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Where to put the weight

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  • Where to put the weight

    Ok, hypothetical question again- but a real use. Suppose I have a circle of aluminum plate, diameter not critical but lets say 1 foot across. It's a base for a mic stand. I also have two lead weights- one is a ring whose OD is 1 ft, and the other is a blob. They both weigh the same.

    Which is more stable, the ring placed on the base, or the blob centered on the base? Or is there no difference? What if the blob was a vertical post centered on the base?

    My feeling is that between the ring and the blob placed on the base, there is no difference in the stability of the base. If the blob was a post of the same weight, the initial stability is again the same, until you begin to tilt the post. At that point much of the weight begins to off-center, and the stability will be lost.

    There will not be a lead post in this project of course- but it could be a steel post of the same weight, which as far as I can see will be just as stable in the vertical position, but which would of course smash the $6000 microphone into your foot with more potential to cause blue toes, and blue air too. Keeping all the weight at the bottom makes sense, but does it matter how it's arranged as long as its center of mass is centered on the base?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Weight should be as close to center or evenly distributed for stability.
    Think: gymnasium volleyball post base
    Last edited by reggie_obe; 12-23-2020, 04:20 PM.

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    • #3
      To me sum of moments makes ring vs. blob pretty well equal.

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      • #4
        Probably very little difference in such a circumstance. Very slight edge to the ring if it can be kept lower in terms of height than the blob, but that difference wouldn't show up until the stand was tilted pretty far over. At that point the difference would likely be inconsequential.

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        • #5
          vibration wise the ring wins out...

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          • #6
            Well, i disagree with the most of youse guys.

            I think the ring will be more stable.

            Look at it this way-to tilt the stand you need to lift the weight that is on the side that you are tilting the stand way from.

            1/2 lb on an 8" lever arm will be a lot harder to lift than 1/2 lb on a 2" lever arm.

            Or take it to an extreme-distribute the weight around a 20' diameter. I think it will be a lot more stable.

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            • #7
              I’d go ring + blob offset from the mic

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              • #8
                Originally posted by andywander View Post
                Well, i disagree with the most of youse guys.

                I think the ring will be more stable.

                Look at it this way-to tilt the stand you need to lift the weight that is on the side that you are tilting the stand way from.

                1/2 lb on an 8" lever arm will be a lot harder to lift than 1/2 lb on a 2" lever arm.

                Or take it to an extreme-distribute the weight around a 20' diameter. I think it will be a lot more stable.
                im not getting your 1/4 ratio, is it not like 1/2lb on an 8" lever VS 1 lb on a 4" lever comparison?

                yet that's why I added the vibration factor, or "dynamics" even though the static pull might be identical now speed things up and everything changes,,,

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                • #9
                  The exact ratio doesn't matter. Just that there is a longer lever when you are using a ring.

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                  • #10
                    Originally posted by andywander View Post
                    The exact ratio doesn't matter. Just that there is a longer lever when you are using a ring.
                    Draw a diagram with weight at a point times distance from edge. Sum these “moments”. Blob at center will turn out equal to ring. (statically)

                    I think AK is saying ring will have more rotational inertia (flywheel effect) and I can’t disagree.


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                    • #11
                      Originally posted by SVS View Post

                      Draw a diagram with weight at a point times distance from edge. Sum these “moments”. Blob at center will turn out equal to ring. (statically)

                      I think AK is saying ring will have more rotational inertia (flywheel effect) and I can’t disagree.

                      If you calculate things around the center of the base, yes.

                      But the base will not tip by rotating around its center point. It will tip by rotating around one edge.

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                      • #12
                        Go with the ring. With the blob there will be more tenancy for the opposite of the blob to be "More tippy". Unless the blob encompasses the boom rod at its connection with the aluminum plate. Then its not a blob, its a ring. JR

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                        • #13
                          So, is the disk rotating or not?

                          If not, and if the blob and ring have the same CG, there would be no way to tell the difference. It seems that the blob would just about have to have a higher CG though, so a simple experiment could determine which it is.

                          I the disc rotates, a simple moment of inertia measurement would give up the secret, even if the CG of the two cases was the same.

                          Ed
                          For just a little more, you can do it yourself!

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                          • #14
                            Originally posted by andywander View Post

                            If you calculate things around the center of the base, yes.

                            But the base will not tip by rotating around its center point. It will tip by rotating around one edge.
                            Where is the center of gravity in the two cases?

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                            • #15
                              Originally posted by SVS View Post
                              Where is the center of gravity in the two cases?
                              Hmm, maybe you're right....

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