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square tubing for pipe fence???

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  • square tubing for pipe fence???

    Hi guys,

    I want to do a pipe fence using square tubing. I wan to use 2 1/2" tubing for the line posts.

    My question:
    Would 11 gauge tubing be sufficient?
    If so, would using 2 1/2" --- 3/16" thickness work for the corner/end posts or should I go with something bigger?

    The fence is 6 feet tall with posts set 3 feet into ground using concrete. The posts will be set 8 foot apart with a top (into the side of the post not running along the top) and a bottom rail. I will put no-climb horse fence on it. It is to keep 2 very large livestock guardian dogs in and maybe horses later.

    Thanks for any help.
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  • #2
    Based on some numbers I found for modulus and moment of inertia it looks to me like the 11 ga is comparable to a 4x4 fir post and the 3/16 wall is stronger but not even close to a 6x6 fir post.

    The spreaders will add strength to the corners for holding the tension on the fence. You didn't say what the spreaders would be made of but without spreaders you would be pushing those corners pretty hard if there were 500 pounds of tension on each side. Maybe with the top and bottom rails you aren't planning on very much tension.

    That fence would probably be fine for horses, but not buffalo.

    The other concern would be rust or filling with water and freezing, at least up here in Minnesota.

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    • #3
      Originally posted by FernTJ View Post
      Based on some numbers I found for modulus and moment of inertia it looks to me like the 11 ga is comparable to a 4x4 fir post and the 3/16 wall is stronger but not even close to a 6x6 fir post.

      The spreaders will add strength to the corners for holding the tension on the fence. You didn't say what the spreaders would be made of but without spreaders you would be pushing those corners pretty hard if there were 500 pounds of tension on each side. Maybe with the top and bottom rails you aren't planning on very much tension.

      That fence would probably be fine for horses, but not buffalo.

      The other concern would be rust or filling with water and freezing, at least up here in Minnesota.
      Thanks
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      • #4
        Sounds fine to me.

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        • #5
          The 11 gauge 2 1/2 tubing will work for what you're going to do I believe but on the stretch/corner posts I would up size the post to 4 inch tubing. The 2 1/2 3/16 will probably work but past experience makes me suggest 4 inch. Plus it looks slicker.

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          • #6
            Originally posted by fencemaker View Post
            The 11 gauge 2 1/2 tubing will work for what you're going to do I believe but on the stretch/corner posts I would up size the post to 4 inch tubing. The 2 1/2 3/16 will probably work but past experience makes me suggest 4 inch. Plus it looks slicker.
            Thanks for the thoughts
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            • #7
              Force Required to Bend the Tube

              Originally posted by aneuploidy View Post
              Hi guys,

              I want to do a pipe fence using square tubing. I wan to use 2 1/2" tubing for the line posts.

              My question:
              Would 11 gauge tubing be sufficient?
              If so, would using 2 1/2" --- 3/16" thickness work for the corner/end posts or should I go with something bigger?

              The fence is 6 feet tall with posts set 3 feet into ground using concrete. The posts will be set 8 foot apart with a top (into the side of the post not running along the top) and a bottom rail. I will put no-climb horse fence on it. It is to keep 2 very large livestock guardian dogs in and maybe horses later.

              Thanks for any help.
              The worst case in bending is where you have a single 6' high pole embedded in the ground and you applied a horizontal force at the top to bend it. The force required for a 2 1/2" 11 g square tube to yield in bending is 435 lbs. For 2 1/2" 3/16" tube the force is 628 lbs. And for a 4" 3/16 tube the force is 1750 lbs.

              Comment


              • #8
                I would say you are fine. What ever you decide on I would span upon material length. So if you are buying 20' lengths go on 10' centers to minimize waste. If you feel the span is to great , add 1/4'' x 2 ''or 3'' flat stock vertical in between. My pig pens are 2'' square tube uprights, 1 1/4'' pipe horizontal, 12' span and 1/4''x 2''flat stock vertical in center of span. Never had a problem with 800 pound boar and 500 pound sows. With material costs I always try to design for minimum waste.

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                • #9
                  Originally posted by BD1 View Post
                  I would say you are fine. What ever you decide on I would span upon material length. So if you are buying 20' lengths go on 10' centers to minimize waste. If you feel the span is to great , add 1/4'' x 2 ''or 3'' flat stock vertical in between. My pig pens are 2'' square tube uprights, 1 1/4'' pipe horizontal, 12' span and 1/4''x 2''flat stock vertical in center of span. Never had a problem with 800 pound boar and 500 pound sows. With material costs I always try to design for minimum waste.
                  Thanks. By vertical, do you mean running the 1/4" x 3" from top to bottom rail?
                  Thanks again for the advice
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                  • #10
                    Originally posted by Arizona Joe View Post
                    The worst case in bending is where you have a single 6' high pole embedded in the ground and you applied a horizontal force at the top to bend it. The force required for a 2 1/2" 11 g square tube to yield in bending is 435 lbs. For 2 1/2" 3/16" tube the force is 628 lbs. And for a 4" 3/16 tube the force is 1750 lbs.
                    Thanks. So it looks like you get much stronger by going up in diameter. Is there a chart that has those figures or did you have to calculate them. I ended up buying 3" 11 gauge for the line posts and 3" 3/16 for the end/ corner posts.
                    Thanks again
                    Ford F350
                    John Deere 510D Backhoe
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                    JD-Tech 5500 Diesel Generator
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                    • #11
                      Calculations

                      Originally posted by aneuploidy View Post
                      Thanks. So it looks like you get much stronger by going up in diameter. Is there a chart that has those figures or did you have to calculate them. I ended up buying 3" 11 gauge for the line posts and 3" 3/16 for the end/ corner posts.
                      Thanks again
                      I calculated them by hand, but here is a web site that will calculate the properties of any square tube for you.

                      http://www.engineersedge.com/calcula...are_case_4.htm

                      One easy way to compare different sizes is to compare their Section Moduli. The bigger the section modulus the stronger the member. If the section modulus of one member is twice that of another member, then that member is twice as strong as the other.

                      Your new 3" 11 gauge tubes are 47% stronger than the 2 1/2" 11 gauge tubes. The calculation of the 3" x 3/16" is left as an exercise for the reader .

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                      • #12
                        Originally posted by aneuploidy View Post
                        Thanks. By vertical, do you mean running the 1/4" x 3" from top to bottom rail?
                        Thanks again for the advice
                        Yes, top to bottom. You could also run diagonally too. depends how much you want to invest in material.

                        Comment


                        • #13
                          Originally posted by Arizona Joe View Post
                          I calculated them by hand, but here is a web site that will calculate the properties of any square tube for you.

                          http://www.engineersedge.com/calcula...are_case_4.htm

                          One easy way to compare different sizes is to compare their Section Moduli. The bigger the section modulus the stronger the member. If the section modulus of one member is twice that of another member, then that member is twice as strong as the other.

                          Your new 3" 11 gauge tubes are 47% stronger than the 2 1/2" 11 gauge tubes. The calculation of the 3" x 3/16" is left as an exercise for the reader .
                          Thanks!!!
                          Ford F350
                          John Deere 510D Backhoe
                          Titan Industrial Gas Air Compressor
                          JD-Tech 5500 Diesel Generator
                          Millermatic 211
                          Hypertherm Powermax 45

                          Comment

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