Science Forums 2

[alexander]

Craig, actually noted, lotsa good points there.

Here are some thoughts on drag coefficients:
Lowering or creating clearance in the car actually would not create any more or any less air drag, well, neglegeably more or less by exposing more or less tyre to the air, ofcourse this depends on how aerodynamic the underside is, but for most new cars, this would actually not change the drag coefficient. The reason most bigger cars, like dodge viper, my mazda and many others that actually have sleek bodies have a higher drag coefficient is because they are made to go faster. My mazda for example can do and handle rather well at 115MPH, and it actually can go and handle a bit faster, the stock tires are rated at 125, and i think they are limited to 125 in Australia, but to make safety regulations Mazda cut the limiter down to 115 for most of the rest of the world. Anyways, Prius on the other hand is set to top out at 96mph. We know that in order for the car to handle at faster speeds, we need to push the car down, so an inverted wing, and a body design and position that makes the whole car act like a wing are used. This causes turbulance that is needed for the wing to push the car down at faster speeds, thus increasing the observed drag coefficient. This is the reason formula one cars have a higher coefficient then most of the other cars (even race cars), they need a lot of down force for such a light car (under 2000lb) to handle at speeds over 100 but below 200 mph. Though, there are always interesting solutions out of this, for example a Koenigsegg CCXR (the Green supercar (1018bhp on e85/100)) has a drag coefficient of 0.36, stock does not come with a wing, and is well capable of speeds in excess of 250MPH (nobody has been crazy enough to take it that fast). They achieve their downforce (350 kg at 250km/h) mostly by using the body angling and by using the venturi effect (though the high speed handling has been shown as problematic without a rear wing (see the episode of Top Gear where they test drive the Koenigsegg CCX (the 800bhp model) and the Stig runs off road and crashes into some tires))

Anyways, on that comment that you cant decrease the drag by lowering the car, well, you can and you cant, you can not decrease the drag, but what ground effects do is they can increase the downforce at minimal drag increase, which can then allow you to decrease the down force generated by the car's wings (and even in most regular street cars there are 2 non adjustable wings) which can cut down the drag of a car while maintaining the downforce, thus overall increasing efficiency. And i could prove this, if i could create a model of my car, run it through some CFD crunching, then altering the design of the body to incorporate ground effects and compensate by slightly altering a couple of body features that produce drag and see if we can drop that 0.29 to maybe that prius range

anyhow i digress, oh i forgot to say, most formula one cars produce their curb weight in aerodynamic downforce at 78-81mph, plus they are open wheel, and we all know about the vortexes created by the wheels moving through air (hence why we see our cars covering the wheels as much as possible). Also they need it for braking, the downforce and the drag, both help in this case, i tell you what, there are not a hell of a lot of vehicles that can generate up to 5.5g on deceleration, claimed up to 1g caused by the air friction, meaning that if you take the foot off the accelerator, the F1 car traveling above 100MPH will decelerate as fast as a sports car under full braking power

Batteries... The biodegradeable Lithium Ions are able to store a lot more power and give it off much more rapidly then the current lithium ions used in the prius, and they have a smaller environmental foot print, less memory and are much more easily recycled... NiMH recycling produced gases and acids that are not very friendly, even though they are "recycled"...

Composite body panels can combine the characteristics of their metal counterparts in strength, much higher durability, and a signifficant reduction of weight, more then that, composite materials in the rest if the car;s body would weild an even bigger reduction of weight.

Tires, I've been toying with the idea of a slanted tire, one that operates at an angle, the tire such that the outer diameter is larger then the inner, also the inner corner can be rounded, which with adjustable suspension can provide low rolling friction, and increased grip patch through a corner. Lastly the thinning of the tire and rim will provide less drag and less weight. Also with a proper suspension this will provide a lot of travel even with a lower sitting car, by the means of tilting the tire... basically a mix between a motorcycle and a car tire, but on steroids... just a thought. riding on a smaller patch until you turn the wheel which shifts the weight and rolls the body of the car making the outer wheels use the full contact patch... You would have to use a harder compound on the inner part vs the outer part, too..