Could anyone provide a link

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Could anyone provide a link

Postby sacharlie » 18 May 2018, 02:39

to a load bearing calculator for aluminum.

The below is great but only for steel.

http://www.atc-mechanical.com/calculators/
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Re: Could anyone provide a link

Postby Burgerman » 18 May 2018, 09:59

Its going to be hard to find one. There are thousands of aluminium alloys. And no aluminium used alone. So first you would need an exact makup. And tiny differences drastically change properties, sometimes in opposite directions. Bending, compression, hardness, tensile strengths are all changed individually. And making it even harder, aluminium alloys get soft when annealed, or made, and can be hardened by heat treatment in different ways, and can harden over time due to temperature changes longer term. And can work harden. So a beam that experiences a bending force for eg, will get much stronger and bend less, over time. And more brittle and liable to fatigue fail because of this too.

So its best to use larger, over strong assembies. For eg a motorcycle frame made of alloy, is massively over strong, and over size. The ideal thing on a bike to remove frame flex and make it handle better. And so also remove hardening and fatigue failures at the same time because of less flex. So alloy is a good choice here only when over engineered markedly.

So any tables or propert sheets should be taken as only a part of the equasion, and good understanding of how the stuff behaves and careful design is the rest.
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Re: Could anyone provide a link

Postby sacharlie » 19 May 2018, 00:37

Well that calculator for steel is producing some very big numbers.
It shows 48" long 2x2 square tube 16ga beam supports 1412lbs and in 14ga 1949lbs.
It says this is a simple beam load which I assume to mean 1412lbs spread out along the 48".
It just seems like a lot of weight. Maybe i'm missing something.
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Re: Could anyone provide a link

Postby Burgerman » 19 May 2018, 01:07

Presumably it means supported by ends, force applied to the centre if we are talking about bending force or rather enough to cause failure. Seems about what you should expect from a square tube in bending. Doesent tell you that even 1lb produces measurable bending though. Even if the figure is tiny. Only the failure force. And that reduces with temperature. And there are many steels, and steel states.

And doubling the length reduces that to half. (Or it may be 1/4, cant remember...)
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Re: Could anyone provide a link

Postby sacharlie » 21 May 2018, 21:52

Looks double the length cuts the load bearing in half.

The battery for the VMI Northstar control module went dead and the "sure deploy" system wouldn't even work. The "failsafe" hand crank method is slow and wears ya out cranking. I've got some 7' telescoping aluminum ramps but are only useful for my manual chair because the track width on them is just 6.25" my mwd q6 has a track of 7".

Anyway I want to build a pair of 4' long ramps to carry in my van? Looking at that 1949lbs on the 48" 14ga 2x2 tubing i'm thinking of having a pair of channels 10" wide by 2" tall fabricated. Figure they should handle me and a powerchair. Would you feel comfortable with that for yourself?
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Re: Could anyone provide a link

Postby Burgerman » 21 May 2018, 22:04

2 x 2 box? You could drive a car up it.
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Re: Could anyone provide a link

Postby sacharlie » 21 May 2018, 22:41

Well channel 10" wide with 2" tall walls. I understand a 2" square tube has 2" wide material running horizonally supporting both top and bottom of the walls but figure it's the 2" tall vertical walls taking most of the load. So with the tubing there is 4" total horizonal material while the channel will be 10" total horizonal material but only on the bottom. Thinking the 10"x2" channel is probably stronger.
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Re: Could anyone provide a link

Postby Burgerman » 22 May 2018, 05:52

No weaker. I think... considerably. kink or deform more easily. But either way I dont see it failing. Depends how hard the material.
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