Torques or Horsepowers?

So what I think I'm hearing above the roar is that the torque rating is the only one I really need to worry about when selecting a car transmission to fit to a lower torque rated, but higher revving bike engine which means I can go smaller and lighter which as that Chapman chap would say is good.

Next step is to compare ratios on the smaller units to see if I can find a stand out unit. This will probably take days to do or even weeks depending upon how much life and job will interfere. I could have a lot of fun being independently wealthy.

So when Mr. Clarkson refers to torques on TG is he referring to lb-ft or some other silly British measure like newton-hands or stone-meter?

GTwannaB wrote: So when Mr. Clarkson refers to torques on TG is he referring to lb-ft or some other silly British measure like newton-hands or stone-meter?

lb-ft. I'm not quite sure why considering that we're the only non-metric country in the world, but all of the car specs in Top Gear are in imperial units.

ReverendDexter wrote:

GTwannaB wrote: So when Mr. Clarkson refers to torques on TG is he referring to lb-ft or some other silly British measure like newton-hands or stone-meter?

lb-ft. I'm not quite sure why considering that we're the only non-metric country in the world, but all of the car specs in Top Gear are in imperial units.

The UK hasn't completely metricated. Their speedometers still read in MPH etc.

92CelicaHalfTrac wrote: Torque is a real number. Horsepower is a function. If things break because of power, it's torque. If things break because they spun too fast, it's probably horsepower.

in other words, breakage a shearing force is from torque overload and spinning faster than it is capable is from POWAAAA!11!111111!!!!!!!1!

" Horsepower sells cars, torque wins races. " Mr Ferrari

I always say "torque" as in " 342 horsepower and 401 torque" ...nowadays it's pretty much 'at the wheels'...and people know what you're talking about anyway.

My heavens I had thought many of you were smarter than all of this.

I think the answer to your question is "torque".

carguy123 wrote: So what I think I'm hearing above the roar is that the torque rating is the only one I really need to worry about when selecting a car transmission to fit to a lower torque rated, but higher revving bike engine which means I can go smaller and lighter which as that Chapman chap would say is good.

Yes and no Transmissions are rated at a gross torque number and a GVWR. For instance, a later T56 is rated to take 450 lb-ft... in a lightweight car. If I put it behind my Powerstroke diesel making 450 lb-ft and then tried to tow 10,000 lbs with it, it will not last long.

So, with what you're doing, you could get away with fudging a little. If you were (for instance) putting a T56 in a 500 lb motorcycle, it would take a good bit more than 450 lb-ft since its not moving much weight. The amount of actual force being placed on the transmission components is a function of the force being input on the drive side AND the resistance force on the output side. Reducing the weight reduces the resistant force on the output side.

Edit: You also should consider that internal bearing speeds come into play. Again, using the T56 as an example; in a car that sees 6000 rpms input speed its fine. If you put it behind a 600cc sportbike engine that redlines at 13,000, no bueno. At around 8000-9000 RPMs the bearings will flutter and eventually explode. Flutter is that vibration you get when you spin a bearing too fast. For instance, have you ever spun the wheel on a board game too fast and all of a sudden its buzzing and slows down? That's the net effect.

Traction breaks transmissions.

All the torque in the world won't matter until the car hooks up.

Trans_Maro wrote: Traction breaks transmissions. All the torque in the world won't matter until the car hooks up.

He said in two sentences what I took three paragraphs to say.

Without traction there is (almost) no torque.

Traction provides the resistance to be overcome by torque.

If we get into the damned lb/ft argument again, I'll spend the entire night rocking in the corner with my hands over my ears yelling "Hush little baby" at the top of my lungs.

Edit: You also should consider that internal bearing speeds come into play. Again, using the T56 as an example; in a car that sees 6000 rpms input speed its fine. If you put it behind a 600cc sportbike engine that redlines at 13,000, no bueno. At around 8000-9000 RPMs the bearings will flutter and eventually explode. Flutter is that vibration you get when you spin a bearing too fast. For instance, have you ever spun the wheel on a board game too fast and all of a sudden its buzzing and slows down? That's the net effect.

I've got a way around that.

I loves me some "ftpnds"

Most bike motors have integral transmissions... so a trans to a trans would give you a ton of gears but probably wouldn't work very well when you factor in the final drive ratio & wheel size.

Harley uses a separate gearbox....

This is sounding interesting!

PS: what ever you do make it hook up the 1st 50-100 feet off each corner especially right handers.

HiTempguy wrote: I loves me some "ftpnds"

And hates you some vowels?

Hey this is what we do at work!!!

Curtis73 is absolutely correct.

Torque is what breaks transmissions. You have to have resistance on both sides of the transmission for the transmission to see torque (The comment "without traction there is no torque" is a good cliffs notes on the idea)

RPM is what usually effects the bearings. Although they do see load from the torque it takes a combination of RPM and torque to break them. Don't get this confused with Horsepower (HP=tq*rpm/5252) You can spin a transmission fast enough with no torque to destroy it.

When torque breaks a transmission it is from deformation. Gear teeth, Case, support shafts, which will cause the contacts point (teeth, dogs, etc) to loose optimal engagement, then they are in weak state and break. You do have the rare overload situation where the gears are way to weak or a transmission has been cost down to use in a different class and the gears are the weak points. In which the gears will shear. Not extremely common but more so in this wonderful cost down world we live in.

Then you have shock loading which is essentially an impact on the whole system which is a magnified torque. To quote LeeLou Dallas "Big BA DA BOOM!"

Then you torsional vibration on longer systems where a heavy load/high traction situation and high engine pulses, causes the whole system to go to a natural frequency. This happens more in diesel boats than in vehicles due to the loading states involved.

Then you have...

Yes, torque transmitted through the transmission is the main problem, then RPM on the bearings

admc58 wrote: Most bike motors have integral transmissions... so a trans to a trans would give you a ton of gears but probably wouldn't work very well when you factor in the final drive ratio & wheel size. Harley uses a separate gearbox.... This is sounding interesting!

I think I have a solution for both situations but I am using an Harley type for this build.

I looked at a CVT option tonight and don't like it as well from a packaging angle nor am I convinced yet it will handle the speed, but I have more people to talk to on that over the next few days to a week.

This really IS sounding interesting - to me at least. There's something about looking at something from a totally new angle and having that Ahh Haa moment that's exciting.

Due to several personal issues I've had trouble keeping much interest in actually doing anything with a car for a while, but this has been like Viagra for the mind and psyche.

I Am Keyser Söze wrote: Curtis73 is absolutely correct.

You had me at "absolutely"

When torque breaks a transmission it is from deformation. Gear teeth, Case, support shafts, which will cause the contacts point (teeth, dogs, etc) to loose optimal engagement, then they are in weak state and break. You do have the rare overload situation where the gears are way to weak or a transmission has been cost down to use in a different class and the gears are the weak points. In which the gears will shear. Not extremely common but more so in this wonderful cost down world we live in.

Which spawns another question for me personally (tiny thread jack). Helical gears put more longitudinal loads on the ends of the case but have the advantage of more surface area on the tooth contact, and straight gears put more radial (side) loads on the bearings and shaft. Is there a generally-accepted crossover point for a given transmission where X degrees is the strongest for the tooth pitch? Or are straight teeth always considered stronger?

Then you have shock loading which is essentially an impact on the whole system which is a magnified torque. To quote LeeLou Dallas "Big BA DA BOOM!"

25 points for using a 5th Element quote. (good lord she's hot)

Then you torsional vibration on longer systems where a heavy load/high traction situation and high engine pulses, causes the whole system to go to a natural frequency. This happens more in diesel boats than in vehicles due to the loading states involved.

Amen to that. At the tranny shop we saw plenty of NV5600s from behind Cummins trucks, but almost never saw them from Duramax trucks... due in part I'm sure to the fact that they're not as common in the GM. But, 600 lb-ft from a Cummins is a whole lot different than 600 lb-ft from a Duramax. The Cummins being a 6-cyl applies a 100 lb-ft surge on the crankshaft every 120 degrees of rotation. The Dmax applies a 75 lb-ft surge on the crank every 90 degrees of rotation. BIG difference in durability at those torque numbers. The Cummins just rattles it to pieces

It also shows up on the clutch. The Dodge goes through clutches quicker - which could be a design difference - but the flywheels tend to show a repetitive pattern of wear. The torsional vibrations seem to cause "micro slipping" of the clutch. That can't be easy on the guts of a tranny.

I know that as the tooth angle increases the axial (thrust) load on the tranny shafts increases and efficiency decreases. Not sure from a practical side what the optimum angle is, but I'm sure it could be calculated to determine the theoretical ideal.

As for Cummins vs Duramax, I wonder if some of the difference in wear you saw was a product of driving style and not so much power delivery per combustion event (even though it is the power delivery that ultimately cause the slippage).

Many people have the idea that it is good to lug a diesel, and the cummins sound/redline might reinforce that myth. Lugging to puts more stress on the engine, clutch, and tranny by requiring higher input torque to produce the same output torque(and work) as faster spinning engine in a lower gear.

curtis73 wrote: Which spawns another question for me personally (tiny thread jack). Helical gears put more longitudinal loads on the ends of the case but have the advantage of more surface area on the tooth contact, and straight gears put more radial (side) loads on the bearings and shaft. Is there a generally-accepted crossover point for a given transmission where X degrees is the strongest for the tooth pitch? Or are straight teeth always considered stronger?

Think balance optimization, you can put a ton of money into a gear, or the case, etc, etc, etc. Or you balance out for what you need. We have optimization programs bases on cost. We use straight cut PM gears for 90% of our transaxles and never have a problem. We have a few Solid steel gears for our medium duty applications. (I am on product side not design, so I know enough to know what we do. Not the nuts and bolts of how we do it) We use helical cut gears in many of our parent company transmissions. You also must remember NVH is a huge factor in many applications. Straight cut are noisy, but are thin for the strength required. When it comes to overall yield strength tooth contact is what is important. You need a small diamter where thickness isn't an issue, go helical, thickness a problem and noise and diameter are not, go straight cut. It is a true balancing game.

25 points for using a 5th Element quote. (good lord she's hot)

Nothing like cloth strips for a costume to wear in public. Solar bandages. Why don't we have these now?

Amen to that. At the tranny shop we saw plenty of NV5600s from behind Cummins trucks, but almost never saw them from Duramax trucks... due in part I'm sure to the fact that they're not as common in the GM. But, 600 lb-ft from a Cummins is a whole lot different than 600 lb-ft from a Duramax. The Cummins being a 6-cyl applies a 100 lb-ft surge on the crankshaft every 120 degrees of rotation. The Dmax applies a 75 lb-ft surge on the crank every 90 degrees of rotation. BIG difference in durability at those torque numbers. The Cummins just rattles it to pieces It also shows up on the clutch. The Dodge goes through clutches quicker - which could be a design difference - but the flywheels tend to show a repetitive pattern of wear. The torsional vibrations seem to cause "micro slipping" of the clutch. That can't be easy on the guts of a tranny.

Micro slips kill CVTs as well. Google Nissan CVT whitepaper. They have done alot of research on this.

Oh yeah the FPT/Cummins engine has a hell of a torque spike issue.

Nasty gear destroyer there.

RossD wrote:

bravenrace wrote:

RossD wrote: Torque. There may be a speed limit to the bearings. And can we not say 'torques'? It's just at easy to type 'ft-lbs'

Actually, the correct term is lb-ft.

x * y=y * x Commutative property Both are the same.

Actually, torque is defined as the cross product of radius times force (written r X F), and the cross product is not commutitive. You won't see any ill effects by commuting in 2D, but when you're using vectors in 3D, it matters.

Torque unit naming is a bit arbitrary. By the cross product definition above, all units should be length-force, but they're not... For example, N-m is the SI unit for torque. I suppose once you get a numerical result, the units become commutitive with themselves, so you could make that argument. As someone else said, though, you have to be careful about getting torque units confused with work units.

Last thing, when you talk about power and torque, you should stick with either units or measures. So if you want to say "horsepower", it is a unit, so name the torque unit too. In other words "horsepower and torque" is mis-matched. Should be "horsepower and lb-ft" (which sounds silly) or "power and torque". I would go with the latter - it is equivalent to asking someone how tall they are instead of how many feet they are.

- it is equivalent to asking someone how tall they are instead of how many feet they are.

Well I have 3 feet, but I'm pretty sure it has nothing to do with being conceived near a nuclear power plant.

Torque is committing crimes with both direction and magnitude, while energy might be committing crimes with magnitude but no specific direction. However it is possible that torque and energy might both be committing crimes of equal magnitude and in equal directions, and when this happens they can be considered equivalent. Basically the same principle as a square is a rectangle, but a rectangle is not necessarily a square.

So while you can't use lb-ft to describe any application of energy other than torque, you can use ft-lb to describe any application of energy including torque. So as it applies to cars, it would seem that either way of writing it is still actually still equivalent.