So I have been using LEGO® for a rather long time and over the years, I started going towards small constructions. While doing this, I began building rather small robots (Mobile Frames for those who know), between ~8cm and ~11cm or approximately 8 to 11 studs.

Those mechs I build are articulated and I want them to have as many articulations as possible (e.g. a leg should have a hip, a knee and an ankle, not only a hip).
The problem is the sturdiness of the whole construction. I have tried multiple options and the articulations are often either too weak to stay in position correctly or too fragile to support other parts, leading to structure vulnerability and eventually destruction of either portions of or the whole robot.

My question is the following : do you know any compact yet sturdy articulation building technique or any small articulation part ?
Bonus : if you can provide a method allowing me to build more or less on the articulation (not sure if that's very clear).

EDIT : For posing reasons, the articulation needs to have some 'friction' to keep a specific angle.

Should there be any problem with the question (wrong formulation, bad English, need for clarification), please don't hesitate to point it out.

  • This doesn't actually answer your question, hence the comment as opposed to an answer, but for larger constructions the 24-tooth clutch gear works well.
    – TLW
    Commented Aug 24, 2016 at 14:57
  • 1
    Well, building tricks are always welcome, especially when it comes to LEGO®.
    – z3r0
    Commented Aug 25, 2016 at 7:04

3 Answers 3


The AT-ST & Endor (9679) uses cogged connectors (4210884 + 4211803, I don't know if the combination of both parts has a name) for the legs. These connectors are pretty strong for their size, they may be sturdy enough for your model if it's not too heavy.

enter image description here

For bigger constructions and higher degrees of freedom, beam with balls and cups can be used, they allow rotations and movements in two axis. For example, the Beam A 5M Ball/Cup Ø10.2 (they are other similar parts on Bricklink):

enter image description here

For example, General Grievous (75112) arms and legs can be adjusted in many ways:

enter image description here

  • Thanks, that is already a good start. However, I also need parts moving on multiple axis (like a human hip or shoulder for example). Any suggestion ?
    – z3r0
    Commented Aug 24, 2016 at 12:44
  • @z3r0 I added the balls and cups, I hope that it won't be too big for your models. Commented Aug 24, 2016 at 12:56
  • Thanks for the idea, unfortunately those parts are way too big for what I intend to do. Do you happen to know any alternative ? Other than that, the cogged connectors seem a rather interesting concept for mono-axis (is it even English ?) articulation.
    – z3r0
    Commented Aug 24, 2016 at 13:00

You could use the plate ball and cup joints like 6043656 and 4329654 (and a few other parts with balls that will fit)

These parts: enter image description here

One caveat though, brick #2 from the left does not have much sturdiness in holding joints together. 1, 3, and 6 are good though.

  • 1
    The two small ones in the middle of the picture seem to have size characteristics close to what I'm looking for. Do you happen to know if that specific ball-cup combination has friction (allowing specific poses) ? If I remember correctly, the other ones don't. Also, do you know if the 1x1x1 ball holder also comes in different shapes (1x2x1 like its left neighbour) ?
    – z3r0
    Commented Aug 24, 2016 at 13:11
  • @z3r0 From experience, the two in the middle do have enough friction, however, there is no 1x2x1 for that piece. Commented Aug 24, 2016 at 13:21
  • Well, I guess I'll try to find some ball-cup combination somewhere to test their friction. Could you please write the designation of the two parts in the middle ?
    – z3r0
    Commented Aug 24, 2016 at 13:42
  • @z3r0 14704 for the 2x2x1 socket and 3614 for the 1x1x1 with ball. Commented Aug 24, 2016 at 13:48
  • In my experience, #5 from the left, when paired with #1 or #6, has no friction worth mentioning. I don't know about the other pairings.
    – Mark
    Commented Aug 24, 2016 at 21:42

I think the best technique for building a sturdy Lego structure is to start with a wide and big base and then stack up with smaller bricks. I took part in a Lego challenge and one of the challenges was to build a big Lego tower. So, I decided to start with a big base. Then, I built up with smaller bricks. When I did my test to see which was the best, I found out that a bigger base is better. I also am doing a science fair on which Lego structure is strongest when dropped. I haven't done it yet but I believe that a square base will be the strongest instead of the other bases I have chosen. I love building with Legos but a big pet-peeve is when they break. That is why I am doing my science fair experiment to see which structure is the best. I will let you know when I have my data.

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