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I've been working on a MOC and tried using the following configuration of inverted brackets to achieve studs out SNOT 180 in a tight space:

Construction image

As you can see from the photo, this doesn't quite work. I can force the parts to lie flat, but it feels like this is putting a lot of stress on these elements.

What is causing this to not work, and why weren't these parts designed to work this way?

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  • There is a definite, but slight lip on those, and the 2x2x1 bracket as well, I don't know why though.
    – Zhaph - Ben Duguid ♦
    Commented Jan 18, 2017 at 23:41
  • I am designing a new part to give to the Lego group to resolve this issue by making a new spacer that can compensate the 0.02 mm space although the recent set 76144 uses and illegal technique on the helicopter's brackets to hold extra studs but i'm bringing this up as an example. my idea is an inverted part that is 0.02 mm smaller than a regular brick with 2 inverted studs on it to allow to builder to make sturdier builds upside down
    – RGBtechnic
    Commented Jan 28, 2020 at 16:38

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The short answer is because the combined height of the two mini inverted brackets is greater than the interior space of a tile (or brick for that matter.) But you knew this already.

I realize it isn't considered standard by the rest of the world, but because the only quality calipers I had access to tonight are customary, all these values will be in inches.

An average of several measurements gives me the following values for the dimensions of several key parts:

  1. average height of a 1x2 - 2x2 bracket............... 0.7221
  2. average height of a 1x2 - 2x2 inverted bracket...... 0.7278
  3. average height of a 1x2 - 1x2 bracket............... 0.4079
  4. average height of a 1x2 - 1x2 inverted bracket...... 0.4131
  5. average exterior width of a 2x2 tile................ 0.7239
  6. average interior width of a 2x2 tile................ 0.6028

Now, we all know that item 1 and 2 will fit flush onto a brick evenly if a plate is added to the other side. enter image description hereenter image description here

We also know that in practice, if you put 3 on a brick and 4 directly under that same position, the SNOT faces will adjoin where plates may be legally connected. enter image description here

But here's the catch: adding the heights of 3 and 4 does not get 1. That sum does not even get 2.

It has to do with where the gap is. On items 1 and 2, the gap is under and above the SNOT part of these elements respectively. But the combination of 3 and 4 leaves the gap between those two plates. You can see this easily by attaching 4 to a brick and then laying a plate behind. You can see that the corner is square and there is no clearance like we see from hanging 1 off the side of a brick-and-plate.

This clearance, by my measurements, is 0.07 inches. This is the height of 4 that is placed at the corner (that leaves a gap between it and 3) This corner is what makes this technique fail. This corner also explains the reason that 3 and 4 are different heights although they suit similar purposes.

Finally, this explains why you can affix two 3 elements to the underside of a tile. Twice the sum of the height of the 3 is still less than the interior measure of the tile once horizontal tolerance is accounted for.

As a closing solution, I recommend using two 3s attached to a tile as that works in reality. But just to prove how complicated this measurement really is, LDD still thinks that your original problem is a legal connection. enter image description here Hope this helps.

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