Angle iron

Discussion in 'Materials' started by fallguy, Mar 17, 2020.

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  1. fallguy
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    fallguy Senior Member

    Does anyone know how to easily determine the strength of an angle iron oriented in an L shape with a load applied to the lower leg? The vertical leg is attached to a fixed object.

    It is 304 stainless and one is 316 stainless.

    From memory, it is 1.25" and 0.125" thick.

    I need 1000 pound rating and gutcheck says I am short.

    If I want to improve it at the connection point of the crossmember, can I just weld all around another piece under the L? Or will welding weaken it?

    I can change one of the angles to beefier stock, but the other one is sort of gonna be expensive to change.
     
  2. fallguy
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    fallguy Senior Member

  3. TANSL
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    TANSL Senior Member

    What do you mean by the "strength of an angle" ?, the yield point of its material, the resistant modulus of the profile, the maximum tension that the profile could support, ..?. In addition to explaining the above, a diagram of the assembly that you have and how the profile is loaded are essential to give a valid answer.
     
  4. jehardiman
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    jehardiman Senior Member

    It's fairly easy if you can find the load case in Timoshenko. Otherwise, it is calculation that could take 5 minutes to 5 hours depending on the complexity.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    I don't think anyone understands what the situation is with the application here, but why not just test it to say 20% beyond what you consider the maximum load would be ?
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    It is a series of Q&As:

    1. Material.
    What are the material properties of the metal being used....do you have this? If not - makes it more tricky.

    2. Stiffness.
    The dimensions of the angle bar will dictate the response from the applied load. So exact dimensions are required.

    3. Load application.
    Where you place the load, on the flange - matters a great deal. As this will influence the load case, as either pure shear, bending or both.

    4. Support
    How you support the angle bar will effect the results. Simple support, fully built in, or partially built in.

    Thus - it is not a simple one liner reply.
     
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  7. fallguy
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    fallguy Senior Member

    I always have a hope for an easy solution. We will draw it up.
     
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  8. Mr Efficiency
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    Mr Efficiency Senior Member

    Where are you getting the 1000 lb figure from ?
     
  9. fallguy
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    fallguy Senior Member

    Well, I realized with brut force we are not strong enough. I applied a 'Dan' load to the angle iron and a 150- 200 pound force bends the iron.

    Here are back to back angles with a welded T shaped crossmember. 1.25" legs, 1/8" stainless (316 and/or 304). We determined the crossmember was too weak. It is bolted from above. I want a design load of 1000 pounds.
    AB3046BB-7B81-4B1A-BCD4-D7C113DCF7E2.jpeg

    closeup; the black mark is going to be another 3/8-16 stainless bolt
    AC64BEFC-07F7-4F35-87A7-14CA704F7F75.jpeg

    So, we had a new T made from 2" angles. The vendor started to drill the holes and asked me to finish them to fit(good thing). The trouble here is this is so strong; the point of failure is the attachment point.

    I am just going to change this side to 2" angle. It won't meet the 1.25" angle on the other side, but will disburse the load better and not bend. I wanted the calc for this, but it is rated fpr about 3-500 pounds only I am quite sure.
    9607B458-0D2C-4846-B92E-1BD60252B208.jpeg

    The other side of the crossmember T is this contraption without the gussets and extra backer. Already welded and also too weak by the 'dan' test. I figure I could gusset it as pictured, but it'll squeak like hell. So, instead I am thinking I could weld wings to the crossmember and make the top of the T much wider (no picture, this is a reading test). But consider the angles sitting on top with long top legs; they could be bolted every 6 inches or so. Then the load is disbursed across say 2 feet of the angle; not 4". The other alternative is forking out loads of cash for all new 2" steel and welding, but the beam has been holed already for 1/8" rivets for the strapping. (You got complex)
    5F51A1BA-3C62-45A9-8DC7-46AB43DA72F1.jpeg
     

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  10. fallguy
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    fallguy Senior Member

    well, I wanted to design the thing so 8 people could stand in the middle and hug; called it 1500 pounds; the crossmember and the cockpit panels and such have some weight; the load is shared with the opposing end 88" away; so I just sort of winged the 1000 pounds

    My son and I sat on the 1.25" Welded tee and it distorted under our 400 pounds, so we upped the angles to 2" and did deflection calcs on that and it is beefy, but I sort of didn't consider the endpoints enough.

    I could draw it all up, but it is really fairly complex...even to drawr..

    I think it'd be best to switch the simple angle to 2" and to modify the crossmember to have two very long legs on the top of the tee on the other end...probably have to have it welded onsite
     
  11. Ad Hoc
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    Ad Hoc Naval Architect

    If it is too complex to draw, how are you going to build it... using what as the guide?
    The drawing will identify your load paths and supports - this is critical to any structural design.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    I don't much like SS for any load bearing structure, what else could you substitute ?
     
  13. Barry
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    Barry Senior Member

    An interesting comment, what is the weakness of SS for a load bearing structure
     
  14. Mr Efficiency
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    Mr Efficiency Senior Member

    It seems prone to busting if there is any flex, and probably more so with 316. I wonder what alloy the De Lorean was made from. It may have been some of the breakages arise from faulty welding, it does seem to require a fair bit of skill. Alloy likely a better idea.
     

  15. Ad Hoc
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    Ad Hoc Naval Architect

    What on earth does that mean..?

    Nope - no difference which ever alloy is selected.

    No more/less than aluminium.
     
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