Oldstroker,

Actually you may be right about eddy current type dynos in particular or even some more of the electrical dynos since I know there are strain gauges on some of the eddy current dynos I have seen (I wasn't looking at all so they might all have them if you are right which you probably are!) so I better shut up! I have been told by several other engineers that do this stuff that they can also measure power as well? I will find out and get back to this.

I do know that they have AC and I think DC Dynos that measure power or tq and can even sell it back to the grid so of course they can or have to measure it. Also as we said there are several inertial dynos as well so you can measure both power or tq independently whether or not an eddy current type electrical brake can or not. Maybe it's more accurate to measure the strain gauge than the ammeter?

Also I know ANY number of dynos can measure sufficient tq at a shop like hendricks where they are only seeing 550 ft pounds of tq or so but they again are much more interested in power absorption because other wise they cannot do sustained testing. At Hendricks and most other NASCAR shops they have a water temp control system which is again POWER removal and absorption though heat. Again tq at a lower rpm is not the same as tq at a higher rpm. The higher hp version of tq heats the water much faster and there's a limit there.

Even when a water brake is applying a TQ it is really absorbing power which has to be removed though some system or water temp and load capability decreases fast. HAve you seen an engine that puts out a 1000 ft pounds of TQ hit an SF 901 when the temp is up. It instantly cavitates and the motor surges like crazy.

When you are quoting tq at the wheels at any rpm or mph you are quoting POWER though not tq. You are doing exactly what I said and are using the power to figure tq backwards. That's why power is all that matters. The TQ just determines what speed it's at depending on gearing.

How about I say I have one engine making 700 ft pounds or tq and one making 700 ft pounds of tq. Which one is faster with all else held equal? You should be able to answer that since tq is important. Are they the sme since they produce the same tq output?

How about engine A has 500 ft pounds of tq and engine B has 600 ft pounds of tq. Which one is faster? One has more tq than another so which one is faster? You should be able to answer that since tq is important correct. You can make acceleration and other work estimates easily knowing nothing but power and you can do or estimate absolutely nothing if you only know the tq an engine produces.

I will be at the AETC if at all possible and at PRI here too so I'd love to meet you too. I know several guys at Hendricks. NO one here said you couldn't use a 901 to test within 1 per cent. Most people believe it is more accurate than that if you control the atmospheric variables and dyno variables.

At 1 per cent they would be hard pressed to find any hp or any thing but curve shape at Hendricks! They are looking for 2-3 right now at a time or .25 % or so. At 1 % they could never see this very well.

 

OldStroker,

I don't have a 150 MW dyno but the main investor in my upcoming shop does. He is out of the country right now. He owns Btech Turbines in Houston Texas. His dad is Meherwan Boyce who's essentially the Warren Johnson of large Turbines. He's literally written the text books on internal combustion engine design for several universities and especially requarding turbines. I do think you are right though and I think they may have a KAHN or Zollner AVL dyno which does use a strain gauge on a HUGE output shaft. I just called out there and they do have at least one dyno that goes 75 MW that is even a water brake which I did not know they even had water brakes that high?

Anyway whether I am TOTALLY wrong about MOST dynos measuring tq and you are TOTALLY right (which I probably am and I'll go with right now!) the fact is that tq is only a part of the important equation that we need to know which is power. I can tell you all sorts of things if I know power output whether I am measuring tq and rpm to find it or measuring it directly. Without the tach pickup a SuperFlow 901 says NOTHING. It prints NO results or numbers since it is a power measurement device first and foremost and not an rpm or tq measurement device. When either falls off there can be no data anymore right but with BOTH it prints numbers?

On a dynojet the tach pickup falls off and data is STILL collected since you are measuring POWER directly. You still see how much power you made you just don't know if the engine was making 900 ft pounds of tq or 200 ft pounds of tq but since power is a combination of them both you have all you need to make some estimates on performance now. You can change the rear wheel torque to WHATEVER you want with gearing but you can NEVER gear power up. You can lose it but you can't gain it. I can put out a million foot pounds of tq all by myself!

 

Either you are one heavy dude, or you have a long torque wrench. (About a mile if you weigh 189 lbs. and put your full weight on it!) Are you sure your name isn't Archimedes?

 

I can gear myself down with a lot of gear or a really long wrench and do it! I just can't do it very fast since I have no horsepower!

 

Torque is the expression of an applied rotational or twisting FORCE. And I believe the definition holds whether you are using lbs/ft or newtons( 1 kg*m/s^2) to record that force.

Power on the other hand, is the time rate at which work is done or energy emitted or transferred.

Torque - the rotaional or twisting force - can and most certainly does exist without horsepower and it can and must be measured. Horsepower on the other hand does not exist, and cannot even be calculated unless you first measure the twisting force which is applied and determine how long it was applied.

Without torque, your car for darn sure is not moving away from a rest, and it doubly-darn-sure ain't going to accelerate, even if you find the mythical frictionless surface.

I stand by my original assertion:

To the best of my knowledge, no-one has yet measured a single horsepower

 

That's just the thing though. The a/f ratio can remain constant, but VE is in a constant state of change. And if the airflow does not increase at least at the rate of increased demand caused by increasing rpm's, then VE will have to decrease. You can have an increase of airflow, without it being a great enough increase to keep VE at a constant level. Since VE is directly linked to torque-output, the torque can decrease even as airflow increases. Factor in the compounding effects of frictional, pumping and thermal losses as the revs increase, and you can end up in a situation where airflow increases and horsepower decreases. Sure, if we eliminate all of the aforementioned losses, then any increase in airflow would result in an increase in horsepower, but it just doesn't happen that way in the real world.

 

How "nit-picky" do you want to get - if you use say a deflection based torque wrench are you directly measuring torque? No, you are directly measuring difference in position (deflection), and assigning that a torque value based on known properties of the metal.
So it could be argued you aren't measuring "torque", but actually just position and then "calculating" torque.

But then are you measuring position? If you are looking at it you are actually measuring the wavelength of light reflected to your eye, and from that inferring certain physical conditions which would point to a change in position.

But then you are actually measuring the result of a electronic potential in a neuron(s) that result from an absorbed photon in the eye.....

etc.

So depending on your definition of "measured" you could definitely be correct in that statement - but your intended corrolary - that "torque" is measured, would also be incorrect - as shown by the logic above.







That is most definitely incorrect - the notion that horsepower is a "imaginary" or purely theoretical unit (while torque isn't) is flawed.
After all, what is torque but force applied at a distance - but without position we wouldn't have force or distance - so using the same logic I could argue that

"Torque on the other hand does not exist, and cannot even be calculated unless you first measure position..."

And again, depending on how nit picky you want to get that is technically true.

So if you want to get down and try and determine a fundamental unit you are going in the right direction, but unfortunately it solved nothing in regards to the hp vs. torque discussion here - they both end up in the same boat


Also though, you can definitely measure horsepower without measuring torque (or even taking it into consideration).

Take a drum of known mass/moment of inertia, determine it's initial and final rotational velocity, then accelerate it over a measured time. From the change in energy of the system you can determine the power required to achieve that change - thus you have determined power input - no torque required.
Or take the previously mentioned example of a water brake - you have a known mass of water, just determine the change in temperature and you have determined the energy input - you know how long it took to do that, so you know the power applied - again, no measurements of a "twisting force" required.


Chris Bennight

 

Nice post...

Its funny how some people think horse power cant be measured or doesn't matter yet as a vehicles horsepower output at the wheels increases it seems to just get faster and faster.

 

I'm not "against" tq or anything I just can't stand when people say crazy stuff like horsepower doesn't matter and can't be measured but tq is what we are after!

I know OldStroker absolutely wasn't saying that. He was just correcting me that most dynos do measure deflection of some kind to estimate tq accurately and then also have a tach of some kind to find power. Only a few measure power and fewer than I thought. I got a note from one dyno guy already that said the strain gauge method is more accurate but you could go either way on some electrical dynos. Apparently they make even 100,000 hp water brakes too as far as he knows from several companies.

You can also do as Chris B says and measure the work something is doing in a given amount of time to find power and then if you know gearing you can backwards figure what the tq should be. These big turbines my friend sells and I am talking about are used to generate actual power so it's well known how much their output is since occasionally they are overloaded.

If I know how fast a car went in the 1/4 I can get Moroso's power-speed calculator and see what power that took. Of course there is no Moroso "torque-speed calculator" since it can't exist!

Actually the funny thing is that most people think I am "PRO TQ" since I like big engines. I just like them because it's easier to make "HORSEPOWER" with them than with smaller more expensive and less reliable high rpm engines and hp is what wins races not tq.

 

if you use say a deflection based torque wrench are you directly measuring torque? No, you are directly measuring difference in position (deflection), and assigning that a torque value based on known properties of the metal.
So it could be argued you aren't measuring "torque", but actually just position and then "calculating" torque.

Actually, you are applying (vice measuring) force until a known position of deflection is reached. Eyesight being notoriously unreliable (mine especially), I prefer a "click-type" torque wrench to alert me as to when I have reached a pre-desired amount of applied twisting force. At any rate, I am applying that rotational force, without regard to measuring the amount, until I reach the limit of the rotational force I wish to apply.

So depending on your definition of "measured" you could definitely be correct in that statement - but your intended corrolary - that "torque" is measured, would also be incorrect - as shown by the logic above.

Actually your corollary is flawed, because a torque wrench is not a dynometer. The torque wrench is used to APPLY force up to a pre-desired amount, while the dynometer MEASURES an unknown amount of applied force.


Take a drum of known mass/moment of inertia, determine it's initial and final rotational velocity, then accelerate it over a measured time. From the change in energy of the system you can determine the power required to achieve that change - thus you have determined power input - no torque required.

I'm curious to find out how you managed to induce acceleration into the drum, so as to cause a change in rotational velocity without applying a rotational or twisting force (i.e. torque). Unless Sir Isaac was totally off his rocker (which admittedly he was sometimes guilty of), an object that is at rest will stay at rest unless acted upon by an unbalanced force.

Or take the previously mentioned example of a water brake - you have a known mass of water, just determine the change in temperature and you have determined the energy input - you know how long it took to do that, so you know the power applied - again, no measurements of a "twisting force" required.

This analogy is triple flawed: First a water brake measures deflection in a torque arm to determine how much force is being applied. Secondly, if you measure a change in water temperature, you are measuring only some of the heat created by the work being done, and even then the recorded temperature can vary depending on where you measure and how long you take to measure the transfer of heat from one medium to another (hardly an instaneous process). Finally, even if the transfer of heat into the water was an accurate indication of the amount of work being done, you would still need to convert the measured temperature into calories, convert calories into joules, and convert joules into watts. Which involves a whole lot of calculation and supports my original point that:

To the best of my knowledge, no-one has yet measured a single horsepower

 

measure the work something is doing in a given amount of time to find power

So what you are saying, basically, is that the work (force x distance) done over known amount of time is used to calculate power. Or put another way, if force, distance and time are MEASURED, then we can CALCULATE power.

Isn't that EXACTLY what I've been saying all along?

 

I just can't stand when people say crazy stuff like horsepower doesn't matter and can't be measured but tq is what we are after!

and i just can't stand when someone puts words in another persons mouth without at least trying to understand what the other person said or meant. i never said hp doesn't matter, i merely implied that it is not the way we should rate an engine's output.

or if i can quote a certain Mr. Lingenfelter (who knows a few things about building engine's that win races and not flawed computer simulations) "You build torque and you sell horsepower!" Which is a formula that James Watt originated 200 years previously.

 

hp is what wins races not tq

so if I put a 240 hp Honda S2000 engine in a 1988 IROC-Z which originally came with an engine that made only 230 hp, I would win more races? and the greater amount of torque the Chevy motor makes throughout would not be an influence?

puhleez, that torqueless Honda motor would be stressed in trying to push the Z towards a 18 second quarter, while the 5.7 TPI was proven to do it in a tick under 15.

 

Well, don't bet your ranch on it.

Sometime let's take up what actually accelerates a vehicle. It will most probably be difficult to get everyone on the same page in the definition of terms. We'll need to agree that Sir Issac had a couple or three of good points.

But that's another story.

 

Don't you see how this is going to work though? So you actually "measure" an electrical impulse created by nerve cluster attached to the tympanic membrane in your ear, etc.

And still, you aren't measuring torque - you are "measuring" deflection - from which torque is *calculated* based on properties of the material being deflected. It's how you measuring the "limit of rotation force I wish to apply" - no matter what it is in the end you aren't going to be "measuring" torque by your definition - rather, you will be measuring something else, depending on how in depth you wish to get - electrical impulses, etc.





But think outside the box for a second - the torque wrench was a simple example of a strain guage type system. It should be pretty obvious that the same logic can be applied to anything - but if you want it worked out, just choose a dynometer and let me know exactly how it "measures" torque!




Take a drum of known mass/moment of inertia, determine it's initial and final rotational velocity, then accelerate it over a measured time. From the change in energy of the system you can determine the power required to achieve that change - thus you have determined power input - no torque required.



Huh, what does that have to do with anything? I just indicated that you could measure horsepower without measuring torque - I never indicated a torque wouldn't be applied in that context - just that it wouldn't be measured.

But just because a torque is applied that is irrelevant. Again, I could argue that position and time are the only real units here, and everything else is a "theoretical calculated unit" - because you can't have torque without either of those. By your reasoning above that would be a perfectly valid conclusion?

Quote:

This analogy is triple flawed: First a water brake measures deflection in a torque arm to determine how much force is being applied.

Okay, so we are measuring deflection, which is a change in position. So we *aren't* measuring torque, but rather deltaPosition, and *calculating* torque based on known properties of the deflected material?

But you missed the point - it wasn't that a given dyno operates in a given way - it was that you can hypothetically determine horsepower without torque. Take a rocket engine - they can generate a tremendous amount of horsepower without any torque (reference: http://www.boeing.com/defense-space/...opul/SSME.html )


Okay, if that is your main point, what *have* we measured to the best of your ability? We certainly have not measured torque directly (only through it's effect on other things).

At what point does the "measurement" end? When it is processed in our brains? In that case the *only* thing we have measured are chemical or electrical potentials. When it is stores in a computer? Again, the only thing measured are electrical signals.

And it's absurd to imply that HP is some kind of ethereal unit that doesn't really exist since it is *calculated* from other units. So is torque - (mass * distance * distance / (time * time)) - so if that is the perspective you take *everything* is a theoretical unit except for distance, time, mass, etc.

Finally, what difference does it make if a unit is calculated or not - whether you consider it some theoretical abstraction, it still continues to be the indicator of choice for performance (as is the context here).