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Re:torque to weight ratio?

  • Lambert
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10 Mar 2019 19:48 #204421 by Lambert
Replied by Lambert on topic Re:torque to weight ratio?
With a bike. The high speed available in first gear is not so much a factor of torque as it is the ability of the engine to rev extremely high and given that torque drops off as power increases over the rev range it's power that is giving you the ability to maintain the high revs. Also with bikes there is so little weight to move that acceleration is always going to be quite vigorous. There's also the implications of aerodynamics bikes having such a small frontal area. Different dynamics to cars. To get the same levels of performance you're going to have to have gert big lumps of power and torque to heave the cars weight and to bludgeon its way through the air.

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10 Mar 2019 20:35 #204422 by Andy2640
Replied by Andy2640 on topic Re:torque to weight ratio?

Lambert wrote: With a bike. The high speed available in first gear is not so much a factor of torque as it is the ability of the engine to rev extremely high and given that torque drops off as power increases over the rev range it's power that is giving you the ability to maintain the high revs. Also with bikes there is so little weight to move that acceleration is always going to be quite vigorous. There's also the implications of aerodynamics bikes having such a small frontal area. Different dynamics to cars. To get the same levels of performance you're going to have to have gert big lumps of power and torque to heave the cars weight and to bludgeon its way through the air.


Makes perfect sense to me.

So surely as with the bike, torque to weight in the jimny is a big factor and is pretty important? Example being, the car bogs down x1 rear wheel and x1 front wheel in mud. The torque is directed to the non spinning wheels and it is able to pull the jimny out with just 2 wheels, and in some cases extra weight bearing down on said wheel/s. SaxJ had an interesting video where nearly all the weight was on one front wheel, the second wheel was kinda moving in slippy mud, but the other 3 were spinning there nuts off. You could see the weight bearing down on the front wheel, but the torque got the car moving. It was incredible.

Dont know where im going with this....... ;-) But me thinking toque is awesome.

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10 Mar 2019 20:45 #204423 by Busta
Replied by Busta on topic torque to weight ratio?
Its always power that is moving things. That's why your car doesn't accelerate through the garage wall when you torque up the wheel nuts.
If the motorbike had 4x the torque, weight and power (aka an F1 car) the results would be much the same. I don't know the ratios, but I'm sure an F1 car could happily pull a 100mph first gear too and do it very quickly!
Now imagine a big diesel engine, that makes 1000/ton torque but at low revs so has a low power/weight ratio? That wouldn't work so well. Because its the power that is doing the work.

Jimny's have low power and low torque and low weight, so they compare reasonably well against bigger cars. But you do need to rev them to make good progress.

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  • Lambert
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10 Mar 2019 20:50 #204424 by Lambert
Replied by Lambert on topic Re:torque to weight ratio?
In that situation it was entirely the traction control that is saving the day. If only one wheel is getting traction then the action of the differentials is to send all the torque and power down the paths of least resistance. Given there's no central diff that means that power and torque are evenly distributed to each axle. If the rear tyres have no traction they will spin pretty much evenly. Then if the front has one wheel with traction the differential will send the available power and torque to the spinning wheel. To remedy the situation the traction control will individually brake each spinning wheel and force the drive to the wheel with traction until such time as all the wheels are rotating at the same rate either because the vehicle is moving again or all four wheels are spinning uselessly and you're in need of the winch.

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10 Mar 2019 20:55 #204425 by Lambert
Replied by Lambert on topic torque to weight ratio?

Busta wrote: Its always power that is moving things. That's why your car doesn't accelerate through the garage wall when you torque up the wheel nuts.
If the motorbike had 4x the torque, weight and power (aka an F1 car) the results would be much the same. I don't know the ratios, but I'm sure an F1 car could happily pull a 100mph first gear too and do it very quickly!
Now imagine a big diesel engine, that makes 1000/ton torque but at low revs so has a low power/weight ratio? That wouldn't work so well. Because its the power that is doing the work.

Jimny's have low power and low torque and low weight, so they compare reasonably well against bigger cars. But you do need to rev them to make good progress.

Sent from my G8441 using Tapatalk


Bingo!

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10 Mar 2019 21:07 #204426 by Andy2640
Replied by Andy2640 on topic Re:torque to weight ratio?
"If only one wheel is getting traction then the action of the differentials is to send all the torque and power down the paths of least resistance"

You can shoot me if im wrong, but shouldn't it be "send the torque and power down the path of . most, resistance.?

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