> Eventually, the dampers in the pillars won’t be able to handle the movement because it’ll be greater than the pillar width. Eventually, the movement will be greater even than the distance between the pillars.
But the tube is "not rigidly fixed" to pylons. It slips past pylons during expansion or contraction:
> By building a system on pylons, where the tube is not rigidly fixed at any point, you can dramatically mitigate Earthquake risk and avoid the need for expansion joints.
In fact, the author quotes the above in the beginning of his article, but then assumes exactly the opposite.
By building a system on pylons, where the tube is not
rigidly fixed at any point, you can dramatically
mitigateEarthquake risk and avoid the need for expansion
joints. Tucked away inside each pylon, you could place
two adjustable lateral (XY) dampers and one vertical (Z)
These would absorb the small length changes between
pylons due to thermal changes, as well as long form
subtle height changes
The tube will be supported by pillars which constrain the tube in the vertical direction but allow longitudinal slip for thermal expansion as well as dampened lateral slip to reduce the risk posed by earthquake.
That said, the quoted text is somewhat confusing. I had to read it a few times before I got the idea.
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.
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).
Tubes are fixed to the pylons, just not rigidly (in longitudinal direction).
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: