I have some steel tubes (18 mm OD) which I wish to use as horizontal members in a storage rack (a bit like shelves). However, the tube flex and bend quite a bit when I put heavier boxes on them. The tubes flex about 40 mm over a 1000 mm span. Ideally I would like the flex to be <5 mm.
Is there any cheap(~$0) & readily available material I can put into the tubes which would stiffen them significantly.
I was thinking about filling them with concrete, but that seems a bit messy and I don't have cement/sand to hand. Would concrete work?
Best Answer
You could truss the tubes as shown in the picture below. The center block helps to support the tube when the truss member is placed in tension.
The truss could be constructed from heavy wire or threaded steel rod. The concept here would be similar to the scheme used on the wider steps of a wooden step ladder.
I would have suggested the possibility to place the truss wire / rod inside the tube but I suspect that the 18mm diameter of the tube is too small to let the center support in such scheme be large enough to make a significant impact.