Quote:
Originally Posted by AeroMcAeroFace
In the Tahoe hybrid thread the car would only ever get 60mpg(US) due to rolling resistance, in the insight thread half of the drag was rolling resistance.
Theoretically rolling resistance is proportional to force applied, so a lighter car would have lower rolling resistance.
A car that generates significant lift has lower rolling resistance at higher speed.
Low drag shapes in ground effect often have high lift coefficients.
I am imagining a car, a bit like an ekranoplan, but never leaves the ground so the wheels always drive the car. Steering angle sensors, wheel slip sensors and brake pedal sensors cause the lift to stop and spoilers to create downforce pop up. Turning at speed can be assisted by aerodynamic aids.
As long as it is aerodynamically stable, in all directions, can dump lift as necessary I see no reason why this wouldn't reduce rolling resistance.
Obviously this is really complex but looking at cars like the huayra, certainly possible. Is it the case though that by the time significant rolling resistance reduction occurs, the speed is so high that rolling resistance is a tiny fraction of total drag?
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I'll try a link to a video with drag charts germane to your question. The proportion of the road load due to R-R compared to the aero portion really falls with increased velocity. So it is part of decision making.
The other thing I'd mention, is liability, and the ability for the system to fail-safe. You don't want the county coroner's office involved with your car.
If you've seen race cars abruptly take to the air at 24- Hours of Le Mans, you'll understand how spontaneously aerodynamic phenomena can occur.
The ECU would have to be programmed to recognize precursor anomalies, and signal lift-kill at the speed of light, in order to protect the occupants and surrounding motorists. Servos, solenoids, pneumatics, hydraulics, or what have you, would have to react instantaneously to the prompt from the ECU output. Things can go south in an instant.
I speculate that the risk assessment, so far, to any venture like this, has been shot down by corporate liability attorneys. Too much pain, for whatever perceived gain.