Power vs Torque Questionnaire -RESULTS

[J.A.W.]

Charting exercises on graphs is of 'academic' interest, but..
..actual experiential torque/thrust - 'seat of pants' visceral feel - is IMO - yet tastier 'proof of the pudding'..

[Charlatan]

Charting exercises on graphs is of 'academic' interest, but..
..actual experiential torque/thrust - 'seat of pants' visceral feel - is IMO - yet tastier 'proof of the pudding'..

The only thing that your pants can possibly feel is traction force, which has no direct relation to crankshaft torque.

Traction force is just Power over Speed, again all there is to it.

[J.A.W.]

Actually - it is a direct/felt relationship..

See here.. http://www.kawtriple.com/mraxl/articles ... bikes2.htm

[xxChrisxx]

I can't --- believe I've been drawn into making a post. I must be a masochist. But...

The only thing that your pants can possibly feel is traction force, which has no direct relation to crankshaft torque.

I think you may want sit down and think about that statement a little bit more.

[J.A.W.]

This vid shows the rising torque curve effect vividly.. https://www.youtube.com/watch?v=1N5rm0glYwY

[J.A.W.]

& yet again here - on a like machine..
.. the application of rising torque simultaneously spins/squeals the back tyre & pops up the front ( see @ ~1:10 in)..

https://www.youtube.com/watch?v=mus_abwLAsk

[machin]

& yet again here - on a like machine..
.. the application of rising torque simultaneously spins/squeals the back tyre & pops up the front ( see @ ~1:10 in)..

https://www.youtube.com/watch?v=mus_abwLAsk

That is a good example... Of why you need to be wary of looking at torque without considering the RPM... If you look back at my cycling torque output you'll see I can generate far higher crank torque than that Yamaha, and my combined rider/bike mass is far less, and yet I cannot generate anywhere near the accelerative "seat of the pants" g-forces as that Yamaha!

Why? Because you're ignoring the effect that the gearbox has in exchanging excess RPM for increased motive force (the "seat of the pants force" mentioned above).

[J.A.W.]

& if you actually read the linked data.. machin..
..you'd see that the - Kawasaki - generates maximum rear wheel torque of over 52 ft/lb at ~6000rpm..
..rising from over 40 ft/lb - on above 3,500rpm..

By all means pedal your bike with any gearing likely to match that output/speed..
& post up the validated chart.. ..as if you could humanly power a moped of such size - likewise..
The motive antics of the machine do include weight/gearing, but the needful torque is still a fundamental..

( Note: the Kawasaki's torque output is irrespective of gearing/weight - as shown - in the linked data)..

[CBeck113]

J.A.W., charlatan is right. Torque is force x distance (aka leverage), and your torque is nothing other than the force between the tire surface and road x the wheel radius. If the force being applied to the tire exceeds the frictional force of the tire to the road surface, then you get wheel spin. If this does not occur, but the forces instead exceed the gravitational force on the front of your vehicle, then the vehicle turns around the input of the force (power), which is the rear axle.

[J.A.W.]

CB-113, & how is it that you do not read the linked data either?

The rotational "force" working on the shafts, gears & wheels - is in fact the "torque"..
.."Horsepower" being the 4th dimensional aspect of time taken/measured rate of the work thereby done.. ..by the torque..

[machin]

& if you actually read the linked data.. machin..
..you'd see that the - Kawasaki - generates maximum rear wheel torque of over 52 ft/lb at ~6000rpm..
..rising from over 40 ft/lb - on above 3,500rpm..
.

Ha ha; note your mistake here; the Kawasaki generates that torque at the engine crank... Not at the driven wheel... The wheel speed is actually much less, and the torque at the wheel Much higher as a result of the gearing effect... Hence the seat of the pants force you feel. WHEN A GEARBOX IS INVOLVED YOU MUST PAY ATTENTION TO RPM (or just simply use Power).

Interestingly Birds have learned to use levers (the simplest form of "gearbox") to exchange the puny force they can generate at their beaks, to a much greater force at the end of a lever, by an identical relation of changes in movement at the two ends of the lever... Makes you wonder, if a bird can grasp the concept...



On the plus side, good to see that we're now starting to consider torque and speed... We just need to apply the figures at the right place and then we'll be done.

[CBeck113]

CB-113, & how is it that you do not read the linked data either?

The rotational "force" working on the shafts, gears & wheels - is in fact the "torque"..
.."Horsepower" being the 4th dimensional aspect of time taken/measured rate of the work thereby done.. ..by the torque..

Torque is force x distance

[machin]

Please forgive my whimsical post. On a more serious note though, If we posed this question;

"you are travelling at 50mph in a car which has a flat torque curve from 1000rpm to the redline at 6000rpm. If you want to accelerate fastest, do you put the car in 5th gear, or 3rd gear?"

Now, I reckon over 90% of people would get that right; you'd choose 3rd gear. Its clear in that example that the flywheel torque alone isn't making the difference (it is a flat curve, so the same in both cases), i.e. So the majority of people already intuitively realise you can't take flywheel torque on its own as a performance indicator...

And from there just a small step to realise that despite the ability of the average person to generate higher torque at the cranks whilst cycling than a motorbike can make at the crank, it is the difference in crank speed (and hence gearing) which accounts for the performance difference between the two...

All us engineers do is give a name to that torque:speed relationship which we call "power"....

[mrluke]

A sensation you experience in the car over time is by definition a "measure" of power.

I can apply 300ftlbs to a bolt (given a long enough bar) but its not going to move the car very far.

[Charlatan]

I can't --- believe I've been drawn into making a post. I must be a masochist. But...

The only thing that your pants can possibly feel is traction force, which has no direct relation to crankshaft torque.

I think you may want sit down and think about that statement a little bit more.

With gearbox, final drive and wheel-radius to consider, you are better off just thinking Power over Speed equals Traction force.