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Thread: Calculations needed - Determine thickness of angle iron to use

  1. #1
    Associate Engineer
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    Calculations needed - Determine thickness of angle iron to use

    I am working on making a track out of angle iron that V-groove casters of a gantry will ride on. A length of angle iron will be welded, concave side down, onto a length of flat steel which will be secured to a concrete floor. Two tracks will be made running parallel to one another, and the four V-groove casters of a gantry will ride along on top of these two tracks; two casters per track. I am having a hard time finding the correct equations for determining the thickness of angle iron to be used under the weight of the gantry and a suspended load. Essentially, the cross section is a beam bent at 90 and rigid on both ends. Is the following equation the first step in the right direction? Thank you.

    https://www.engineersedge.com/beam_b...m_bending4.htm

    Beam Equation.PNG

  2. #2
    Technical Fellow jboggs's Avatar
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    A few tips:
    1 - You said the rails are fully supported on a concrete floor, so I don't see where a bending analysis is even required.

    2 - The bending diagram you referenced is for a beam supported at each, and only at each end.

    3 - The angle iron/v-groove caster approach is a very common arrangement. We have several in our plant. However, in my experience it is not wise to have angle iron guiding the casters on both sides. The vertices of the two parallel rails will never be at the exact same separation as the vertices of the two opposing casters. Thus leading to uneven operation and accelerated wear.

    There are two solutions. If you insist on having angle iron on both sides you should allow the caster wheels on one side to "float" on their axles thus allowing them to find their own center.

    My preferred solution is to simply have a flat rail on one side. You can use the same wheels all around. Those on one side ride the v-rail. They provide the support and guidance you need. Those on the other side ride the flat rail and simply provide support. If you do this you have to account for the fact that the support rail on the flat side must be slightly higher than the support rail on the v-side. Refer to the attached image.

    Capture.PNG
    Last edited by jboggs; 09-24-2020 at 01:09 PM.

  3. #3
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    jboggs, thank you for the tips. I am sure you saved me some headache since I would have put two angle tracks down. The analysis I am looking for is in the structural integrity of the angle iron itself. Perhaps I am worrying too much, but I want to be sure that the rail cannot buckle, bend or crack under the downward force of the casters.

  4. #4
    Technical Fellow jboggs's Avatar
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    Have you sized the wheels? If so, contact the manufacturer's application engineer and get their recommendation on angle size etc. I would say as long as its fully supported on concrete over its full length and big enough to lift the wheel up off the flat support rail, that's probably good enough. Which brings up the thought of foundation preparation. Any concern there?

    Also, you might want to design it so that the rails are easily replaceable in case of damage.

  5. #5
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    Thank you for the recommendations.

    I am sorry, I do not understand what you mean about foundation prep. The rails will be mounted to a pre-existing concrete floor in our manufacturing facility. I will design them and their connection in a way to easily replace in case of damage as you suggested.

  6. #6
    Technical Fellow jboggs's Avatar
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    I have no idea of the loads you are dealing with or the precision with which these carriages must move. Are the carts rolling on the floor now with no damage? If so, great! No need to over-think this thing.

    In our plant we have some rolling assemblies that weigh 4000 to 5000 lbs each and have to be guided into a very precise position. We designed concrete foundations so that the loads were distributed properly and so that the rails could be installed (and re-installed) precisely. Your rail and floor plates should distribute the point loads from the wheels over a wider area of concrete.

  7. #7
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    Ahh, I understand where you are coming from. This is actually being made to help transfer steel coils weighing around 1500 lbs or less depending on the size of the coil. Normally, we would roll the coils or have them on special coil pallets, but they are quite narrow and therefore easy to tip over. This hoist and gantry system would help keep the worker away from the coil while maneuvering it across the production floor to load it onto our de-coiler.

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