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Review: 42131 Cat D11 Bulldozer

Posted by Huw, 25 Sep 2021 15:30

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42131 Caterpillar D11 Bulldozer is this year’s flagship Technic model and the most expensive Technic set ever. It’s also the first of the US plant manufacturer’s vehicles that LEGO has produced.

With a price of £420/$450, over 3,800 pieces and four motors, it should therefore be something special…

The prototype

The Cat D11 is the largest and most powerful bulldozer in the company’s range. The current version, the D11T, which was introduced during 2008, is also among the most technologically advanced.

David Drew at English Wikipedia, CC BY-SA 3.0, via Wikimedia Commons


There is just one new part in the set: a 7-wide caterpillar track, design ID 69910. It’s compatible with the 5-wide version but made from a softer material which probably helps improve grip on hard surfaces, although it does seem to come apart more easily. There’s a 1-plate high ‘cleat’ on one end which gives it a realistic appearance.

There are a few parts in new colours, including a 5×7 frame and a 1×5 half-beam in yellow. You can find out more at New Elementary.

The sticker sheet is relatively modest given the size of the model.

The set contains four motors and a Control+ hub. Two of the motors are large angular motors that were introduced with Spike Prime last year, but moulded in light and dark grey. The other two are small Technic motors. Unfortunately, I forgot to take a photo of them all together before I started building, but you’ll see them clearly enough in the photos below.


Construction is divided into eight stages and parts are packaged in numbered bags. Gone are the days when you had to spread thousands of parts out before you could start building, thank goodness!

The angular motors and hub are built into the chassis at the commencement of construction. The motors will drive the tracks directly, via the geared wheel hubs that were introduced during 2019.

The smaller motors are attached to a fairly complex gearbox. One of them acts as a gear shifter while the other provides power to one of four functions.

The mechanism is buried deep within the model, so any mistakes at this stage will require the model to be completely stripped down. To prevent such a tragedy there’s a test function in the app that can be used once the gearbox has been mounted in the chassis to ensure everything’s working as it should. [Hint: pay particular attention to the position of the orange 1×2 beam relative to the orange shift ring on step 120.]

The front of the machine houses a detailed 12-cylinder engine underneath the cowling that’s partially visible when opening the doors, as you’ll see below.

The caterpillar track guide assemblies are fairly complicated and the only repetitive part of the build. The front wheel is attached to a rack-and-pinion which enables the track to be tensioned correctly.

The cab section is far more complex than I had anticipated, in part due to the mechanism that enables the ladder on the side to be lowered and raised. There are some odd angles involved in its construction, both for this mechanism and in the cab, where the seat is positioned at an angle.

The instructions state that the real machine is so large that it has to be transported in pieces and assembled on site, and set designer Markus Kossman suggests that “you assemble this model exactly like the real bulldozer”. That seems to be the case to some extent, particularly the way the cab is positioned on the chassis and attached with a just few pins once in place.

It would have been cool if the whole model was constructed as sub assembles that were clipped together at the end, but unfortunately that is not the case.

The arms (for what of a better word) on the side connect to the blade and the linear actuators on it adjust its angle.

The main part of the machine is now complete, leaving just the blade, which is also surprisingly complex and very substantial.

The completed model

The completed model is massive, measuring about 55cm long, 38cm wide and 24cm high.

Much has been said about the yellow tracks and from what I can gather the machines are delivered with them painted yellow which seems a bit of a waste of time given that after an hour or so’s use over rough ground the paint will have been removed to expose the metal underneath.

Personally I think they make it look too yellow. Perhaps brown would have been a more suitable colour, providing contrast with the rest of the model.

Here it is with a goat and minifig for scale.

There are a lot of realistic details all over the model and thankfully the designer has not resorted to the over-zealous use of System parts to accomplish them.


With the exception of tensioning the caterpillar tracks, which is accomplished using gear wheels on the side, everything else is controlled via the Control+ app on a compatible smartphone or tablet.

The Control+ hub is buried in the chassis so switching it on requires pressing a red lever in the engine compartment, which presses a pin down onto the hub’s switch.

Once it’s paired to the app, and the firmware updated the first time you connect, you’ll be prompted to calibrate the model. This operates each function in turn and sets the limits of movement. I had problems doing this the first time, but that could be because I am using a beta pre-release version of the app. I managed to get it to complete calibration by connecting the hub to the Powered Up app and writing snippets of code to test the movements manually before trying again.

With all that done you can finally play with it. The main control screen is shown below. I’m not going to explain it all but suffice to say it’s all fairly logical, and it works well.

On this control screen the speed and direction (forward/reverse) are set using the controls in the bottom right, and the speed of the individual tracks can be tweaked using the yellow sliders in the bottom left, which turns the vehicle one way or the other.

If that’s all too complicated, a second control screen provides joystick control of movement.

It actually moves at a decent speed, and runs well on hard and soft surfaces. It can be turned on the spot with clever use of the yellow sliders, so consequently it’s quite fun to drive around. Unlike come vehicles, such as 42129 4×4 Mercedes-Benz Zetros Trial Truck, you don’t need acres of space to drive it in.

The app also provides a way to program sequences of movement which I think can be played back: I’ve not had a chance to investigate it fully yet.

The motorised gearbox has allowed four separate movements to be implemented using two motors: lift the blade, tilt the blade, raise and lower the rear ripper, and raise and lower the ladder leading to the cab. Its operation is seamless: you don’t need to switch from one movement to the other, you simply press the appropriate control in the app and the gearbox moves automatically to suit.

The blade is raised/lowered and angled using two pairs of linear actuators, which on the real machine are hydraulic cylinders. They are operated independently and unfortunately run at a snail’s pace, particularly the raising and lowing pair.

I suspect the range of movement is realistic, from fully raised and angled back…

.. to fully lowered and tilted forwards.

The ripper at the back is also operated via linear actuators which raise and lower it to ground level, also at a snail’s pace.

Finally, the ladder on the side can be lowered to enable the driver to access the cab. The mechanism to achieve it is pretty complicated, as I said earlier, and I’m not entirely convinced it was worthwhile implementing it.


It’s big, imposing and, appearance-wise, appears to be a fairly faithful reproduction of the real ‘dozer. It is perhaps too yellow, though, as I said above.

It’s a long and involving build, one that takes about 7 hours, so not something you’d want to do all in one sitting. There is a complicated gearbox and a few other mechanisms to be conquered, and some repetitive sections, but overall I enjoyed it.

As a parts pack — albeit an expensive one — it’s pretty good. There are a lot of the new beams with perpendicular holes and hundreds of yellow pieces. The 116 caterpillar track links will no doubt come in useful for MOCs, although they offer no advantage to GBC builders other than adding some variety. There are no large wheels, tyres or specialised pieces, which is a good thing. The two angular motors are the most useful and sophisticated of the Powered Up motors and can be recognised and used with the Mindstorms and Spike Prime hubs.

I’m not a big fan of Control+ but I have to concede that this is a decent model and perhaps the best implementation of the system to date. It’s still a PITA finding your phone, enabling Bluetooth, firing up the app, then connecting to the hub before you can play with it, but the last part at least does seem to happen almost instantaneously and without problem now.

Many Control+ models suffer from a lack of haptic feedback on the controls, but I didn’t find that to be an issue with this one. The only annoying thing really is the glacial pace at which the blade moves up and down.

Now, I must discuss the price. It’s a big model and technologically as advanced as Technic sets get, but £420/$449 is an obscene sum of money to pay for it, particularly when compared to 42055 Bucket Wheel Excavator, a motorised set of a similar size but without Control+, which was just £180/$280.

However, having said that, it will not be long before it’s reduced by 30% at Amazon, just like last year’s equally expensive 42100 Liebherr R 9800 is at the moment, which will take it down to around £300. Still expensive, but somewhat more realistic.

Would it be a better model if it were manually operated and priced at around £299/$299? I’m actually not sure! I was averse to Control+ but this has persuaded me that, for the right model, the cost it adds might be justified.

It will be available at from 1st October.

No goats were harmed during the production of this review.

Thanks to LEGO for providing the set for review. All opinions expressed are my own.

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