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# Thread: Strength of pipe versus formed C channel

1. Senior Member
Join Date
Sep 2006
Posts
316

## Strength of pipe versus formed C channel

I got my patent, 7,707,794. Now I'm trying to write up a press release and have a glitch. I know that channel is strong two ways while pipe is strong all ways. Somewhere there's a formula or chart that shows equal weight channel is so many times stronger than pipe channel's strong way.

Come on engineers, give this never-got-high-school-diploma dude a hand.

What I'm wanting to compare is 1 1/4 schedule forty pipe and 2 X 4 inch 14 gauge C channel or purlin.

2. Harv

Check this out first
http://en.wikipedia.org/wiki/Beam_(structure)

The portion of interest is the Structural Characteristics piece.

Modulus of Elasticity is a property of the material, and doesn't change with shape.
The Area Moment of Inertia (Second Moment of area) is what defines the properties of the shape. For standard steel shapes, it's usually listed in the steel handbook as I with units of in^4.

For some explanations of how it's calculated look at
http://en.wikipedia.org/wiki/Second_moment_of_area .
Ignore all the math in the middle and scroll down to the portion for various cross sections.

Looking in my tables - 1.660" OD, 0.14" wall Round tube (1 1/4 shed 40) has an I value of 0.184 in^4

Calculating for 14 gauge (0.078") 2x4 C channel I get
Ix = 1.59 in^4 where X is the hard way.
Iy=.416 In^4

It's been a while since I did the math and I'm a bit rusty, so I could have made some mistakes - might want someone to check it over to be sure, but I think I have it right. I don't have my steel handbook at work, or I would have just looked it up to be sure.

I have the math on my scratch pad. I can scan and e-mail if you want it.

3. Senior Member
Join Date
Sep 2006
Posts
316
Originally Posted by Big_Eddy
Harv

Check this out first
http://en.wikipedia.org/wiki/Beam_(structure)

The portion of interest is the Structural Characteristics piece.

Modulus of Elasticity is a property of the material, and doesn't change with shape.
The Area Moment of Inertia (Second Moment of area) is what defines the properties of the shape. For standard steel shapes, it's usually listed in the steel handbook as I with units of in^4.

For some explanations of how it's calculated look at
http://en.wikipedia.org/wiki/Second_moment_of_area .
Ignore all the math in the middle and scroll down to the portion for various cross sections.

Looking in my tables - 1.660" OD, 0.14" wall Round tube (1 1/4 shed 40) has an I value of 0.184 in^4

Calculating for 14 gauge (0.078") 2x4 C channel I get
Ix = 1.59 in^4 where X is the hard way.
Iy=.416 In^4

It's been a while since I did the math and I'm a bit rusty, so I could have made some mistakes - might want someone to check it over to be sure, but I think I have it right. I don't have my steel handbook at work, or I would have just looked it up to be sure.

I have the math on my scratch pad. I can scan and e-mail if you want it.
Thank you so very much. Here's another problem I'm a little like Temple Grandlin of autistic-isn't-bad-as-you-think fame. I can read something and if I can't convert it to a picture in my mind it's really difficult for me. So I can read wiki and still be just as confused and lost as I was before.

Dumb it down for me please. This is one of those things that I know but don't if that makes any sense.

I'm attaching a couple of photos to show what I'm doing.

4. Senior Member
Join Date
Sep 2006
Posts
316
Originally Posted by Big_Eddy
Harv

Check this out first
http://en.wikipedia.org/wiki/Beam_(structure)

The portion of interest is the Structural Characteristics piece.

Modulus of Elasticity is a property of the material, and doesn't change with shape.
The Area Moment of Inertia (Second Moment of area) is what defines the properties of the shape. For standard steel shapes, it's usually listed in the steel handbook as I with units of in^4.

For some explanations of how it's calculated look at
http://en.wikipedia.org/wiki/Second_moment_of_area .
Ignore all the math in the middle and scroll down to the portion for various cross sections.

Looking in my tables - 1.660" OD, 0.14" wall Round tube (1 1/4 shed 40) has an I value of 0.184 in^4

Calculating for 14 gauge (0.078") 2x4 C channel I get
Ix = 1.59 in^4 where X is the hard way.
Iy=.416 In^4

It's been a while since I did the math and I'm a bit rusty, so I could have made some mistakes - might want someone to check it over to be sure, but I think I have it right. I don't have my steel handbook at work, or I would have just looked it up to be sure.

I have the math on my scratch pad. I can scan and e-mail if you want it.
harvey@harveylacey.com and once again, thank you very very much

Others - there is an error in the numbers above. 0.416 should read 0.270. As I keep telling the kids - check your work!!!

6. Senior Member
Join Date
Sep 2006
Posts
316
Originally Posted by Big_Eddy

Others - there is an error in the numbers above. 0.416 should read 0.270. As I keep telling the kids - check your work!!!
You are the man Big Eddy!

He explained without using too many big words. I might not be able to do it but I understood what and how he did.

Thanks again. I had called the editor and told him to replace "many times" with "eight times". That sounds so much better.

What I have is a patent on structures like buildings and fences using my brackets and clips. I didn't know it five years ago when we started the patent process but my structure is the best one out there for the latest trend in security fencing. That is the use of expanded metal instead of chainlink or welded wire.

I'm attaching some photos of a sample I made for the press release.

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