Quote:
Originally Posted by Mixer
Torque is what makes a car accelerate or pull a load.
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Power is what makes a car accelerate or pull a load.
Power = Force * velocity
Force = mass * acceleration (Newton's second law)
Therefore
acceleration = Force / mass = Power / ( velocity * mass )
So... the faster you are already going, or the heavier you are, the harder it is to accelerate for a given amount of power. Makes sense right?
Quote:
Originally Posted by Mixer
You make statements like this it is clear the wind sails directly between your ears, unimpeded.
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Unfortunately you are wrong, but that's ok!
Torque is an intermediary force that can easily be manipulated by gearing. Power however is the
direct rate at which chemical energy is extracted from fuel or battery and turned into useful work.
A typical car multiplies the torque produced by the engine by 15x in first gear (5.0 first gear ratio, 3.0 diff ratio).
Can it multiply the power by 15x? No, not under any circumstance that would void the conversation of energy. Therefore power is
far more fundamental than torque, after all it is all about manipulating energy. That a twisting force is exerted on the crankshaft due to the way a piston engine is designed is largely incidental.
A vehicle's torque can be easily changed by gearing, power however is the
fundamental rate at which the vehicle can do useful work.
With large torque but zero power, a vehicle will go nowhere and do nothing.
acceleration = Force / mass = Power / ( velocity * mass )
If torque is very large, say an elephant hanging off a breaker bar attached to the crank pulley, but power is zero... Then nothing will happen (aside from snapping off your crank pulley bolt!).
A lot of people don't understand the relationship of power and torque, I am happy to explain.
It took me a while to understand myself.
Fun fact:
1 Nm = 1 joule
The units are equivalent, you can Google it.
And what's power? Joules per second (the definition of a Watt)
So what does that make torque? It's just the energy extracted from the fuel per one rotation of the engine.
So a 200 Nm engine running at 8000rpm is equivalent to a 400 Nm engine running at 4000 rpm. The former is like a small hammer tapping really fast, the latter is like a big hammer tapping slowly, ultimately they both do the
same job because they are producing the same amount of
power.
It's certainly not torque that "makes" things move. For example, wheel nuts on average car are torqued to 110 Nm and you are certainly not intending for them to budge one iota!