Attempt to design a barbell during lockdown Attempt to design a barbell during lockdown - Page 2

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Thread: Attempt to design a barbell during lockdown

  1. #11
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    Quote Originally Posted by Snake Plissken View Post
    Did you take a material science class back in your college days Rip? You never struck me as someone that would just know this off the top of your head (not as an insult, just you're known for getting people under a bar and not in a crossfit box).

    But if I wanted to nit pick, it's technically a function of radius. Second area moment of inertia of a cylinder is (pi/4)r^4 about the horizontal.
    Yea, but if youíre after relative whippyness, donít the scale factors cancel in the ratio? r1/r2 = d1/d2. So the relative whip would go as the relative width^4? Which is about a 15% difference for 29/28.

  2. #12
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    Quote Originally Posted by VNV View Post
    Yea, but if you’re after relative whippyness, don’t the scale factors cancel in the ratio? r1/r2 = d1/d2. So the relative whip would go as the relative width^4? Which is about a 15% difference for 29/28.
    Considering 2 bars with identical properties then yes, but the way something to the 4th power comes out, it makes a huge difference compared to what you might think. 29/28 or instance is a diameter difference of about 3%, but when you work out 14.5mm^4/14mm^4, you get a ratio of about 1.15, a 15% difference. Point is a 1mm change in bar diameter makes a drastic difference in the flexural rigidity (D=EI=(Young's Modulus, 200GPa for generic steel)*(pi/4*r^4)). So a 27mm deadlift bar vs a 29mm power bar has a massive 33% relative difference if you calculate the ratio. That's easily enough to let plates sag on the ground while you gain an inch or so of distance before plates break the floor with a deadlift bar.

    And I understand that radius and diameter don't matter, I'm just trying to get into Rip's bottom 3% lol

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