MSimon wrote:
Of course for the straightaways loading is no problem. I could see designing a track follower. It is just a question of getting a good enough system frequency response. The problems come with loading in the curves.
Oh yeah... I'm not a rail buff but I've gathered that the steel wheels handle all this automatically with a carefully calculated set of curves for the cross-sections of both the wheel and the top of the rail... so that the flange on the inside of the wheel doesn't have to actually touch the rail even on a curve.
So how could a follower imitating an actual railroad truck assembly duplicate that performance without the speed advantage of physical contact?
KitemanSA wrote:If you are going to use the rails, why not just use a train? I guess I just don't get the issue here.
It really is on topic... in this case getting a high-speed rail system starting from a low-speed infrastructure.
If I wanted to go with fly-by-wire for each car I'd just skip the whole "air cushion" part and use electromagnets for lift, propulsion and steering. Now that would be something that only fusion could enable...
Lock-Mart has had a proposal on the table for high speed rail for more than a decade, but it won't run on low speed tracks. Honestly, I don't think there's a safe way to do that. Tracks that are not made for high speed forces are just not going to work. If you take the burden off the rails with something like hover, then you don't need rails at all.
The Lock-Mart proposal is interesting in that it surveyed the competition:
With how cheap NIB magnets have become, embedding them in the rail itself in order to make levitation very inexpensive is a commercially viable option, and avoiding the need for superconductors is useful as well, though one imagines you'd revisit that option now that YBCO is getting cheaper and the cryo-systems more advanced.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis
The reason that american trains maintain the speed limits they do is because of rail inconsistency and the excessive cost of maintaining those rails to allow higher speed. High speed rail in the US, to be competitive, must be able to deal with the mediocre quality rail, and not require new track.
The point of hover is to lessen the force of friction.
In a rail carriage, the vast majority of the friction is in the wheel carriage.
The rails then become a guidance mechanism, not a load-bearing mechanism, for the hovertrain.
Friction is caused by the net force; that is why it makes sense to reduce the loading by a ground effect air cushion system. It would reduce the load on the bearings, and thus the friction. Lower friction means the same horsepower can move the train faster. It also means that the train will transmit less of the rail inconsistencies to the passenger compartment. This way, a hovertrain could reasonably be expected to reach speeds of 200kph on a typical American railbed.
The ballast used for rail beds is usually very coarse: 1-2" aggregate. It won't blow around even with very high overpressures.
I've seen very small personal hovercraft kick up 2" stone in a parking lot and send it through the windshield of a truck. Your rail bed is all going to go missing if you try to float a train over it.
High speed train lines in the US exist because they bank the curves severely. The real issue is the train running off the tracks because of lateral forces created in turning. Hovertrains aren't going to generate any less lateral force, even if their wheels are connected to the rails, which they would have to be in a turn, so they are going to have exactly the same limitations as existing high speed rail. They're limited by their track design.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis
GIThruster wrote:I've seen very small personal hovercraft kick up 2" stone in a parking lot and send it through the windshield of a truck. Your rail bed is all going to go missing if you try to float a train over it.
High speed train lines in the US exist because they bank the curves severely. The real issue is the train running off the tracks because of lateral forces created in turning. Hovertrains aren't going to generate any less lateral force, even if their wheels are connected to the rails, which they would have to be in a turn, so they are going to have exactly the same limitations as existing high speed rail. They're limited by their track design.
The question is: can enough lateral force be created by directing an air stream. And can it be controlled well enough (system frequency response) to keep the hover car/train near enough to the tracks?
Air is kind of slushy compared to magnetism. If the rails could handle the side forces only (magnetically) could the cars be designed light enough to go really fast?
Then comes the question. How do you handle scheduling so that slow trains don't impede the fast ones?
Engineering is the art of making what you want from what you can get at a profit.
GIThruster wrote:I've seen very small personal hovercraft kick up 2" stone in a parking lot and send it through the windshield of a truck. Your rail bed is all going to go missing if you try to float a train over it.
High speed train lines in the US exist because they bank the curves severely. The real issue is the train running off the tracks because of lateral forces created in turning. Hovertrains aren't going to generate any less lateral force, even if their wheels are connected to the rails, which they would have to be in a turn, so they are going to have exactly the same limitations as existing high speed rail. They're limited by their track design.
A skirt takes care of the first, besides the fact that the rail itself is a barrier.
The second could be handled by making the electro-magnetic traction control general, instead of just using it on the engine.
