Torquing Misnomers

[Auberon]

Forgive me please but I can't NOT comment:
To start this please remember: ".......Love that torque"

I have been reading the tyre threads quite intently and still wonder where the "power" goes.
The term power appears frequently herein as a misnomer.

The engineering/physics of this is NOT to do with power. The power is still there.

The correct term to eliminate confusion is TORQUE.

To explain, ever so simply, the greater the diameter of the tyre, the greater the torque it can impart to oppose that generated by the drive-train (which remains the same (to a maximum)).
THUS:
The drivetrain imparts a COUPLE at the extremeties at which it contacts the wheel (the studs but more appropriately the axle). The magnitude of a couple is known as its MOMENT or TORQUE although the term tourque is usually restricted to a moment tending to TWIST A SHAFT.

This is verily RESISTED by the tyre as its leverage AGAINST the couple increases in direct proportion to diameter.

Thus, torque is lost.

The problem is fundamentally, that the diamter of the drivetrain does not change, so it is the torque that is the losing factor: not power.

TORQUE = TURNING EFFECT.

Power is the work done by torque per unit time.
OR if you prefer:
Power in rotational motion is equal to the product of the torque and the angular velocity with which the TORQUE is applied.

Lots of different names appear around the world for bits 'n pieces but physics and engineering is the same world wide so can we please get this right.

I'm not even going near moments of inertia and dynamics.

.......love that torque.
Cheers
Auberon

 

[speedracerbubba]

Even easier explanation is using gear ratios since every gearhead understands what that does (especially when you go from high range to low range in a vehicle like the 4wd jeep).
When doing dyno runs my brothers car only made ~450hp at the wheels. Turned out the guy entered the gear ratio in the dyno as 4.10 instead of 3.55

 

[tjkj2002]

Yep torque is a twisting force and horsepower is a fictitious #.HP is calculated by the torque produced by the engine,dyno's measure torque the computer calculates HP.At 5454 rpm all engines produce the same torque and HP.

 

[Boiler]

Not sure I agree with this in whole...

An engine puts out a specific amount of torque at the driveshaft. That torque divided by the wheel diameter equals the force applied at the ground, parallel to the ground, which propels the vehicle.

With larger tires, torque divided by radius (which grew) results in a smaller force.

Force / mass = acceleration, so if you decrease the force and hold mass constant you'll have less acceleration. Tire weight plays into this as well, as there is more rotational inertia to overcome, so using larger tires of the same weight would decrease acceleration due to geometry, and if they are heavier it decreases acceleration due to inertia.

Torque output of the engine didn't decrease. In fact, that's a basic principal of engineering. The sum of moments (torque) equals zero, meaning torque in equals torque out.

 

[tommudd]

So then

Which came first the chicken or the egg?

 

[Auberon]

Which comes first

Boiler,
You seem to agree with my point that torque is the same. That is my main point.

An engine is designed to produce torque until it becomes linear (so Sir Isaac could play a part) when the tyre begins to be turned by the torque after its resisting MOMENT OF INERTIA (whilst static) has been overcome.

And.....it is not, with respect, a simple matter of dividing by proportionate radius in a dynamic (kinematic) situation.

You also stated that if torque in equals torque out we wud have equillibrium (as these are opposing couples/moments).

I believe there is some confusion between Newtons second Law ie Force/Mass/ acceleration.....I purposely tried to avoid a discussion of kinematics as we wud be integrating on the net.....no thanks. This is a Law of Physics of the static world, not the dynamic one - it just leads to dynamics if the sum of forces overcomes resistance (in this case a couple) to overcome the resistive couples of the tyre.

Now to the tyre:
We have a couple of couples.
At take off (cos its way simpler):...the engine puts out torque often magnified by the torque converter in a STATIC situation until it overcomes the resistive torque of the wheel / tyre.

With kinematics we cannot simply divide by the proportion of changed radius.
We are still talking about a turning moment to start motion (moment of inertia), OPPOSED by a static motion, inertia and coefficient of friction, defection of the tyre wall, compression of captive gas, dependent on temperature, the moment of inertias of the rim.....and this is where the problem lies (mainly) apart from arresting the ANGULAR MOTION of big suckers of tyres. This is in no way complete.

To my original point:
TORQUE is our starting point NOT........POWER....
so with whom are you disagreeing....the laws and rules of physics or me.

The wheels on the truck go round and round .

Which comes first, torque or power. Well:

POWER = work done by torque per second

So to derive Power, torque must do work over time.
Therefore, to answer tommud, torque has to come first, by definition.

To take the simple formula:
T = F r where T = torque, F = force and r = radius is fine when we realise that in its simplistic form, one set of turning forces are working in a clockwise direction, the other are in an anticlockwise direction and until one set of torque overcomes the other, we have a static situation (equillibrium).

Cheers
Auberon

 

[KeswickDave]

You guys are making my head hurt!

But seriously while I have nothing to add, it's an interesting read... carry on

 

[Ry' N Jen]

I read this in someone's sig once.
"Horsepower dictates how fast you're going when you hit the wall. Torque dictates how much of that wall you take with you when you hit it."

Well said Lad!

 

[Boiler]

Wow, you blew my mind there. I guess I could have just said that increasing the radius of the tire will decrease force applied to the ground, not torque. Which is why one would regear, to increase force applied at the ground. At least that's what regearing is going to do.

 

[tjkj2002]

Wow, you blew my mind there. I guess I could have just said that increasing the radius of the tire will decrease force applied to the ground, not torque. Which is why one would regear, to increase force applied at the ground. At least that's what regearing is going to do.

In a sense.................

lest say you have 200hp at the rear wheels(on a chassis dyno) with 3.73 gears and 31" tires,if you put on 35" tires you will have 150hp(hypothetically speaking) with the same engine and same gear ratio.Then you swap in 5.13 gears,where 4.88's is the stock conversion,you would get 225hp(agian hypothetically speaking).So in a sense you can increase your power by regearing without having to modify the engine,but at a cost though.

 

[Boiler]

but at a cost though.

Less tire revs per engine rev? Thats why I could never understand why milage goes up, or is it just because you operate in a more efficient range of rpm?

 

[tjkj2002]

Less tire revs per engine rev? Thats why I could never understand why milage goes up, or is it just because you operate in a more efficient range of rpm?

less top end(top speed).

 

[belvedere]

Here's a couple of articles:

http://www.howstuffworks.com/question622.htm

http://www.allpar.com/eek/hp-vs-torque.html

 

[tjkj2002]

I'd bet almost every drag racer would disagree with that 2nd link,you never shift at redline since that is a sure way to blow your engine.You shift right at the end of your power rpm range,where you built the engine to make at least 75%+ of it's peak power.

 

[belvedere]

My deepest apologies. My reason for posting the links was not to instruct people (in a Jeep forum) how to shift a drag car, but rather a few basics on torque and HP. For instance, people who think that tire size or gearing affects HP.

 

[Auberon]

Apologies for typos it's 0538 presently:
Budke - oh how true!
Belvedere - spot on.
I like article 1.
The 2nd article is a tad loose only because it makes a valiant effort (sorry to old Mopar drivers) at describing a very specific subject and tries to make some sense in simple speak of the confusion between kinemetics and statics.
I would only contend that you can measure torque and need to for reasons which will become apparent and this is one of the primary factors used in the design of rotating componentry.....along with moment of inertia which is closely related etc.

SO WHAT DOES POWER MEAN: nothing really:
Power is void of intuition. For interests sake.... 1 HP was originally first used by James Watt (1736-1819) for grading the power of steam engines.
One horse power was the ESTIMATED work that could be done by a strong draft horse over time.

Redline choice isn't a point of arguement - it too, is arbitrary and quite adequately used as an illustrative point in the second article belvedere put forward. Cool.

Regarding Jeeps:
For longevity, we don't wanna run our Jeeps near their maxima - we can already torque out components with what the VM motor puts out.

The second article makes some other good points, too, that is why I earlier introduced the effect of the ******/driveline.

This is why I have tried to avoid kinematics - too hard for this site.
The only point the article makes that I wud contend is that torque is not arbitrary - even for screws and bolts - it is measurable and usable in determining strength of materials/componentry.

The article describes another world, and as you said belvedere adequate illustration....relating to POWER, not for criticisim.

I would also say that the article, even well written for a specific example, states well and clearly that Sir Isaac doesn't belong in the realms of kinemtics.
Here here!

I believe the second article mentions that one shouldn't change gear under the wrong conditions, you can say goobye to your engine.

tjkj: Power can be made by regearing? Let me at it. Athough it is currently about as useful as cold fusion to the common man.
Doesn't regearing re-torque the shafting? Given that P is a function of torque in an angular sense per unit time, then correcting shift points are compensating for the contra-rotating (resistive) torque of the tyres.

Boiler: < tyre revs / engine rev - it goes up? (I assume you mean improves) because kinematically it takes more turning effect to overcome equillibrium state 1 - a static truck. If you do this infrequently, and keep rolling, then the moment of inertia of the larger tyres, helps you keeps rolling much like a large flywheel which had its moment of inertia helping keep a steam engine or hit and miss motor truning as the mass is near it periphery: the spokes have little effect on "I" whereas the "ring" will be significantly more contributary.

I suggest trying this fuel monitoring in heavy stop-start motoring with larger diameter tyres.

Food for thought:
I do hesitate to add this but:
our primary motion is linear....pistons are linear - to make it useful to us, it must be changed via the crankshaft to rotary (which you will all be aware has a flywheel of sorts to keep it rotating smoothely)......transmission..... rotary..... driveline..... rotary. Rotary motion begets torque.
The tyre then converts this to linear motion.

In summary, until the next installment:
Don't we have our Jeeper caps on here even if some of us are drag racers. Please let's not hijack the thread from its rather simple point that seems to finally becoming established.

All I want is for us to use the right term in the right place so we don't appear to be well, you know....dumbarps

One closing question which could be regarded as rhetorical but I am sure it won't:
What parameters would one use to determine the size of hollow or soid rotary components if we did not use torque....and moment of inertia.

Cheers
Auberon
Apologies....I noticed I started using engineering shorthand in a couple of paragraphs.

 

[belvedere]

Auberon - Thanks for the excellent post. Though I have a pretty decent grasp of concepts like torque and HP in my mind, it's not always easy for me to put things into words. That's why I posted the links, even though everything in the articles may not be relevant to the discussion at hand.