h a l f b a k e r yAmbivalent? Are you sure?
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In case of train wheels (unlike vehicle with tyres) most
of the friction is at axle and
very little at track. This is because both wheel and track
are made up of metal. If we could get rid of axle
friction, the train
will
very efficient since there is no friction.
Idea is to get rid of
train itself and keep only wheels.
A smallest setup will have two wheels connected by an
axle. Wheels will be on track. They will be hollow wherein
they will carry only solid cargo, the kind which does not
mind
being rotated at high speed.Axle will be pulled ahead
magnetically by methods such as linear induction motor.
Cargo will be fixed to the inside of wheels so that it does
not move in transit.
This method should get rid of most of friction. Obviously
this method is not suitable human transport.
Optionally, if air resistance is to be tackled, then the
whole setup could be placed in an evacuated tunnel.
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so, how do you stop? also, how do you go? even if you still have an engine the inertial energy would be tremendous and the individual units of cargo would have zero braking ability. I'm sure you can overcome this somehow. |
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Jets or rockets are good, but they can't be inline with the axles - this would tip the vehicle over sideways. Perhaps you mean in line with the rails - but that would require a bearing to keep them horizontal as the wheel rotated. No, the rockets have to be mounted circumferentially on the rim, like a catherine wheel. If mounted in opposed pairs, they could be used for slowing down as well as speeding up in either direction. But I still don't see what stops this thing slewing sideways, jumping the rails and carrering across the countryside. |
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bun for wreaking havoc o'r the countryside |
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Forward thrust is provided magnetically, by linear
induction motor (LIM), just like maglev. There
could a strip of wiring at the center of track. Axle
could be fixed with another wheel at the centre,
which is parallel to other two wheels. This wheel
actually gets pushed ahead by LIM. (So, in all
there will be 3 wheels connected by axle and all
parallel) LIM would be able to stop the wheels as
well. |
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About Yaw problem, some more thought needs to
be given. |
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Your assumption is wrong. Bearing friction is low. The two biggest losses are braking and aerodynamic. |
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You'd need a very well-balanced load if the wheels were
turning fast. |
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Also, as [ldischler] pointed out, I'm not sure if bearing
friction is a significant factor. |
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You could start and stop it using Lorentz forces, like a rail gun. |
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Bearing friction isn't a problem, really. |
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// ... wheel and track are metal. // |
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The bearing races and the bearings are metal, too. The idea ignores that--modern bearings are made of metal. |
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Bearings are better, even, because they have lubricants in them. And bearings are sealed against rust and grit. And the races have no seams, dents, cars driving over them nor kids putting pennies on them. |
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Bearings are like railroad wheels, except *better*. |
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I would tolerate this idea if there were some interesting appoach to solving the issues of transport-in-wheel. It doesn't even address the lack of suspension and the crippling increase in unsprung weight. I am fishboning. [-] |
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//and the crippling increase in unsprung weight// |
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Sounds like something guys brag about. |
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The biggest load is weight from all those multi ton train cars. Even with zero friction you'd need most of your engine's horse power to move just that. |
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Remember, bearings are rolling slippery balls well oiled to keep them sliding smoothly so even if you're dealing with a massive load... |
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ok, done. Made my doodoo joke for the day. |
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The bearings also cause little loss because they move relatively slowly. |
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Embed electromagnets in the edge of the wheel. Turn on each electromagnet as it approaches the track. The thrust would be low, and there would be losses due to induced currents in the track, but it's the best I can come up with without extra moving parts. |
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//How to stop yaw?//
//You'd need a very well-balanced load if the wheels were turning fast.// |
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If it had an inner cargo drum that was gimballed then the speed should not matter as long as the acceleration/deceleration is gradual enough to keep the load bottom heavy. |
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//gimballed// But then you're right back to having bearings. |
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Yaw problem: I suspect heavily rimmed wheels might
tackle that. |
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Aerodynamic resistance is in higher proportions only
at higher speeds. Since this is only a cargo vehicle,
higher speeds may not be very necessary. |
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Optionally to increase the cargo carrying capacity,
two wheels can be joined by a hollow cylinder, thus
replacing axle. This cylinder can be stuffed with
cargo. Cylinder's edges act as wheels. LIM can be
used for propulsion and stopping just like maglev. |
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//rimmed/ you mean flanges; these would massively increase friction. |
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////gimballed// But then you're right back to having bearings.// |
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hmmm, if the propulsion system is magnetic then the inner drum could be suspended magnetically as well.
There would still be drag but no 'moving' parts at least. |
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//Since this is only a cargo vehicle, higher speeds may not be very necessary.// |
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Slow moving cargo with no driver--free candy! |
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I suppose a solid cylindrical load such as metal stock (or wheels for something else) would not need much to keep balanced aside from precise centering and perhaps some counterweighting as is done to balance auto wheels. |
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For loads that are extremely well secured but not as rotationally well balanced, some sort of heavy duty self-balancing flywheels on either side of the load might work, with counterweight position automatically adjusted for distance from center and angular offset at loading time. Once matched to the load, the moving parts of the self-balancing mechanism could lock in place so that no internal friction takes place in transit. You could potentially use a tungsten alloy for an extremely dense counterweight. |
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If it's all taking place in near vacuum with very precisely machined rail and wheel rim surfaces, I could see there being significant improvements over bearing systems. Just put it on a moon or planet with little atmosphere if you don't want to worry about maintaining the partial vacuum. If the delivery is not particularly time sensitive, then braking losses could be diminished by relying mostly on friction to gradually slow the vehicle down over its journey after an initial momentum is imparted. |
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[Dan Fakeman] //solid cylindrical load such as metal
stock// Not necessarily solid. I often see rolls of steel
plate transported on railroad flatcars. They're heavy
enough, apparently, to require positioning one roll over
each axle; they're the right shape for this idea; they're
probably rotationally well-balanced; and they have a
convenient hole right at the centerline. |
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This idea gets rid of friction maybe too well. Flatcars have
brakes; is there a replacement for those in this idea? The
train presumably requires a certain ratio of braking force
to inertial mass. The locomotive can't supply that
(probably not enough traction, but even if there were, the
train risks jacknifing). The solution might be brake vans
(cabooses) at the rear of the train -- but the problem with
those is, it's tricky to avoid compression/rarification waves
traveling up & down the train. That results in a huge
amount of jerk, more wear on couplings, with risk of
catastrophic failure. One
solution might be couplings with springs & dashpots, to
take up slack, with, maybe, brake vans interspersed at
intervals in the middle of the train. But now, you've gone
to a lot of trouble to replace the friction. Sure, the
friction now is highly coordinated, only there when you
want it. But it's also complicated, high-maintenance,
and expensive, compared to the old friction. Is the fuel
savings for your traction engines really worth this? |
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// The biggest load is weight from all those multi ton train cars. Even with zero friction you'd need most of your engine's horse power to move just that. // |
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Water has no "limiting friction". In the absence of other forces (water currents, wind) a vessel of ANY size (mass) can be moved by a reatively small force applied over an extended period of time, albeit very slowly. |
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Mere inertia is not an issue. In the absence of frictional losses, any force, no matter how small, consistently applied, will cause a body to experience an acceleration. (c.f. Newton, Isaac). |
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Likewise, a "pure" rolling wheel (without an axle or bearing) has no limiting friction, only air resistance to cope with. |
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Air bearings exhibit very low friction, but the high pressures, close tolerances and unpleasant consequences of failure limit their application. |
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Air resistance increases with the square of velocity; there's your problem. |
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And that 3000 tons you're trying to pull up the side of a mountain. It doesn't matter if it's floating on a magic carpet, 3000 tons of freight getting pulled up even the slightest incline requires a lot of Hp. |
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Unless we're talking about rolling over a perfectly flat plane. I assume this invention is something to use in the real world which is all lumpy and up and downy. |
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I guess the main question is whether this thing would be worth it having that big profile hitting the wind as it rolled compared to a train. I'm saying probably not. |
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And speaking of the real world, tracks deform as a train rolls over them. If you move all your weight to one point as opposed to distributing it over lot of points it'll be like pushing a bowling ball across a soft mattress increasing your resistance. Might not make a big difference but probably more than what you'd save, if you'd save anything, getting rid of those wheel bearings. |
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Just make the tracks out of really thick forged Titanium sections; it's stiff enough not to deform, resistant to corrosion, light and durable. |
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Might get a bit pricey but yea, that'd help. |
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Light? It's the second time this weekend I've seen someone mention the lightness of something that just sits there. Although lightness would be a plus during construction, wouldn't it? |
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Somebody up there was talking about a train of these wheel-only widgets. Where did a train come into it? I thought we were talking about a single vehicle made of two wheels, with magical propulsion and voodoo yaw-control. A train of these would be nice, and solve a lot of problems, but it also brings bearings back into the picture, Shirley. |
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Not talking about a train of these, just comparing the present invention to the current vehicle commonly used to run around on rails. |
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Trains have lots of wheels to distribute it's load across whereas the mega-hamster-ball we have here would concentrate all it's load in one spot. |
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That's what I was tlakinga about. |
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Original idea was to have train of these wheels (
say, 100's) so as
to distribute weight and reduce wind
profile.Packing entire weight of train into one
wheel would be impracticable. |
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Maglev kind of propulsion should not be too
dificult to arrange in this case, I reckon. Yaw
problem i.e. essentially derailment is what needs
to be researched. I am not sure amount of flanging
that current train wheels have would be sufficient
to handle YAW in this case. |
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Oh, I didn't get that. I though it was one big thingy. |
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Better think of something else wrong with this to
cover my stupidity. |
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You'd also have a hard time balancing the cargo
perfectly so it rolled evenly. |
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