gyenesvi

Hi Eurobricks! Let me present one of my models built for the 2025 Buwizz camp, this one is for Ultimate off-road category. This is a descendant of last year's Blue Bird Ultra4 Buggy, aimed at making it more competitive. Well, I did not score a good place with this one either, but I thought I make a writeup about it before dismantling. The model turned out to have a couple of tricky flaws that are worth sharing, so this will be more of a problem analysis than a success story. The problems I identified with last year's model was the front axle being overly complex and a bit weak and the steering being very unprecise. Having caster on the front axle required routing the steering shaft through CV joints, which introduced a lot of lag to the system, becoming somewhat slowly responding and giving me a hard time driving through obstacles. Hence, I decided to change that on the successor. On the other hand, the rear suspension and the drivetrain held up pretty well, so I decided to keep that. Furthermore, I decided to keep the body as simple and light as possible, and I think I managed that quite well :) For the front suspension, I decided to simplify and ditch the positive caster, I don't feel that it would add much to the controllability anyways. This allowed me to drive the steering rack directly. Also, to maximize steering response, I decided to use a double steering rack with tensioned links with the racks placed one stud further from the axle center. Furthermore, I used shorter springs placed on the top to avoid complications resulting from the long spring going through the top A-arm and weakening the construction. Here is the new front axle. As neat the construction may look, unfortunately it is not as bullet proof as I though it would be. It has the following problems: Since the A-arms are necessarily built from thin liftarms (6 and 7L), those can slide apart much more easily that thick liftarms could, even though I tried to pin them together as much as I could. The reason why it needs to be built from these thin ones is because the 6L thick liftarm does not exist, and also the top and bottom arms need to be connected to be stable, taking up space. So anyone trying to convince me that the 6L liftarm not being produced is not a real problem because the thin version exists will never succeed.. The other problem is caused by the planetary hub's (2L) steering link mounts, and this one is nasty. It's more often in the way than it is useful, I really don't like its design, should have been like the Audi hub. For one, that is what's not allowing the connecting thin liftarm between the top and bottom A-arms to be shifter outwards 1 stud, and ultimately allowing 7L liftarms to be used in the A-arm. But it has an even more nasty problem that I did not foresee. When the suspension articulates a lot (and this one does, especially on high bumps and jumps), that part that sticks out can hit the steering link and pop it out. And that happened during the race after a big jump. So the conclusion is that it's hard to build a really strong suspension even if it's the good old double wishbone one. The rest of the chassis was similar to that of the blue buggy. This time I put the 4 motors to the back as much as possible, with the trailing arms going around it. First I though I would put the Buwizz units to the sides and put one seat in the middle, but I decided that I wanted a light weight look with open sides, and there was plenty of space in the back for the Buwizzes; this allowed to full seats. I managed to make some nice triangulated support around the seats into the floor paneling that made the structure solid with minimal parts. However, putting all the electronics to the back may have contributed to other problems, as there was more weight resting on the rear suspension / drivetrain. For one, the 12T gears did start skipping more often than in last year's buggy. More problematically, the extra weight on the back made the rear suspension become a bit too soft, sitting a bit low, resulting in less ground clearance and more rocks being hit. But the real big problem, that turned out after the race, during filming a video, was that the weight is probably too much for the trailing arms, and while bashing the model hard, turning around at high speeds and occasionally hitting rocks as well, I managed to break both of the rear trailing arms (11L flip-flop beams, not at the same time) right under the point where the spring is connected. So I think this suspension should only be used if there's less weight resting on it, or it needs to be beefed up, with different mounting points for the springs. Anyways, here's a video that I've recorded. Unfortunately, I had to record with a camera without image stabilization, so it came out somewhat shaky, but maybe it resonates with the general mood of the bumpy roads it is driving on :) It does drive pretty well though, with the suspension working a lot, and it is fun to play with, but at some points I really felt this speed is too much for the plastic. For example sharp cornering at high speed on this kind of surface can put a lot of stress on the parts.. The rest of the design, the bodywork is as simple as I could get it, I am actually happy with my first use of flex axles along with some tubular structures, they complement each other nicely. I like the overall character of the buggy, despite it's flaws, and its performance is certainly great when it holds up :) Here are more photos and renders of it. More pictures are available on Bricksafe. The Studio model is available for free on Rebrickable, due to all the shortcomings I did not make instructions. Let me know what you think! Best, Viktor

Indeed! Looks like a mini version :) There has been a few nice Bronco MOCs in the past years, not just mine, and I've been wondering whether this set is a response to them by Lego. If yes, I'm glad :)

Only the best is good enough :) Build for real! But seriously, I wouldn't be surprised if this was a way to clear out the dumb battery boxes. Also, Lego has already done an independently motorized one, and a motorized one with parallel gearboxes, so this way of motorizing was the only one not done yet (maybe for a reason). Plus @Unbrickme was asking for distribution gearboxes all the time, it may all be because of him (just joking) and now he's the first one to ditch it all, lol.. Anyway, I like the new triangular panels, totally worth the price

Not sure why people are drawing big conclusions about next year based on the first few leaks.. probably just initial wave, which is typically smaller sets..

Cool! Which might not be a problem according to the first video reviewer..

Looks really good, can't wait to go an buy it at the weekend :) The chassis does not seem to be too tight in the back, so I am wondering if a more proper 2-link rear suspension with a ball joint would be possible at this scale. Only thing I see against it is that the HoG steering from the spare tire would have to be routed differently. Also, I'm curious if it would be possible to make this AWD with a front live axle instead of the independent suspension (which I know would not be realistic in this case, just for the exercise).

Really nice design and explanation!

That's really cute, and must be a nice construction on the inside!

I missed that in 42176 as well. Is that part of the controller interface in the phone app? So basically it's just a bit slower by default, and this turbo charge turns it to max speed that the hub can do?

This is beautiful, huge, and functional! I especially love the way the cab is shaped. What are those parts used for the bumper?

Oh, I see now, I thought there would be more space.

I asked @ZENE about this on their website, whether it's possible to buy, but never got any response.. So looking forward to the response, bro.. Also, the video at 1:40 shows a motor that has a square front face with pinholes that is different from the one on the website. Is a new revision of the housing available?

Looks great and it's amazingly function packed! But I'm also missing some 'ends' at the bottom of the outriggers. Maybe some 1x1 technic bricks upside down on both sides of the 5L beam, connected by a 1x3 tile?

Does anyone understand what she's saying about the RPM differences at 2:30? Where does the difference come from?

Just look at all the technic MOCs people are doing. How many vans do you see? Simple as that. Same goes for cars in general. Tons of MOCs are cars. The distribution of MOCs is all the market research TLG needs. So the problem is not that there are too many cars. Rather the features those cars have. I wish TLG would look more into the features of MOCs people are trying to build but are struggling with because there aren't good enough solutions for. The new shorter suspension parts are a good step in this direction, because many people have been trying to build smaller cars with AWD and front suspension. I hope this trend of improving drivetrain and suspension components, especially at smaller scales continues. In general a trend I see is that a large majority of car MOCs is RC, many at smaller scales than official RC sets, but with the current electronics components it is notoriously complicated to build smaller RC cars, even though better electronics components would technically be possible.

@R0Sch I believe this piece cannot accept a bar in its pin (at least other colors cannot).

I also noticed such behavior in some models, but my assumption was that it has to do with a combination of low weight on the back / too stiff springs / too much power / lack of low speed control. Curious how your final model will behave in this respect!

Well, we mostly lower the current limits, not increase it, to prevent shutdown of the buwizz unit. But it seems your problem is not that it would shut down, so until that happens, it's okay to increase it I guess.. Just test it properly (like try to sprint uphill suddenly) because if it starts shutting down during race, that's not going to be a pleasant surprise :) Nice progress otherwise with link geometry, I always wondered whether going so far with those details like squat line actually matters in case of lego models. My gut feeling is that it only matters with more power/speed than typical lego motors provide, but at two Buwizz motors' power and smooth suspension flex, it can start to matter.

I can agree 100% ! I think link geometry is difficult on its own, and then the stud system of lego imposes constraints on that because you can't have any link length, just full stud lengths, and on top of that we are stuck with only a couple of actual lengths that exist (though the max length of 9 does not help too much at this large scale). By the way, I found that there are 3 link setups that can work well in lego: parallel links: as they can work with the same link lengths, and don't introduce caster problems. However, in this case you need panhard rods for sideways stabilization, so this is only applicable for trucks and cars with a front/end, so not good for buggies, for them you need triangulation. semi-triangulated links: in which case the lower links are parallel and the upper ones are triangulated. In this case, the lower links are best to be constrained at the chassis end to move only a bit sideways (no ball joints, only pins/axles). This works well with long custom links built from liftarms, as any length can be made, and also this one allows springs to be attached to the links. This setup is actually used in real buggies, including the constrained sideways rotation of the lower links. double-triangulated links: the lower links are triangulated outwards from the chassis, while the upper ones are triangulated inwards. In this case it works with links of equal length, because the outward and inward triangulation can be made equal, and that makes the link shortening the same on the upper and lower, so the geometry can play out nicely without creating caster problems. Also, if you set this up well (links not too steep), then you can get away without making complex mounting points to the springs that allow them to rotate around two axles, which in itself can be a complicated thing to do solidly if there's not much space / point to mount to at the axle end for example. Lego could improve sooo much in this area with more parts, like longer links and more ball pins/ball socket parts.. Yes, you got that right. It only has to slide 1 stud out of the 3L CV joint to let this happen, which is not that much.

Nice that you look up real world suspension geometry, I did also dig a lot in this topic! I agree that GC is enough and turning the motors side-ways is a good idea for extra speed and also to lower COG, that is more important. As for rear caster, I think it's only relevant for the incoming CV joint's angle, as @lmdesigner42 says, but I think this should actually be taken seriously. The problem that can easily happen if your caster is negative (or moves to negative during articulation) at the rear is that the CV joint is pulled apart and its operating angle increases, and the sliding CV joint can actually easily slide apart completely. I think there's an unavoidable design flaw at that part, that if the gap between the two sliding parts increases big enough (one stud), then the axle piece from the non-sliding end can slide out, into the non-sliding end, and then fall out. For me this typically happens when the angle and the distance between the two pieces increases during articulation (allowing which is ironically its main purpose), so I find that the only way to minimize the chances of happening is to decrease the gap/angle between the two, which can be achieved by slight positive caster. The front is more complicated, because the same trick at the front would lead to negative caster, which then is not so good for the steering geometry. So I find that the best we can do is to keep the caster around neutral at the front. Also, for crawlers, positive caster is not needed to improve handling; that's only useful for faster cars I think. As I hinted already, another thing to consider about link geometry is how the caster changes during articulation, not only how it is in resting state. At least, equal length links help achieve keeping the caster the same when they are parallel.

Nice looking so far, I like the small improvements here-and-there over the official model's bodywork due to new parts since then, and also the many improvements in the chassis. I understand the goal of a WIP topic, but why open 8 topics of 8 unfinished (and somewhat similar) models at the same time? Moreover, why make a detailed video of an unfinished car? Would be more productive to finish some first I guess..

Just what I thought.. but I'd be inclined to think that the recolor request came from Nike, to make these parts blend in more..

I agree, that's the setup I want to experiment more with for the front. I've used it for the rear on my Toyota Hilux truggy, and it worked well.

Can you please post these recent sets in the General parts thread instead of here, as they don't have much to do with all the parts listed in this thread, neither do they list parts that we'd wish for. Thanks!

Thanks, glad you like it! Originally I built it with the 12/28 differential, because I was cautious with speed, that was my first build with Buwizz motors. But I realized it is too slow and it can take more and changed the diff to 20/28 in the final one. That's an option indeed, though I have doubts that a Buwizz 2 can power two buggy motors in a stable way, even a Buwizz 3 shuts down quite a easily in case of faster offroad models if the current limits are not set. Are you planning to use the Buwizz app to control it? Sure, go ahead and use it! The suspension articulation did make up for a lot of it, actually that is why I left it open to see how it works, but for a race I'd just go with locked diffs. Practically all (non-lego) offroad RC cars use locked diffs.. Well it's a useful technique if you want a ton of articulation, especially if you have shorter hard springs only. Mounted around the middle of the link, it effectively doubles the movement of the end of the link. Whether you need that much also depends whether the axles will have space for all that articulation, because if something else will limit them sooner, then it's not required so much. I think I'll keep using this more for the rear axle, but I am also experimenting with more traditional setups for the front. Thanks, that was one of the main goals of the model!