Hyperloop and other vactrains

General discussion of passenger rail proposals and systems not otherwise covered in the specific forums in this category, including high speed rail.

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Re: Hyperloop and other vactrains

Postby lpetrich » Thu Jul 12, 2018 11:15 pm

That link with its title: Chicago's Hyperloop Announcement Met With Questions : NPR
SCHAPER: Musk says his company's boring technique will dig the tunnels many times faster and cheaper than conventional tunneling. But both that technology and the autonomous vehicles are unproven.

I'll believe it when I see it about the tunnel boring.

As to the vehicles, there are plenty of existing ones that can do the target speed of 150 mph. They are high-speed trains.
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Re: Hyperloop and other vactrains

Postby bostontrainguy » Fri Jul 13, 2018 8:27 am

The tunneling is the hardest part. Once a very straight tunnel is built between two points the cheapest thing to do is put in tracks and run a train. Makes no sense to do anything more. Why risk using unproven expensive technology?
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Re: Hyperloop and other vactrains

Postby mtuandrew » Fri Jul 13, 2018 11:49 am

I’m having trouble understanding how his tunneling apparatus is any better than a conventional TBM, except that he makes smaller tunnels and doesn’t really have underground stations. In reality, he’s building a 100mph version of the Chicago Tunnel Company.

Also, Musk’s “Loop” concept doesn’t include high-vacuum tunnels, only the Hyperloop does that. Wouldn’t be enough time to reach anywhere near top speed between the Chicago Loop and O’Hare or Midway.
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Re: Hyperloop and other vactrains

Postby lpetrich » Sun Jul 15, 2018 5:35 am

Narrower tunnels?

There is a certain problem with high-speed travel in a tunnel. A vehicle has to push the air out of the way. That is why high-speed trainsets have very aerodynamic ends. If there is not much space between the vehicle and the tunnel, then it will be hard to squeeze the pushed-aside air through it.

Consider the Gotthard Base Tunnel - Wikipedia, designed for 250 km/h travel. It uses twin single-track bores, and each one has a diameter of 8.83 - 9.58 m. Its tunnel clearance is 5.20 m (rail top to overhead conductor). From Loading gauge - Wikipedia, UIC GC loading gauge is 3.15 m width and 4.65 m height. This is plenty of space for pushed-aside air.

Urban-transit systems have narrower tunnels. For instance, BART's Transbay Tube has a diameter of 17 ft / 5.2 m. For equal width and height, this means an envelope with a width and height of 3.7 m, something that seems roughly correct. Measuring a picture in HSLRST / Archimedes Bridge Studies gives us:

Height of tunnel floor: 0.87 m
Width of BART train: 3.42 m
Height of bottom of BART train: 0.38 m
Height of top of BART train: 3.42 m
Max speed: 80 mph / 129 km/h

Cross-section fractions:
Gotthard Base Tunnel, GB C: 0.24
Transbay Tube, BART: 0.54

Some London Underground rolling stock seems like it closely fits its tunnel roofs, and it likely has a greater cross-section fraction.
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Re: Hyperloop and other vactrains

Postby Literalman » Sun Jul 15, 2018 2:32 pm

Makes no sense to do anything more. Why risk using unproven expensive technology?
Maybe it's intended to prove the technology. If hyperloop takes baby steps in Chicago and doesn't fail, then maybe Musk will get a chance to try it on a bigger scale somewhere else.
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