42100 Model C – Tracked Carrier

An alternate model of the #42100 Lego Technic set, as a heavy tracked carrier, featured motorized tracks, outriggers, operating crane, fake engine with speed control, remote controlled with PoweredUp app, with building instructions.


Direct purchase of the instructions

Rebrickable partlist (2770 parts). Preview of the instructions at the end of the article. Presentation Video (YouTube). Ensure you your smartphone is compatible with the Lego app “Powered-up”.


After completing my 42100 first alternate as a Vibroseis Truck, I wanted to make a second alternate, in a more classic way, with more parts and sturdier design to have a better offroad capabilities. So I have chosen the heavy tracked carrier from Powerbully as an inspiration, and started the design by the chassis and the motorized functions.


This creations use the 7 motors in the set donor. The first two XL motors are used for the drive of the tracks through gearing (20/28 and 12/36) which brings more speed than the official Lego Set. They are placed symmetrically in the chassis, and act also as part of it. The tracks use pendular bogies design, a feature I wanted to create at the beginning, comparing to the fixed bogie on the original set. The chassis has been designed accordingly to allow small rotation of the bogies, which helps to cross easily on obstacle.

The second functions is the outriggers, which required a lot of design iteration to implement. They are driven by a L motor, placed underneath the rear platform, which drives an axle on each side through gearing. These axles drive then 4 linear actuators which are placed symmetrically to maintain a compact design of the stabilizers. They can not lift the model because of the operating force angle, but cover a large area around the model. Additional pads can be added, and stored on the rear platform.

The next functions are on the operating crane. The crane rotation is operated by a L motor placed underneath the rear platform, which drives a spur gear on the turntable, through multiple gearing (no worm screw in this set). The final spur gearing has been chosen for its reliability comparing to the bevel one, which tends to make cracking sound under pressure.

The crane has two sections. The first is driven by a XL motor placed in the chassis, and act as a part of it to hold the turntable. It drives directly the linear actuator through a U-join, ensuring a strong lifting. The second section is driven by a L motor placed in the arm, which drives also a linear actuator. 

This geometry has been chosen to have a strong crane which can lift the Diesel Generator. Indeed, I wanted at first to create a side folding crane, but the linear actuators were too long for the scale, and the placement of the motor did not fit the design. It results in a wobbly and weak crane at first. So I redesigned the whole crane based on a heavy model with no side folding functions, which ensure a better lifting force and stability. The second section of the arm can be extended with a manual pin, and the hook can be rotated by hand.

The last functions is about the fake engine. As on my previous 42100 alternate, I wanted to have a fake engine which is not connected mechanically to any other functions. In order to create an idle function, and make it run faster if needed (operating crane for instance) as real. That is why a L motor is dedicated to this fake V8 engine and drives also two fans though gearing. The detailed engine is revealed by a cover, but the fans can be seen through the side windows.

To finish with the openable elements and some details. The cabin door can be opened, revealing a detailed interior, with seats, dashboard, and even pedals.

The rear platform is packed with some equipment, such as a big Diesel Generator with opening side cover, and also a pallet of fuel tanks. I have built at first a container, but it was too big and heavy to be lifted by the crane. So I have decided to divided the equipment in many other which are easier to handle.

Design Process

There is a lot to say about the design process, you can watch the Design Secrets of this creation on YouTube for more details (soon available). The main idea is that the functions drive the design in this case. I have started by making the functions that I wanted which affected the design : pendular bogie, outriggers, crane, and then work on the rest.

Work in progress of the 42100 model C chassis

It was very important to have a sturdy chassis to handle the weight of the model. That is why some electronics parts act as a part of the chassis, like the hubs. And that multiple beams and frame are used to reinforce the chassis from underneath to the top. The result is a flat underneath of the chassis, with 3-studs ground clearance, and accessible battery box. As the hubs are inside the chassis, I have created two small devices to push directly the physical power-on button of each hub, one on the rear platform, and one behind the cabin.

Then I worked on the design and focused myself to have a sturdy look with a neat design. It has been done by the choice of the parts with the color and their orientation, but also the details and proportions. This time, I have chosen to use the original stickers as an advantage, by decorating more the model. For instance, with the warning label near the exhaust or hot parts, or for decorating the Diesel Generator or the front part. They add nice details, but are not mandatory if you have not applied them.

The model is remote controlled using the official Lego app : PoweredUp App (available for Android and iOS). I have created a custom profile with slider, joystick and the program block to operate the model. It is pretty basic but works very good. I have also created a 36 pages tutorial to explain step by step how to do, and this tutorial is included in the instructions (you can see a preview at the end of the article).


To finish with some limitations. I would have liked to make a folding crane, which can lifted the initial container, but it was not the case for the explained reason above. The consequence of the heavy crane is that it looks a bit massive and so the global proportion of the rear platform is a bit small. Apart that, I am really happy of the result, functions work good, the set is playable and sturdy, and I am satisfied with the design, especially the treatment of each white and dark grey surface in terms of finishing, details, and the way I handle the original sticker.

Pictures and Video


Dimensions : 43cm (L) x 21cm (W) x 26cm (H)

English spoken video of this article [Design Secrets : 42100 Model C – Tracked Carrier on Youtube]

Building Instructions

The instructions are 536 pages, step by step high resolution computer generated instructions with partlist, color coded cable with layout, flexible parts, in the same way as official Lego one. It also includes 36 pages step by step tutorial in PDF to configurate the model for PoweredUp App (available for Android and iOS). Please ensure you first that you smarpthone is compatible with this app and testing on your 42100 material.

Regarding the bill of material, as an alternate model, if you own the #42100 Lego set, you have all the needed parts. But you can checked the exact bill of material on Rebrickable and export in whatever format you want :

Want to know if you can build the 42100 Model C – Tracked Carrier ? The model has been indexed to rebrickable, check it !

You can buy the instructions with the following button for 15€ excluding tax. You can also buy other building instructions and get an automated discount, including my first alternate model of the 42100 as a Vibroseis Tracked Vehicle, you will get 15% off for 2 PDF, and 20% off for 3 PDF on the total). The automated discount is available for all the instructions for sale on nico71.fr.

42100 Model C – Tracked Carrier

42100 Model B – Vibroseis Tracked Vehicle

After your payment, you will be redirected to a page for downloading your instructions, and will receive also the link to download by email. Please check the spam box and be patient to receive it. If you have trouble to download your copy of the PDF after payment or open the document, do not make a paypal dispute, please contact me using the contact form. The link to download the instructions expires within 48h. Contact me if you have lost your instructions. Note that you can print it, but not copy or distribute. Thank you for supporting my work 🙂

Here is some preview of the building instructions :

(3) Comments

  1. Avatar photo

    Hi. I just finished builiding and testing the Carrier. Works like a charm. Very cool model and great functions. I really enjoyed the build and I’m looking forward to show it to my 4 year old son (who helped me a bit ;-). We have also already built the Dozer, which too was very cool and worked perfectly.
    Thanks for your models. It’s great to have alternate builds for such huge sets as the Liebher that are no lesser functionaly complex than the original.
    Great work!

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