homestudiobldr wrote:So, what does this mean to a layman trying to actuall accomplish this construction wise? Just yesterday, I posted a reply on another bbs to a thread author offering Scotts interpretation of building one of these poly devices in the simplist manner that I understood from a past post of Scotts. Maybe I'm missing something here, but does this mean that Scotts poly building technique doesn't work, or ALL polys with shapes other than a sine wave don't work...or what?
Terry Montlick wrote:d = sin(π*x/L)
where 0 <= x <= L
Scott R. Foster wrote:I applaud your research on the ME maths - but I reckon the real shaped rendered does have some constraints arising from how bending forces propagate through a given substrate.
the poly shape we are describing arises from buckling via compression, not just the tug of gravity. In commenting on that fact, Eric has suggested that the Euler - Bernoulli beam equation is the source for mathematical description of the resulting curve. Note how the bending mode on the left appears to match a typical poly precisely in both method and yield.
Bob wrote:Terry Montlick wrote:d = sin(π*x/L)
where 0 <= x <= L
Obviously x needn't go as far as 0 or L, but would most often be a subset within those boundaries.
It means absolutely nothing of consequence to the layman.
Scott's poly building technique will work, because it simply applies pressure at the sides to bend out the middle. This will mathemagically form a half sine wave shape.
Something in my belly was telling me the same thing. I just wanted to hear it from a non laymans belly.It means absolutely nothing of consequence to the layman.
Just to be clear to laymen... if you are doing it right you don't necessarily get an entire half of a waveform.
B will diffuse better.
In each case L is the same, but only a subset of x (a small range of x) is used, not the entire 0 <= x <= L :: at least for 'graph A' and 'graph B'. I can't imagine anyone doing 'graph C', which I think is 0 <= x <= 2L, but even the left up hump of 'graph C' doesn't look to me like the way plywood would bend.
Obviously I've played around with C a bit in this equasion: [ d = C*sin(m*π*x/L) ]
So when I wrote "Obviously x needn't go as far as 0 or L, but would most often be a subset within those boundaries", what I mean is
in 'graph A' the x goes from 0.44 to 0.56
in 'graph B' the x goes from 0.48 to 0.52
homestudiobldr wrote:Actully, and I may be wrong, but I was under the impression that polys don't diffuse at all. They scatter.
Terry Montlick wrote:Exactly. The pictures are of the buckling of a thin column -- yet another synonym for a rod.
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