21 April 2017

NEXOGON: The Technic connection

Posted by Admin
This week we return to the geometric properties of the new LEGO® NEXO KNIGHTS™ piece, Rotor w/ 4.85 hole (Design ID 27255). Brian D'Agostine of Portland, Oregon is no stranger to writing about LEGO pieces and techniques - his blog, Dag's Bricks, has been running longer than New Elementary for a start!

When I asked to be accepted into this parts festival my first inclination was to explore the geometry of the shape and figure out the dimensions in detail. I was also, by extension, interested in the geometric patterns that could be created in 2D and 3D space.

With a convention coming and my workload increasing weekly I was relegated to watching others post their discoveries and hoping I could finally get around to my write-up. Others had posted some exploration of the piece but there were still a few more aspects that I had wanted to explore.

For instance, what is the relationship between the 2x2 stud areas and the hole in the middle? The more I explore LEGO pieces the more I realize that even relationships that don't immediately seem relevant end up being so. In this case the hole is a very even and expected spacing from the 2x2 stud areas; a 2x4 Technic plate immediately proves this.

However, when we place a Technic pin in the top side of the hole, a 2x2 plate on one of the ends, and the 2x4 Technic plate to match up with the central hole, we can see that the flange on the pin only comes flush with the top of the plate, not through. The pin must be recessed into the Nexogon by half a stud then.

Some have reported that the Technic receptacle on the bottom will not clutch over a stud. This is true. Including the receptacle, the piece has a total height of 3 plates. However to get a Technic pin to work properly, 2.5 plates (or 1 brick width) is needed. So while the business portion of the Technic pin is 4.8mm (stud diameter), the flange is a touch more at 6.2mm.

This touch at the end of the receptacle, as well as it being recessed enough, mean that a typical stud will not fit. It will accept longer studs such as those on a minifig torso or the 1x2 modified tile with minifig head post from LEGO Minecraft (Design ID 24445).

What about the 3.18mm bar on the long edges? Of course I would expect it to evenly correlate with the middle as well. It's not difficult to adjust the camera angle perfectly to make something look correct, but I can assure you that a 1x2 plate with clip on the long end (Design ID 63868) lines up perfectly.

So the odd geometry of the Nexogon is then determined by these two relationships, and has nothing to do with trying to create a perfectly square area at the 2x2 studs.

Next time, the droids have a hand at it!

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  1. Okay, this is finally getting to my biggest question about this piece. It's been demonstrated in a few cases that the hub is a full three plates (or one brick) tall, which is too tall for a Technic pin connection that's designed to fit through the width of a brick. So, where exactly is the extra half-plate of height hidden on this thing? Is it top, bottom, or split between the two?

    1. I haven't fully explored and confirmed (shame on me!). Since a stud won't fit into either end I believe the difference is spilt. You would think that that would make for some odd geometry though. But the smaller diameter of a pin is not a full 2 plates wide due to the flanges. So I'm thinking that the recess is about half a plate on each end of the Nexogon tube.

    2. The pin hole is designed to take a pin from either end, so each side has a recessed portion that allows the pin to click into place without coming out the other side. So… both top and bottom, I guess?

  2. @Brian:

    The total difference would be half a plate, so if it's split between top and bottom then it should be 1/4 plate each. And if that's the case, it seems like the Technic connection there would be largely useless, since that same 1/4 plate (or 2 LDU) would prevent any Technic parts from connecting properly with a standard 2L Technic pin. One or both ends would remain pinched, which constitutes an illegal connection per the Design Department's rules. Basically, the only way you'd be able to use this with a legal connection would be to always use a 3L Technic pin, or one of the three types of axle-pins. Even the half-pin would sit deep enough that the little bit of stud that's still protruding would be useless as an attachement point, though I suppose you could always stick a bar into the half-pin.

    Ironically, it might pair perfectly with the old style 8-tooth gear, which always had the problem that it had shoulders that were too small, allowing it to slip inside the recessed pin hole collars on Technic bricks, which in turn allowed two 8-tooth gears to be misaligned to the point that they almost didn't touch anymore.

    1. There's a half-plate recess on both the top and the bottom. It's wide enough that the pins can click in but not so much that the "collar" slips into it. This allows a 100% legal connection from either side, but not both at the same time.