Science Forums 2

[CraigD]

Originally Posted by alexander

Lowering or creating clearance in the car actually would not create any more or any less air drag, well
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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
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You make lots of good points about the tradeoff between increasing downforce and decreasing drag, Alexander.

A point I’ll add is that I believe that, due to rule restrictions strictly prohibiting them in nearly all motorsports since the mid 1970s, car enthusiasts tend to forget about the idea of active downforce generation, which usually involved movable wings (eg: the 1967 Chaparral 2F Can Am car), though after movable wings were made illegal, also included at least 2 “vacuum cleaner cars”, the 1970 Chaparral 2J Can Am car and the 1979 Brabham BT46B, which used motor powered fans. Both were banned after 1 season of racing, despite Brabham’s efforts to convince officials that the fan was primarily for engine cooling, with downforce being a “secondary effect”.

Though effectively banned in race cars, there’s no prohibition on active aerodynamics in passenger vehicles, so one could in principle have a car that produces zero aerodynamic downforce, and thus had its lowest possible frontal and rolling drag, until needed for lateral or straightline traction. Such an approach could, IMHO, be used to make a car with racecar-like (or better) speed and handling, yet when driven sedately, high fuel efficiency

Originally Posted by alexander

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"...

I think you meant to say “current NiMH used in the Prius” – as of the 2010 model year, the Prius continues to use a nickel metal hydride battery, rather than the generally better performing LiIon type. To the best of my knowledge, the only Priuses with sizable LiIon batteries are ones with aftermarket plug in conversion, such as by Hymotion, which uses a more environmentally friendly 90 MJ lithium iron phosphate (LiFePO4) battery (vs. the more common, less friendly lithium cobalt oxide (LiCoO2)) in addition to, rather than replacing, the manufacturer installed 24 MJ NiMH battery.

Though there’s been little talk and press about them, I’ve a hunch, and a hope, that nearly all present day batteries will soon be rendered obsolete by Lithium-titanate battery batteries, which appear to offer about a 30 times improvement over the best LiIon batteries, due to the molecules of its anode physically moving less during charging and discharging than those in a graphite anode. We discussed this a few months ago in and around the post “Lithium-titanate batteries - Wow! (by about a factor of 30)” – a key link from that post is this manufacturer’s background/overview paper.

Originally Posted by alexander

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.

I agree.

However, I think it’s place too much importance on vehicle mass reduction is a potential pitfall, because no matter what, a car is still essentially a mass hauler, with typical 200 to 1000 kg of passengers and cargo that can’t be eliminated. Safety concerns put additional constraints on materials, as do practical issues of durability. While a single-piece graphite unibody could be fantastically light and strong, it would also likely require replacement if damaged in even a fairly minor collision, resulting in an entire car that’s effectively a single field replaceable unit!

Another somewhat startling issue with ultra-light vehicles is that when you get out of them, they can blow away in a strong breeze! At present, this is seen mostly in boats and airplanes, but by my best guess, is a conceivable issue with a very advanced low mass car.

Originally Posted by alexander

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.

Through the early 1980s, there pedal bicycle tires built on something like this principle had some popularity. These tires were V-cross sectioned, with a narrow raised ridge in the center, had very high pressure (150+ PSI), riding up on the narrow ridge when going strait, then falling over onto the wider side when cornering. They actually did seem to go faster in a straight line, but tended to cause psychological problems, because the felt weird – I tried some, and found that when I stood up to pedal hard, I had to focus on not tilting the bike, as it felt like it would go out from under me if I did. In bicycling, being afraid of you bike can be as bad for performance as exhaustion or low tire pressure.

Originally Posted by alexander

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.

I don’t see how this can work – if the suspension depresses more than the ground clearance, the cars belly will hit the road, no matter how the suspension tilts or traverses the wheel.

Active suspension controls, such as a high speed, electronically controlled system to allow suspension depression with little resisting force for a short distance, then smoothly increasing greater force as the distance increases, can make for both short, firm suspension and jolt and vibration free ride. A system with very rigid wheels (eg: a thin layer of tire directly on a composite wheel) and a suspension that converts motion into recoverable electricity, can reduce rolling drag, eliminating energy that would ordinarily heat the car’s tires and shock absorbers.

Then, there’re that cyber-punk fictional classic, smartwheels, which can potentially eliminate almost any form of rolling resistance for which they’re properly programmed.

Originally Posted by alexander

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..

Seems a good idea to me, though I’ve though mostly about tires made to run on a small central strip when inflated to a high pressure, then settle into a normal contact patch at a lower pressure, because it seems like something that could be practically installed as an aftermarket replacement, based on technology currently existent in automatic tire inflation systems seen presently mostly in large trucks and RVs.

Fun stuff, all of it