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I spend long periods away from home and my Lego bricks due to my work, so I end up doing a lot of design in computer with the likes of LDD, LDraw/bricksmith, and mecabricks.

The problem is that none of these have any "physics" in them, I can't ever see how strong or stable the model is.  So I end up spending hours agonising over the way the bricks are stacked, worrying over whether or not they will lock together solidly enough in real life.  I also spend ages checking brick link and Lego bricks and pieces to make sure the pieces I use are available in the colours I choose, but that's another story. 

When I finally do treat myself and buy the bricks for one of my creations, they invariably fall apart.  A couple of years back it was a 50 piece micro-scale particle detector that took 2 hours to get together and exploded at the slightest touch (and I do mean that literally, bits went flying all over the room!).  My latest fiasco is a model of the Mercury-Redstone rocket, which I designed to go with the Lego Ideas Saturn V.  It's just a stack of 2x2 round bricks with three axles inside due to it's height, yet despite my best efforts to put the axle transitions well inside bricks, the rocket easily falls apart into three neat chunks (one for each axle).

So, what's the secret? When you design in computer do you care at all about how the model would behave in real life?  And if you do care, do you have any tips on making sure that the model holds up well when physically built?

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49 minutes ago, NathanR said:

So, what's the secret? When you design in computer do you care at all about how the model would behave in real life?  And if you do care, do you have any tips on making sure that the model holds up well when physically built?

It’s a secret. We don’t tell secrets. :wink:

More seriously, I think (hope? I don’t want to be alone!) everyone has that problem. Even tools that check connections (LDD, Stud.io) are sometimes wrong: connections that’re not solid enough or that don’t even hold. (Not even talking about wrong models….)

For instance, your axles in a brick round 2x2: LDD told me it was okay to have two pin-axles meet half-way, IRL, it didn’t hold. That’s because the axle isn’t held all the way inside the brick. Only the top of the brick holds the axle. Fortunately, I had a plate round 2x2 on top of the brick (round brick + round plate + round tile with hole = 5 plates high = 2 studs = the axles of 2 axle-pins), so I just needed to put it under the brick to hold the first pin-axle and the top of the brick to hold the second. It works for me because it’s not heavy/high and the stud connections between plate and brick is enough to hold the whole thing. I don’t think that can help you with your rocket though :sceptic:

Anyway, after some time, you learn (by testing or looking at official models) where your models will be weak and need to be made stronger and how to do it (SNOT is great for that). You also need to not build too sturdily, too packed: that makes some parts of the build too heavy for no reason and weaken the connexions.

Yeah, some Physics student will come and say it’s all computable… till they realize testing with real bricks is way easier and more accurate, besides being where the fun is :tongue:

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I could be totally wrong, but I think the secret is using digital tools to get the look & feel correct as far as complex geometries that give the general shape or specific stand-out features of a model the look you're going for, then the rest for physical stability comes down to live prototyping and making adjustments from there.  At least, that's how it is for me!  I tend to build more complex MOCs from the outside in.  Like, if I'm making something with a lot of complex or compound curves and trying to get a shape right, I do that in the computer with not connection points, just pieces floating in space to get close to what I want, then I work on how to support them in a stable way and adjust things from there.

Probably a lot easier if you're a Master Builder and have unlimited physical bricks at your fingertips, but I bet you it's somewhat like that for them too.  I mean... probably a lot closer to a buildable model digitally, but I'm sure there's still a lot of real-world manipulation and design as well.  :classic:

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deraven has a good method. I have the same problem as to stability of large projects. What I have found is that 'trial and error' works well. Be prepared to fail and start over. Be prepared to change your drawings time and time again. I do one starting drawing that I KNOW WILL BE DELETED. Then I start building and revising it. I use stud.io and make EXTENSIVE use of SubModels. When some of your model works, draw it and save as a submodel. Then continue building and drawing.

I just finished a circular tower made up of 5 sections each 15 bricks high. Drawing was no trouble (HA!) but when I went to build I had to revise my plans several times to get the internal bracing correct. Treating each section as a submodel sped things up and my final drawing just had the 5 submodels.

I'd respectfully disagree with building from the outside in. Drawing yes, since that establishes the look of what you want to accomplish and drawings do not require that a physical structure be able to support itself. Having the outside drawing available when building from the inside out works (IMHO) much better. In the example above, adding the bracing required many dis-assemblies of the outside to accommodate the bracing.

Ed

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9 hours ago, knotian said:

When some of your model works, draw it and save as a submodel. Then continue building and drawing.

Definitely this.  But depending on the overall size, just keep in mind that all those sub-models will need to be properly and securely integrated together in the end.  I've gotten too carried away on focussing on getting detailed sections just right while not spending enough time thinking about integration, and then ended up re-working many of them again because of that.

9 hours ago, knotian said:

I'd respectfully disagree with building from the outside in. Drawing yes, since that establishes the look of what you want to accomplish and drawings do not require that a physical structure be able to support itself. Having the outside drawing available when building from the inside out works (IMHO) much better. In the example above, adding the bracing required many dis-assemblies of the outside to accommodate the bracing.

I see what you're saying there, but maybe I didn't do a good job with my brief explanation.  The exterior digital design stage of my building is basically what you're describing there with your drawing stage.  That is, if I'm working off an existing real-world reference object, I'll have a bunch of photos or drawings for reference, then work on replicating the shapes/details in the computer of the exterior, then I build from the inside out, but knowing the specific parts arrangement I'll be ending with (or close to it) based on the computer design of that part.  As I noted above, in some cases those pieces are literally just floating in 3D space in the computer, so it's not like I'm fumbling with a bunch of loose pieces frantically trying to build inward from them. :laugh:  Obviously the process is a little different when designing something with a lot of interior space (like a building or ship), in which case I kinda build toward the middle (work on the interior rooms/spaces to get the layout and details right, also work outside-in for some of the exterior details, and then merge them as needed with all the in-between structure in real bricks.

I mean... it's not like the Lego designers working on the Saturn V set started from the inside and got to this arrangement without knowing exactly what they were trying to support on the outside:

34405136392_b23a2d8d1e_c.jpg?w=625&ssl=1

But then, I'm no Master Builder... so maybe they DID.  :wink: :laugh:

Edited by deraven

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I once built a stream train in LDD, and then in real life via Design by Me , and but I sadly realized the wheels didn't fit and I scrapped the build. Of course, this was 2009 before the big train wheels were in ldd, but it served as a lesson to me. The lesson was this: if unsure of a connection, try it out in real life first before ordering ton of parts from Bricklink. This saves time (in waiting for more parts to arrive) and money. (in ordering parts that may not be needed anymore.) Sometimes waiting to order parts helps out in the long run anyway, as prices may go down or new parts are uploaded into LDD via patches* to alleviate your potential problem. (*Though that does not happen that much anymore...

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Thanks for the responses, it's definitely been food for thought.  It's a shame that so much of the design process boils down to "try it with real bricks", I mean I know that's the whole point of having Lego building as a hobby, but it gets frustrating for me given how far away I am from my collection of bricks. I suppose it doesn't help that I always seem to end up working in odd scales, or that I'm always trying to build such exact scale miniatures... Guess I just need to keep plugging away at it.

 

 

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I just built one of my models. Oh boy! Those pesky hinges! Some are too strong and prefer snapping out to hinging, and some are too weak and the #@! thing won’t stand up! :angry:

That kind of thing in a free CAD? Not for tomorrow. :wink:

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