Can someone explain torque to me?

[avrflr]

Crikey what WSBK races have i been watching for the last 10 years (6 wins by ducati?)

ok it was rigged by the italians, but......

I've been watching the races of 916-999cc twins beating 750cc 4s. I also watched when the grand prix switched to 990cc four strokes and Ducati got utterly humiliated, leading to successive cc limit decreases for the jap bikes and increases for the Ducatis. I've also been watching bike racing in NZ, that isn't intended to be a Ducati benefit, and they lose. Badly.

Which races have you been watching again?

More to the point, on group rides on the road, I don't recall ever seeing a twin at or near the front.

[GSVR]

I've been watching the races of 916-999cc twins beating 750cc 4s. I also watched when the grand prix switched to 990cc four strokes and Ducati got utterly humiliated, leading to successive cc limit decreases for the jap bikes and increases for the Ducatis. I've also been watching bike racing in NZ, that isn't intended to be a Ducati benefit, and they lose. Badly.

Which races have you been watching again?

More to the point, on group rides on the road, I don't recall ever seeing a twin at or near the front.

If you want more info on the 750 vs Ducati years read Aaron Slights book. Same rules existed in NZ when the Britten ruled the roost. But the Britten probably still would have won.

[Badjelly]

There's a big problem with this thread, as with all discussions I see about torque: the word is used in various different ways, most of them confused.

To my mind the only useful way to use the word torque is in its technical sense, which has been given by several previous posters and also here

http://en.wikipedia.org/wiki/Torque

The torque of a force F acting at a distance d from an axis of rotation is F x d, and the ISO units are newton metres (N m). In terms of the output of an engine, connect your engine to some sort of hydraulic clutch arrangement, run the engine at whatever speed you like at full throttle, then measure the force x distance you need to hold the revs constant. Then power is torque multiplied by rotation rate. If you express torque in N m and rotation rate in radians per second (never mind) you get power in watts (W).

I won't go into all the other meanings, but you can read them on this thread. Torque determines acceleration and power determines top speed, whatever. They're kind of true and kind of untrue and too vague to be of much use in my opinion.

For an illustration of the misuse of torque figures, consider automotive diesel engines. These are normally quite low revving and develop humongous amounts of torque, which the manufacturers like to quote. The problem is, because the maximum revs are so low, the engines need to be geared very high, so all that humongous torque results in not-so-humongous forces at the back wheels.

[Badjelly]

Here's something useful I found on the WWW:

http://www.calsci.com/motorcycleinfo/Horsepower.html

[Mikkel]

I didn’t say torque equalled acceleration dude, I said:

I didn't quote you - what made you think my post was pointed at you?

Well said, Mikkel. To all the people who think torque = acceleration, just put a diesel motor in your bike and own the racetrack!

Oh you can - just take Audi at Lemans...

Torque has no time component, acceleration does. If you are standing on a spanner, failing to turn a nut, you are applying torque, you are not making power (because no work is being done), nor are you accelerating. Torque and acceleration are NOT DIRECTLY related.

Power has a time component (as does acceleration) so the two are directly related. But you can build a "dyno queen" motor that makes lots of horsepower but still produces crappy acceleration.

I'd rather look at it this way:

Work, w, is equal to force, F, times distance, x. Differentiating on both sides with regards to time, t, yields power, P:

dW/dt = F * dx/dt <=> P = F * dx/dt

dx/dt is the rate of change in distance with regards to time - or speed, v, as it is commonly know. Now let's say you're sitting on your bike doing 80 km/h (or 22.22 m/s to keep the units right) in a gear where your engine is sitting at RPMs capable of putting out 100 kW. That means you could potentially have an amount of force equal to 4,500 N (or the equivalent of ~460 kg * 1 g) at your disposal. Some of this force is spent overcoming air resistance and the rest goes on to being used in Newtons 2nd law: F = m*a, Force equals mass times acceleration.

However - things are of course not that simple... Because unlike a helicopter a motorcycle is driven by an internal combustion engine operating at varying speeds. It doesn't do you any good to have a lot of power if you can't change the engine speed. And this is the part of the "equation" that is difficult to put down in an actual equation! This is where bottom-end torque "wins" in that it makes the engine easy to deal with... It's output is more easily accessible - i.e. it has a wider powerband.

Edit:
Oh, I forgot to debunk the power = top speed myth as well.

If you take a hayabusa and chuck a turbo on it, remove the limiter, etc. The top speed will not change unless you change the gearing to utilise the new power. The red line in top gear will still be at the same RPMs - which will equal a certain speed. (This is of course assuming that the haya would be able to redline in top gear before).
Mind you - you'll get there a whole lot quicker.

Mind you - if a major manufacturer makes a vehicle they'll design the gearbox to match the power of the engine... Sometimes they make a gearbox that doesn't aim for top-speed but in stead aims at enabling the operator to keep the engine in the powerband at all times - that's a close-ratio gearbox.

[Virago]

What do they cost dude?

Any more than 8 or 9K and I'd be looking at one of the XB9 variants. Far more capable donk, bugger all heavier and better suspenders.

The Savage is definitely cheaper, proving that torque is cheap...



(Badum tish)

[Ocean1]

The Savage is definitely cheaper, proving that torque is cheap...



(Badum tish)

OK, I'll pay it.

But dayum dude, I've just eaten.

[Ocean1]

I've been watching the races of 916-999cc twins beating 750cc 4s. I also watched when the grand prix switched to 990cc four strokes and Ducati got utterly humiliated, leading to successive cc limit decreases for the jap bikes and increases for the Ducatis. I've also been watching bike racing in NZ, that isn't intended to be a Ducati benefit, and they lose. Badly.

Which races have you been watching again?

More to the point, on group rides on the road, I don't recall ever seeing a twin at or near the front.

You need to get out more dude.

Some of us don't care a jot about capacity, we're not racing. If you wanted to compare different configurations you might more usefully ask what work is done from the same fuel, but to be honest I don't much care about efficiencies either, I just find torquey donks more suited to what I do with bikes.

[twotyred]

Torque... it's when you've got a woody, and you bend it down to take a pee, and your feet leave the floor

aww man you made my beer come out my nose!!!

[Morcs]

The simple way to remember it is:

Torque X engine speed = Horsepower.


You cannot have heaps of horsepower without a lotta torque.
And 'torquey' bikes tend to be low revving.

[Hitcher]

I have been told that I am a bit of a torque wench.

[sidecar bob]

More to the point, on group rides on the road, I don't recall ever seeing a twin at or near the front.[/QUOTE]



The reason for that, is that people with incredibly small penises & an overwhelming need to prove themselves usually dont buy twins, or race sidecars.

[Edbear]

I have been told that I am a bit of a torque wench.

I thought that was "talk wrench"...

[Edbear]

The reason for that, is that people with incredibly small penises & an overwhelming need to prove themselves usually dont buy twins, or race sidecars.

Whew!!!

[McJim]

I always thought that that in laymans terms torque is a measure of how inexorable the engine is. Lots of torque very inexorable, iddy biddy torque - easy to stall.