Torsion Box Construction and Material Questions (look inside)
-N.
The last few projects are either 90% built, or all planned out and just
a few easy things are left to make. One remaining project that I haven't
designed yet is an artist's drawing table.
I now have a temporary Melamine veneered 3/4" particle board that's
drafted into drawing board use, and it's dimensions are about 4' x5'.
She's a heavy mutha.
I'd like make an exceedingly superior drawing board and do some sort of
torsion box fabrication. Size would be about 4' x 6', thickness to be
determined. I could use a little help: this is new territory for me.
One feature I'd like to have is that the skins (or veneers, not sure
what surfaces are called in this sort of construction) should be soft
enough wood that they can easily accept push pins with moderate finger
pressure. I don't want to have to hammer them in, then try to remove
them and the head comes off, then the "pin" comes out only with the
pliers. Self-healing properties on the skins, such that pin holes
recover fairly well after the pins are removed would be beneficial. A
tight grained wood to yield a smooth drawing surface is Paramount.
Lightweight is King.
Burly is Queen.
In a bookstore today I saw a furniture book that featured a torsion box
desktop and made with small strips of wood which functioned as the inner
torsion box grid: beside it for comparison was a commercially
manufactured core...it was made of honeycombed corrugated board (II
imagne that is how hollow core doors are also made)?
Where would I purchase such or similar a honeycombed core? Either
corrugated board, or some other lightweight material?
I'm not certain what wood the skins should be...that and the other
questions are the reason for this post.
Thank you for your ideas.
Cheers,
-n.
--
Cheers,
Neal
To contact me very carefully remove the Firing Pin from my email
address.
Steve Boyes
best as the holes tend to get bigger and the paper moves, Better to use
masking tape. It holds down well but does not tear the paper like Selotape
when you remove it. For the surface you need something a bit softer than
Melamine. In UK & Australia you can get special plastic for covering drawing
boards by the meter but I dont know what it is called , expensive but worth
it. If you use that it doesnt matter what the table is made of. The biggest
size of commercial sheet drawing paper is A0 is 841mm x 1189mm or 33" x 47"
so 4" x 6" will be plenty big enough.
Dont know anything about torsion boxes, I did most of my work on a flat
bench.
Steve
"-N." <n.w...@firingpinverizon.net> wrote in message
news:3D7DAB63...@firingpinverizon.net...
bridger
some of the corrugated cores I've seen have been ordinary cardboard
cut into strips and bent into alternating zigzags. the torsion boxes
I've built used strips of soft wood.
I'd make the top from 1/2" birch plywood, the bottom from 1/4". for a
short dimension of 4 feet I'd go no thinner than about 3" overall
thickness. more is better in torsion boxes....
you need a way to keep it all flat during assembly. that's the tricky
part
Bridger
On Tue, 10 Sep 2002 07:18:43 GMT, "-N." <n.w...@firingpinverizon.net>
wrote:
michel
there is a vinyl covering sold in almost any drafting or office supply store
designed just for drafting tables. then set the door with hinges on uprights
( set to your confortable height) and DO use drafting tape - not pins- not
masking tape. should do ya fine
rainbows over yer blues
michel
mc...@yahoo.com
-N.
This is for artwork usage, drawing, not really drafting.
I've used the vinyl covering and dislike it, the surface is not what I'm after.
I use tape but I also use pins on my drawing board at times. Sometimes I tack
my drawing paper, and sometimes I tack reference materials. Most door skins
are kinda coarse grained, they use Luan?
I'd really like to build my own. I'm after the BEST solution, not the most
expeditious.
If my skills permit, I may even machine my own custom hardware/wall mount that
is sleek and retracts fully out of the way and permits angle adjustment to the
drawing board.
I'm also going to have a look into making a foot or finger switch operated
hydraulic or pneumatic adjustment system for height and angle if it would prove
to be useful...but if I can achieve hi strength and ultra low weight with the
right board design (what about surfboard technology imported and hybridized???)
a manual adjustment system should nicely suffice
.I've been studying a bunch of electronics/pneumatics/engineering/metalworking
over the past year and a half, and I'm at a point where it's all coming
together and I can put it to some inspired real-world use.
But I want to figure out the torsion box options first.
Thanks a bunch.
Cheers,
Neal
michel wrote:
--
-N.
See my additional follow-up posts.
I want to make a drawing board that is wall-mounted.
Space here is limited: 'Operation Motherfucker' has entailed 6 months of
full-on design, tool and materiel procurement, and non-stop fabrication (debt
too). Looks like it's not quite done.
The drawing board will likely mount above my woodworking bench (which will be
completed shortly after 11 years of on/off work). I want total adjust ability
in height and angle, and want it to fold up, business side against the wall to
protect a loaded drawing in progress. May or may not use the workbench as a
base for it to rest on...I don't want to be stuck with being focrced to have
the bench there in case it decides to explore other parts of the apartment.
Workbench will be on castors as is everthing else here (it's on a temporary
mobile base, but I'll have to workout the details of a good mobile
system...btw, I'm in NYC: and in Brooklyn, like Star Trek, Space is the Final
Frontier). I'm thinking it might be a good idea to have reloadable drawing
board 'modules' many lightweight torsion boxes, super lightweight, which
quickly disengage from the main wall hardware....then I can make a couple
floor-to-ceiling slide out panels in my painting rack and store several drawing
board reloads with works-in-progress on these panels. I work on a million
things at once, everything cross pollinates everything else, and I'm looking
for a system of quick-change drawing boards. From my woodworking experience
(and a few weeks ago I heard Norm utter these same words of wisdom regarding
crosscut TS jigs)...if it's heavy and you need to lift it to use it, it's NOT
going to be used.
Inking at times is best done vertically. Depends on the medium and the
technique and personal preference. I want there to be nothing standing in my
way between my next drawing board and the products that roll off it.
A while back someone mentioned foamcore as a possible torsion box material, but
he didn't have direct experience with it. I may need to open this thread up to
engineers and to other craftsman: maybe as woodworkers we are thinking too much
in terms of wood at times for our own good. Wood is wonderful, but can be even
more wonderful when mated with other materials and technologies.
Ideas that I've not yet voiced or heard any feedback on:
Aluminum honeycomb core.
Foam variation and options
Surfboard technology
Other lamination technology that isn't torsion box construction per se.
Keep your eyes open and if you hear anything or see anything of interest,
report back.
Thanks a bunch for your input.
Cheers,
Neal
David DeCristoforo
can make a honeycomb frame using 1/2" X 1" strips of lightweight pine
lumber. Use "cross lap" joints at the intersections and miters at the
outside corneners. Make the "cells" no bigger than 2" X 2". Make the
frame any size you want. Then laminate a sheet of 1/8" poplar ply to
each side. Easy way: lay a sheet of 3/4" ply or MDF on the floor. Make
sure it's flat. If not, shim it until it is. Lay down one of the 1/8"
ply sheets. Apply wood glue to all of the edges of the honeycomb frame
and lay it on top of the 1/8" ply. Lay the second sheet of ply on top
(don't forget the glue). Lay another sheet of 3/4" ply or MDF on top
of that. Toss on a bunch of weight (sandbags work great). Net result
will be a very rigid and lightweight unit. The poplar ply makes a good
drawing surface with a bit of "give" and it will easily accept pins.
However, there is (to my knowledge) no wood that will "heal" like a
vinyl drawing board cover so you may have to "resurface" your top from
time to time.
DD
On Tue, 10 Sep 2002 07:18:43 GMT, "-N." <n.w...@firingpinverizon.net>
wrote:
>"Operation M-ther F-cker" is finally drawing to a close.
Charlie Spitzer
it's a sound insulation product, comes in 4x8' sheets, and you can't get it
at the borg, who look at you funny if you ask for it.
regards,
charlie
cave creek, az
"David DeCristoforo" <d...@afes.com> wrote in message
news:21psnu4u2163lngpv...@4ax.com...
Fred the Red Shirt
A hollow beam is called a box beam. For example, if I make a book
shelf and make the shelves out of hollow boxes instead of solid
wood, the shelves are box beams.
A box beam becomes a torsion box if it is loaded in, well, torsion.
That is if there is a significant twisting load (moment) around
the long axis of the box. If I anchor one end of the book shelf to
the side of the bookcase and anchor the back of the shelf to the
back of the book case but leave the other end of the shelf floating
then when I put books on the shelf it becoms a torsion box. (first
I'd have be become kinda peculiar to build the bookcase that way
but that is beside the point)
For reasons that are not well understood (at least by me) a closed
box beam resists torsion much better than an open section with the
same moment of inertia.
But if it isn't being loaded in torsion, it is just a plain old
box beam.
--
FF
David DeCristoforo
get a look at some. Have to check around and see if I can find some.
DD
Mike Hide
picture. This has to be the be all and end all molehill to mountain projects
ever.
If he wants a self healing thumbtack surface ,then instead of cogitating
about the design for the last ten years he should have been growing a very
short tree with a wide, flat trunk all set in a tub on wheels so he could
move it around.
but hey call me a cynic.....mjh
--
mike hide
http://members.tripod.com/mikehide2
"Fred the Red Shirt" <fredf...@iwon.com> wrote in message
news:7b50982e.02091...@posting.google.com...
Fred the Red Shirt
> I will go along with you Fred where the hell did torsion boxes come into the
> picture. This has to be the be all and end all molehill to mountain projects
> ever.
LOL.
In all seriousness I think that two or three years ago an article
appeared inone of the woodorking mags in which the author used box
beams for bookshelves and described them as torsion boxes. I glanced
through the article and it wasn't clear to me from the illustrations
just how the shelves were supported in the bookcase so I'm not
certain if they really were torsion boxes or box beams. I do recall
that they had a lot of (probably unnecessary) reinforcement inside
the box.
In a torsion beam internal reinforcements perpendicular to the axis
contribute almost nothing to the strength of stiffness of the box.
Additional members parallel to the axis help a little more but it
is the outer shell that carries the load.
>
> If he wants a self healing thumbtack surface ,then instead of cogitating
> about the design for the last ten years he should have been growing a very
> short tree with a wide, flat trunk all set in a tub on wheels so he could
> move it around.
>
There are any number of times that I have set off to design
something new starting from basic priciples of design and after
several otpimizations have arrived at a tried and true
design that has been in use since before I was born.
I've independently 'invented' the split-ring telescope mount
numerous times.
--
FF
Charles Self
> Whomosote? Never heard of it. Insulation you say? Hmmm, I'd like to
> get a look at some. Have to check around and see if I can find some.
> DD
Homasote is the name. Standard construction sheathing product, looks
like it is made of dried dog shit, but works very well, has a
reasonably smooth surface, R value probably about 1.5, give or take.
Don't know if they have a web site, but up until maybe 5 years ago,
the company was located in New Joisey. It might not make it out West.
Tied to some other large company, whose name is hiding behind a senior
moment right now, maybe Jim Walter?
David DeCristoforo
market that resemble dried dog shit. Problem: when you ask the clerk
at Home Depot where to find the stuff that looks like dried dog shit,
he's not going to know which end of the store to point to. Same
problem at MacDonalds.
DD
On 11 Sep 2002 11:48:59 -0700, charli...@woodcraft.com (Charles
Andrew Barss
: A bit of pedantry here.
: A hollow beam is called a box beam. For example, if I make a book
: shelf and make the shelves out of hollow boxes instead of solid
: wood, the shelves are box beams.
: A box beam becomes a torsion box if it is loaded in, well, torsion.
: That is if there is a significant twisting load (moment) around
: the long axis of the box.
That's not the understanding I have. All references I have seen to
torsion boxes describe/define one as a hollow (and very shallow, like
a thick shelf or a door) box with a large number of
cross pieces internal to it, glued to the skins that form the two major
faces of the box. The glueing of the inner ribs to the faces allows the
box to greatly resist torsional force; but I never heard that such a thing
had to actually *be* in torsion to be called that.
-- Andy Barss
Mike Hide
Imagin a cantelevered closed box beam with a load applied at its center of
gravity ,then thats a box beam .Any load not applied through the CG results
in a torsional moment on the beam,then it becomes a torsion box.
the internal structure ensures the skins do not collapse under load . the
skins are generally designed to take shear loads and can be quite thin
,resulting in a lightweight structure . Generally the skins are not designed
for high local bearing loads ,if they do, then their thickness must be
increased to take it. mjh
--
mike hide
http://members.tripod.com/mikehide2
"Andrew Barss" <ba...@bast.u.arizona.edu> wrote in message
news:alm36d$mme$1...@oasis.ccit.arizona.edu...
-N.
I have it mounted over an entire wall in my studio and it's been there 15 years. I got it on the first
materials run I did after moving into this space. I put it there to do drawing on because it takes push
pins very well. It's my painting wall as well.
I didn't realize it at the time, but it's sold as a sound deadening product. I works very well for that a
well. I couldn't imagine having an artist studio without the stuff.
Cheers,
Neal
David DeCristoforo wrote:
--
Larry Jaques
posted recycled pixels stating:
>Seems like there are more and more "new" building products on the
>market that resemble dried dog shit. Problem: when you ask the clerk
>at Home Depot where to find the stuff that looks like dried dog shit,
>he's not going to know which end of the store to point to. Same
>problem at MacDonalds.
Damn, I _knew_ I should have swallowed that gulp of coffee
before reading this reply...You owe me a keyboard, David. ;)
--
Remember: Every silver lining has a cloud.
----
http://diversify.com Comprehensive Website Development
Fred the Red Shirt
The inclusion of inner ribs in a box beam does almost nothing to
reinforce it against torsion, and very little to reinforce it against
normal forces or bending moments. Internal ribs do help to prevent
buckling.
It may have become commonplace among some folks to refer to all box
beams as torsion beams, just like a lot of folks call water heaters
'hot' water heaters but there is no reason to use the more complex
term for the simpler case.
--
FF
Nova
> Homosote has been a round for awhile.
<snip>
About 90 years. See:
--
Jack Novak
Buffalo, NY - USA
Mike Hide
A cantelevered box beam with closed ends loaded asymmetrically is a torsion
box. mjh
--
mike hide
http://members.tripod.com/mikehide2
Joe
"Mike Hide" wrote in message
> Aircraft wing structure consist of torsion boxes.
>
> A cantelevered box beam with closed ends loaded asymmetrically is a
torsion
> box. mjh
>
Twist a hollow box beam, and opposite sides will tend to flex inward -
especially the wider sides. Add internal cross pieces as described below,
and it's a torsion box. The torsional stiffness is greatly increased by the
internal supports. Without the internal supports, it might still be called
a 'box in torsion' but it wouldn't be 'torsion box construction'.
Joe Gilman