'slipping past pylons' during expansion would be a pretty terrible solution though. Can you imagine how hard it would be to keep it straight and level, to the tolerances required, while not even being able to fix it to the pylons? To say nothing of the fact that some of those precast tubes are going to be precast straight, and others precast curved. They're not interchangeable.
> To say nothing of the fact that some of those precast tubes are going to be precast straight, and others precast curved. They're not interchangeable.
I don't know enough about steel and construction, but I think the tubes could all be made straight. Hyperloop curves have very large turn radius. Steel tubes are not completely rigid, they can curve a little by themselves.
Fair point - maybe that would allow the necessary flex.
The minimum bend radius they allow for the 300mph segment is 3.67km. If you made a complete circle it would have a circumference of 23km, and comprise 769 30m segments. Each segment would need to contribute 0.46deg of the 360deg curve.
To achieve this over 30m you need to deviate the end of the pipe by 24cm from where it should be... which actually sounds like a hell of a lot to me, especially if it's flexed through this range regularly (as it would be if constantly switching places with a truly straight segment).
True, but that means you're going to have some absolutely awesome bearing system that gives almost zero friction along the major axis of the pipe while also giving almost zero slop in the other axis. Which is damned hard. Adaptive maglev bearings maybe? ;-)
Why do you want zero friction along the major axis? Linear speed of pipe movement through the bearing would be very low: not more than couple hundred feet per day. And what do you mean by zero slop?
By the way, if you want to continue speculating on Hyperloop thermal expansion issue, you can join my speculations - I wrote a few comments under this blog post:
