torsion boxes, why no triangles?

[JimTaylor]

Torsion is a twisting force. A single sheet of ply can twist, so any frame will add torsional stiffness to the sheet. The more braces add to the stiffness. The different directions of the braces resist twisting in the direction of the brace.
In a bench top (MFT) the braces stop the top sagging to ensure that the top is flat. Why the term MFT, all benches are surely multifunctional. Is my workshop a MFWS?
Wood you pay as much for a sheet of ply or mdf with some holes in it, but call it a MFT, well much more valuable.

 

[MikeK]

Why the term MFT, all benches are surely multifunctional.

The term “MFT” is the short name for Festool’s Multifunktiontisch. The term has become accepted to describe any table that serves more than one purpose, such as cutting, layout, and assembly.

 

[Adam W.]

What, like a workbench ?

 

[Jacob]

Torsion is a twisting force. A single sheet of ply can twist, so any frame will add torsional stiffness to the sheet. The more braces add to the stiffness. The different directions of the braces resist twisting in the direction of the brace.

Yep. So, in the sense that it is used, every box is "torsion box" . In fact every structure is a "torsion" structure, except possibly those designed to allow torsion, if they exist. It's a redundant term, coined in 2003 by JE Gordon, but misunderstood. .

In a bench top (MFT) the braces stop the top sagging to ensure that the top is flat. Why the term MFT, all benches are surely multifunctional. Is my workshop a MFWS?
Wood you pay as much for a sheet of ply or mdf with some holes in it, but call it a MFT, well much more valuable.

MFTs are actually Limited Function Tables, to be realistic. Designed as a track saw accessory as I understand it. Nothing against them BTW, some people find them useful!

 

[JimTaylor]

Bracing counteracts other forces than just torsion, I suppose torsion box sound better than stability box or bracing box.
There are far to many acronyms today, the meaning is usually only known by the person using it.

 

[mudman]

Yep. So, in the sense that it is used, every box is "torsion box" . In fact every structure is a "torsion" structure, except possibly those designed to allow torsion, if they exist. It's a redundant term, coined in 2003 by JE Gordon, but misunderstood. .

MFTs are actually Limited Function Tables, to be realistic. Designed as a track saw accessory as I understand it. Nothing against them BTW, some people find them useful!

Why do you seem to care so much that you have to argue the toss on and on ad infinitum without adding anything of any pertinence to a thread?

I think nearly everyone would understand "box construction" to mean a many-sided shape that encloses an inner space and most everyone will also understand a "torsion box" to be such a shape that has had internal members added to stiffen the structure to provide better resistance to torsion forces, this may be a variety of strictures such as a door, an aircraft wing, a supertanker etc.

Torsion Box is not a redundant term, most everyone, apart from you, would understand what the term means and how it differs to a "box".

And by the way, there are many references to torsion boxes many can be found from patent searches, how about this one: US patent for ski construction of the torsion box type. from 1977?
Or a Bone Implant from 1995?
How about one for a Mine Roof Support from 1991?
Or a Tank Car (it's not that exciting) from 1973?
And the earliest reference for a Dipper Handle End from way back in 1926?

The term has been around for a long time

 

[Jacob]

Why do you seem to care so much that you have to argue the toss on and on ad infinitum without adding anything of any pertinence to a thread?

I don't care that much, just interested in the way the term is used and misused.

...

The term has been around for a long time

Interesting. Only applied to a very few designs where torsion is a particular issue? "Torsion box" not really a common term at all until picked up by the woodwork fraternity fairly recently, even though the principles are widely used in many structures, including things which are not even boxes.

 

[JimTaylor]

I don't care about the term, it is just an interesting thread on why things get their name.

 

[mudman]

I don't care about the term, it is just an interesting thread on why things get their name.

Hi Jim, my reply was to Jacob not yourself.

 

[sometimewoodworker]

Not really a common term at all until picked up by the woodwork fraternity fairly recently

However the references above rather contradict your oft stated claim that

term"torsion box"is relatively recent and seems to have been coined by JE Gordon "Structures or Why Things Don't Fall down" -

it has probably been used more in recent years and despite your idea that, the majority of users are not correct in their statements that they are using or making torsion boxes, you are incorrect.

It is certainly likely that some people don’t understand the principles and misuse the term, however it is hardly rocket science. That some people are using the structure in a way that it doesn’t benefit them is certainly likely. That your opinion that the majority don’t understand is an example of hubris on a rather impressive scale.

 

[Jacob]

However the references above rather contradict your oft stated

Actually they don't - at least what I have read so far. Quick flip, references to torsion but no "torsion box" as such. "Torsion box" doesn't appear in older dictionaries either.
PS the ski patent uses the term but without making it clear what it means. I wonder if the design ever got used?

claim that

it has probably been used more in recent years and despite your idea that, the majority of users are not correct in their statements that they are using or making torsion boxes, you are incorrect.

It is certainly likely that some people don’t understand the principles and misuse the term, however it is hardly rocket science. That some people are using the structure in a way that it doesn’t benefit them is certainly likely. That your opinion that the majority don’t understand is an example hubris on a rather impressive scale.

What is the principle of the "torsion box" exactly? Does adding more stiffening to a box make it a "torsion box". Is that it?
And why would it be called a "torsion" box in particular? What has torsion got to do with it?
What is the difference between a torsion box, a non torsion box, a stressed skin or a monocoque construction?
How much and what form of stiffening do you have to add to a structural box to turn it into a "torsion" box.
Is a sheet of ply a "torsion" sheet, in that it is stiffened by adding veneers?
etc etc

 

[sometimewoodworker]

What is the principle of the "torsion box" exactly?

A torsion box consists of two thin layers of material (skins) on either side of a lightweight core, usually a grid of beams. It is designed to resist torsion under an applied load

see Sandwich theory

Does adding more stiffening to a box make it a "torsion box".

It very much depends on the reason for the stiffing and the intended use. So, maybe yes maybe no.

And why would it be called a "torsion" box in particular? What has torsion got to do with it?

See the definition above.

What is the difference between a torsion box, a non torsion box,

The design and intended use.

In general a torsion box is rather larger, often many times larger than a box.

stressed skin or a monocoque construction?

For that you probably need structural engineering, though likely they are sub (or super) sets of similar structures.

How much and what form of stiffening do you have to add to a structural box to turn it into a "torsion" box.

Enough!

Is a sheet of ply a "torsion" sheet, in that it is stiffened by adding veneers?

So what is a "torsion" sheet? Other than an invention of yours to try to develop a new term?
I don’t have an advanced degree in solid mechanics, so since it seems that you are claiming that level of knowledge do please enlighten me.

 

[Jacob]

see Sandwich theory

Read through your link to Sandwich theory. Very interesting!
No mention of torsion or torsion box.
Nothing much to add really. I rest my case!
PS read through your article on torsion. No mention of "torsion box".

 

[sometimewoodworker]

Read through your link to Sandwich theory. Very interesting!
No mention of torsion or torsion box.

Why should it?

PS read through your article on torsion. No mention of "torsion box".

Why should it?
this a small example that only someone like by brother would actually enjoy

is that a description of a torsion box? I don’t have the background to understand it.


FWIW you are following the link’s down not up.

 

[Jacob]

Why should it?

Because you quote it as though it contains a definition of "torsion box" but it does not.

Why should it?

because you quote it apropos the topic of "torsion boxes": but it makes no mention of them

this a small example that only someone like by brother would actually enjoy
..........
is that a description of a torsion box? I don’t have the background to understand it.

If it was it would say so. Could be a description of a banana for all I know.

 

[Sachakins]

Well then, what you think about " Belt and Braces"

 

[Jacob]

Well then, what you think about " Belt and Braces"

Just "box construction" covers all bases.

 

[mudman]

Just "box construction" covers all bases.

Definitions of what a torsion box can be found in many places. Usually as a description of the particular context that they are used. It seems that this type of construction came out of the observation that the wings of planes in the First World War were falling off due to twisting stresses that came about under certain maneuvers. Mr Fokker determined what was causing them and modified the construction to build the wings in such a way as to prevent this, thus the torsion box came into being. The timing of this could also explain why the earliest US patent that mentions the torsion box was 1926 as a name for it hadn't been given to it much before this.
"Box construction" may cover all bases, but it is so generic that it is useless unless you are describing a place to store your toys. It covers boxes which can be a very wide spectrum of "things". A supertanker is essentially a box, a wing is essentially a box but no one says that they are exporting their oil in a box or mention that an airplane has lift generated due to the way the air passes over its boxes. Here, we are talking about a specific type of box construction. If the OP had asked "boxes, why no triangles?" No one would have known what on earth he was talking about.
Everyone knows what a torsion box is in the context of this thread and you are just being obtuse and argumentative as usual. I really do wish you would give it a rest, but I have no doubt you will feel compelled to have the last word.

 

[Jacob]

Definitions of what a torsion box can be found in many places. Usually as a description of the particular context that they are used. It seems that this type of construction came out of the observation that the wings of planes in the First World War were falling off due to twisting stresses that came about under certain maneuvers. Mr Fokker determined what was causing them and modified the construction to build the wings in such a way as to prevent this, thus the torsion box came into being. The timing of this could also explain why the earliest US patent that mentions the torsion box was 1926 as a name for it hadn't been given to it much before this.
"Box construction" may cover all bases, but it is so generic that it is useless unless you are describing a place to store your toys. It covers boxes which can be a very wide spectrum of "things". A supertanker is essentially a box, a wing is essentially a box but no one says that they are exporting their oil in a box or mention that an airplane has lift generated due to the way the air passes over its boxes. Here, we are talking about a specific type of box construction. If the OP had asked "boxes, why no triangles?" No one would have known what on earth he was talking about.
Everyone knows what a torsion box is in the context of this thread and you are just being obtuse and argumentative as usual. I really do wish you would give it a rest, but I have no doubt you will feel compelled to have the last word.

The "torsion box" in that 1926 patent, for a very heavy digging machine with a torsion problem, has no resemblance to the so called "torsion box" designs favoured by woodworkers, which have nothing to do with torsion in any sense.
They are just boxes, or box beams, with or without extra stiffening, perhaps sandwich constructions etc. etc.
True that aircraft wing makers and others had to design for torsion, but not wooden shelf or worktop builders - unless they are cantilevered out in unusually windy situations in very draughty workshops etc .

PS Just noticed JE Gordon's book was published 1978. The popular notion of a torsion box probably took root after that. He only uses the expression once (p268) in inverted commas, though he talks at length about torsion in general. Very interesting book.

 

[mudman]

The "torsion box" in that 1926 patent, for a very heavy digging machine with a torsion problem, has no resemblance to the so called "torsion box" designs favoured by woodworkers, which have nothing to do with torsion in any sense.
They are just boxes, or box beams, with or without extra stiffening, perhaps sandwich constructions etc. etc.
True that aircraft wing makers and others had to design for torsion, but not wooden shelf or worktop builders - unless they are cantilevered out in unusually windy situations in very draughty workshops etc .


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PS Just noticed JE Gordon's book was published 1978. The popular notion of a torsion box probably took root after that. He only uses the expression once (p268) in inverted commas, though he talks at length about torsion in general. Very interesting book.

I don't know if you've noticed, but a torsion box is an enclosed structure with lateral and longitudinal bracing. With the flat, door and bench version most here are familiar with, you can think of it as a series of I-beams fixed together to give a rigid structure that will resist longitudinal, lateral and importantly here, torsional forces. Sounds rather like "internal flanges longitudinally disposed".
And if you think very carefully, you may be able to work out how the lightweight construction of a torsion box that is capable of resisting stresses may well be useful as shelves or worktops. But then, I sorry of suspect you'll put your energies into another spurious rebuttal with the added laughing emoji.