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  • In 1974, a French train smashes through a speed record, exceeding 250 miles per hour.

  • But this train is unlike any other before it.

  • It doesn't have wheels.

  • It hovers on a cushion of air, and because of that, it can travel efficiently at very

  • high speeds.

  • Maybe, you've never heard of hovertains, but by the 1970's, they were seriously being

  • considered as the solution to slow, antiquated railways

  • which, in many countries were in decline.

  • In the 1960's, railways were in trouble.

  • In developed countries, ridership was plummeting and railways were in decline.

  • In Britain, some routes were still served by steam locomotives.

  • And the public was beginning to view rail as slow and outdated.

  • Trains now had to compete with newly built superhighways and intercity air travel.

  • And even Japan's newly introduced Bullet Train, a technical marvel for 1964, was initially

  • only running at speeds of up to 130 miles an hour.

  • Part of the problem was most rail lines in the developed world, were built a half century

  • earlier, with their sharp twists and curves, they just weren't built for speed.

  • But the trains also had a problem.

  • And it had to do with the shape of their wheels.

  • Train wheels are not perfectly cylindrical, they're cone-like in shape.

  • And this is what keeps them on their track, especially around curves.

  • While the wheels also have flanges, these are really just a backup in case limits of

  • that conical shape are exceed.

  • The conical shape of train wheels is a brilliant innovation.

  • But there's a problem, and it's called Hunting Oscillation.

  • At higher speeds, the cone-like shape causes a train to increasingly rock from side to side.

  • The flanges start hitting the track, which increases resistance, making higher speeds

  • inefficient and causing wear and damage.

  • Given enough speed, Hunting Oscillation can even cause a train to derail itself, on a

  • perfectly straight track.

  • This meant that trains essentially had a speed limit built right into their basic design.

  • So in the 1960's, the thinking was that maybe it was time to get rid of wheels all together.

  • The French have already built the Aerotrain. Designed to reduce the running

  • friction problems of wheeled trains by doing away with the wheels.

  • It's called a hovertrain.

  • By feeding high pressure air through lifting pads, the train would float on a cushion of

  • air much like a hovercraft.

  • The track would act merely as a guideway.

  • Without the rolling resistance of wheels, a hovertrain promised efficiency and much

  • higher speeds.

  • And leading the way for this promising technology was a French engineer named Jean Bertin.

  • By 1973, Bertin and his team had built a hovertrain that could carry 80 passengers.

  • French officials and the media marveled at its combination of speed and smooth ride.

  • Bertin called his designs Aerotrains.

  • Over the years, he had worked tirelessly to develop several prototypes, proving the viability

  • of the concept.

  • With each success, he secured a healthy dose of government funding.

  • The most advanced Aerotrain was powered by a turbofan.

  • pretty much straight off an airliner.

  • It produced over twelve thousand pounds of thrust.

  • At the front, a 400 horse power gas-turbine supplied high-pressure air to hover this twenty

  • tonne loaded train a quarter of an inch off its guideway.

  • And the guideway, was essentially poured concrete.

  • An Aerotrain could easily hover over imperfections.

  • That meant that hovertrain lines were potentially easier to build than conventional rail and

  • cheaper to maintain.

  • On March 5, 1974, an Aerotrain proved it could travel at nearly two hundred and sixty miles

  • per hour.

  • And it might have gone even faster, had its test track had been longer.

  • The success of Bertin's prototypes led to plans for Aerotrain links throughout France.

  • And just a couple months after the record breaking speed-run, a contract was signed

  • to begin construction of the very first line.

  • Outside of France, the world was also taking note.

  • The British, who had invented the hovercraft, could see the enormous potential of hovertrain

  • technology.

  • They constructed their own hovertrain test track in 1970.

  • And in some ways, Britain's research into hovertrains was even more advanced.

  • Their prototype, the RTV-31 Tracked Hovercraft was designed around another important innovation.

  • The Linear Induction Motor.

  • Although Bertin also experimented with Linear Induction Motors, most of his Aerotrains were

  • fan or jet propelled.

  • But a Linear Induction Motor is more efficient.

  • Instead of the rotary movement of a conventional motor, it provides a linear force for forward

  • movement.

  • Without any of the noise or pollution of a turbofan running at ground level.

  • The British were aiming to build a transportation system that could travel at two hundred and

  • fifty miles per hour.

  • The Americans, not ones to be outdone were also researching hovertrain technologies.

  • In 1965, the High Speed Ground Transportation Act was passed.

  • It was an effort to introduce faster rail to America.

  • Funding was put towards developing new technologies and even licensing Bertin's Aerotrain designs.

  • Various hovertrain prototypes were developed, some powered by Linear Induction Motors, others

  • by Jets.

  • But the most developed prototype was the Urban Tracked Air Cushion Vehicle.

  • With its sleek windowless cockpit and Blade Runner styling, it certainly looks fast.

  • It was designed to operate in heavily travelled urban areas and had a top speed of about 150

  • miles per hour.

  • The Tracked Air Cushion Vehicle was a fully developed prototype that underwent regular

  • testing on its track in Pueblo, Colorado.

  • At the start of the 1970's, hovertrains looked poised to revolutionize rail.

  • But just a few years later, not a single country was pursuing the technology.

  • Ambitious plans for Aerotrain links throughout France never materialized.

  • All that's left today are the abandoned test tracks.

  • A global recession in the 1970's pressured governments to cut funding for ambitious transportation

  • projects.

  • And some critical technical challenges were never really worked out.

  • At high speeds, hovertrains could travel more efficiently than conventional trains but at

  • low speeds, they wouldn't stand a chance.

  • But that's not really why they failed.

  • In the 1970's, the first maglev train were already in development.

  • They would use electromagnets to levitate over a guideway instead hovering using high

  • pressure air.

  • And so Maglevs promised even greater efficiency and speed over hovertrains.

  • But Maglev's also failed to revolutionize rail.

  • After nearly four decades, there's only a handful of them operating in the world.

  • High speed rail today is still based largely on conventional wheeled trains.

  • It turns out that the problems of railways were overcome not by one revolutionary leap

  • forward, but by incremental improvements.

  • Existing rail networks were modernized with sections of track that could handle higher

  • speeds.

  • New signaling technologies were developed along with more advanced suspensions.

  • Precision machined wheels and yaw dampers allowed for train wheels with less cone angle.

  • And that reduced the hunting oscillation problem.

  • Instead of Aerotrains, the French invested in their high speed TGV rail service, which

  • today routinely travels at 200 miles per hour.

  • The British came up with unique solutions like a train that could tilt into corners

  • and take sharp curves more quickly.

  • The Americans, at least for the time being, mostly stuck with cars.

  • Hovertrains or Maglevs or any other radical alternative to rail has to compete with nearly

  • a million miles of rail line already in existence.

  • With stations and infrastructure built-out in nearly every city in the world.

  • Turns out, it's easier to adapt new ideas to the existing world than to have the world

  • adapt to radical new ideas.

  • Which is why incremental improvements often win out in the end.

  • Although, there's a new solution in the works.

  • A train runs in a new kind of track.

  • It's actually a reduced pressure-tube, so there's less friction and air resistance.

  • Driven by linear induction motors and air compressors.

  • It promises to travel at over 700 miles per hour.

  • It's tube-like tracks could suspended or underground [voice fades out].

  • I used some conceptual terms in this video, like friction, rolling resistance and magnetism.

  • These are foundational concepts, the kind that is crucial to understanding how machines

  • work, whether it's a hovertrain, or supersonic jet.

  • But it's one thing to be made to memorize a concept and the formulas, and another to

  • actually develop an intuitive understanding, one that'll actually benefit you in the

  • real world.

  • And that's why I love Brilliant.org . It's not only a highly effective way to learn math

  • and science, but also a lot of fun.

  • Brilliant gets you engaged by letting you solve problems and learn through doing, instead

  • of just listening to a lecture and jotting down notes.

  • They strengthen your reasoning, creativity and problem solving skills, which are essential

  • to everyday life.

  • A great place to start acquiring the critical building blocks for understanding physics

  • is 'Physics of the Everyday'.

  • Go to Brilliant.org/mustard and sign up to get started.

  • And also, the first 200 will get 20% off the annual premium subscription for a fun and

  • engaging experience.

In 1974, a French train smashes through a speed record, exceeding 250 miles per hour.

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The Problem With Fast Trains: What Happened to Hovertrains?

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    joey joey に公開 2021 年 05 月 28 日
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