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I-Beams for Torsion Box?

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Forum topic by mawilsonWCR posted 05-16-2021 05:02 PM 267 views 0 times favorited 7 replies Add to Favorites Watch
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mawilsonWCR

34 posts in 119 days


05-16-2021 05:02 PM

Given the price of lumber today, does it make sense to use wood I-beams for torsion box construction?

My assembly table plan calls for a torsion box top. i was thinking 1×4 webbing, and that may still be an option as is 3/4” or 1/2” plywood. Watching a video this morning got me wondering if I-beam might also work. Fuzzy morning thinking is 1×2 flanges with grooves for1/4” webbing.

What do y’all think?

-- No trees were harmed while sending this message; however, a rather large number of electrons were terribly inconvenienced.


7 replies so far

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HowardAppel

87 posts in 4152 days


#1 posted 05-16-2021 05:06 PM

You can buy corrugated cardboard webbing, what is essentially what is inside of hollow core doors. I have used before and works great, although I do prefer 1x. Comes in varying thicknesses depending on what size you are making.

I don’t understand your question though—are you talking about using joists for the skins?

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Fred Hargis

7023 posts in 3611 days


#2 posted 05-16-2021 07:19 PM

I’ve built 2 and used 1/2” plywood cut into 4” strips for both. Was more than adequate and cheaper than 1×4. I suspect the flanges would work…but I have to wonder why you would do that when the plywood is so much easier.

-- Our village hasn't lost it's idiot, he was elected to congress.

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Knockonit

849 posts in 1320 days


#3 posted 05-16-2021 07:26 PM

there seems to be an abundance of pallets around my location, would not the half inch plus or minus slats on a pallet work well for this, if the rough ness bothers you, well run’m thru planer or sander a tad.
just a though
Rj

-- Living the dream

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clagwell

370 posts in 910 days


#4 posted 05-16-2021 07:39 PM

No need for the flanges – the torsion box skins serve that purpose. All the webbing does, in either a torsion box or I-beam, is keep the the top and bottom apart by resisting the vertical compressive forces. The skin or the flanges take the shear stress.

1/4” webbing should be adequate as long as it’s kept perpendicular to the skin.

-- Dave, Tippecanoe County, IN --- Is there a corollary to Beranek.s Law that applies to dust collection?

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mawilsonWCR

34 posts in 119 days


#5 posted 05-16-2021 08:59 PM

Fred and Dave, You have a valid point. The skins on a torsion box would act like flanges.

Rj, There is a pallet yard near me, but they are in the sales business. The two free sources nearby have dried up. I’m not a huge fan of pallets, anyway.

I probably ought not seriously consider design options on Sunday morning.

-- No trees were harmed while sending this message; however, a rather large number of electrons were terribly inconvenienced.

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tvrgeek

1937 posts in 2767 days


#6 posted 05-16-2021 09:27 PM

News suggests the lumber shortage is about caught up.
Personally, I kike the feel of a massive heavy top.

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mawilsonWCR

34 posts in 119 days


#7 posted 05-17-2021 12:01 AM

tvrgeek, My assembly table will have an adjustable height top powered by a linear actuator so I need to manage the weight of the top. I am planning for a ~3/4” top skin. Right now the design calls for 1/2” plywood and 1/4 hardboard sacrificial top (reality is both those dimensions will be light). I’m even considering holes in the webbing to further reduce weight.

-- No trees were harmed while sending this message; however, a rather large number of electrons were terribly inconvenienced.

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