LEGO Technic 42108 Mobile Crane [Review]

Did you know that the very first LEGO Technic mobile crane was released more than 40 years ago? The lovely 855 Mobile Crane became the eighth product in the Technic lineup since its start in 1977. Despite its simple design, it had every essential function of a real machine. A handful of mobile (and stationary) cranes have been released since then. The year 2020 brings yet another one, 42108 Mobile Crane. During the previous decade, the variety of LEGO Technic pieces have evolved a lot, and multiple new mechanisms have been introduced, too. The question is, how many of those new concepts are implemented in the latest set and how different is it from the previous versions of mobile cranes? Let’s build and test this 1,292-piece set, which retails at US $99.99 | CAN $139.99 | UK £89.99, and find out if it is worth a purchase.

The box and the packaging

The current style of LEGO Technic boxes is quite fresh and attractive. I’ve heard both young and adult fans speak well for the designs; however, the image on the front of the box seems to be a bit cramped. I would prefer it to have more space around the model.

Numbered bags inside contain the pieces divided into 3 building stages. Although the model consists of more than 1,200 parts, each assembling stage feels like building a medium-sized LEGO Technic set.

A hefty building guide and a shiny sticker sheet are here, too. The stickers look quite generic; it feels like I have seen them in other sets before, but obviously, they are brand new and unique for the set.

The build

The set has no particularly exciting pieces, so we start assembling right away. The model is divided into three equally engaging building stages. The first one is done as soon as you finish the chassis. Here you can spot the all-wheel steering mechanism, which is one of the main play features of the model. Actually, the mechanism is much simpler than one might expect, but it involves a bit of repetitive building. The steering is symmetrical, meaning the first and the fourth, and the second and the third axles have the same turning angle, respectively. If you want to modify this chassis, make sure to examine that of 8421 Mobile Crane set; only three of its axles can steer, but it also has a differential.

After the second building stage, the crane only lacks the boom, the operator’s cab, and some panels to finish the model’s exterior. At this point, it becomes clear that the design of the chassis is very lacking.

Because of the model’s scale, the inner frames are so narrow and simple that a lot of parts are exposed. However, criticizing the set for its basic design would be wrong. During the assembling, it becomes absolutely clear that this is an entry-level model that is perfect for someone without any experience of building with LEGO Technic pieces. On the bright side, the new mobile crane comes with the new extra-long linear actuator. As of today, 42100 Liebherr R 9800 Excavator set is the only other LEGO product you can get the new actuators from.

It takes about 2-4 hours to finish the model. No doubt, the last stage is the most engaging as it includes the assembling of the boom and involves a handful of gears and a string.

The complete model

Before putting the new mobile crane to the test, we suggest taking a look at its exterior. Design-wise, the new mobile crane is a perfectly balanced combination of different types of Technic elements. Smaller panels efficiently hide everything that can spoil the models exterior, while neatly shaping the boom and the area behind the operator’s cabin. The use of the panels is very clever, and it’s the strongest feature of the model’s design.

The crane owes its fresh and neat look to the panels, but it’s exterior isn’t flawless. Under certain angles, it’s very hard to ignore the chassis’ oversimplified look. However, since this not what a Technic beginner builder will hunt for — and the set is an excellent choice for anyone starting their Technic collection.


The mobile crane as a toy concept is an amazingly playable thing. It combines so many children’s favorite play features that it is almost impossible to play the wrong card releasing such a building set. Almost. Any child will be let down if anything doesn’t work right! Let’s put the model to the test and see whether it is up to the mark.

Driving the model around is pure pleasure. Unlike many other LEGO Technic sets, this mobile crane has no steering gear in the back; instead, you can easily steer the wheels using any of the signal lights mounted on the driver’s cabin — just like the steering systems of the sets from the 1980s and 1990s. Smooth steering is always excellent, but it is never the most anticipated play feature of a mobile crane. Once the crane is finally on the site, it’s time to start operating it. First, you activate the outriggers. And — oops! — all four outriggers are entirely independent. We won’t call it a surprise since we’ve just built the model, and we are aware that no extension mechanisms are running through the chassis.

But here is what actually makes things looking sad: while the rear outriggers can be activated by turning gears, it’s amazingly hard to pull out the front ones since there are no gears, handles, or hooks. Actually, there is one red pin with a joint ball inserted into each leg, but because of how tiny the pieces are, only kids will find it useful and playable.

There is a bunch of ways to build outriggers with LEGO Technic elements and also lock them securely when activated. However, the biggest issue of this model’s mechanism is how terribly unreliable it is. These outriggers are so flimsy and unsteady that they pop back into the chassis randomly during regular play.

Criticizing any part of my favorite hobby always makes me sad at heart, but another test reveals more flaws in terms of the set’s playability. Because of the model’s very modest size and weight, its lifting capacity leaves a lot to be desired. What is more ridiculous, the model carries a wonderfully designed extending boom, but it’s simply too heavy for the chassis; at certain angles, it can easily tip over the whole vehicle. This is when you discover that the outriggers are merely decorative, while the buildable pillar included in the set is the only cargo suitable for the mobile crane.

It didn’t take us long to realize that we got a toy with very arguable playability and limited functions. This is absolutely not what we expect from a medium-priced product. Some will say that you can easily upgrade the model using your own pieces and turn it into a capable construction machine, but is it really what we expect from a LEGO toy?

Final thoughts and recommendations

You don’t have to be a keen LEGO enthusiast to notice that every LEGO product eventually finds its audience. Although the new LEGO Technic 42108 Mobile Crane is definitely not the most playable toy of this year’s lineup, it doesn’t make it an entirely terrible product. As was mentioned above, this model will be a solid choice for any LEGO Technic beginner and is also full of excellent Technic elements. And even if young builders will be disappointed with the new model, at least they will learn how not to engineer mobile cranes.

LEGO Technic 42108 Mobile Crane comes with 1,292 pieces and is available for US $99.99 | CAN $139.99 | UK £89.99 as well as some third parties on Amazon, Bricklink and eBay.

The LEGO Group sent The Brothers Brick an early copy of this set for review. Providing TBB with products for review guarantees neither coverage nor positive reviews.