I'm on Cloudy Nights for the first time in a week because I've been visiting relatives near Seattle on my vacation, so I'm just catching up.
I like the thought process indeed!
I have a thought which I'd like you to consider for execution which may help significantly both in placing the pads on location and may eliminate the concern of the straps bending laterally in use.
Since the centerline of each strap sees no torsion and is expected not to move except trivially under loading vertically, fine wires in the plane of those strap centerlines attaching straps across intersections to triangulate should have no detrimental effects that I can see. They would essentially be what we call zero load trusses and their function would be simply to maintain shape. Piano wires could be used and could manage the trivial compressive and tensile loads from actual variation from design.
For construction tiny holes could be drilled in the straps and the wires passed through them with bends as needed at each hole. Wires could extend at least a few millimeters through each strap and be bent and epoxied to the opposite side of the strap, or continue to terminate through yet another strap.
The point of this design suggestion is that any method of attaching straps to each other along the centerlines of the straps should have no impact on the intended design and may go a long way towards maintaining and establishing shape.
Good thinking, Jonathan, and I hope you are safe from the voracious fires that have been consuming NSW. Many in the west coast of the states can sympathize with the plight of your region.
Hi JT, the fires mean very smoky days and very smoky nights, but fortunately for us no more immediate threat. Tragedies elsewhere sadly, not to mention the environmental waste.
My initial thoughts is that wires might get a bit fiddly compared to, say, gluing in pieces of rubbery foam cut to shape for the job. I briefly even considered potting the entire thing in silicone, but to be honest I'm doubtful its even going to be an issue.
The thing is, the flexure part works just as well using angle, and even with slotted RHS tube, so there are many options out there to avoid buckling. And just like the curved spiders, the critical thing is the thickness of the vane material itself. A 3mm thick aluminium vane is many times stiffer than 1.3mm angle, and ditto for 1.2mm RHS tube (with one side slotted so its technically no longer a tube).
Here are the materials I've tried so far...
Of these, the order of flexibility is as displayed with the stiffest at the top right (50x3mm Aluminium) and the most flexible at the bottom left (25x0.7mm Steel Rule). Fair in the middle is the 25x25x1.2mm aluminium tube with a slot cut down one side.
As you would expect, the 50x3mm flat was exactly 2.5 time stiffer than the 20x3mm flat.
Also, in each case flexure was linear with the weight applied, whether flat, angle or slotted tube.
My initial impressions are that these two simple and direct relationships continue irrespective of whether the material is flat, angled or slotted tube (so long as the latter are not constrained at their ends). That may not be news to ME's living in the world of unconstrained beams, but I was a little surprised to see that emerging and will look at it more closely when I get the chance.
Obviously anyone with access to FEA could confirm or dispel that very quickly.
Caveat: we're talking about the flexibility to twist along the length here, not the ability to bend in any other way.
Edited by Oberon, 21 December 2019 - 08:29 AM.