Came here following a co worker who’s building a proton pack. I had just built a 3D printer, and he asked me about printing a clippard valve based on some 2D scale drawings he’d found, probably here now that I think about it.
So I was learning Blender and decided that was an excellent first project for my new toy. Modeled it and printed it for him, turned out pretty good. Later, he sent me some low quality sketchup model of the bumper and asked about doing it. Having fun with blender, so I took up the challenge.
I had to clean up the sketchup model, it was a complete mess at the polygon level, practically remade the whole thing. It was also too big for the build platform on my Prusa, so I had to split it into three parts. I voided a slot on each and printed a tab that aligns the parts for gluing back together. It took a LOOOONG time to print, but turned out great.
If anyone wants to print their own bumper or valve, the objects are on my thingiverse page, linked below. There’s instructions there, read em, or waste plastic on the bumper! 
So here I am, to follow my friends build notes and see all the other builders projects as well.
http://www.thingiverse.com/loughkb/designs
Kevin.