Bartybum

Lego's aversion to backhoes is one of the seven ancient wonders of the world at this point lmao, it's something to be studied

So I've been looking at alternatives to the standard four-panel boom, namely because a single segment costs like $15-20AUD and I think I've come up with something that could work. I'd be interested if anyone could build a couple and test how rigid it is. Overall I'm pretty happy about it, but man would things be so much easier if only we had 3L and 5L liftarms with friction pins sticking out at either end, in the same manner as part 15100. I think CaDA has them in fact. The clutch strength of the 15100 pin connector can be annoying, but it's perfect for this application to stop the chords from getting pulled out. A round 3L connector would simplify things a great deal here too. Moving on, however, the first challenge I've tried to address is torsional rigidity. I've done so with the help of the trusty 5x7 frame and a double-pinned connection to the chords (the long straight segments). What this achieves is that it rigidly fixes the chords to the 5x7 frames, so that there's no local rotation of the connection. I've explored both orientations of the 5x7 frame, both shown below. I'm only confident in the horizontally oriented one, namely due to its neat connection to the chords. Having the frame oriented vertically is possible, but the arrangement of parts is messier in comparison. The second challenge has been to maintain a similar aesthetic to the real crane's truss segments, at least from the side where the appearance is most visible. This means having crossbeams only at either end of each segment, with diagonal braces running down the side. Because of there only being one Pythagorean triple aesthetically practical for this 7-stud deep truss - (6,8,10), or a 7L*9L*11L liftarm triangle - the length of the truss segment has approximately doubled to 33L vs the original's 15L. This has actually worked out nicely, since it better matches the proportions of the segments in the real thing. Since there's obviously no 33L liftarm in the Technic parts catalog, so I've split the chords up into three parts, in this case 7+15+11, with 5L liftarms connecting each part. I'm slightly worried the 5L connection may be too short, so if anyone builds this I'd also be interested to see how rigid it is with 7L instead. It'd be interesting as well to see how the flexibility of the black 2L pins affects the axial stiffness of the chords, and to what extent it increases bending of the overall truss. Final weight comes out to be ~110g, versus 93g for two of the original four-panel truss segments, so about a 20% increase in mass. Something I'm a bit apprehensive about is the rigidity against lateral skewing, especially since I've forgone any diagonal braces along the top and bottom surfaces. In any case, pictures !! The first is with horizontally oriented 5x7 frames, and its connection to adjacent segments: Second is the vertically oriented 5x7 frame: Would be very interested in any feedback :)

Sounds quite complex but I think I follow. Crazy how there's much more to consider than you think at first glance.

I'm quite surprised that you actually need it to be honest, I would've thought the forward weight of the booms should be enough to keep it taught. Do you have any feedback system in place to make sure the LA and winch don't go out of sync? I noticed that in the second video the winch appears to go slack for just a second.

Mmm yeah you might be right there. There don't seem to be any polished shafts like you'd expect from hydraulic cylinders. They might just be locking struts during construction, which are then released during operation.

Oh dude that's so cool, great job I wonder if it's possible to do this in the PU environment? Could you explain why the derrick boom uses both linear actuators AND a cable to change its angle here? I would've thought the cable should be enough. Including linear actuators seems to make it redundant. In the real crane, are the linear actuators used as hydraulic cylinders to move/lock the derrick in place, or are they just dampers?

I think you're correct there, these new panels definitely look cleaner than pure liftarm lattices. Yeah testing it just now in front of me, the blue pins definitely loosen a millimetre or so, but the black pins stay put. You're also correct about the rigidity of it all - this truss is stiff as hell. That reminds me of another thing I noticed about the design. You only need to load up the hook to approximately half capacity on the C+ profile before the slew bearing and the superstructure begin to bend over. A shifting counterweight would've been a really cool feature to try implement. God there's a lot of things about this set that open it up to a pimp-my MOD. I'd be so tempted to try something if not for the fact that I bought this set at a bargain only to resell at a higher price lol

That's actually a good point, I hadn't considered the idea of it being adjustable, at least visually. You can of course just fill water to a lower level with the aid of visual markers on the bottle, but you'd still be left with a potentially oversized counterweight for your MOC. Perhaps you could just have more bottles? Although, the problem here could be that you start running into size constraints. While pieces coming loose from twisting is another fair point, this set is at a common size for crawler crane MOCs, most of which would appear to get away just fine with regular liftarms (just check out VirtualMakerLuca's LR11000 moc below: I imagine pin lift-out should be mostly mitigated with diagonal crossbeams. On a side note, I wonder if a truss is possible using just flip-flop beams for the longitudinal beams, with normal liftarms for the diagonal crossbeams. It's also worth pointing out that the friction pins, even on this set's truss, can become dislodged with a bit of twisting. There's only three pins per frame connection, and nothing at all to stop the frame from expanding horizontally. It would add more pieces, but that's only really an issue for weight and therefore playtime (perhaps that was a problem they ran into?). I don't imagine cost would be an issue here, given how low cost and optimized liftarms and pins are for Technic.

So I just copped this absolute monster secondhand for a 50% discount, and my god I'm impressed. There's definitely a different feeling you get between criticizing a set online, and then seeing and operating it in person. That being said, wouldn't have paid full RRP for this. $1050AUD is unreasonable. Something I noticed during construction, slightly to my disappointment, was that unlike the Arocs, BWE or MkII mobile crane, this set's construction didn't really feel modular like I had hoped, especially the undercarriage. I was expecting to first build the core in its entirety, then each track, then combine the two with a marriage of completed subassemblies. Instead it all sort of just melds together into a single amorphous assembly with a huge mishmash splattering of yellow and DBG colours. I feel like this set would have benefited from a highly modular construction for transport, especially since it's enormous (its side profile literally occupies an entire square metre, if not more). Imagine building it like the real thing! Another pretty interesting thing was how crazy fast the structures come together when you build them with giant frames. Those 3x19 frames are nuts, and there's a stupidly high amount of them in this set. Something about the play that I'm not a fan of is how limited the range of motion for the arm is. You can't lay out the boom and jib (with the default C+ profile) on the floor like you do during the construction of a real crawler crane. This would've been a nice addition to the building process, and would've improved the authenticity of it. The weights also feel like an odd choice. I wonder if they had considered designing aesthetic hollow boxes to fill with special moulded water bottles. Besides, everyone who has this set has access to running water, so why not just do that? It'd use MUCH less plastic. I also wonder how necessary the new lattice frames were. Could this not be built more economically with liftarms and a large amount of friction pins? Perhaps it would've been too heavy, who knows. Something that I did like about the lattice frames though, was how excitingly fast the boom came together because of them. Last thing of note is how malformed the proportions are. Even ignoring the inaccurate boom configuration (which I'm happy to forgive), the top jib supports feel quite aesthetically sloppy, and the proportions of the superstructure and undercarriage don't accurately portray just how enormous the real crane is. It's especially obvious how narrow and top heavy the undercarriage looks - I think it could've used two or three extra studs in either direction, and sprockets the next size down. All that being said, quite an impressive accomplishment of the designer. The set works pretty flawlessly - does what it says on the box.

Oh my god I've always seen the thumbnail to this video but never got around to actually watching it. That's incredible. Probably helps that it uses higher voltage electronics :P

Possibly worth testing. The momentum theory calculations to get initial power estimates vs rotational speed shouldn't be particularly challenging here. Some potential practical challenges: Low aspect ratio of the sail will lead to aerodynamic losses compared to a blade with high aspect ratio, will increase the required flight power. You can somewhat offset this by mounting the blades further out to increase the effective span, as long as you replace the inboard span Flutter at high rotational speeds due to the thinness of the blade may cause resonance issues. You can tune this with tip weights to minimize torsion The rigid leading edge will introduce aerodynamic penalties due to turbulent flow. You can somewhat mitigate this if it's on the underside of the blade (the pressure side) Rotors are inherently unstable so you'll either need a swashplate with active control, or the whole rotor needs to be mounted on a gimbal. Depending on the system loads, this may be infeasible with Lego ball joints (which have a high amount of slack)

Hehehe this is awesome, very cute build

Am I going insane or is there some technical reason two motors wouldn't work? The dumb hub has two ports, after all

People will only complain about wanting RC if the gearbox version isn't done well. Here, as you correctly point out, it isn't done well.

More kinetic sculptures would be cool. Imagine a clock powered by gravity that you can hang on the wall, or something like this that you can tune to be accurate:

Oh shoot nvm I'm totally wrong about the bevel gear profiles, all good !!

I never understood this. The bevel gears already have involute profiles running down the centreline, so they can be readily used as spur gears. The bevel profiles are only on the side.

Hahahah we have very different taste in sets I see

Markus Kossman is the GOAT. Absolute bangers - 8275, 8288, 42009, 40243, 42055, 42100, etc etc

I could imagine a solution for inline engines with one-stud piston spacing like here, but not for V-type and opposed engines

Shorter suspension links make for shorter vehicles, pretty much

Omg my prayers have been answered Compact live axles here we go !!

Dear lord yes!!! And this part with no friction:We do have it with cross-axles but they don't have any clutch power

Considering the small scale and some of the absolute goofball sets we've gotten in the past, I think the proportions here are alright. I reckon the cab height problem can be solved pretty easily by replacing some of the yellow pieces with black ones to bring the black colour lower, see quick and dirty edit below: The only other thing would be having a new tyre mould for the 30.4x20 rims, rather than what they went with here. Alternatively, you could swap the yellow wheels for black ones, and add some sort of 4-stud diameter yellow hub assembly to make the rims look smaller.

Sweet heavens I remember being absolutely in love with the complexity of the Concorde build, it's probably my favourite Lego building experience ever. It's got the entire suite of construction techniques - Technic, small bricks for SNOT, large City clamshells, long beams, tiles, C-clips. It's got everything. Having watched Balazs' review of the Shuttle Carrier, it looks like it's gonna be even more interesting than the Concorde, even if the final thing's aesthetics look a bit dated. The only thing that's probably not gonna be as enjoyable is the Shuttle, it looks like a kinda boring and basic build