h a l f b a k e r yClearly this is a metaphor for something.
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Oiled Rails
Cheaper than Maglev. (the main reason for rails is low friction so...) | |
Rails server three purposes: (1) low friction on the one hand for fast and energy eficient travel, (2) direction control - no need for steering, and (3) friction for stopping, by using the brakes.
The Maglev system and similar systems (like aeroduct.com) create a route for very fast transportation.
But why not work with oiled rails, for low friction (and wheels running on these rails for even lower friction, and then for brakes add another rail used only when stopping, or have the oil sucked in, so that the train stops (or how about soap and water sprayed), or have an inflatable substance pertrude from tracks to stop train.
This ultra quiet and super fast train slides silently on its tracks.
[addition to original idea:]
And of course the propulsion will be achieved by other means, such as rope, conveyor or tractor for inclines or using electro-magnetic or jet power. Then again, the soapy idea could work well for these cases. (Tracks have two pipes inside which emit soap or oil in different places or alternatively, the train has "soap/oil" control.
Help the bombardier
http://www.transpor...1763%26sCateg%3D1_0
I'm the bombardier [thumbwax, Oct 05 2004]
[link]
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oiled wheels + oiled rails = no traction |
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No traction - exactly! Tell me why Maglev is better (besides being much more expensive and having even less traction?) |
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Wait, I realize UnaBubba what's missing in the idea. [fixed idea] |
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What do you mean by that [unabubba]? |
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Rolling friction isn't the same as regular friction. Wheels don't slide over tracks, they roll! The resistance is due to microscopic deformation of the rail that causes a little bump to form in front of the wheel. |
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Oil doesn't change that. Oil is already used where the sliding actually occurs- at the bearing of the axle. |
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What's wrong with a rope? (like the ropeway trains) for braking/propulsion, but NOT for guideway and support. Granted that it's better to spray only a bit ahead and back. Wheels (=oily bearing) with in addion low friction on tracks themeselves may be very useful. No? |
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The reason MagLev works at all is because the magnets in the train and the rail work like a linear electric motor. they push against each other at a distance. The reason a wheeled train works is that the wheel and the track push against each other at the point of contact. Friction is all that keeps a wheeled train moving. Putting oil on a track is like putting a sheet of ice under your car's wheels. |
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The coefficient of friction of steel-on-steel is about equivalent to that of a car's tires on ice. The only way that the engines make any headway is through weighing so frickin' much. |
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If you put oil on the track, the only analogy that I think would come close would be to spin one's wheels in mid-air. |
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The traction is needed only for propulsion and
braking. I realized that I had not explicitly written
that, since I thought it was obvious and corrected
the idea already back in Nov 02. |
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There are two kinds of friction here: Traction and rolling friction. |
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A steel wheel on a steel rail has a coeffecient of friction around 0.1 which is plenty for a train to accelerate or brake while passengers remain standing or seated without seatbelts. |
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A rubber tyre on tarmac has a coeffecient of friction closer to 1.0 allowing Joe Numpty to jump on the brakes when he finally sees the junction. |
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The rolling friction of the railway is very, very small. A man can push a 20 ton coal wagon on level rails, while he'd have a hard time pushing a 2 ton truck on level road. |
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A rack and pinion (like the mountain railways) has as much traction as you could ever want, but rolling friction can still be very low. |
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A plain bearing rail axle runs grease between metal surfaces. This gives lower rolling friction than a greased rail because the wheel might be 10 times the diameter of the bearing surface, so there is a mechanical advantage of 10:1 between the contact patch and the bearing. |
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The conventional design of railway has friction in exactly the way it's needed. |
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There is nothing to be gained and much to be lost by oiling the tracks. (-) |
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If there was nothing to be gained, MAGLEV would
be out of the question. MAGLEV is extremely
expensive in both maintenance and running.
There are also health concerns regarding
electromagnetic phenomena affecting passengers. |
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I am NOT talking about the propulsion, only
focusing on the elevation. But according to
[lumpy] the idea the way it was presented would
not suffice. I would need some sort of wheel
replacement emitting pressurized oil in order for
this to work, and for that there are already
existing atmospheric railways using air instead of
oil... So thanks anyways for discussing and
considering this idea. |
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Nope, MagLev gains by eliminating the friction at the axle bearings, trains really don't care about the friction at the wheel (except for propulsion). |
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huh?! Now what does that mean? If there is no
friction at the wheel, then there's no friction at the
axle either (because its doesn't need to turn). |
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But then I already accepted the point that this won't
work as stated, without ... read my previous anno. |
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If there is zero friction at the point of contact of the wheel and the rail, then you are correct, and what you have is a sled. |
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However, the problem of maintining a surface with such admirable tribological attributes in a world full of dust, dead flies, corrosion, bird droppings and empty soft drink cans is a little clallenging. Since the wheel is part of the vehicle, you have it "under control" and can shroud it, but the rail is out in the open for everything to have a go at ... |
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Bear in mind that even if the coefficent of friction between the wheel and the rail is 1, this makes NO difference as - importantly- the point at which the wheel touches the rail does not move relative to the rail, unless it skids. |
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It therefore makes more sece to concentrate attention on the axle; a frictionless axle acting as a pivot for a wheel with unity contact friction is beloved of mathematics and physics examiners as it represents the "ideal case". |
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Near-frictionless bearings (jewel point, air, magnetic, flexure) can be made, but are regrettably not cost-effective for general use, particularly in appilcations like trains where the bearings are predominantly heavily side-loaded. |
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I didn't say no friction, I said it doesn't care about friction. Not the same thing at all. As has been mentioned above in a properly operating wheel, the point of contact is stationary with respect to the ground. |
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Since it is stationary, there is no energy expended to overcome friction. Any resistance generated at the wheel is caused by deformation of the two contact surfaces. This is due to the fact that in an ideal wheel, the contact is a line. Unfortunately in the real world, said line would have infinite contact pressure (any weight over zero area). Instead the wheel deforms to increase the contact area to the size needed. Some of this deformation is recovered as the wheel leaves the ground, but some isn't. |
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As a result of this, any substance on the rail that the wheel had to push through to deform (such as oil or grease) would ever so slightly increase the rolling resistance. |
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This is also why steel wheels on steel rails are as efficient as they are, they deform an absolutely minimal amount. In some cases, to climb a steep grade sand is added to the rails. This increases the coefficient of static friction (the one that keeps the rails and wheels from slipping) and allows the train to climb steeper grades, but does so at the expense of crushing the sand finer, increasing the unrecoverable energy. |
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