Advice wanted: Technic frame for 40-foot Star Destroyer

[Jurss]

With mindstorm bases the build could become pretty heavy.

Maybe then You could really go for "brick frames"

And combine with brick beams.

Or maybe consider newest cross/flip-flop beams together with frames. Those new beams are somehow weaker, but there are more possibilities to connect them in 3 directions.

[Davidz90]

I did some quick prototyping. Not suitable for main spar, but should be fine for secondary beams:

spar by David_Z1, on Flickr

Of course this can be scaled up. As I imagine it, the sides would be covered by two layers of overlapping 6x16 plates. Grey frames provide some attachment points and keep plates from popping out. The grey frame is slightly stressed (construction is little bit wider than 4 studs), but not enough for permanent deformation. Besides, with larger frame, the bending would be even smaller.

 

EDIT:

Taking some lessons from bridges, I got this (just some speculation, no guarantee that this would work):

structure by David_Z1, on Flickr

There are arches, but done by bending straight sections - at this scale it seems much easier to do. Also, pre-stressed structure sags less under additional weight of panelling. Secondary beams form equilateral triangles. 

Edited January 31, 2022 by Davidz90

[Erik Leppen]

Has anyone considered an "exoskeleton approach"? What I mean is, you probably get the strongest result if the structural parts are as far apart as possible, so that the weight-bearing construction is as tall as possible. The main beams will then be closely under the panel surface. And if you can use the panel surface as part of the weight-bearing structure, you'd probably get an even stronger result.

For the rest, I do agree with the one who said that structural things like this can only really be tested in real life. Of course, it's a fun design challenge to build such a frame digitally, but I think no matter what you come up with, building it in real will always surprise you.

[Davidz90]

I agree that "exoskeleton" idea is a good one - that is why the two secondary spars on my (rather poor) drawing are close to the top and bottom.

Here's a small render how 40 studs tall H-beam based on 16x16 plates could look like. Central part is 7 layers of plates. Side flanges (red) are bricks, additional small spars (green plates) keep them attached. 

hbeam by David_Z1, on Flickr 

Sorry if I'm spamming the topic; I never considered designing something this big, and I'm having a lot of fun doing so  

[mdemerchant]

1 hour ago, Davidz90 said:

Here's a small render how 40 studs tall H-beam based on 16x16 plates could look like. Central part is 7 layers of plates. Side flanges (red) are bricks, additional small spars (green plates) keep them attached.

This flange design will be very unequally good at dealing with compression and tension.  Under compression it will be very strong but under tension it will be much weaker because it's only the beams attached to the web holding it together then.  This could be fixed with running more beams in that direction to better pin the flange together, preferably on the outside of the flange for maximum effect.  The green construction is a clever way to strongly attach the flange to the web but is it actually possible to assemble in real life?  How do you get the green plates on?

[Davidz90]

2 hours ago, mdemerchant said:

This flange design will be very unequally good at dealing with compression and tension.  Under compression it will be very strong but under tension it will be much weaker because it's only the beams attached to the web holding it together then.  This could be fixed with running more beams in that direction to better pin the flange together, preferably on the outside of the flange for maximum effect.  The green construction is a clever way to strongly attach the flange to the web but is it actually possible to assemble in real life?  How do you get the green plates on?

You are right that the flange is weak in tension and could be reinforced with more longitudal beams, the green plate takes space outside already, so running beams along it would take no extra space.

Good point with the green plates. There should be enough flexibility to press them into place; alternatively, some different pin/axle setup would be needed to attach the flange as the last part. Or just use one orange plate instead of three - it still should hold just fine, and the central part could use more 16x16 plates instead of smaller ones.

[edit] Ok, I'm stupid, the solution is simple. Build whole plate assembly, including green plates. Then use 3l pins that go two studs into  the longitudal technic beams. Then attach one layer of transversal beams with 2x6 bricks between them. Then attach second layer of transversal beams to the bricks. Then use 3l pins through the two layers of transversal beams. The sticking out pins can be used for another, outer layer of longitudal beams.

Overall, I think that the only weak point is the slight possibility of plates delaminating in the middle; making the beam single 16x16 plate wide would avoid that... but then it is much smaller and weaker.

Edited February 1, 2022 by Davidz90

[amorti]

My favourite thing about this thread is how no one has simply said "you're clearly mental, it's time to put the bricks down, now".

Considering how far you're talking about reaching and how weak/bendy Lego is at those lengths, it's going to take a lot. For my part, I'd suggest getting a mobile bridge building game, and seeing what works there. Or putting the bricks down...

[Davidz90]

9 minutes ago, amorti said:

For my part, I'd suggest getting a mobile bridge building game, and seeing what works there.

As an engineer and a long-time bridge building games veteran, I'd say - arches with equilateral triangles inside 

Edited February 1, 2022 by Davidz90

[Kdapt-Preacher]

I have a lot of thoughts about a lot of the responses here. I think my biggest takeaway right now is that I need to step back and do some sketching and 3D modeling to nail down exactly what this thing is going to have to look like before I can make informed decisions about the structure. For example, right now my plan is to base the sides on the 9-40-41 Pythagorean triple, which makes tying everything into the frame very easy, but that makes the ship about 3% narrower than I think it ought to be. On one hand, 3% isn't very much, and I think it would take somebody a lot of effort to ever notice that small a discrepancy, but on the other hand, my motto has always been 'death before compromise', and it seems like if I'm going to put this kind of effort into something it really ought to be right... but I need to go back to all the images of the original studio model and other depictions of the ship and really measure things out to decide what all the angles are going to look like and whatnot, since the choice of Pythagorean triple (if it even works out to one) will be a major factor in deciding where the struts need to go. I'll get back to you all.

 

On 1/31/2022 at 1:20 AM, howitzer said:

There's another software, called LeoCAD which is optimized for large models with many parts, so you might want to check it out. Not sure how much further it can push the limit though, as it might very well be that your computer is just not fast enough for the amount of bricks you want. 

This is good to know. I've vaguely heard of LeoCAD but didn't know that it was optimized for larger models. I'll almost certainly end up needing this, at least to load the thing for renders eventually.

On 1/31/2022 at 6:23 AM, howitzer said:

I think B&P limits the number you can buy though. Not sure what's the limit (might depend on the part) but I'm quite sure the limit is well below the hundreds or thousands you'd likely need for a project like this.

It's 200 of every part, as far as I know. Getting stuff directly from LEGO would be fantastic, but I think it would have to be through the LUGBulk program or something similar. Bricks & Pieces is unlikely to get me anywhere fast.

On 1/31/2022 at 7:34 AM, Davidz90 said:

I did some quick prototyping. Not suitable for main spar, but should be fine for secondary beams:

EDIT:

There are arches, but done by bending straight sections - at this scale it seems much easier to do. Also, pre-stressed structure sags less under additional weight of panelling. Secondary beams form equilateral triangles. 

That's a useful concept. I'm going to make a (non-LEGO) 3D model of the thing so I can plan out where major beams will need to go. My current thought is that the smooth hull sections will be principally supported by beams running perpendicular to the spine of the ship, but I don't know whether that'll really end up making sense or not. I think the two greatest structural challenges here are supporting the strip of detailing in the groove at the edge of the ship where the upper and lower hulls meet (which looks tiny, but is about 20 studs high and 1000 studs long, and will be densely greeblied with small parts, so it'll be heavy) and supporting the engines in the back (there'll have to be a column in the middle of the fantail section, but I think that'll be the greatest concentration of weight overall, and it's the thinnest part of the ship, so there may be limited room for beams).

You're almost certainly right that bending long straight sections into shape is probably the easiest way to do this, but from a philosophical perspective I'm not sure how much I like that. It's almost certainly going to be the case that there'll be some flexing going on here (especially since it's looking like getting that perfect angle on the hull may involve using something that's close enough to a Pythagorean triple to work perfectly in practice but technically isn't actually in click--I'm looking at some combinations that end up being off by 0.03 studs or something like that, which would never be noticeable here), but there's illegal and there's illegal... I recognize that my reluctance to accede to practicality makes me in many ways a poor candidate for this project, LMAO, but I suppose if I was limiting myself to goals that make sense I wouldn't be seriously considering this.

On 1/31/2022 at 3:16 PM, Erik Leppen said:

Has anyone considered an "exoskeleton approach"? What I mean is, you probably get the strongest result if the structural parts are as far apart as possible, so that the weight-bearing construction is as tall as possible. The main beams will then be closely under the panel surface. And if you can use the panel surface as part of the weight-bearing structure, you'd probably get an even stronger result.

For the rest, I do agree with the one who said that structural things like this can only really be tested in real life. Of course, it's a fun design challenge to build such a frame digitally, but I think no matter what you come up with, building it in real will always surprise you.

Yeah, I've thought about that. I think it would be a great approach if it could be done, and if we were working in sheet metal or something that would be clearly the best way to do it, but at present I haven't come up with a vision for how to make it happen in practice. From a design perspective, the lower hull panel would have to be ridiculously strong, since it'd have the weight of the whole side of the ship trying to buckle it, and the fact that that section is mounted at odd angles to everything else (in both dimensions) will make it hard to reinforce. From a building perspective, it would be very hard to actually assemble the thing if the hull isn't made in small sections--it would be immensely difficult just to lift and maneuver the (minimum!) 12-foot-long hull sections, especially if the model couldn't support itself while that was happening, whereas a more typical frame is more amenable to being assembled in chunks at least small enough to lift without a crane. My thought at the moment is that keeping the whole structural frame oriented along the typical LEGO axes and limiting the parts that have to be connected via turntables and whatnot to relatively non-load-bearing sections will save a lot of headaches even if it's less efficient from a strength-to-weight perspective, but I'm open to being convinced on that point.

12 hours ago, Davidz90 said:

I agree that "exoskeleton" idea is a good one - that is why the two secondary spars on my (rather poor) drawing are close to the top and bottom.

Here's a small render how 40 studs tall H-beam based on 16x16 plates could look like. Central part is 7 layers of plates. Side flanges (red) are bricks, additional small spars (green plates) keep them attached.

Hmm. My gut reaction was that a beam 40 studs tall is crazy overkill, but honestly I have no idea whether it really is or not. Certainly I would trust it not to go anywhere, which is more than I can say about most of the other designs I've thought about. Those 16x16 plates cost about four times as much as a 1x16 Technic beam and certainly provide more strength oriented vertically like that than 4 Technic beams would, although they also weigh more than four times as much, and that beam design would be much harder to connect to the rest of the structure than a more traditional vertically-oriented Technic spar (especially given that the sides of the ship mean that there're going to be a lot of bits coming into this at odd angles). It's something to think about, certainly. Once I've done my 3D modeling I'll have a more accurate sense of how much weight is going to be on these things and how long a span I'll them to be able to bridge.

12 hours ago, Davidz90 said:

Sorry if I'm spamming the topic; I never considered designing something this big, and I'm having a lot of fun doing so  

I'm delighted that this is getting as much attention as it has--there's plenty of room in this thing for multiple minds to work on it, and I need all the advice I can get. Keep it coming!

10 hours ago, amorti said:

My favourite thing about this thread is how no one has simply said "you're clearly mental, it's time to put the bricks down, now".

Don't worry, my family's got that bit covered. But everybody over here is so supportive, it really seems like an even better idea than it did a couple of days ago...

[2GodBDGlory]

53 minutes ago, Kdapt-Preacher said:

Don't worry, my family's got that bit covered. But everybody over here is so supportive, it really seems like an even better idea than it did a couple of days ago...

I suppose it's easier to be supportive when it's not your own garage and life savings at stake... 

[Jurss]

3 hours ago, Kdapt-Preacher said:

Getting stuff directly from LEGO would be fantastic,

There is some chance, that if You really model it in digital, lego could catch up with some support.

But, if lego would be build such a show display thing, they would build it around some steel frame.

[agrof]

This is quite an ambitious idea, so much, that it would attract the world for sure. But what about to solve this just by changing the conditions? 

Problem Nr 1: You Sirs, stick way to much to gravity.

Solution Nr 1: It is a spaceship, right? So build it in space.

To Do: Now You only need convince sponsors like SpaceX and LEGO. What a marketing opportunity for them!

My work as consultant, ends here. 

Edited February 2, 2022 by agrof

[allanp]

18 hours ago, Davidz90 said:

I agree that "exoskeleton" idea is a good one - that is why the two secondary spars on my (rather poor) drawing are close to the top and bottom.

Here's a small render how 40 studs tall H-beam based on 16x16 plates could look like. Central part is 7 layers of plates. Side flanges (red) are bricks, additional small spars (green plates) keep them attached. 

hbeam by David_Z1, on Flickr 

Sorry if I'm spamming the topic; I never considered designing something this big, and I'm having a lot of fun doing so  

Would this not be way stronger rotated 90 degrees, so it's an *l* (bloody font, trying to say *capital letter i beam* beam instead of a H beam? 

[Davidz90]

3 hours ago, allanp said:

Would this not be way stronger rotated 90 degrees, so it's an *l* (bloody font, trying to say *capital letter i beam* beam instead of a H beam? 

Yes, of course this is actually I-beam. Called it H-beam due to the above-mentioned font issue 

9 hours ago, Kdapt-Preacher said:

That's a useful concept. I'm going to make a (non-LEGO) 3D model of the thing so I can plan out where major beams will need to go. My current thought is that the smooth hull sections will be principally supported by beams running perpendicular to the spine of the ship, but I don't know whether that'll really end up making sense or not. I think the two greatest structural challenges here are supporting the strip of detailing in the groove at the edge of the ship where the upper and lower hulls meet (which looks tiny, but is about 20 studs high and 1000 studs long, and will be densely greeblied with small parts, so it'll be heavy) and supporting the engines in the back (there'll have to be a column in the middle of the fantail section, but I think that'll be the greatest concentration of weight overall, and it's the thinnest part of the ship, so there may be limited room for beams).

Thanks for nice feedback! My intuition is that for sides, it would be best to utilize the triangular shape of the ship and use two spars, coming perpendicular from upper/lower parts of the spine (flanges in case of my H-beam) or secondary spars running just under the skin, and meeting at the edge. That would provide a lot more support for the edge strip and also shorter the distance between spars and the skin. Something like this (of course this is only a scale model, and rather rough one):

structure2 by David_Z1, on Flickr

There is one main spar (red), two sub-spars (white) and side spars (blue). Magenta lines are some minor cross-braces.

Edited February 2, 2022 by Davidz90

[Kdapt-Preacher]

9 hours ago, Davidz90 said:

Yes, of course this is actually I-beam. Called it H-beam due to the above-mentioned font issue 

Thanks for nice feedback! My intuition is that for sides, it would be best to utilize the triangular shape of the ship and use two spars, coming perpendicular from upper/lower parts of the spine (flanges in case of my H-beam) or secondary spars running just under the skin, and meeting at the edge. That would provide a lot more support for the edge strip and also shorter the distance between spars and the skin. Something like this (of course this is only a scale model, and rather rough one):

There is one main spar (red), two sub-spars (white) and side spars (blue). Magenta lines are some minor cross-braces.

It's going to have to be something like that, although I think that putting the main structural members at angles to the spine like that would be a lot harder than that concept makes it look. Those diagonal secondary spars are fully twelve feet long, so they're going to need support themselves, and if they're supporting any significant fraction of the weight of the ship there'll be quite lot of force concentrated at those joints.

The vision that I currently have for the cross-section (I don't think I'd go so far as to call it a plan yet, since I haven't really done any of the math) is something like this. Those correspond to vertical columns and main spinal members (the purple squares, in front view) 40 studs thick, and secondary horizontal spars 20 studs thick. Obviously there would have to be structure supporting the bottom hull as well, but I'm omitting that here so you can see the main supports more easily.  Keep in mind that this is the absolute widest part of the ship, and it tapers fast, so by the time we get to the next set of columns six feet or so in front of this it'll already be narrower than the outer two columns in this diagram; the outermost pair of the next two columns will be farther inwards. The whole smooth hull surface consists of a series of separate 80x80 panels, so that'll be supported by a network of small struts that probably won't look exactly like what I've drawn there, but you get the idea. The supports under the cityscape region will depend on exactly what that ends up looking like, but basically the top part of the frame is just going to be a platform that I can sit that on.

[Davidz90]

I see. Yes, with three columns side by side, your concept makes a lot more sense than mine, and definitely has less weird angles. For whatever reason, I assumed that the sides need to be fully self-supporting. 

As for the white secondary spars - indeed the angled connections could be an issue. Again, I guess they could be attached in parallel to the main spar and then bent into submission, but that is not your goal. If we assume that all the side connections come directly from main spar or central columns, then the upper secondary spar could work like cable in suspension bridge - working strictly in tension and keeping main spar straight. In such a case, the angled connection can be even freely rotating without sacrificing any strength and the spar needs no additional supports. The tension could even help holding them straight when supporting some part of the skin weight. 

Edited February 2, 2022 by Davidz90

[Leonardo da Bricki]

In the sketch above, you will almost need to mirror the same structure around the horizontal centerline in order to properly support the underside panels. Another thing that might help, especially with wanting to include the city-scape potion of the ship, would be to have 4 support pillars, especially at the widest part. You could then transition into having 3 pillars as it tapers, and this would also allow the weight to be a bit more evenly distributed across the back of the ship, and help support the engine structure.

[Milan]

You need a steel frame inside. I know that is something you don't want, and it will increase weight, but it will be able to keep it together and in one piece, since the model wont be able to lay flat on the floor
Here is the guy you might wanna talk with: @Angeli

He has built many oversized MOCs, including this 5 meters long Millennium Falcon, with a background story with all the issues and problems regarding logistics, construction and transporting the model.
(He hasn't been active for the last few months, but if you think he may help you, and are unable to contact him, let me know)

 

[Kdapt-Preacher]

6 hours ago, Davidz90 said:

As for the white secondary spars - indeed the angled connections could be an issue. Again, I guess they could be attached in parallel to the main spar and then bent into submission, but that is not your goal. If we assume that all the side connections come directly from main spar or central columns, then the upper secondary spar could work like cable in suspension bridge - working strictly in tension and keeping main spar straight. In such a case, the angled connection can be even freely rotating without sacrificing any strength and the spar needs no additional supports. The tension could even help holding them straight when supporting some part of the skin weight. 

I don't think we actually need any vertical support where the secondary spars are. There shouldn't be any weight running along the dorsal midline of the ship like that forwards of the cityscape section, which will be built on basically just a flat platform (more or less). The only thing there is the line where the two hull plates meet, and the panel construction of those means that they won't be resting on a center spar (like they are in the UCS ISD, for example). I think your suspension bridge analogy is right; the only thing we need from them is to hold up the spine. I have a vision for how that bit could work but I'm not sure I'm articulating it well; I need to actually mock it up.

6 hours ago, Leonardo da Bricki said:

In the sketch above, you will almost need to mirror the same structure around the horizontal centerline in order to properly support the underside panels. Another thing that might help, especially with wanting to include the city-scape potion of the ship, would be to have 4 support pillars, especially at the widest part. You could then transition into having 3 pillars as it tapers, and this would also allow the weight to be a bit more evenly distributed across the back of the ship, and help support the engine structure.

Yeah, I know. There's a lot less going on on the bottom of the ship than there is on top, though, so overall I'm not very worried about that. The smooth hull sections are comparatively very light, only around 1 lb/square ft, which shouldn't be much of a problem from a structural perspective, and if the large horizontal beams are sufficiently sturdy the lower hull panels can basically just hang from them without requiring as much additional support as the upper hull will.

6 hours ago, Milan said:

You need a steel frame inside. I know that is something you don't want, and it will increase weight, but it will be able to keep it together and in one piece, since the model wont be able to lay flat on the floor
Here is the guy you might wanna talk with: @Angeli

He has built many oversized MOCs, including this 5 meters long Millennium Falcon, with a background story with all the issues and problems regarding logistics, construction and transporting the model.
(He hasn't been active for the last few months, but if you think he may help you, and are unable to contact him, let me know)

Ah, I remember seeing that thread a while back when it was posted. I know that a steel frame would make this far more practical, but I'm going to see how far I can get without one. Unquestionably, it would absolutely have to have a steel frame to be transportable, but I'm not setting that as a requirement for the moment. Even if it could be transported, I don't know where you could possibly transport it to; the difference between 5 and 12 meters is pretty significant in terms of the amount of space and time you'd need to get it set up at a convention or something, and you'd need also bring some kind of dedicated viewing platform to even see the top surface anyway. Realistically, ( I mean, for a given definition of 'realistically'...) I can't see any world where this is set up as anything other than a permanent exhibit somewhere.

Edited February 3, 2022 by Kdapt-Preacher

[Kdapt-Preacher]

6 hours ago, Leonardo da Bricki said:

In the sketch above, you will almost need to mirror the same structure around the horizontal centerline in order to properly support the underside panels. Another thing that might help, especially with wanting to include the city-scape potion of the ship, would be to have 4 support pillars, especially at the widest part. You could then transition into having 3 pillars as it tapers, and this would also allow the weight to be a bit more evenly distributed across the back of the ship, and help support the engine structure.

Forgot to respond to the other half of this. Yeah, I'm fully open to increasing the number of pillars and the precise placements of the support beams. It may very well make more sense to have an even number of columns and major beams in the wide area of the ship and only transition to a single central one once it gets down into the narrower part of the bow. I'm hoping that the 3D modeling will help me work out the weight distribution and what the optimal positions will be.

[Jurss]

11 hours ago, Milan said:

You need a steel frame inside. I know that is something you don't want, and it will increase weight,

I'm afraid, that pure (strong) lego build will be much heavier than that thing with steel frame covered with some lego made panels.

[Davidz90]

I strongly believe that this build is possible without steel frame. However, it is funny how the supposedly "overkill" 40 stud beams look absolutely tiny in your cross-section. One thing I'm not too sure about are the purple spars between columns - it is questionable if they help much there (unless columns are attached to them forward/back from this cross-section). As others said, I think that the first thing that needs to be specified is the number and distribution of columns on which the ship rests; the more the better, but that hurts aesthetics. After all, the only span that needs to be bridged is column-column distance. Also, it is an open question if its better to use parallel spars that end as the ship narrows (easier to build) or side spars coming towards center, forming a large triangle to which all columns are attached (stronger in ideal world, where angled connections are not an issue).

[agrof]

I strongly believe, that this build is not possible in this size without a steel frame. Of course one can build it in CAD, but it is like building in space, without gravity. I know, I made such mistakes, when sample production showed that I missed something to consider during the CAD phase. 

In my work we did already some very long steel solutions (transport packaging), and speaking of experience, it was already tough task even by using steel welded frame construction (like bridges), with constant FEA checking.

Sure, this must not stop anyone of trying, and I am really open minded to be proven wrong. Just need to see some real life tests. 

[Davidz90]

Some more engineering ramblings:

Executor_schem_A by David_Z1, on Flickr

Executor_schem_B by David_Z1, on Flickr

In the first one, pillars end on the lower spar and the bottom is parallel to the ground. In the second option, pillars end on the upper spar and the upper surface is parallel to the ground. Again, I couldn't resist putting main spars at an angle, but they are only connected with triangular framework so it should be no issue.

Generally, I agree that some real-life tests are definitely needed. At the very least, it would be very useful to test one full-length main spar. Or even 50% model of the spar, holding at least 25% of projected weight on the full one. 

[allanp]

Another idea might be to take inspiration from how real life ships are built and not build beams, but instead to build boxes. These boxes would fit together like the modular buildings to make something much bigger, but in your case they could also come apart for transport and storage. The boxes would have to be seriously over built with a good way to hold them together. The sides of the boxes would line up to create beam like lengths that run the length and breadth of the model where you need them most. The unseen sides of the box wouldn't have to be completely filled in but could be made rigid with triangular trusses. Each box could also have its own removable stand, so that you're only having to work out how to support each individual box instead of the entire model. This would make transportation and subsequent assembly of the model much easier. If they all have their own stand you're literally just placing them together like a modular town. If you then find that a box can be fully supported by the surrounding boxes you can then remove the stand for that box. It's difficult without complex simulation software, or building and testing for real, to fully comprehend how such a large model will hold up if built for real. But with boxes you only have to worry about each box. This could allow for a fully Lego build without the need for superglue or a steel frame, that could be transported and set up easily....if you have access to a semi truck. The disadvantage is that, if each box is about 1 square foot, you would have several hundred if them, each probably the full height if the model (like chunks in Minecraft). So you couldn't ever make it any smaller. At least with a steel frame, or with brick built beams, it could be dismantled into much smaller piles of detailed panels and brick built beams/steel cross sections.

Another approach you could take is taking inspiration from cable stayed bridges or tower cranes, and extend the support legs up higher than the internal framework and use cables suspended from the top of the support legs to support the middle of long unsupported sections (especially the rear engine area that's probably gonna be over 6 feet of unsupported Lego). Parachord (or whatever it's called) may not be Lego, but it's much lighter, much cheaper, much stronger in tension than Lego and can be rolled up into a ball, it would save a lot of weight and Lego. But a foreseeable disadvantage here is that cranes and bridges are only strong when fully built and their upper faces orientated toward the sky. So you would have to take that into account while building and transporting.

Edited February 3, 2022 by allanp