Lego Technic Zetros Trial Truck
Building the new Mercedes Benz Lego Technic model
They say the best presents are the ones you buy for yourself. Well, I say that. And this year for my birthday, I treated myself to the new LEGO Technic flagship set, the Mercedes Benz Zetros Trial Truck. It's expensive, but it is £79,725 cheaper than a genuine one. The Zetros is a real thing, sold by MB as the bigger, tougher brother of the Unimog, which itself eats G-Wagens and Defenders for breakfast. It is available with 4x4 and 6x6 drivetrains but the Lego version is the former with a functioning four wheel drive mechanism, working differential lock and super low gearing to allow it to climb very steep gradients.
Unboxing the beast
The box is about 60cm square and contains 6 numbered bags, some of which contain smaller bags, comprising more than 2,100 pieces. There are 4 Power Functions motors to control the steering, drive the wheels and to engage the diff lock. These are supplied their juice from a battery box that holds 6 AA batteries. A USB rechargeable option would be nice but is not currently offered. Once built, the truck is controlled from the Control+ app available from the App Store.
The manual is over 350 pages long and details more than 600 building steps. I think Lego manuals have gone downhill a bit recently. Some steps are incredibly basic and ask you to add just 1 component to the in-progress build. Another criticism is that it isn't always obvious where it wants you to add the new component. In the Liebherr rip off that I wrote about before, the new components have a red highlight to show where they go. The Lego manual just shows them in-situ and you have to work out where they are and the difference from the previous step. This is even more of an issue when you have been building a sub-component and you need to work out how to align the pins/connectors on the sub-build and marry it back to the chassis.
Another annoyance is the number of stickers. Some of these should have been pre-printed onto pieces, such as the dashboard and steering wheel boss. Others, such as the sponsor stickers, make the pieces less useful for re-purposing in other builds. Then again, they don't have to be applied as they are purely cosmetic and do not affect the function of the truck.
Anyroadup, on to the bricks and pieces.
Bag The First
There are actually three bags in phase 1
The first phase of the build results in most of the chassis being created, including the motors for the drivetrain and the diff lock. This is one of the more complex and challenging aspects as it is important to get all the gears and axles aligned correctly, otherwise the diff will not engage and the drivetrain will not work (more on that later...)
And joy of joys, Lego is serious about cable management and provides clips to allow you to route the motor cables in the chassis so that they don't snag on moving components (Mould King take note). This is very important as the cables would otherwise hang under the chassis and impede progress when the truck is in motion and prevent full steering lock.
Cable management heaven
After 3 days of on-off building over the pre-holiday weekend, the chassis was complete.
Bag 2 United 0
The second bag of bags will complete the chassis and add one of the most interesting features of the Zetros: a working lockable differential that can be operated remotely via the Control+ app.
I don't pretend to know how locking differentials work. My Defender has one and it includes all sorts of warnings about transmission wind up and reversing after use. All I know is that it works. And in the case of the Lego version, it also works, as later videos will attest.
The diff mechanism is attached to stiff shock absorbers and 'floats' on the chassis via some chunky universal joints that allow the axles to be attached but not fixed.
Bag 3 Is The Magic Number
The third bag completes the drivetrain by adding the front differential and most of a fake engine. It would have been nice if the engine had moving pistons and rods, like the Defender and many others. I also made a really stupid mistake when putting the front diff onto the chassis, as I mounted it 180 degrees the wrong way. This was not apparent until after I finished assembly and fired it up for the first time, when the front and rear wanted to go their separate ways. Fortunately it was fairly easily rectified by unfixing a few grey connectors underneath and flipping the diff the right way.
Original front diff position - red gear should be at bottom, not top
Bag 4 Life
The fourth bag completes the engine and most of the front cab. The Zetros has three front seats and the instructions get you to build it as left-hand drive. I decided that I would build it as UK-spec, with the steering wheel on the correct side.
Harry and pals sitting in the cab before the RHD conversion
Before doing the conversion, the engine block is added and this is mildly significant in that it is the part of the truck that has the most non-Technic pieces. Here there are a whole eleven 'system' pieces with old fashioned studs to hold them together.
The RHD conversion was not complex since the steering wheel is not connected to the front wheels and neither is the gearstick. There is an extra 'mirror' on the passenger side that also needed to be switched. Here is the Winter Solider modelling the conversion.
Bag 5 Getting Ink Done
The penultimate bag completes the front of the truck and adds about half of the stickers. I hate Lego stickers, especially the long ones and ones that need to be centred correctly, otherwise they look obviously wonky. [/rant]
No, I don't know the significance of the yellow duck
Bag 6 Danger! Danger! Steep Gradients
The sixth and final bag finishes off the upper and lower bodywork as well as adding the chunky tyres. I made another boo-boo here by fitting one tyre the wrong way around. It was more aesthetic than anything. There are also four flags to build, which are supposed to be used to create courses to navigate around. Here is the final model.
Ink done. He wanted a 13 and he got one. Not 31. Some of you might get it
Except it wasn't quite final, for a few reasons. Firstly, I had to update the Control+ app as it didn't have the Zetros as a controllable vehicle. Once I had done that, I switched on the battery box to sync it with my phone and it said a firmware update was needed (on the truck). So it downloaded and installed that. Once that had finished, I tried to get the truck to move and that's when I discovered that the front wanted to go backwards when the back wanted to go forwards, and vice versa. After a lot of head scratching and swearing, I discovered the fault in the front diff position and managed to flip it without too much drama. But a lot of swearing.
I then set about testing it by taking it for test drives around the kitchen and from the kitchen floor to the top of the dining table, a climb of 38 degrees. I also used some spare pieces to build a mount for my iPhone so that I could video what the truck was up to. I used an iPad to control it.
Climbing to the stars
The truck doesn't go balls-out fast. But that means it is easy to control when climbing steep angles on fairly narrow surfaces. I also took a video with the phone mounted behind the cab.
The locking diff is also not a gimmick. It can be turned on and off via the app, and if it's disengaged while climbing, the truck will lose traction pretty quickly and start slipping back. So far, 38 degrees is the most I have tried but am going to attempt 45 or more when I get the time.
There is a bug in the app that sometimes locks the front wheels pointing to the right. This can only be fixed by closing down the app and restarting it. Apart from that, it's a hoot to play with and I'm looking forward to building some obstacle courses, one of which will be a 40 degree climb up 14 steps from the ground floor to the top of the house. Just need to work out how to bridge the gap between each step.
Next project is a Space Shuttle!