3 ms·

It seems to me the fundamental inescapable problem with hovertrains was simple: they’re loud. Sound is a pressure wave, hovercraft require high pressures; there

by scythe 7y ago

It seems to me the fundamental inescapable problem with hovertrains was simple: they’re loud. Sound is a pressure wave, hovercraft require high pressures; therefore, they are noisy. Even if you solved momentum drag, track maintenance, and everything else, nobody will let you build it near their house. (Maybe a maglev train could hover only at low speeds inside a station. Maglev works better for moving trains rather than stationary ones. But then it’s not a hovertrain.)

jessriedel 7y ago
It's not at all obvious to me that the noise from the pressure levitation system of a hovertrain is louder than the noise from drag, which the hovertrain and maglev both share. Do you have a link?
klingonopera 7y ago
TBH, I would've expected a Maglev train to "touch down" in a station, at least that is what I would do if I were to have designed it... Anyone here ever rode on the Maglev in China can provide more details?
- detaro 7y ago
  They can touch down/"take off" while stationary (not sure if they do it while stopping in stations), but don't have wheels, so they have to hover to move at all. If both sides of the maglev system fail, they have skids designed to slow them at a safe rate, but that's emergency use only.
- russdill 7y ago
  Just an engineering aside, you'd probably want braces to engage the train rather than the train to lower. If it lowers you have to raise it before it starts again which would require extra energy and substantial force.
  - klingonopera 7y ago
    I think a kind of "landing gear" would be preferable, as its operation could be station-independent, which in turn centralizes maintenance, therefore reducing running costs. AFAIK, there currently isn't an actual Maglev network in operation (just point-to-point - no traffic, no stops), but if there would be, I think it's easier to have any train be able to stop anywhere on the track than to have it stop at specific locations only. But other than that, yes, you're definitely right that any change of elevation of the entire train should be avoided as much as possible. EDIT: I just realized, my last paragraph isn't necessarily true either, i.e. compare the situation to start-stop-sytems on cars, there's a sweet spot in efficiency, when turning off the engine and starting it would cost more than letting it run all the time.
rangibaby 7y ago
Japan Rail’s solution to the noise problem was to bore a tunnel hundreds of kilometers from Tokyo to Osaka via Nagoya
- scythe 7y ago
  Looking at the Chuo Shinkansen, it seems that the tunnel allowed the train to turn less through the mountains, considering that turning is pretty hard to do at 500 kph! Also: >JR Central aims to begin commercial service between Tokyo and Nagoya in 2027, with the Nagoya–Osaka section originally planned to be completed by 2045.[5] The government is however planning to support a speed up of the timeline for the construction of the Osaka section by up to 8 years to 2037 with additional funds.[6] Imagine a US government construction project being finished ahead of schedule.

by scythe 7y ago

jessriedel 7y ago

It's not at all obvious to me that the noise from the pressure levitation system of a hovertrain is louder than the noise from drag, which the hovertrain and maglev both share. Do you have a link?

klingonopera 7y ago

TBH, I would've expected a Maglev train to "touch down" in a station, at least that is what I would do if I were to have designed it... Anyone here ever rode on the Maglev in China can provide more details?

detaro 7y ago
They can touch down/"take off" while stationary (not sure if they do it while stopping in stations), but don't have wheels, so they have to hover to move at all. If both sides of the maglev system fail, they have skids designed to slow them at a safe rate, but that's emergency use only.
russdill 7y ago
Just an engineering aside, you'd probably want braces to engage the train rather than the train to lower. If it lowers you have to raise it before it starts again which would require extra energy and substantial force.
- klingonopera 7y ago
  I think a kind of "landing gear" would be preferable, as its operation could be station-independent, which in turn centralizes maintenance, therefore reducing running costs. AFAIK, there currently isn't an actual Maglev network in operation (just point-to-point - no traffic, no stops), but if there would be, I think it's easier to have any train be able to stop anywhere on the track than to have it stop at specific locations only. But other than that, yes, you're definitely right that any change of elevation of the entire train should be avoided as much as possible. EDIT: I just realized, my last paragraph isn't necessarily true either, i.e. compare the situation to start-stop-sytems on cars, there's a sweet spot in efficiency, when turning off the engine and starting it would cost more than letting it run all the time.

rangibaby 7y ago

Japan Rail’s solution to the noise problem was to bore a tunnel hundreds of kilometers from Tokyo to Osaka via Nagoya

scythe 7y ago
Looking at the Chuo Shinkansen, it seems that the tunnel allowed the train to turn less through the mountains, considering that turning is pretty hard to do at 500 kph! Also: >JR Central aims to begin commercial service between Tokyo and Nagoya in 2027, with the Nagoya–Osaka section originally planned to be completed by 2045.[5] The government is however planning to support a speed up of the timeline for the construction of the Osaka section by up to 8 years to 2037 with additional funds.[6] Imagine a US government construction project being finished ahead of schedule.