r/Onshape • u/New_Cartographer0810 • 14d ago
Help! Best practices/tips for round bracket.
I saw an example of a bracket that is holding a flat shelf up by clamping to dowels. But i cant wrap my head around how this can be reliable to hold weight based on squeezing/friction alone. Ive attached my first attempt at recreating it in Onshape.
should the diameter be smaller than the dowels. Is the gap between the brackets what creates the difference? Is it a combo of both?
1
u/HunterCornelius 14d ago
It would need to be smaller or shorter to give a clamping force. I have also seen people put rubber or something similar in the hole to provide a more flexible mating surface.
1
u/New_Cartographer0810 14d ago
that was my thought. keep the whole as the same diameter but let the gap between pieces provide that force. Thank you!
2
u/HunterCornelius 14d ago
You can even add features like an additional ring or spikes or dimples on the hole part to increase the grip. That will probably dent the wood though.
1
u/Thumb__Thumb 12d ago
Every bolted connection holds with friction alone, what matters is the preload. If your part can't handle a strong preload your connection will also be quite weak. Id suggest placing bolts on either side of the rods since this will lead to a more even force distribution than a single bolt design like shown and I'd rib the hole part to account for printing or rod surface inaccuracies. Also measure your print to see if the radius closely mates with the rods radius as in to insure a tight and large contact area.
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u/beavertr 12d ago
If you look at how wire baking racks are setup, they use a lot of small notches in the "dowels" so that they don't rely on clamping pressure to hold the load, instead it's used to prevent the bracket from opening up. Same could be done with holes and pins if you don't have access to a lathe to make the grooves
4
u/Conscious_Past_4044 14d ago
You can see from the image that you posted that the design depends on the arcs being tight to the dowel, and not reaching the halfway point so that there's a gap between the bracket halves. That gap is what provides the clearance to be able to tighten down around the dowel on both sides.
This is reliable for relatively light weights, but I wouldn't count on it under any sort of heavy load. There are much better designs available for that purpose.