Darryl Keil Last Activity 2025-05-12 11:03 AM
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Mad_WOrld

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Subject : Question about Honeycomb Torsion box
Posted : 2010-12-09 4:07 PM
Post #36220
I'm going to be building a bookcase for the wife soon and I want to try my hand at a torsion box.
The bookcase shelves will be 12" wide and 54" long. She prefers a 1 1/2" thick shelf but I can go up to 2" if I need to.
The shelves will hold books and knick knacks, I say no more than 100lbs per shelf at any time.
I'm thinking on using honeycomb for the grid work.
I'm thinking a 1" honeycomb with 1/4" skins (mdf?) that will be veneered, sound like it might work? Or would 3/8" skins be better? Or do I go the max and build the shelves 2" thick?
Thanks


 
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craig tufankjian

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Subject : RE: Question about Honeycomb Torsion box
Posted : 2010-12-10 8:19 AM
Post #36222 - In reply to #36220
Aside from the honeycomb approach, what I like to do with shelves that are going to have heavy weight applied to them, such as bookcases , is to sandwich extruded steel tube,3/4 x 3/4 between two 3/8 skins which will give you a 1 1/2 shelf. see photo. you can cap the ends of course.

Depth of the shelf will determine the amount of steel tubes used. 12 inch depth will require two tubes and a deeper shelf will require three. See attached photo.

http://i244.photobucket.com/albums/gg28/customone/Picture20.png


 
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Enrico Konig

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Subject : RE: Question about Honeycomb Torsion box
Posted : 2010-12-10 10:49 AM
Post #36223 - In reply to #36222
Craig,
Using 3/8" skins, does one need to fill the gaps between the steel extrusions if one is to vacuum press veneer onto the top and bottom surfaces?

thanks,
Enrico



 
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craig tufankjian

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Subject : RE: Question about Honeycomb Torsion box
Posted : 2010-12-10 11:15 AM
Post #36224 - In reply to #36223
Enrico,

Never had a problem with collapse due to the voids, the use of a 3/4 inch caul on top to distribute the pressure from the vac press is a good idea

because the extruded steel is very accurate you can fill the voids with 3/4 rigid foam which is the exact same height.

obviously the larger the voids the better the chance of collapse if not supported. if one uses the two tube approach, one in front the other in the back, then yes, something should be put in the middle to avoid collapse, even a scrap 3/4 block of wood in the center.

I don't think honeycomb will prevent a shelf from sagging over time without being supported.


even honeycomb in the center is a good idea to fill the void.


 
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Mad_WOrld

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Subject : RE: Question about Honeycomb Torsion box
Posted : 2010-12-10 3:23 PM
Post #36225 - In reply to #36224
I'm also trying to keep the weight somewhat down and being some of these shelves will be up top I don't want a top heavy situation.


 
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Don Stephan

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Subject : RE: Question about Honeycomb Torsion box
Posted : 2011-01-08 6:32 PM
Post #36231 - In reply to #36224
Craig:
Thanks for the very informative post and picture. I'll have to remember that use of tubing.
Wondering though what adhesive you use with the tubing, and how you prepare the tubing. I'm assuming you wipe it thoroughly with lac thinner or similar to remove any residual oil. Do you rough it up with sandpaper to give adhesive more bite?
Don Stephan


 
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craig tufankjian

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Subject : RE: Question about Honeycomb Torsion box
Posted : 2011-01-09 2:35 PM
Post #36233 - In reply to #36231
Don,
gorilla glue..... that stuff sticks to anything. slather up two slabs of greasy pizza with that stuff and an hour later you got a calzone.

get the stuff on your hands however and its there for a good month.

If you use aluminum tube , no need to clean it.


 
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Don Stephan

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Subject : RE: Question about Honeycomb Torsion box
Posted : 2011-01-08 6:36 PM
Post #36232 - In reply to #36224
Yesterday I pressed a couple shelves - 3/4" honeycomb between 1/4" ply skins. 12" x 96", with 3/4" x 1" poplar frame sandwiching the honeycomb. Very light, but not as stiff as I had hoped. I'm thinking that a solid wood honeycomb of 1/2" strips perhaps 3" on center would have been much more rigid. Much less gluing surface, but the strips have some stiffness which honeycomb does not.


 
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Don Stephan

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Subject : RE: Question about Honeycomb Torsion box
Posted : 2010-12-27 6:43 PM
Post #36229 - In reply to #36220
Mad:
I've never been able to understand the engineering data on the honeycomb manufacturer's web site so I can't estimate deflection. My very rudimentary guess is that the more intermediate skins the stronger the package, but I'm not positive that's true. I've always guessed that for the same number of skins, the thicker the honeycomb the stronger the package, but that's only a guess.
Wouldn't it be nice if there was an engineer on the forum who would calculate some basic packages, even if done so anonymously so we couldn't all pester the kind one for additional options?


 
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Mad_WOrld

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Subject : RE: Question about Honeycomb Torsion box
Posted : 2011-01-03 4:42 PM
Post #36230 - In reply to #36229
An engineer would be nice. hint hint.


 
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craig tufankjian

Posts: 308

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Subject : RE: Question about Honeycomb Torsion box
Posted : 2011-01-09 2:44 PM
Post #36234 - In reply to #36230
If anyone really wants to see honey comb construction at its best, buy an Ikea cabinet and cannibalize the thing. Those Swed's got it down to a science.
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