Ramper Clamper
thingiverse
I've come up with a pretty unusual concept that I'm sure someone could turn into something practical. The Ramper Clamper has little ramps in it, and with the right bolts in place, it would definitely clamp onto a round object of the correct size. As for how it would work, I imagine bolting the upper and lower pairs of outer sleeves tightly together first. Then you'd slide them over the inner sleeves. Next, use long bolts to connect two sets of outer sleeves over the inner sleeves. Loosen up the long bolts to allow some slack. Two poles or structure tubes could be clamped end-to-end by pushing the outer sleeve pairs towards each other and then tightening the long bolts to secure them tightly. This is purely a conceptual idea, I haven't actually tested it yet. I might add a few more parts based on this same idea later on.
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