Plastic Deformation

Here is a topic to discuss plastic deformation of parts and what should be considered limits on use of stressed pieces, AKA the legal limit. This discussion was getting largely overblown with experimental and theoretical engineering clashing in argument, so let’s try to separate that here. I also decided to create this topic as I myself wanted to join the conversation, but I am still working on calculations as proof of evidence. So, until then, discuss here to your hearts (respectful) content.


so basically, what constitutes an illegal technique and what doesn’t?

Officially, I believe it’s any connection that causes stress to any pieces involved. Come common examples would be plates wedged between two studs, bushings inside a socket, and technically a stud inside a pinhole. That being said, Lego themselves have broken this rule a number of times.

I personally don’t use a connection if it permanently damages the piece in a significant way, with some exceptions. This gives me a surprisingly wide array of extra techniques at my disposal.

I should have seen this coming. Finally, we will be able to decide how many PSI of pressure constitutes an illegal technique :stuck_out_tongue:

There was a lot of discussion in the other topic about this specific technique I used here:

My view is that since the part experiences deformation only in its elastic range there is no damage to the part and so it is ok to use. Standard ball sockets are a good comparison because they also experience deformation in their elastic range but clearly to a lesser extent. Both parts will experience creep if stressed for a long time.

Just to quote what I said in the other topic:

Stress applied in the elastic range of the part will completely reverse once the stress is removed. The part will not be deformed. This is the concept behind how stuff like springs work. Stress beyond a certain (Yeild) point is irreversible or plastic. So stress in itself is not an indication of a damaged part, in this case we know the stress is elastic because trying the connection and then removing it does not damage the part.

The creep I mentioned is a different concept that parts that are kept within their elastic range but at high stresses will over time deform. As I said this does happen on a year time frame with this connection. But my point is that this is a very small amount and does not change the utility of the part at all. The same likely happens with standard ball sockets.

I wish I was with my collection right now and could show a picture of a part I used this way for a long time. It’s a useful connection to have in your back pocket if you need a super strong joint and people shouldn’t be afraid to use it!

If we want to go full engineer on it there are a few instances in that quote where I say stress when I mean strain just for clarity to people not versed in engineering lingo.

Think I made my position pretty clear so I don’t really want to debate further but I guess the main thing I would want to advocate is that people should be able to build how they want to. In a contest setting people can vote how they want to if they don’t like how a MOC is made.

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Any technique I don’t like is an illegal technique.



Yep I guess that’s a fair definition.

Actually its the best one yet. All hail Emperor Hawkflight!

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Is holding a pinhole between two ball joints illegal?

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If I understand you correctly, I don’t think so, because I don’t think there’s any stress on that connection. It’d be like putting two non-runthrough standalone balljoints on a 3L axle through a beam.

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Well, the whole debacle of a conversation that stemmed from Gamma-Ray’s connection technique seems to have cooled down, and I just returned from an evacuation, so I’m not going to care to give specific numbers here. All I will say is that, given normal conditions, noticeable deformation occurs on the scale of many weeks. Deformation on the level that could leave the piece stretched to the point that it couldn’t easily be re-bent and reused is on the scale of many months. Finally, deformation on the level of plastic tearing is on the scale of years. So here are the points to take from it.

  • You can use the technique, and if you exchange the pieces relatively frequently you can avoid damage to the pieces.
  • To say that there is no damage is completely incorrect.
  • To say that any damage due to short term use can be reset is also incorrect.
  • To say that the pieces are completely ruined, to the point of non-reusability, by this technique is only true on larger time scales.

So here you go. Take it or leave it, these are my findings.

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I have a tube piece that became permenantly curved after being in a curved position for a long time. A while ago, a built a contraption out of Lego to force the tube to be straight, but even after leaving it there for months, it was still curved. :rage:

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