Wednesday, February 8, 2017

CoG Machine

I finally found the time last week-end to assemble my CoG Machine, made from 2 kitchen scales, some aluminium and 3D printed parts. The 2 scales are glued on a wood place using some cartridge sealant. Prior to that, I did a trapdoor below to access the batteries. The 3D printed support is also sealed on the scale plates so everything is fixed together.

Just as a reminder, as lots of people asked me how it works, just look at the drawing ont he right and extrapolate to obtain the formula giving the location of the CoG from the leading edge, knowing waht the scale measure at the vertical of the leading edge and what the second scale measure X cm behind.
The advantage of this method compared to the usual CG balance is the repeatability of the measure.

I know that, since my first post on Facebook, some CoG machines are in construction here and there ;) ! This is good to know !


  1. Hello,
    Where is this post : "I know that, since my first post on Facebook, some CoG machines are in construction here and there ;)"
    Many Thanks .

    1. on facebook :)

  2. Fascinating concept. I have to think about that a little...

  3. Hello Pierre,

    It is not who knows a lot who is intelegent - but who applies what he know. Thanks for showing a new way to apply knowledge.
    Now - the CG machine in it self will also contribute to the over all placement of the CG between the plane and the support mechanism - now, if the CG of the support coincides with the CG of the plane, you would not have to compensate. But, otherwise yes - now, if you have done this in your spredsheet calculations, I do not know.

  4. Hello again Pierre,
    I have finally had time to look over the math and formulas related - and I have gotten to the conclusion - If you put the CG mechanism on the scales, zero out the scales with the mechanism on the scales - you take away the contribution that the CG mechanism itself would induce. Simple.
    I will make one and use it - it is much more easy to use that the alternatives, more stable and more exact.
    Thanks for the idea,
    Jens Chr