I need a shaft that can be stretched along its length while also being resistant to torque enough to be a functional shaft (see pictures). I have a rotating sphere within another rotating sphere, hence the use of universal joints. But due to the universal joints I can't use a shaft that is long enough to slide up and down. You can see in my images where there's a shaft missing. I don't know of the existence of any rubber that is sturdy enough to withstand the torque applied while also being stretchy enough to span that gap. Perhaps there's other ways to achieve what I am trying to achieve without the use of universal joints (I am open to suggestions).
Perhaps I could 3D print a sort of origami shaft that unfolds?
This is getting to be a bit ridiculous lol what I'm trying to make shouldn't be rocket science