h a l f b a k e r yContrary to popular belief
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Keeping rubber solidly adhered to the road is the goal and loss of adhesion is failure. As long as the center of gravity is low enough to prevent rollover, a vehicle’s tire patch is a key limiting factor to how well a car corners and accelerates.
I submit that the ultimate performance car should
have eight wheels! These wheels would be either span the width of the vehicle or be mounted in tandem. Power would and braking would be applied to all wheels. The objective is to develop a car that simply does not need to brake in the corners. What are the limits?
The Tyrrell P34 F1 had dual tandem front wheels, while F1s Kurtis Kraft-Offenhauser KK500G, March 240/771, Ferrari 312T2 (T6), and Williams FW08B sported dual rear wheels. These cars were never fully developed because initial models were neither faster nor slower than their four wheeled equivalents; cost, complexity and pit times eventually did them in.
With engines now routinely exceeding 300 hp in lowly production cars, and exceeding 700 hp in exotics, it is time to rethink how this power is put down to the road.
(?) 75% baked...
http://www.simonper...-come-around-again/
Panther Six and a more recent attempt [Ned_Ludd, Aug 06 2007]
More Panther, etc.
http://www.oto6.fre...s/6rouespanther.htm
[Ned_Ludd, Aug 06 2007]
Quite a number of six-wheelers
http://www.oto6.fr/
[Ned_Ludd, Aug 06 2007]
The Friction of Automobile Tires
http://www.physics....1/tirefriction.html
[ldischler, Aug 06 2007]
Moon Patrol!
http://spyhunter007...s/moon_patrol_b.jpg
catchiest video game music of all time [bungston, Jun 14 2011]
Fan car for more downforce
http://en.wikipedia...ne_and_transmission
[not_morrison_rm, Jun 15 2011]
My M35, as promised
http://postimage.org/image/m216ko50v/
Some time ago, I promised to post a pic of my truck; here's a typical action shot. I'm on the left; at center, The Good Fairy Jenny adjusts one of the fuel pumps. [Alterother, Sep 22 2012]
[link]
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The idea is true genius. I would suggest extending it to wheels the width of the vehicle, ala road-rollers. |
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Does adding more tires really increase the total contact patch area? I thought patch size related to vehicle weight and tire pressure. |
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//Does adding more tires really increase the total contact patch area?//
I'm thinking of tanks. They have great traction. |
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The link "Friction of Automobile Tires" suggests that it's not the contact area per se, but where the maximum force lies within that area. And they talk about wider tires being better, but obviously this would not be the case in a turn. |
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The theory falls down as soon as you incorporate both deformation of the tire and the variable treading which is now common. |
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I seem to remember from somewhere that the area of rubber on the ground is dependent only on the tyre pressure. |
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Edit: Just saw the anno by [Galbinus_Caeli], but that's not where I remember it from. |
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I imagine that in a simplified model, yes contact patches correspond only to tire pressure and the weight of the vehicle, because each additional tire decreases the load carried by each individual tire, shrinking it's patch. In practice, I think that it's not really a linear relationship, and benefits would be had by adding more tires, though there would be a point of diminishing returns. |
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It's important to note the 6-wheel F1 cars were not made to improve grip, but to improve aerodynamics. Two small tires have a smaller aerodynamic profile than one large one. |
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On the other hand, the losses due to weight, friction, and mechanical complexity IMO outweigh the benefits, as they did in F1. The current solution is AWD, not more tires. |
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Thank you, [5th]; adding extra tires would only
significantly improve traction if they were drive wheels. If
not, the additional contact would, as pointed out, increase
weight, complexity, and drag, but it would also hamper
steering. Now we must examine the benefit vs. detriment
situation of adding extra drive wheels: would the
decreased motive efficiency and extra w&t on the
drivetrain be worth the negligible improvement in traction?
In off-road applications, yes. But if you're talking about a
high-performance street machine, IMHO you're barking up
a tree with too many tire swings. |
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I own a 6x6 truck, so I sort of know what I'm talking about. |
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I've thought, for a pickup truck, to replace the single-axle set of normal-width rear tires with two lighter axles bearing skinny tires. When the truck is operating unloaded, one of axles could be tucked up, resulting in better fuel economy (from using skinnier tires). Then they could be dropped to give better weight distribution of a load and/or provide better traction. This might actually be worth it with an electric drive. Either way it would look cool. |
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[FlyingToaster] I was thinking the same thing about electric cars (with wheel motors of course). Currently, it is a challenge to keep the unsprung weight to a reasonable amount, but with more wheels each requiring less power and braking, it should prove easier. It would also be easier to build in the complex computer control systems to distribute torque, compared to using differentials. |
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[Toasted] yeah, '76 M35. I got custom double-beadlock rims
made and replaced the dual rears with wider singles (a
little narrower than the total width of the duals), which
surprisingly did bump my fuel economy up slightly, from
unmentionably terrible to merely horrible. It also improved
overall on-road handling and off-road capability, the latter
since the
new tires are ~45" (up from 39"). Plus it looks wicked cool,
not the point of the endeavor but a not-unexpected bonus. |
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[marklar] NOW we've found the right tree. Commence
barking! |
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Adding wheels also adds weight for suspension, which a 20 ton tank is willing to accept, but a sports car probably isn't. |
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But with dynamically-managed suspension, that should be less of an issue. |
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Break down the problem into smaller parts: |
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1. Steering
2. Power delivery |
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Accepting the convention of steering from the front, then a single wheel pair is probably enough (even considering the need to over come torque steer) as long as the drive is from the rear. |
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With power delivery, contact area is all. So instead of one pair of large rear wheels, the ultimate dragster would have a number of full-width rollers, but the point is to keep all these rollers in contact with the road surface at all times. |
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This isn't practical on a vehicle that has to handle corners at speed (differential scrubbing). |
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For a performance car that can do bends, you need many narrow wheels (tyres), each of which rotates at a slightly different speed when in a bend, but locks up and acts as a roller on the straight; it would look a bit like a disc harrow (q.v.). |
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Multiple composite rollers would allow greater power transfer, but the CG of the vehicle would need to be very well forward, and you'd need special systems to keep all the "rollers" in contact with the surface all the time. |
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//differential equations// <groan> <considers suggesting "torque conversions", reconsiders> |
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O Woe, O Misery, Doom and Desolation .... |
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C'mon, they're probably only first-order, and with luck they'll be Exact or Separable ... |
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Wouldn't it be simpler to make the wheels taller than the vehicle? |
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Oh great, another contributor who picked up their understanding
of basic physics from Whacky Races … |
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// retaking A Levels // [marked-for-tagline]
Rephrased to "Retake A-levels" |
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erm, how about making those 4 tyres actually do some work? It's not so much the amount of rubber, more the amount of down force on them. |
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How to get down force without extra mass? Well done quite a while ago in F1 by using draught excluder strip around the edge of the car and a big fan to suck the air out, so extra down force without the mass. How effective was it - it got banned as it was just too good. Still don't know why road cars don't have this. See link |
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// why road cars don't have this // |
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1. High wear rates on the "skirt". |
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2. Requires a very even, consistent roadway; no potholes, raised grids, speedbumps. |
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3. Power demand of fan system. |
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[Toasted One] Got some somewhere. Upload here or email? |
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I can't see how creating a partial vacuum underneath
the car would be easier than blowing air upwards.
Reminds me of my Emergency Rocket Braking idea |
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Hi, he 'Music' was back,, I had a '1500' Watt hair drier,
once,, spec's migh have changed ????,. |
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here's good: it's relevant, besides my "Things To Do" list has always included "get a M37 and/or M135": M35's close enough :) |
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//can't see how creating a partial vacuum underneath// Cockerell, soup can, vacuum cleaner, in reverse? |
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"My plenum chamber runneth over ..." |
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>1. High wear rates on the "skirt".
>2. Requires a very even, consistent roadway; no potholes, raised grids, speedbumps. |
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Yeah, but no, but...ithe 'skirt' is just that plastic bristle stuff you you keeping the breeze out from under a door. It's cheap and expendable., they spent ages faffing about with materials and the cheapest turned out to work the best. |
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As the skirt is considerably more flexible than (for example) the underside of that Presidential limo, don't matter if it goes over some bumps, grids or bankers. Ok, it'd have to be quite a skinny banker. But, I'm guessing this is for people who want to drive quickly and I'm guessing that those potholes, raised grids, speedbumps etc might put that dampers on that as well? |
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Oh and just run the fan off the the closed circuit steam engine attached to the exhaust manifold, at which point someone is going to say 'the exhaust gas won't exhaust properly as it's too cold' and I will say 'well, water cooled exhaust manifolds seem to work on most marine engines...' |
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[Ao] "this content is currently unavailable". |
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We're having... issues. Stay tuned. |
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Definitely something to be said for a vehicle that can create its own parking space when necessary. |
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With an 8' x 12' bed, it practically carries a parking space
around on its back. |
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This talk of bigger wheels or more wheels misses the
point. The fundamental problems is the fact that
the tyre is separate from the road. |
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The better solution is to have the road made of
multiple parallel strips of rubber. A car, wishing to
join the road, then wraps two of these strips around
its wheels (in the form of a travelling loop). It can
then winch itself along at a considerable speed. |
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Parallel strips of steel would be far more durable, and
although the rigidity of steel would make impossible your
novel travelling loop concept and thus sacrifice a certain
amount of traction, it would allow vehicles to carry much
heavier loads. |
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Steel strips would be more efficient and allow any number
of wheels to be used if the curves are sufficiently gentle. |
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Especially if the vehicles were linked in some sort of
chain... |
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