Quote:
Originally Posted by jyl
The reason I'm talking power is because in cycling, that's the common language. It takes pedaling at 250 watts to the crank, to ride 20 mph on flat ground in calm air. So when I saw the claim that this drive will produce 200 watts at 20 mph, that was interesting - if true, the drive could propel a bike at 20 mph with the rider barely exerting himself.
Plus, as established here, I don't understand power.
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You seem to ignore the concept that power is a derived quantity, it is the mathematical product of force and velocity. If
either of those change, power changes as a consequence.
when pedaling an input force is applied to the crank, the force is changed by the mechanical properties of the drivetrain to a different force as a thrust at the rear wheel. The other input variable is the cadence(speed at which the force is applied) this is also altered by the mechanical properties of the drivetrain. Opposing those 2 input variables is friction and aero which also have a velocity dependence. If the mathematical product of the inputs exceeds opposing mathematical product there is acceleration, if the opposing variables exceed the input there is deceleration. There is constant speed when the input and opposing power are equal.
1 N at the pedal 2 1 rpm, is much less power than 1N at the pedal at 100rpm. There will be 0 friction and aero resistance at 0 mph, both will rise w/ speed