Calculating wheel torque from engine torque

[berkeman]

Thread closed for Moderation...

 

[berkeman]

Thread re-opened.

 

[thichiuem]

To Jack_action and OldYat47
It looks like you are in 2 different frames of reference:
Acceleration increases, torque increases, that's ok, but if you know the torque of 2 motors, is it true that every motors with greater torque will have a greater acceleration? that's not yet.
Wish you will have good Ideals to us.

 

[jack action]

but if you know the torque of 2 motors, is it true that every motors with greater torque will have a greater acceleration?

The vehicle with the greatest torque will produce the greatest acceleration.

At zero velocity, any motor can produce any level of torque with the proper gearing.

At any other speed, the maximum vehicle torque only depends on the vehicle power output, which is the same as the motor power output (less some drivetrain inefficacies). So gearing the maximum motor power output to the desired vehicle speed will give the maximum vehicle torque and thus its maximum acceleration at that speed.

@OldYat47 is long gone.

 

[thichiuem]

@jack action : Between an elephant and a horse, which acceleration is greater?

 

[cjl]

Probably the horse, even though the elephant has a much higher power output. Acceleration is based on power to weight though, and in the case of horses vs elephants, a lot of other biomechanical factors that really aren't relevant to the discussion at hand.

 

[jack action]

@jack action : Between an elephant and a horse, which acceleration is greater?

I read that a horse can produce a peak of 15 horsepower. I cannot find a similar value for an elephant, but when comparing with horses, they seem to be able to pull a similar weight ratio compared to their mass, maybe even larger. This would suggest that their acceleration would be similar from a standstill start, maybe even larger.

But horses will be able to reach a higher maximum speed, meaning they accelerate faster at higher speeds (while the elephant's acceleration goes to zero). But this may be like comparing two identical vehicles with different transmissions: One accelerates fast at low speeds but reaches quickly a top speed, and the other accelerates slower, but over a much wider speed range. With the horse and the elephant, that would be comparing their biomechanics.

As an aside, on a 40-yard dash, this is what a professor of applied physiology and biomechanics had to say:

Squirrel: The nutty rodents can hightail it at up to 14 mph—on a good day

Elephant: Although much more massive, they can sprint at roughly the same speed as a squirrel

 

[thichiuem]

That is to say, you must have the same frame of reference.
To compare two equivalent cars (in terms of mass, gear ratio, wheel radius, ...) it can be said that the vehicle with the greater torque has the greater acceleration.
As for comparing 2 cars (assuming there is no loss), because P=ma*v, the car with larger P/m will have a greater acceleration.
Thank you for your reply and would like to learn more.