That's the kind of discussion I'd love to have! Of course, you need linear bearings [1] at each column. But what kind of bearings? Ball or roller bearings? [2] Plain/solid bearings? [3] Something else? What are the forces the tube would produce while expanding? What would be the linear expansion speed? What bearings would be able to sustain those speeds and forces? Would the tube and the pillars be able to sustain them? Do bearings with necessary parameters even exist? How expensive would they be? So on and so on.
Unfortunately, I haven't seen such discussion yet. I could try doing the calculations myself (starting at [4], for example). But I'm afraid I would make some silly newbie mistake in the process.
> Remember: the tube is not only moving hundreds of meters at the ends, it's moving >>1m along (very nearly) its entire length.
Yes, of course the tube is moving by hundreds of meters along most of its length. The questions are: how fast? with what load against the pillar?
[1]: https://en.wikipedia.org/wiki/Linear-motion_bearing
[2]: https://en.wikipedia.org/wiki/Ball_bearing
[3]: https://en.wikipedia.org/wiki/Plain_bearing
[4]: http://www.pbclinear.com/Blog/Calculating-PV-for-a-Plain-Bea...