Posted by Charlie on Tuesday, February 13, 2001 at 2:43AM :
In Reply to: No, you won't get anything near that... posted by casebro on Monday, February 12, 2001 at 9:29PM :
Huh? Your physics is a bit off. It doesn't take any "horsepower" to spin a tire or any other round object a constant rpm. It does consume energy to speed it up and it stores energy (rotational kinetic) till it's slowed down. Since our trucks don't have regenerative braking it does waste energy to spin up big heavy tires and slow them down with friction brakes. Clearly, it would be more energy efficient to drive around and 20" diameter solid steel wheels, or perhaps 20" diameter 5" wide rubber tires at 150 psi. But it wouldn't ride very well and it wouldn't do well in axle deep mud. Theoretically any vehicle with an electric motor that's capable of regenerative braking, IOW using the motor as a generator and feeding power back into a grid in order to brake, wouldn't "care" from an energy efficiency point of view what wheel diameter is.
If someone is realistically concerned about energy efficiency in heavy clunky trucks there's only one answer - DIESEL. And when hydrogen comes on line you can bet the turbocharged direct injection compression ignition internal combustion engine will still be the item to beat.
Charlie
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