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Thread: Determining the correct tubing to use in an old design that specifies Dural AU4G

  1. #1
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    Determining the correct tubing to use in an old design that specifies Dural AU4G

    Hello! I am working with the following design:

    It uses railing fittings and tubing in the following dimensions:

    5 m tube 35 x 31 mm (chassis, frame, front fork) 1.38in
    0,60 m tube 35 x 25 mm (central frame tube)
    0,50 m tube 30 x 26 mm (used for reinforcements)

    Dural is an obsolete trade name described as an aluminum and copper alloy used in aerospace because of its high resistance to stress and its lower density than steel .As a result of various evolutions of the designations and standards, it was then called AU4G (Standard NF A 02-104), and from now on 2017 (Standard NF A02-004 / EN 573-1)

    From this I gather that 2017 Alu/alloy tubing of the above dimensions should be exactly equivalent to the original but when I search for 2017 tubing it seems like it basically does not exist. I can only find 2017 in rods and wire.

    I looked at 6061 T6 seamless tubing and can only source 1.375 X 0.058 locally which is thinner than the 35 x 31 mm called out in the old plans but I don't know if this is even a valid comparison.

    All I really need to know is what tubing material can I find that is between 1.31in and 1.38in that has similar mechanical properties to "Dural" in the above sizes? I hope for the corrosion resistance of 6061 T6.

    I would certainly consider using 1.375″ OD x 0.049″ WALL x 1.277″ ID Seamless Stainless Steel 316 Round Tube and


    1.375″ OD x 0.065″ WALL x 1.245″ ID Seamless Stainless Steel 316 Round Tube as I can source it locally.

    As you can tell I know nothing about the subject. I can WORK with metals and I do nice work but this old standard has got me stumped.

    A little help?

  2. #2
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    6061-T6-Aluminum seems to indicate that I should be using slightly thicker tubing if I am using 6061 T6. Unfortunately My only local source is too thin.

  3. #3
    Administrator Kelly Bramble's Avatar
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    You are assuming that the original design was optimized or structurally just right. Either do an analysis - if possible or seek out and compare similar designs structural materials to determine if this product seems adequate.

    It may turn out that less is adequate.
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

  4. #4
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    I am assuming only that the original designer builder is not lying when he says he has put 800KM on his trike without having to do any repairs or adjustments. My intended use will subject the cart to far less stress than when used as a kite buggy. The original design is perfect for my purposes I just want to understand the standard.

    All I really need to know is what tubing material can I find that is between 1.31in and 1.38in that has similar mechanical properties to "Dural" in the above sizes? I hope for the corrosion resistance of 6061 T6.

    I would certainly consider using 1.375″ OD x 0.049″ WALL x 1.277″ ID Seamless Stainless Steel 316 Round Tube and


    1.375″ OD x 0.065″ WALL x 1.245″ ID Seamless Stainless Steel 316 Round Tube as I can source it locally

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    Actually to be accurate the materials are almost perfectly matched to the design in that the builder lengthened the back axle 20% and it bent causing camber. With the original length it did not bend even after 800KM of bumpy buggy riding. This indicates it it JUST strong enough for the application at that length and so is roughly at optimum weight (for this material) as well.

    It may not be engineering but it is logical.
    Last edited by garyboyco; 11-20-2017 at 08:58 PM.

  6. #6
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    Quote Originally Posted by garyboyco View Post
    6061-T6-Aluminum seems to indicate that I should be using slightly thicker tubing if I am using 6061 T6. Unfortunately My only local source is too thin.
    This post had a link to a comparative materials website. I guess no url's are allowed.......

  7. #7
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    I only posted here because I saw where other non engineers had posted very similar questions and have gotten thoughtful answers.....Does nobody here understand AU4G (Standard NF A 02-104), and 2017 (Standard NF A02-004 / EN 573-1 and how to decide what is the most appropriate replacement material?

    Basically when using seamless tubing can I use 6061 T6 in place of "Dural" AU4G? Should I increase the wall thickness somewhat?

    Please I just need some basic information to get me started.

  8. #8
    Administrator Kelly Bramble's Avatar
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    Without an analysis - and I'm no going to do one.. and since nobody can offer an informed opinion I would go thicker on the walls not thinner.

    When in doubt, over engineer your end item.
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

  9. #9
    Principle Engineer Cragyon's Avatar
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    Yes, use the next size up tubing/stringer material or do a stress analysis on the original design.

  10. #10
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    Great information

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