hex rod and 120 v bearings...rev 1

[jseiler]

i'm happy with the v bearing, shoulder bolts, and hex rod, now its time to mount it. I want to mount to 40s 80/20. The simple solution is drilling it and screwing it down on washers (If I had picked larger hex, it would have cleared v groove. I'm flirting with the idea of taking it to a welder, having them clamp it straight and welding it to 1.25 or 1.5" cold rolled and drilling parallel holes to match, then I can keep screwheads out of the way and it would be really still, essentially like angle iron. Is this something a welder
is likely to do easily without jacking it up and making the hex all warped?
I'm not worried about small amounts of warp, i'm looking for .01 repeatability
and i'm getting that in my proto.

can this be spot welded? that would be great because one could rotate the hex rods to make by drilling the welds and cleaning it up with jbweld.

the hex is 416 stainless. the cold rolled could be stainless or cr, whatever would work best.

question 2. how does one mount 20 pitch rack on 8020? I couldn't find any pics where anyone had done that. I might have to use the same solution for that one, have mounting rails made. shopbot uses vhb tape, but my vhb tape doesn't seem to hold well enough to justify that.

I'm going with a standard type nema23 or nema34 with a low backlash gearhead for the x drive. I think ultimately this will be more trouble free
and cheaper than belt for a long and extendable axis. if you look carefully
you can build an equivalent to a vextra gearhead motor for a lot less
than 300 if you get lucky on ebay.

goals:
buildable with available materials in a weekend with a drill press, miter saw, and drill/router templates and common tools. cheap rails. would not rack due to small misalignments in the rails. tolerant of joined sections (just add more rollers and make sure your transitions don't stick out). standard motor mounts. extendable x and y axis. under 2k for 3x3 not including support table. that could easily be a simple welded frame ot 80/20.

gantry
i built a frame from 2 pieces of 40s lite and used 3 8" supports. I reinforced this with 3" (?)triangle brackets. seemed pretty stiff. I'm thinking about making this a torsion box with aluminum sheet and t-bolts and washers.

is this worth the weight? would vhb between the sheet and extrusion help the stiffness of the torsion box?

support frame. laminated plywood torsion box for flatness, cheapness, rigidity. mount rails and spoil to it. eventually allow easy vacuum.

x drive-dual rack/pinion driven by a single motor through a low backlash gearhead.

i'm looking at the linistepper for drive. if not, i'll blow my budget with geckos.

ideas, ideas, any ideas? No one seems to want to work with hex rod.

J