January 5, 2016 | ProgressTH | 3D Printed Files on Thingiverse
We've put up all the files, including the SketchUp file we've developed the frame and joints in, on Thingiverse. Find them here.
The basic unit is a cube with 18mm holes on each face. These are then combined into different shapes to create standard joints and mounts. There are "spacers" that fill into the holes.
In fact, the original design was supposed to be box-shaped, and only because we didn't buy enough pipe for the design, did we redesign the joints to make a triangular shape. Feel free to make your own configurations!
You can drill holes into your PVC pipe and put a bolt or dowel through these spacers and the pipe to keep joints from slipping (see photo).