Design principles

[dpb]

On 5/12/2013 10:15 AM, dpb wrote: ...

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Or, you could simply use a horizontal support fastened to the two uprights w/ "enough beef" to support the load--tubasix would do nicely and still be thinner than it appears your verticals are now...

I just went w/ the solid center support (or you could replicate the ends in the middle as well) as it's simple and adds both vertical support as well as racking by forming a truss member that is pretty much lacking anywhere else at all (as others have also noted).

[dpb]

On 5/11/2013 3:58 PM, dpb wrote: ...

Of course it's more than I thought/expected--forgot the divisor of 4 for radius. So the load/bin is more like 300 lb instead of 1200. That's a lot more in line w/ what gut feeling was; don't know why it didn't register before now...

V= (3.14/4)*(5/12)^2 *2*27 ~ 3/4*~2/6*27 --> 27/4 ==> ~7 cuft/opening

So, the deflections below are going to be ~1/4th those numbers which is getting marginally acceptable; if went w/ tubafor instead of 1X probably be fine w/ only slight modifications. Still this assumes the solid or near solid center support, though, of course.

[Alexander Lamaison]

In the existing design there were also two beams in the middle running between the front and back verticals, under each set of shelves. The extra support in the middle that you suggest, is that to provide extra support for the shelves, or to help keep the frame square?

As it happens, I was planning to tack some thing slats accross the middle anyway, just so that I could use each side of the bin independently. But I didn't include that on the diagram as it wasn't meant to be structural.

Wow, thanks for leading me through all of that. It's really helpful.

I'll adjust my design accordingly and post links again when I'm done.

Thanks,

Alex

[Alexander Lamaison]

Ok, new words.

Truss:

from a quick Wikipediaing, am I right in understanding that, to get a stable structure, you should join the planes together? And this is called a truss. The brace and gusset previously mentioned, as well as your suggested solid support, do this by joining two planes together. Do this in both directions, and you have a truss?

Racking:

Googling was no use here. It just tried to sell me shelves. What is racking?

Thanks,

Alex

[Alexander Lamaison]

I had to read this 3 or 4 times to work out why this version was correct. Thanks for the update :)

[none]

On Tue, 14 May 2013 09:40:08 +0100, Alexander Lamaison

Racking is when some type of shelving structure starts to lean over in a particular direction and then usually collapses. It often ends up in a cascade failure.

[Alexander Lamaison]

Haha, that's spectacular. :D Thanks

Alex

[dpb]

On 5/14/2013 3:40 AM, Alexander Lamaison wrote: ...

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Strictly speaking, a truss is a coplanar system of structural members joined together at their ends to form a stable framework. The simplest form of truss is three members in a triangular shape--clearly you can see that pushing on any given corner is resisted by the compression of the two opposing sides and if the material is ideal it's perfectly rigid to loads in plane.

The suggested solid piece serves the function that a strictly truss-like mechanism would of an 'x' but adds the needed vertical support the shelves need in the middle so while not strictly a truss in the simple definition by being solid it provides the resistance to serve the purpose as well as the support.

[dpb]

On 5/14/2013 3:26 AM, Alexander Lamaison wrote: ...

A) Didn't appear obvious to me they were there; but then again, I only looked at it very briefly to get the overall rough dimensions...

B) Both. See response above to note on 'truss' and 'racking'...

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I see you did find the erratum posting that loading is much more like expected when one correctly includes the 1/2 factor in the diameter when computing volume so I'll retire unless have further specific questions...I just _knew_ something didn't make sense but kept overlooking it.

[dpb]

On 5/14/2013 8:23 AM, dpb wrote: ...

And, while repeating the end design in the middle would provide the vertical support, unless the attachment is very rigid there's little resistance forward/back to racking by doing so. A set of solid vertical

1x4s if the shelves were mortised into it very tightly would provide some resistance by the twisting moment of the shelves, but there's not an overall strong resisting member overall.

OTOH, either a solid plank or the ply has length on all sides for connection and ends up, therefore, providing that rigidity.

[Alexander Lamaison]

Could I achieve the desired result, instead, by repeating the end design but having the planks run diagonally?

Alex

[dpb]

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Certainly helps. The question then hinges on how they're fastened to be as near a rigid connection as possible and how that connection will fare w/ time and use...