The Big Blue – 42042 Crawler Crane Set Review

Most of The Lego Car Blog team are die-hard petrol heads, who exclusively build Technic supercars, filled with working features and Power Functions. However, this writer is not really a car expert nor a Technic expert either. I was recently defenestrated at a TLCB party for having suggested that it might be fun to try to build a spaceship. Fortunately, I survived the incident. The TLCB executive penthouse offices are actually located on the ground floor of a small industrial unit near Wolverhampton. Much chastened, I have resolved to learn more of the art and craft of big-scale, motorised Technic models. What better way to do this than to build one of the monsters of the current Technic range: the 42042 Crawler Crane.

Lego Technic 42042 Review

The set came in nicely large box, with the usual high-quality photos showing the various functions of the crane. The back of the box shows the “A” and “B” models. In contrast to Sariel’s review, I thought that the box was nicely full when I opened it. Tipping the various bags out of the box took me back to childhood Christmases and the excitement of opening the old Technic sets with their studded beams. The first thing that struck me was that the various bags were numbered, just like big System models are nowadays. As I built the model, it was great that I only had one bag open at a time. This made finding the right parts quicker, less frustrating and more fun. A previous big Technic model that I have built had numbered bags but you had to open most of them early in the build, which defeated the point of them in my eyes.

The instruction book is neatly presented and strongly bound. It’s a nice artefact in its own right. Lego instruction books are a lot better at differentiating between dark grey and black than they used to be and this one was easy to use. Disappointingly, for a model in this price range, you have download the instructions for the “B” model from Lego’s website. As the “B” model looks to have the same chassis, there wouldn’t even be the expense of an entire second book. The stickers for the model are in the same bag, which had kept them flat in my case. However, I can see that there’s scope for them to be creased and mangled by the heavy instruction book and so it would be better if they were mounted on a separate card.


Once I started the build, it turned out that there were actually multiple bags to open for each stage of the build. It was still a lot quicker than sorting through all 1,401 parts in a big pile. First up is the chassis, based around the ubiquitous but strong 64178 differential frame. Building progresses rapidly, with lots of pieces per page. This contrasts noticeably to System sets, especially the ones aimed at younger builders. For most of the stages, I had just five small piles of parts to look through, thanks again to the numbered bags.  After the main chassis, you build each of the sponsons for the tracks. When the two are mated, you begin to realise quite how big this model is going to be. Building the second sponson is a bit boring, as it’s a mirror image of the first but that’s inevitable with this design. When I attached the sponsons, I thought that 5L axles with end stops will be awkward to remove when I disassemble the model. I couldn’t work out why Lego hadn’t used ordinary 5L axles instead. Perhaps one of our Technic expert readers has an idea? Page 48 of the instructions has another step that might prove hard to reverse on disassembly.

By page 54, the chassis was done and it was time to get a coffee and then sit down to assemble each of the huge, 45 link tracks. Whilst I clicked the links together, I reflected on the size and complexity of the finished chassis. It reminded me that much of what you pay for in a Technic set is the immense amount of R&D time that must go into a model like this. To speed up the assembly of the tracks, I made standard 10 link lengths and then clipped them together, adding the last five.  Strangely, for a set of this size and price, there is no spare link of track. Technic is a harsh mistress. Be careful opening the bags of parts and accidentally losing some. By the end of stage one, I had just five spare pieces and no spares of the small cogs or blue, 2L axle/peg connectors. By the end of the build, I had just over a dozen spares, including the 1×1 round transparent plates used as lights.

Stage 2 looks fast, with just three bags of parts. It builds the gearbox and includes four of the newer sliding gear change collars and a pair of the white, 24T, torque limiting clutch gears. There are also some of the new and very useful 1L collars. Once more, the complexity of the design reminded me of how much design and development time you’re paying for in a big Technic set. This also applies to the design and quality of the individual pieces. Just one L motor drives the all of the functions through this gearbox. That two functions can operate simultaneously, is a testament to the power of modern Lego motors. The end of this stage leaves very few spare parts again. I was actually a blue 2L connector peg short and had to nip upstairs and get one from my collection.

LEGO 42042 Review

By now I was 96 pages and 1 ¾ hours into the build. There were four more bags of parts left to go. From now on, you add parts and modules to the main model, so it’s a good idea to position it so that you can get to all of its sides. Unless the drive is engaged, the superstructure can rotate freely on its turntable, so the process is fairly easy.  The instructions took me through building the two “H” selectors for the gearbox next. Make sure that the two gear sticks are in neutral (along with the sliding clutches in the gearbox) and then the whole thing neatly hinges closed. The base of the crane’s boom attaches by page 142. This is done by pushing a 7L axle through both it and a frame on the superstructure. I found it rather fiddly to line everything up. This will be another thing that will be awkward to remove during disassembly. I’d recommend using an even longer axle for the job.

Stage 4 and I was 3 hours in and on page 153 of the instructions. The numbered bags felt a bit pointless for this stage. Once they were all open, I was left with six large piles to search through for each piece. They also took up a lot of space on my kitchen table, which was rapidly filling up with a monster of a Lego machine! As I worked my way through the trusses, I was reminded of reading Professor J E Gordon’s classic, “Structures, or Why Things Don’t Fall Down”. This book has excellent chapters on the basics of trusses, bridges, chariot wheels and birds pulling worms from the ground and is well worth a read if you’re planning your own large-scale Technic structures. I was also surprised as to how many right-angled triangles you can make with Technic lift arms and fell to thinking of Pythagorean triples. Keeping these ratios at the back your mind must let you build strong triangular Lego structures quickly and easily. Eh? What? Oh, right. Back to 42042!

Lego Technic Crane Review

Attaching the strings requires some care and attention. Each colour-coded coil has to attach to the correct winch. It also has to be knotted correctly, so that the knot doesn’t foul the mechanisms. The string is a far superior product to that which came with the likes of the 8854 Power Crane of my youth. It feels stronger, thicker and less prone to twisting and tangling. This part of the instruction book has been very well designed. There are lots of red highlights to make sure that everything ends up in the right place.  The last thing to build is the rather neat grab. This is very similar to the one on 42006, using a small linear actuator to move four grabbing “fingers”. After four hours of building, it was time dig out six AA batteries and take the crane for a spin!

This is the sort of Lego set that I would have wanted as a kid. It’s also like the classic large Meccano sets of my father’s generation. It’s big, with a 60 cm boom and it’s motorised too. The crane trundles along quite quickly for a model which weighs around 1.5kg and is powered by a single Power Functions L motor. It’s a bit disappointing that it doesn’t steer but you can select forwards or reverse on the gearbox. Adding steering would have obviously added complexity and price to the model. Check out YouTube for various steerable modifications.  The lack of steering means that there’s only one axle running through the middle of the main turntable. This means that your crane can drive along, with its superstructure infinitely rotating (well at least until the batteries go flat or you run out floor space!). The boom raises and lowers quite quickly. The only time the motor seems to struggle is when the boom is horizontal with the extra section added. The winch works well and quickly too, as does the hand operated grab. The gear/control sticks are easy to access and use, making the whole thing great fun to play with.


I like the change from Lego’s yellow machines. I think that the model looks good, even without using the stickers, of which I’m not a fan. The white line around the superstructure is a neat touch and the battery box on the back could be a big radiator of some kind. It’s also easy to remove to recharge the batteries. Yes, if this was a MOC it would have better detailing and the exhaust pipe would actually be connected to something. However, Lego have to bring the set in a price point and so it’s inevitable that compromises will have been made.  As somebody who isn’t a Technic specialist, I bought this as an educational resource and also as a parts pack. Mine came at 25% off from I was also attracted to the unusual blue Technic parts, which hopefully will prove useful in MOCs. If you’re a mainstream Technic builder, then yellow seems to be the way ahead and the model might be less attractive as a parts pack to boost you collection.

My overall verdict is that in terms of the number of parts, the mechanical design, the looks and the shear playable fun this set is well worth the money. I think that this is a worthy addition to the long line of Lego cranes. You can judge for yourself by reading this historical review by one of our Technic experts. 42042 doesn’t have the glamour of the Unimogs, supercars and lorries in the Technic range and so it will probably be fairly easy to find at a discount somewhere. Go on, dive into the big blue and treat yourself!

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