torsion boxes, why no triangles?

[TheUnicorn]

...conventional MFT construction with lightening slots...

sorry, what's a lightening slot?

 

[Jameshow]

sorry, what's a lightening slot?

Hole in a web which lightens the structure yet retains strength. Seem on aircraft, cars, beams, bridges etc...

 

[Sachakins]

Using triangles within a torsion box will not be any stronger or weaker than normal square box torsion boxes.
Triangles are used to give greater strength and stability in compression mode, as in bridge spans, or as in lightweight plywood beam laminations. In these Instances the triangle structure is many times stronger for much less weight.

 

[sometimewoodworker]

n.b. any box is a "torsion" box - it's a redundant term with no special meaning, but popular with woodworkers!
What you are talking about is a box with stiffening internal braces.

that is an interesting point of view, completely false, but interesting.

There are many examples of torsion box structures, the main examples are in woodworking, airplanes and shipping, so the maritime and aerospace engineers all disagree with you. Example (EP3037343A1 - Aircraft wing torsion box, aircraft wing, aircraft and support member for use therein - Google Patents)

As you know the principle is that there are 2 thin skins supported/separated by a web structure. Take away any of the those parts and you have a structure that is weak, with all 3 the structures are strong and rigid. The web (usually square or rectangular can be really thin and, by itself, weak as can the surfaces, but fastened together are strong.

That, that is not the way you, or most hobbyists, build doesn’t make the term in anyway redundant. It is likely that you (as do I) usually over engineer your structures to the extent the internal structures add little to the pieces, but that has nothing to do with meaning of the term

 

[Jacob]

that is an interesting point of view, completely false, but interesting.

There are many examples of torsion box structures, the main examples are in woodworking, airplanes and shipping, so the maritime and aerospace engineers all disagree with you. Example (EP3037343A1 - Aircraft wing torsion box, aircraft wing, aircraft and support member for use therein - Google Patents)

Yes there are many examples but the use of the term"torsion box"is relatively recent and seems to have been coined by JE Gordon "Structures or Why Things Don't Fall down" - describing the struts and spars of biplane wings which resist torsion (twisting) i.e. the struts and spars tie the two wings into a "box".
But the practice of stiffened hollow structures or even single skins is a lot older and generally does not involve torsion at all.
The term seems to have been picked up mainly by amateur woodworkers and is probably now with us for good, but in most manifestations of a "torsion box" no torsion is involved at all. They are just box structures, with or without extra stiffening.

 

[Adam W.]

It sounds snappier on youtube than saying a "timber sandwich construction with a waffle core", innit.

 

[Jacob]

It sounds snappier on youtube than saying a "timber sandwich construction with a waffle core", innit.

Well yes. And snappier than just "stiffened box" or "reinforced box" - the main point of which being stiffness/strength, lighter weight, less materials etc, not the solving of a particular "torsion" problem.

 

[sometimewoodworker]

Yes there are many examples but the use of the term"torsion box"is relatively recent and seems to have been coined by JE Gordon "Structures or Why Things Don't Fall down" - describing the struts and spars of biplane wings which resist torsion (twisting) i.e. the struts and spars tie the two wings into a "box".
But the practice of stiffened hollow structures or even single skins is a lot older and generally does not involve torsion at all.
The term seems to have been picked up mainly by amateur woodworkers and is probably now with us for good, but in most manifestations of a "torsion box" no torsion is involved at all. They are just box structures, with or without extra stiffening.

I would say that the more correct way to describe torsion boxes is that for some users/designs there is no torsion involve. However for the majority of uses (IKEA, and others, doors made from paper and 3mm plywood are an example) they are torsion boxes with the torsion being resisted on occasions.
There is no need for a torsion box to have any torsion involved for the majority of the time.

however what are a torsion boxes but box structures with extra stiffening?

a horse has always been a horse even when the name horse was not given to it.

Likewise torsion boxes have always been torsion boxes what ever name was used.

 

[Garden Shed Projects]

The torsion boxes that feature on youtube do employ triangulation of sorts. Using long strips if plywood on edge, even with holes cut out at intervals, have inbuilt triangulation. If you then run ply strips at 90 degrees this will stop the longer strips from distorting so allowing the loads to travel in line down the longer strips. Much like herringbone noggins between floor joists, putting them in takes out a lot of the bounce.

 

[Jacob]

I would say that the more correct way to describe torsion boxes is that for some users/designs there is no torsion involve. However for the majority of uses (IKEA, and others, doors made from paper and 3mm plywood are an example) they are torsion boxes with the torsion being resisted on occasions.

Same applies to any door however constructed. They have to resist the same torsional forces. A frame, ledge, batten door is a torsion resisting construction

There is no need for a torsion box to have any torsion involved for the majority of the time.

however what are a torsion boxes but box structures with extra stiffening?

A box is still a torsion resisting structure even without the extra stiffening

..... torsion boxes have always been torsion boxes what ever name was used.

it's a new term but it doesn't really describe what it's usually about i.e. construction of stiff but lightweight panels.
In the case of aircraft wings, ships, a few other things, torsional stresses are critically important, but not for most other uses of light weight panels.
OK I'm being pedantic, but nearly every time someone starts getting excited about torsion boxes, "torsion" has nothing to do with it!

 

[sometimewoodworker]

Same applies to any door however constructed. They have to resist the same torsional forces. A frame, ledge, batten door is a torsion resisting construction

Of course it is and of course your traditional door does the same job as 2 3mm plywood panels joined with cardboard. However the material used in the trad door are many times heavier and more expensive than the torsion box door (hollow core)

A box is still a torsion resisting structure even without the extra stiffening

again of course it is but add the correct stiffening and it is many time’s stronger.

OK I'm being pedantic, but nearly every time someone starts getting excited about torsion boxes, "torsion" has nothing to do with it!

Or it could be that you have a different understanding than the others using the term.

 

[Jacob]

......


Or it could be that you have a different understanding than the others using the term.

Or I'm old enough to remember when box structures hadn't yet begun to be called "torsion boxes" for no particular reason. About year 2000?
"Stress-skin" and "monocoque" construction are the same idea but the terminology is much older.

 

[yetloh]

How many of us really care? Certainly not me, it is just a convenient term understood by woodworkers and in no way devalued by that fact.

Jim

 

[Orraloon]

The discussion so far has been bracing. Well at least its not about sharpening.

 

[Jacob]

How many of us really care? Certainly not me, it is just a convenient term understood by woodworkers and in no way devalued by that fact.

Jim

But if you leave out the "torsion" then term "box construction" serves just as well.
It's just interesting that the term "torsion box" arrived as if from nowhere a few years back, but doesn't mean what JE Gordon meant when he first coined the expression, in 2003 apparently, and has nothing to do with torsion.

 

[Adam W.]

It probably arrived with MFT.

 

[MikeJhn]

And then you have the geodesic structure like the Hanley Page Halifax or even the Lancaster that where all torsion box construction.

 

[Jacob]

And then you have the geodesic structure like the Hanley Page Halifax or even the Lancaster that where all torsion box construction.

But not known under that vague collective name until 2003 it seems, and "torsion box" is not a form of construction.
Halifax and Lancaster were "stressed skin" constructions and "geodesic" was Buckminster Fuller's own coinage for his dome constructions.

 

[yetloh]

Oh dear. Does it really matter? Now, if it was about broccoli, 90% of what is sold in supermarkets as such is not broccoli at all, but tasteless calabrese, I could understand it!

Jim

 

[Jacob]

Oh dear. Does it really matter? Now, if it was about broccoli, 90% of what is sold in supermarkets as such is not broccoli at all, but tasteless calabrese, I could understand it!

Jim

No it doesn't matter, don't worry about it!