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## #76 2013-11-22 08:30:10

Yusuke00
Member
Registered: 2013-11-19
Posts: 43

### Re: Measure length without bend ?

Why don't you make it a function and then find it by integring?

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## #77 2013-11-22 12:32:08

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Measure length without bend ?

The problem is we can know everything about the bending process but with real pipes straightening is not the inverse of bending. The pipe obviously had to stretch on one side and compress on the other. By how much? We need to know a lot more about the strength of the material, temperature etc.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #78 2013-11-22 12:38:17

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

### Re: Measure length without bend ?

Well, you cannot look at either the inner or the outer line for the length, but, maybe you can look at one in between.

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #79 2013-11-22 12:40:29

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Measure length without bend ?

I thought my post up there sort of showed that the whole question is kind of without an answer.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #80 2013-11-22 12:43:27

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

### Re: Measure length without bend ?

I know, but we can approximate. If we simplify the model, we will get the answer.

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #81 2013-11-22 13:07:43

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,850
Website

### Re: Measure length without bend ?

Hi;

It is foolish to fit a curve over that pipe and do something like that because the image is just a product of google search and is not the actual one. Moreover, it may not be to scale.

Hi Lynx;

Last edited by Agnishom (2013-11-22 13:23:34)

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #82 2013-11-22 13:10:39

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Measure length without bend ?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #83 2013-11-22 13:13:52

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,850
Website

### Re: Measure length without bend ?

Could you please fix my latex? Please make point 8 and point 0 a little more big

He got the image from a search. It is not likely that every pipe is the same. Even for a little visual difference, you'll get different results

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #84 2013-11-22 13:19:36

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Measure length without bend ?

So far I am only seeing "Submit Query", it needs more work.

I asked him if the picture represented the pipe. He said yes, I also told him it would be an approximation. Then I asked him how accurate he wanted the results. He supplied all of that. The question was answered based on that and is reasonably accurate.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #85 2013-11-22 13:28:35

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,850
Website

### Re: Measure length without bend ?

Could you please shed light on how to fix the latex?

I asked him if the picture represented the pipe. He said yes,

Hmm, my literature teacher thinks that the journey of a river represents the journey of life. Many people think that the country represents a motherlike figure.

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #86 2013-11-22 13:31:13

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Measure length without bend ?

The great Hastings used precisely that method on airplane wings and he was the best there was. If it works for planes...
Here the problem it is not a static shape.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #87 2013-11-22 13:33:52

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

### Re: Measure length without bend ?

Last edited by anonimnystefy (2013-11-22 13:34:05)

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #88 2013-11-22 13:34:57

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,850
Website

### Re: Measure length without bend ?

Why doesn't the OP reply to all the questions that are being thrown to him?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #89 2013-11-22 13:37:27

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Measure length without bend ?

That I can not say. But it will be difficult to ask him if he will not reply.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #90 2013-11-22 13:38:32

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,037

### Re: Measure length without bend ?

Hi Agnishom

You are having LaTeX problems because of '}. See my previous post.

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #91 2013-11-22 13:46:45

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Measure length without bend ?

Latex fixed, remember MIF latex is a subset of Latex.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #92 2013-11-22 20:40:53

phrontister
Real Member
From: The Land of Tomorrow
Registered: 2009-07-12
Posts: 4,594

### Re: Measure length without bend ?

I deleted my post that contained the link to http://www.wisc-online.com/Objects/ViewObject.aspx?ID=FAB1902, as it contained a lot of stuff that didn't help to solve SuperLynx's problem (sorry if anyone spent time following it through).

Any solution will be imprecise because of the physical measuring required, but the following method may give an answer that is close enough.

The length of the pipe is the length of its centreline, which in the case of a pipe that has one bend comprises three components: the two straight
bits, which are easy and boring to work out, and the curved bit, which is much more interesting and exciting to find.

That centreline arc length can be calculated like this:
r = the radius of the circle that fits in the inner curve of the bend.
d = the pipe's outer diameter.
CLR = r + d/2 (the distance from the circle's centre to the pipe's centreline arc is known in the pipe-bending industry as the 'centreline radius', or 'CLR')
a = the bend angle (ie, the number of degrees by which the two straight sections deviate from each other).
The idea now is to:
- use the CLR to work out the circumference of the full circle that uses the centreline arc;
- then divide that by 360 to obtain the length per degree;
- and then multiply the result by the number of degrees ('a') in the bend angle to find the total length of the centreline arc.

Add the result to the lengths of the two straight sections (s1 and s2) either side of the bend, and we're done.

So, putting all that together into a formula:

Last edited by phrontister (2013-11-23 02:11:54)

"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

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## #93 2013-11-22 23:15:46

phrontister
Real Member
From: The Land of Tomorrow
Registered: 2009-07-12
Posts: 4,594

### Re: Measure length without bend ?

Here's an image to help explain the formula in my previous post.

"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

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## #94 2013-11-23 00:33:29

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,850
Website

### Re: Measure length without bend ?

Wunderbar!

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #95 2013-11-23 02:40:51

bob bundy
Registered: 2010-06-20
Posts: 8,323

### Re: Measure length without bend ?

phrontister,

Wow! that's a beautiful diagram.  Haven't seen one of that quality since doing A level technical drawing.

So we have a mathematical answer; the practical blacksmith solution and now my wife has offered her solution:

Mrs B wrote:

Get a tape measure and measure it.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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## #96 2013-11-23 03:09:27

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,850
Website

### Re: Measure length without bend ?

Mrs B is a genius.

Wunderbar!

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #97 2013-11-23 13:18:29

phrontister
Real Member
From: The Land of Tomorrow
Registered: 2009-07-12
Posts: 4,594

### Re: Measure length without bend ?

Hi Bob,

For my technical drawing program I used M\$Word. I'd still be drawing it if I tried it in CAD...in which my skills are zero.

bob bundy wrote:
Mrs B wrote:

Get a tape measure and measure it.

Bob

That's the best idea yet!

So, measure the whole length of pipe - following the curves - along the line of the inner face of the bend and then along the line of the outer face of the bend, add the two measurements together and divide by two to get the centreline length...which, assuming no compression or stretching occurred along the centreline during the bending process, should be the original pipe length.

The tape must remain in contact with the pipe for the entire length of both measurements, of course.

Last edited by phrontister (2013-11-26 10:32:40)

"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

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## #98 2013-11-23 13:54:49

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,850
Website

### Re: Measure length without bend ?

Is the problem not a very hypothetical one?

The pipe is bent and will be forever, and for me, atleast, it is very hard to imagine it without a bent

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #99 2013-11-24 21:46:22

phrontister
Real Member
From: The Land of Tomorrow
Registered: 2009-07-12
Posts: 4,594

### Re: Measure length without bend ?

Another method that should give a pretty close approximation of the original pipe length would be to use a digital length-measuring pen (or some such) and run it along the length of pipe on the centreline.

This can be made to work well by using a suitable jig.

I still like my fluid-measuring idea, though (see post #73)......which I've left open as a puzzle to try.

Last edited by phrontister (2013-11-25 19:26:01)

"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

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## #100 2013-11-28 15:11:24

SuperLynx
Member
Registered: 2009-06-28
Posts: 335

### Re: Measure length without bend ?

I hope this helps !

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