I also noticed that any lingth of tube (stainless steel 2-3mm thick) tend to bend, which may be crucial for heavy duty tasks or lengthy pipes. I ended up with making kinda SBR our of the pipes by printing securings that attach to tube every 15-20 cm.
However, you won’t be able to cure center pipes, that’s why I refrained from MPCNC eventually and moved to my own build similar to rootcnc.
I’m doing my first build and while the parts are printing I had time to overkill my tubes a bit. I printed 20mm sleeves to slip over 1/2" conduit and used JB Quick to adhere them, spacing them equidistant along the length. I then inserted the assembly into the 3/4" tubes and slathered JB Weld (longer working time than Quick) at the sleeve locations. There is absolutely no flex in these tubes now![attachment file=116875]
That’s neat Dave. Clevee idea.
Can you share some measurements? How long are they? And can you compare the flex somehow by propping up both ends, putting a set weight in the middle and measuring the height under the middle for a normal and a filled tube, with and without the weight? Do you have any normal tubes left?
Nice. One of the better ideas, as far as this sort of thing goes. How far apart are your spacers? Like every 6 inches or so?
Also those tubes look very nice and smooth for conduit. I’m guessing you sanded them?
My build uses 30" x 36" tubes. I plan to measure the difference with my dial indicator but I visually checked by pressing down with two finders on the un-lined and lined 36" tubes. The single wall tube flexed very noticeably, the lined tube did not budge. Like I said, I’ll do a more scientific measurement just for the effort vs return factor. The spacers were 18mm x 18mm with a 14mm hole and I used five in each tube. I intentionally made them loose to allow the JB to fill the gap and bond. The conduit I bought was hot dipped galvanized (all that my local H.D. had) and were very rough. I took them to work and sanded them down on our mini lathe. Since galvanized coating does not receive paint well, I tried my go-to paint for 3D parts: SEM 39143. Its a little expensive but it sticks to everything and dries quick! I fully expect it will wear at the bearing surfaces over time however.
Here’s some pix:
So… Torsion torus? 
That looks like the filament Ron had at MRRF, Awesome stuff. I wanted to make a “pro” version with that exact color!
Copper and black is a classy look. I used CC3D Copper Silk. It printed like butter and hopefully it has enough strength characteristics as well. Time will tell but she sure looks amazing!
By the way, great design! The parts printed flawlessly and fit perfectly.
Well done!
Dave-
Hi Dave,
Did you fill the gap between the conduits using JBWeld ? Or did you apply JBWeld only the sleeves ? Can you detail the length of the sleeves and the spacing between them ?
Julien,
I applied JB liberally around the sleeve as I was fitting the inner conduit into the outer but I did not completely fill the gaps between the sleeves.
The sleeves are 20mm wide and spaced approximately 5” apart on the longest tube. I used 5 sleeves. Two on ends, one centered and two equidistant between the center and ends.
Have fun with your build!
Dave-
