frank_lima,
I like that plasma cutter idea.
I might go ahead and build the aluminum cart because my partner in this project knows how to weld.
And such an aluminum truss-cart would look really cool. Fine, I admitted the real reason I want it. The top bar would be 3" x 4" I-beam, unlike my crude sketch.
Wood definitely makes more sense from a cost and ease-of-construction standpoint as Nick was quick to point out earlier.
Bruce
I would recommend steel over aluminum. cheaper, not appreciably heavier and much much easier to work with. I also offer you should work on your truss design a bit, way overkill for the load. IMHO. Use steel and don’t over weld it and you may have a shot at getting it straight and flat.
ioport51,
I like your idea of using steel over aluminum.
I lean towards stainless as I want the thing to live at DMS for a long time.
Steel is twice the weight of aluminum but also twice the stiffness; so I might re-design that cart in steel, and do 3D, to use angle instead of tube.
When you say “I also offer you should work on your truss design a bit, way overkill for the load. IMHO.”, that is to please the Machine Shop gurus [and me] who want things as accurate as possible.
Bruce
You will want to stay away from angle. It’s not nearly as stiff as you would like. It tends to move a little easier than say tube. So it takes more of it to stabilize it.
Before you build this, make sure a committee is willing to provide space for it. Loans and donations must be accepted by the committee in advance. Catch-22 is: They may want to see final product before agreeing to accepting it to ensure it works properly and is something that can be used.
DMS is not responsible for any damage done to loaned equipment or equipment that wears out.
TBJK,
Thank you for the advice on angle vs square tube; that rings true.
Photomancer pointed out that I need better structural analysis before I attempt a design on an expensive metal cart. My current design comes from doing a Google Image Search on “truss bridge” and mentally taking the average of the pictures.
Until I figure out how to do proper structural analysis in Fusion 360 or the like, I will buy a couple of Rubbermaid carts to haul just the two I-beams connected together and whatever hardware is needed to make the 12’ pole with holes.
Bruce
Photomancer,
I’m trying to figure out which committee to ask for space.
After your reality check on accuracy, I don’t think Big Susie belongs in Machine Shop at all, especially because she is designed to be used creatively and even for art…
How about Creative Arts?
Big Susie is more like the Shapeoko than anything else; my stepper motor drivers (TinyG) are an advanced version of what is in the Shapeoko right now.
I understand that DMS is not responsible for any damage and/or wear.
Edit: Bruce