I wonder if you could heat the straws to make them expand slightly, and then slide them over the rods with a little WD-40 or something.
I have not tried this. But if you do, do not melt the straws! You don’t want that, as the straw will then deform and change thickness in uncontrolled ways. You want warm, but not melted. Maybe warm/hot tap water on the straws?
Sorry, just a random suggestion. I thought of this because of two things:
(1) When a jar cap was hard to open, my mother would heat it under hot water from the tap. The lid would expand, and it would be easier to open. I don’t know if this is because the cap heated more than the glass and/or the coefficient of expansion for metal is much larger than glass. The latter is true, the former is probably true too, but I’m not sure.
(2) In metal-work, there are extremely tight and nearly-permanent friction-fit parts. These are done by heating one part (say a precision hole) to make it thermally expand just enough enough for another part to fit (say an axel). After the two parts are joined, they let the hot part cool down to normal temperature, and by thermal-contraction it super-tightly squeezes the other piece. This is only a friction fit, but it can be so exceptionally tight that it is effectively a solid-join. In some machines, such a join is even used to transmit mechanical power.
Sincerely,
–Lagrangian
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Hope it is ok I used one of your pic’s
