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Drilling hole in 1-3/8 pipe for fulcrum

  1. Nov 10, 2011 #1
    Drilling hole in 1-3/8" pipe for fulcrum

    I am designing a small crane for a special purpose. I am using a 17 ga. steel 1-3/8" ten-foot pipe as a fulcrum. I am going to drill a hole 2 feet from one end to run the axle through. That will leave 8 feet on the other side.

    Is there a table or formula to determine how much load strength this will have? More importantly, what would the strength be depending on what size hole I drill? Is a 1/2" hole acceptable?
     
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  3. Nov 20, 2011 #2

    nvn

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    bnaudie: You have a steel pipe having outside diameter d1 = 34.925 mm, wall thickness t1 = 1.4732 mm, and length L1 = 3050 mm, used as a class 1 lever. Unless you can give us the material specification number of your pipe, we can assume it is steel ASTM A53, grade A. Therefore, we can currently assume the pipe allowable bending stress is Sba = 136.7 MPa, and allowable bearing stress is Sbra = 191 MPa.

    Consequently, your fulcrum can withstand a maximum force of P1 = 340 N, not because of your current pivot pin (axle) hole size (d2 = 12.7 mm), but instead because of the bending stress on your given lever. This means the force you can apply to the tip of your 2440 mm lever arm can be a maximum value of 68.0 N.
     
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