We've all had builds that tend to fall apart (come loose) after some play time. The best example is a crawler that tumbles downhill and ends up in various pieces. Yet, on several occasions I have done few MOCs (or my own builds) where it was easy to introduce some robustness (more sturdiness) into the build. I intend on making few LXFs to illustrate, but hoping to see some tricks/improvements fellow Lego'ers have come up with.

Well, for starters I always use a liftarm placed perpendicularly from the chassis and lock it in place with some pins to keep the structure from giving out on the sides. This usually prevents the gears from skipping if it is placed near a motor or lots of gears.

I see a lot of AFOLs building motorised models the way* that Lego builds their sets. Generally I don't think that's ideal; Lego's sets are designed to be easy for kids to put together and are mostly not completely motorised. I'll bring up this classic from way back when:

acclime3 by mahjqa, on Flickr

You never see Lego build this way to get drive from the tyres to the fake engine. It just isn't necessary for that application.

* A simplification, obviously.

For a model at that scale, I don't think you need that complexity for getting a rigid build.

One problem is that the more robust the model gets, the heavier it gets. I'm not sure which grows faster with the part count: weight or strength.

To my limited experience, it seems that the robustness is inversely proportional with the "beautifullness" and building experience of a model.

I'm struggling with these three parameters (strength, weight/performance, and style) all the time up to a point when I to give up on Lego, only to realize that even he best/most hyped/legend models have those flaws my models have. Like not fully constrained floating body parts (that you have to adjust carefully), or having a "soft" body, twisting chassis, wheels hitting he whel-arc and hat they can't be picked up without extra care, or that they have very crappy performance if they are strong.

For a model at that scale, I don't think you need that complexity for getting a rigid build.

It really depends how you define need. If it's for a race, maybe you do.

I'm not sure which grows faster with the part count: weight or strength.

But the fun part is trying to find that balance for your particular application. I think we talked about this before: perfection is an impossible but addictive target.

To my limited experience, it seems that the robustness is inversely proportional with the "beautifullness" and building experience of a model.

I disagree about the beauty; one of the things I really enjoy is figuring out an elegant and robust build. For instance, I'm really pleased with the construction of my A-team van and find its structural arrangement eye-pleasing; but maybe that's cause I remember the process of building it.

I'm struggling with these three parameters (strength, weight/performance, and style) all the time up to a point when I to give up on Lego, only to realize that even he best/most hyped/legend models have those flaws my models have.

And we are back to the impossibility of perfection. Good that you don't give up.

Like everthing else, builds are a tradeoff. Simplicity, low weight and good looks usually go at expense of one another. A robust solution may not look very nice, or work very well. A complex solution may be flimsy. The lime car VMLN8R posted had a single priority: it had to work. It was built for a race at a meeting, so it could absolutely NOT be allowed to fail.

So I sacrificed:

- Complexity: I replaced the differential with two 12-tooth gears

- Functionality: no differential usually means that steering won't work as well. Luckily, the race was held on a very slippery floor, so the diff wouldn't have made a difference in that case.

- Looks: I limited the exterior to technic panels and flexible axles. I only used studded elements where they couldn't be knocked off easily, or where it wouldn't matter if they did. Also, I used big bumpers to protect the front wheels. This limited my design options somewhat.

So.... it's all about priorities.

I was talking about my experience. But I'm not a good builder. I'm only good at the looks of a model.

I think 9398/41999's chassis a great official eample of a sturdy build.

And as others said, if you want something fast, reliable and efficient KISS, if you want something complex in order to be complex than its tricky and usually less reliable (example automatic gearboxes with many gears..)

I always have a problem with making truck trailers strong so the don't bend with weight on them, especially the goose neck on a low loader. I am working on one at the moment but struggling with it.

I always have a problem with making truck trailers strong so the don't bend with weight on them, especially the goose neck on a low loader. I am working on one at the moment but struggling with it.

Studded would be proboably better for a trailer, because 2 parallel plated layers of studded bricks are many times more rigid than studless.