, and applied it to a second..making it "modern" ???


I never implied it was "modern" ... my point was anyone can make up a mechanical power unit as they desire. Just like the "Squirrel Power" example I made. The HP as defined by Mr. Watt is here to stay in the USA.

Originally Posted By: Shannow
If the US wants to report their latest in mousepower as it's a bigger number, doesn't make the unit useful for the rest of the engineering world.

You asked me what unit would make more sense, and I answered...the Watt...


Well, I happen to live in the USA so I'll be using HP. I don't say the "Watt" is useless when I see engine power expressed in KW. You have access to conversion factors just I and everyone else does. I have to convert stuff all the time.