I know what they are
I know basicly how to build them
but I don’t know how to determine the size of them for an application.
i’ve looked for books on them, and while I’ve found a number that makes reference to them, the description of the book doesn’t indicate that they will really tell you how to size them.
could someone point to something to help me determine specifics?
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bobl Volo, non valeo
Replies
"determine the size of them"
how deep for length and width and load capacity
thickness of edge piece
thickness and spacing of the web
etc
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bobl Volo, non valeo
Bob, I'd start with this. a 3/4'' x4'' frame..say 16'' x 48''..inside create aprox. 4x4'' compartments out of 1/2'' stock. I half lap the joints..like a cardboard insert in a beer case..LOL.
a these joints can be glued, and stapled (wide crown) on the edges..a skin of 1/4'' ply is GLUED to the CORE and edges on BOTH sides..make it big and flush trim the ply later.
now you have the most lightweight, strong 16x48 x 4 1/2'' hunk of something you can make.
Any questions?
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
thanks
can I use those materials to make a 2ft by 16 foot that will hold 450lbs safely?_____________________________
bobl Volo, non valeo
if this is in regards to a scaffold walk board, I'd say no. Only because I have not 'tested' it, and it depends on the actual span and point loads.
a variation of this would be fine for SOME things, but for YOU to be on..I can't say yes go ahead, with certianty....only for your own saftey, not because I don't think it'd work.
My walk board is 24'' by 16'...2x4 rails , with 6 cross pcs. 7/16 osb on top..glued and screwed..holds me and a helper fine. But again, I can't say do it, with a clear consience.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
yes, that's my immediate use, as a walkboard.
but like I said above torsion boxes fascenate me. ever since I read about them in FWW.
every once in awhile I go looking for information. my having to replace my platforms just spurred it this time around.
i've looked for books on amazon and I get hundreds of hits, but the excerpts just seem to mention them.
google searches get hits. pages where people have built one for a specific purpose and how they did.
but never how they picked the specific design._____________________________
bobl Volo, non valeo
I've built a table and a desk top using the idea, only I put 2" Styrofoam sandwitched between 1/4" plywood. But for something to walk on, I'd go with wood in the middle of the sandwitch--or steel studs?
Edited 9/24/2004 8:19 am ET by Danno
What the Heck are they? Never heard of 'em.
Don
A torsion box is a furniture guy's term for a structure which gets used all over the place -- airplanes, skis, buildings, etc. It is two fairly thin skins bonded to some lightweight spacer. In buildings, hollow core doors are a good example. In airplanes, they use honeycomb aluminum clad with aluminum. In skis, they use honeycomb plastic clad with fiberglass.
There are two good things about torsion boxes. One is that their stiffness to weight ratio is very high. Two is that you can build flat stable structures with materials that are pretty floppy by themselves. For instance, you can make a serviceable door with two sheets of 1/8" ply and some cardboard for the spacer.
Jamie: Thanks. Makes sense now.
DonThe GlassMasterworks - If it scratches, I etch it!
For a plank or platform structure two thin pieces of plywood with foam in-between (like the prefab foam-filled wall panels) will work pretty well, Strength can be improved further by alternating pieces of the foam with strips of wood, and using wood around the edges will concentrate strength where it's needed most.
Of course, the strength of something like this is pretty unpredictable without some engineering computations and/or testing. Picking a glue compatible with both wood and foam would be critical.
There are other terms you may be more familiar with: Stress-skin construction and monocoque designs.
The general idea, I smear it a bit but the basic idea in each case is similar, is that for a very long time if you wished to build a structure, a house, car or airplane for example, you built a structural frame and then filled in the gaps with a skin whose primary purpose was to separate the inside of the structure from the outside. The skin was not structural. The frame and skin each performed different rolls.
In stress skin designs, or if you wish to use the term torsion boxes, the skin takes on a structural role. Even though the skin is thin the combined cross-section of the skin amounts to a a large but thin structural member.
In this case there is still a roll for a much lighter frame, holding the skins in proper alignment to allow the skin to act as part of a much larger, and much wider, beam. Spreading loads over a much wider area allowing for a much lighter and efficient, in terms of strength per kilo weight, design.
This technique has been used in cars, where frames have largely disappeared, and airplanes where heavy beams and struts have been greatly reduced in number and size.
When you said monocoque, you said it all. Very familiar w/ them & construction methods for aircraft.
Never heard torsion box before, but it makes sense - sorta.
Thanks.
DonThe GlassMasterworks - If it scratches, I etch it!
In reading the post and replys I have to ask Are you building a plank ? I only ask because I built one for my own house for doing the soffit and facia ( Aluminum). I used OSB and steel (2x3) studs and I have to say that sucker is strong and stiff ( not unlike the Fri. drink) Cool tomorrow is Fri. I digress. If you are I can help you with the ideas. Although mine is 14"wide and 12' long. In any case if I can help let me know. Mike
yes, that's my immediate use, so any information would be appreciated.
the things also fascinate me, and I want to learn more about them too._____________________________
bobl Volo, non valeo
I got the idea from an article inFHB about headers and thought if you turned it flat you can use it for a plank.
What I did was to take 7/16 OSB riped 14" x 3 out of a 8' sheet, then got a hold of 2x3 x12' steel track ( 2 of these) and a stick of 2x3 lumber. the track runs the lenght of the sides and I spanned the 14" way with lumber the ladder has "rungs "every 19.2 and that gets me one at the skin joint.
I screwed thru the tracks into the wood with 2" pan heads and used adhesive painters caulk. Which was sticky and thin enough to spread to a nice skin when I screwed the O
SBto the tracks and the wood
I also tucked the tracks in a little so I can clamp to it or clamp it down with out the clamp heads up on the walking surface.
As for the torsion box I watched David Marks build one for furnature assembly. He has a show called WoodWorks on the DIY network so I would check their web site and gets some goodies there. DIYnet. com Hope this help. Mike
Get a hold of Jim Blodget ....
he's got a walk board desing he's posted a coupla times ...
I think he uses 2x4's on edge ... with 1/2 ply skin ....
he also builds in a crown ... think he laid a 2x on the flat at midpoint ... when building his ... then uses it crowned up ... so it flattens a bit under load.
bet he'd ba able to guess at how much weight it'll hold ... I think he's been using them for years.
Jeff
Buck Construction, llc Pittsburgh,PA
Artistry in Carpentry
he's provided me the info on how he built it_____________________________
bobl Volo, non valeo