Technic Heavy-Duty Excavator (42121) Review

The build was a pretty quick one, at around an hour and half. Perhaps an hour and 20 minutes if you follow the instructions better than I did and avoid minor re-work.

Opening the box provides a set of stickers and four major bag components.

Bag 1 is focused on the digger arm and is a relatively straight forward build. I’ve not come across the actually digger part before in any of the sets we have. I’m always interested in the various gearbox functions and this set provides a couple of methods to control the digger. More on that later.

The second bag extends the digger arm and creates the foundation for the mounting mechanism and cabin. It’s quite enjoyable to see how two seperate mechanisms are encapsulated by the same arm. One of them extends the arm, and the other mechanism hooks the bucket to allow scooping.

Bag 3 has us working on the main body of the excavator and starts introducing stickers into the build. By the end of this bag, you can use both knobs to control the bucket scooping and extension and start to see the machine take shape. You are also building the underlying tracks that support the body in this bag set. Although clipping the individual treads together is a little tedious, once built, you can independently rotate the cabin from the body just like in real life. The location of the tread mount is also well positioned to provide adequate support for the excavator even when the bucket is at full extension.

As we move to Bag 4, we’re finalising the model with some exterior body work and also the main cabin for the driver. Unfortunately it’s not to minifig scale. It’s about 20% too small to fit a minifig in the cabin. Although it would have slightly put off the scale, I would have liked to see a slight revision inside the cabin with the controls mounted a different way. Doing so may let you sit a minifig in the cabin.

Bag 4 also provides a few safety cones (to keep the OHS inspectors happy) and some rubble to play with. You can see Oscar and I relaxing amid the rubble below.

Overall this was a reasonably fun build. For us, Technic sets are mostly about the fun playing with them after they are built. I find there is less “wow” moments, but certainly there is enjoyment in watching how it technically fits together. I would have loved to see an extra gear with a knob on the top to allow you to “steer” the tracks rather than manually doing moving the tracks. However, that’s a very minor gripe.

It’s a set I’d recommend overall if you like to play with the sets or like to display with other Technic sets, but wouldn’t currently be my first choice given all the fantastic sets out there. See our Top Picks for those.