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Thread: What size wooden beam

  1. #1
    Associate Engineer
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    What size wooden beam

    I have no idea if this is the correct forum to ask this under. So if it isn't, my apologies. I am trying to figure out what size LDL or dimensional lumber to use for a chain hoist I have. The hoist is a 1/4 ton. I doubt I will ever lift anything that heavy, but you never know. The span I will be using is 23'. I will only use this hoist connected to a strap or I bolt or something right in the very middle of the span. I'll have to figure out how to support it with wooden beams or manufactured lumber. I have looked at online calculators and they went WAYYYYYY above my head in determining what size beam to use. I don't know what the cost difference is with a steel I-beam versus a manufactured LDL. I just expect the LDL to be cheaper. Is there a quick and simple formula that a layman can use? I did get straight A's through Algebra 2 in high school, so I can still figure out simple math. What size beam to use and than what size lumber to use for supports. I hope I've given enough info to get some kind of a simple answer.

  2. #2
    Technical Fellow Kelly_Bramble's Avatar
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    First, estimate which size beam you would like to use...

    Commercial Lumber Sizes Table

    Then, determine the Area Moment of Inertia

    Area Moment of Inertia Rectangle

    Modulus of Elasticity for Wood

    Structural Wood Lumber Engineering Data

    Put all the data into the engineering beam deflection calculator that best represents your loading configuration.

    Beam, Stress and deflection equations and calculators

  3. #3
    Associate Engineer
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    First off, thanks for the info.

    OK, here's what I got. Using 3 2x12's glued and screwed together

    Modulus of Elasticity psi 1,600,000
    Moment of Inertia 533.7
    Load Total 1200
    Line Pressure Load 10
    Distance (Is that inches or feet)
    Length (Same ?)
    Distance to Neutral axis/Plane (What is this)

    So, what does this tell me?

  4. #4
    Technical Fellow Kelly_Bramble's Avatar
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    Length (Same ?) = span of the beam = I think 23'

    Distance to Neutral axis/Plane (What is this)

    This is the distance from the top of the loaded beam to approximately the center of the beam. Consider that a beam being bent --- the top surface is placed in compression and the lower surface is in tension. Somewhere between there will be a transition from tension to compression - this is the "Neutral axis" location.

  5. #5
    Associate Engineer
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    Thanks for the info Kelly

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