h a l f b a k e r yYeah, I wish it made more sense too.
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Make the tires, harder by using tougher material, and less air. Improve the suspension to compensate for increased shocks/jerks. Improving the suspension by using any techniques, such as air suspension etc, should not affect fuel efficiency. However making tires harder will reduce the drag noticably.
Where energy is wasted on the highway
http://www.fueleconomy.gov/feg/atv.shtml
Rolling resistance is 6-8%, but this is almost 1/3 of the total mechanial energy after all the other losses. [ldischler, Feb 26 2012]
Michelin Energy Saver
http://michelinman....ails#techspec_table
[DIYMatt, Feb 26 2012]
Northbound (?) elevated, M6 - Spaghetti Junction
http://www.normanfield.com/spaghetti.htm
A slow load but appears to be in the Birmingham neighborhood that [8th] is referring to... [normzone, Feb 27 2012]
[link]
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Harder tires => less contact area with the road => slides around more easily... no? |
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yes. So tyres can be made wider then, for better grip. |
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Most of the drag is in either the drivetrain, or is aerodynamic - and therefore viciously speed-dependant (square law). |
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The main reason I was sad when Aptera went bust. I was so looking forward to that car. They had a series hybrid version (gas engine functions as generator to power the electric motor) and they claimed after the battery was drained and the generator was fired up, it could still get better than a hundred miles to the gallon. With the aerodynamic shell it had, I wouldn't doubt it. |
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To the matter at hand: Harder tires = a LOT rougher ride. Hope you know a good chiropractor. |
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//Aptera went bust// awww. |
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You hadn't heard? Sorry, didn't mean to break it to you so rough. I thought everybody knew already. |
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Harder*, wider tires, improved suspension for better road
handling... you, my friend, have just described a race car.
Baked at high speed, I'm afraid. |
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* there are many different meanings of the word 'hard'
when describing tires. |
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As speed increases, say above above 80 mph aerodynamic component of the drag becomes more and more significant. But I think, at lower and medium speeds, tyre and drive train drags will be relatively significant. This is the reason, railway is 3 times more efficient than automobile and boats are 6 times. |
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//railway is 3 times more efficient than automobile and boats are 6 times.// |
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Uh... first I've heard of that. Where'd you get those figures? |
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somewhere on lowtechmagazine.com |
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Railroads are indeed far more efficient than automobiles--
300-400 mpg/ton (not including idle periods, which drop
the figures marginally)--but for different and more
complicated reasons. I dunno about ships, but I imagine the
figures are similar, and again for different reasons. The
advantage of the automobile is that it can go virtually
anywhere, not being restricted to tracks or waterways. In
terms of utility and function, it's like comparing apples to
pork chops. |
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//it's like comparing apples to pork chops// |
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Widely known to exist. Links provided. |
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Who would want to go any slower ? |
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Nobody in your country. I thought Americans drove too fast
until I experienced the M4. In the rain. On a motorcycle.
When I got home, all the cars seemed to be going in slo-
mo. |
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The whole reason "rail"way exists is because of metal rails and metal wheels isn't it ? metal on metal means very low rolling resistance.This is reason why a train with just two engines can pull 4 km long goods train. |
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//train, which can weigh many hundreds of tons//
a train can weigh 15,000 to 20000 tons. Just the loco itself goes about 200 tons |
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I think at some point police needs to get involved. |
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Thank you, [8th]. Saved me the trouble of explaining all
that myself. |
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Concerning motorcycling in sleet, I'll have to take your
word for it, for I will never do that. Rain, yes; sleet, snow,
or hail, no. I'll take the Jeep instead. |
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Ooh, can I play? It may not qualify, but I will complete the entry form anyway. |
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San Francisco, Golden Gate bridge, city-bound. |
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Rain and wind, to the point where the bridge sways back and forth, and you can FEEL IT. |
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1972 Kawasaki H2 750. One dollar fare to enter the city, at the terminus of the bridge. |
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When I got there, the toll booth personnel, warm, dry, laughing, declined to accept my dollar, bowed to me and waved me by. |
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Actually, I'm relatively certain that my incident last May
has you all beat, unless we're talking about hair-raising
rides that ended successfully. |
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As someone who has been intimately involved with the spec'ing out of tire profiles for future vehicles, I can tell you that there indeed are a number of tradeoffs that we have to balance when considering the tire material. |
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Tires choices do have a comparatively large, measureable effect on fuel economy. Choosing harder tires will indeed decrease the rolling resistance. However, braking performance suffers drastically, and nobody ever wants to come out dead last on a braking test. |
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If you make tires wider, then you must either pay for that in vehicle turning circle radius, unsprung mass, stiffer springs, and either smaller underhood packaging size or you must make the vehicle physically wider. As there are Federal and international restrictions on vehicle widths, this is inadvisable. In the US, if you exceed 80" wide, you must add clearance lights to the vehicle. You also pay in fuel economy due to aerodynamic losses, in which tires also play a large factor. |
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Generally, the styling trend towards larger wheels and tires has had a negative effect on several vehicle key architectural design goals. |
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Yes, [Alterother], but getting assistance from a deer constitutes teamwork, and this is in the solo division. |
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Another major factor in train efficiency (most relevant to light weight, high speed passenger trains, but still affecting freight) is the fact that it is a train. That means that each carriage is in (very) close proximity to the preceding car, resulting in an essentially continous aerodynamic profile along the train, minimizing drag for the entire train. This is the same effect that is found by drafting on the highway, but without the chance of each following car ramming into the preceding at high speeds. |
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Also //As speed increases, say above above 80 mph// I'm not sure about for cars or trains, which are slightly more aerodynamic, but on a bicycle aerodynamic resistance comes equal to rolling resistance at a whopping 12mph, and of course rolling resistance is (roughly) constant, while air resistance goes up as the square. |
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[MechE] Correction: rolling resistance is (roughly) independent of speed, while air resistance goes up as the square. Power consumption due to rolling resistance is (roughly) linear with speed, while power consumption due to air resistance goes up as the cube. |
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You're right, I was thinking in terms of force for wind resistance and power for rolling resistance. Of course that just makes my point even stronger, at practically any speed above that of a running human, wind resistance is a major contributor.
[original comment edited] |
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