This is a followup of sorts to my earlier question about A metal tube that ‘unzips’?. I’ve been thinking about that Storable Tubular Extendable Member device, and wondering if it is possible/practical to make a home version without advanced fabrication facilities. RolaTube and other groups make such things out of fiber-reinforced heat-cured resin, but I’d like to stick to metal.
My thought was to take a standard metal tape measure and somehow increase its transverse curvature*, so that it was more like a slit tube than a shallow arc. This would give me a tube of about a quarter inch diameter or so. I’m not sure if this is possible to do in a home shop, or what the best approach would be to achieve this without ruining the ‘spring steel’ quality of the tape measure. I’d want it to still be able to be flattened out and wound onto a spool, like a regular tape measure.
I pictured pulling a roughly 6’ section of tape measure through a series of holes of decreasing size drilled in a metal plate, forcing the edges to curl up and over. But perhaps this would only work if the metal was heated so as to lose its temper, and then re-treated afterward to regain the ‘spring’. Alternatively, I could draw it through a hole smaller than 1/4" in diameter and hope that the curve relaxes to the degree that I want.
Can anyone offer any suggestions about how this effect might be achieved? Perhaps by starting with a different material, or finding such a coiled metal slit tube pre-made at (wherever)?
My guess is that the radius would be too tight.
You can have steel foil, that would be flexible enough, but its so thin it won’t act like a tape measure steel…
You can easily damage the steel tape measure by bending it… Try to increase its radius ? its rather stiff in that way… try to flatten it out ? it won’t. Its too darn strong and remembers this curvature very strongly…
Sure you could anneal it and make it soft, but then it will stretch and tear and crack too easily too.
With heat treatment, that is heat it to soften it up, shape it, and then quench it to set it into the new shape… you can have your cylinder, but it can’t be flattened out any more than the measuring tape… its annealed cheap mild steel (like a 30 cent screwdriver or a piece of home fencing wire…) or its hardened steel… (its malleable or not malleable… ) you can’t have both .
Well, drawing the tape through a die plate did cause it to curl up more, but at the cost of introducing ripples into the edges. The ripples were irregular, and produced some sharp points. When trying to draw the tape down further, it tended to snap at those kinked spots.
Work hardening will become an issue if you eventually manage to reduce the radius of your tape measure’s cross section into a (near) cylinder. Coiling/un-coiling such a tube will result in breakage in short order.