However, that's only half the story because the digger is entirely dependent on a smartphone app to function: it's just an expensive ornament without it.
Thankfully, the Control+ app is very good indeed. It enables you to operate and control the model like never before.
I first took a look at the app in my review of 42099 4x4 X-Treme Off-Roader in August. It's now been updated to support both that and this set so on startup it now asks you to choose one of the two models.
Connecting to the model involves switching the hubs on one at a time and waiting for them to pair via Bluetooth. It takes a minute or so to do, but so far it has worked faultlessly, connecting first time and maintaining the connection for as long as I want it.
Confirmation that both are connected is provided before letting you loose at the controls.
The first time you connect you are prompted to calibrate the model. The linear actuators are moved from one extreme to the other so that, via feedback from sensors in the motors, the limits are determined.
You can also recalibrate at any time from the main menu. I've had to do it a couple of times when things stopped working as I expected.
The main screen provides controls for every movement. The sliders at the top move the caterpillar tracks forward and reverse, the joystick on the left rotates the body and operates one joint of the arm, the one on the right operates the other two joints while the small buttons next to it open and close the bucket.
The indicators in the middle show tilt and yaw when it's not on level ground.
It takes a bit of trial and error but once you've mastered it it's easy to manipulate the digger like putty in your hands...
However, if you swipe left you'll be presented with an even easier way to control it.
On this screen you can move each joint with your finger and watch as the arm on the model moves in sympathy.
The black 'shadow' in the background shows the current position of the arm which, as it moves, approaches the position you've set.
Controlling the model like this is very intuitive and a lot of fun, and certainly something that is just not possible with traditional remote controls: a single swipe of your finger sets up to four separate motors into motion to obey your command.
If that was all that the app did it would be quite enough to satisfy most people, but it has a lot more tricks up its sleeve...
The most powerful feature of the app is the programming interface. Here you can program the model to perform a sequence of movements then play it back, save it, and even create your own blocks of movements that can be incorporated into other sequences.
There are 30 or so blocks for moving each of the motors by degrees or distance and as far as I can tell there's no practical limit on the number of them you can string together so you can create very complex sequences.
When the program runs the current step is highlighted.
If dragging and dropping steps onto a timeline is too much hassle there's an easier way: you can also control the digger in the normal way while recording its movements. When you click on 'Record action' you're returned to the main control screen where you can move the model about to your heart's content.
When you've finished and pressed the stop button you are prompted to save the sequence and choose a symbol for the block. Then, you can drag it onto the program timeline as you would any other. This is a far easier way of achieving complex and compound movements.
Saved programs can also be assigned to the four buttons on the main control screen for easy access.
However, there is no way (that I could find) to use loops or other programming constructs to repeat actions, which is a shame.
Challenges and achievements
There is a gamification/tutorial aspect to the app, too. I haven't delved that deeply into it but as far as I can tell you are challenged to perform increasingly complex movements and in doing so you learn how to do them. This is certainly something that youngsters would find fun.
Turning it off
Unless I'm missing something, the only way to turn off the hubs -- certainly the easiest way -- is to turn off Bluetooth on your phone.
Verdict on the app
As I said at the start, the app is excellent. It lets you interact with the model in ways that until now have been impossible. It really brings it to life.
Pairing it to the digger in the first place requires a bit of faffing about: find your phone, turn on Bluetooth, start the app, turn one one hub, wait a bit, turn on the other, wait some more. There have been times when I've felt like given the earth mover a quick spin but have been put off at the thought of having to go through all that.
Other than that, I can't really find anything to criticise, because it's worked perfectly and provides a very rich user experience which will keep you entertained long after you've finished building the model.
42100 Liebherr R 9800 is a big, beautiful and expensive set. But, it's entirely dependent on the smartphone app which will not please everyone, and may well give many a reason not to buy it.
However, I believe it was absolutely the right direction for LEGO to take its technology platform because it opens up so many possibilities.
At the moment the Control+ hubs and motors can't be used in your own models because there's no way to control or program them, but that is set to change when the generic Powered Up app has been updated to support them. As far as I know it hasn't been announced when this will happen but I'd like to think it would be before the end of the year.
42100 Liebherr R 9800 is now available at LEGO.com for £399 / $449. That's a huge outlay for a toy, albeit a very sophisticated one. Precedence suggests that the price will tumble and indeed it's already available for a 20% discount at Amazon.de so I suspect other retailers will follow suit in due course.
Thanks to LEGO for providing the set for review. All opinions expressed are my own.