I personally think that you are over-thinking the whole heat and mechanical stress issue. :)
The thing that I like about Andy's CP implementation with the spherical magnets is how easy it is to change out rods. I have two different sets, and can change them out (obviously with a printer re-calibration) if I need longer rods to print a wide part or shorter rods to print a tall/narrow part. Since the end mill bit is already paid for, I might as well make several sets of rods to recoup my investment.
Expanding foam is evil. I have seen people warp window and door frames by using too much of it, and could picture it blowing the welded seam out of cheap tubing just like a water pipe freezing in the winter. There is much to be said for sandwich core construction with foam at the core, but I don't think it is a good idea in a tube.
If you want weaved CF, you could always get a 4mm OD aluminum tube, wax it up as a mandrel, and put some bi-axial CF sleeve over it. Wet out the sleeve with epoxy, cover it with electrical shrink tubing, heat the tubing until it shrinks (who needs an autoclave!) ;) and let the epoxy dry. When done, slip the aluminum tubing out from the inside, cut the shrink tubing from the outside, and wet sand to finish. Or, you could go one step further and search this site for the DIY filament winder that someone posted the designs for last spring. :)
Personally, I think that pultruded CF is overkill for strength on my Delta.....
The thing that I like about Andy's CP implementation with the spherical magnets is how easy it is to change out rods. I have two different sets, and can change them out (obviously with a printer re-calibration) if I need longer rods to print a wide part or shorter rods to print a tall/narrow part. Since the end mill bit is already paid for, I might as well make several sets of rods to recoup my investment.
Expanding foam is evil. I have seen people warp window and door frames by using too much of it, and could picture it blowing the welded seam out of cheap tubing just like a water pipe freezing in the winter. There is much to be said for sandwich core construction with foam at the core, but I don't think it is a good idea in a tube.
If you want weaved CF, you could always get a 4mm OD aluminum tube, wax it up as a mandrel, and put some bi-axial CF sleeve over it. Wet out the sleeve with epoxy, cover it with electrical shrink tubing, heat the tubing until it shrinks (who needs an autoclave!) ;) and let the epoxy dry. When done, slip the aluminum tubing out from the inside, cut the shrink tubing from the outside, and wet sand to finish. Or, you could go one step further and search this site for the DIY filament winder that someone posted the designs for last spring. :)
Personally, I think that pultruded CF is overkill for strength on my Delta.....