Case IH Quadtrac



  • 4 wheel (tracks) drive
  • Articulated steering
  • Three point hitch
  • PTO
  • Pendular tracks
  • Pendular rear body (rotating hitch)
  • Steering wheel turns when steering
  • Lights

I think this might be my best looking model so far. As usual I am also proud of how much functionality I managed to place within a chassis that is really just 5 studs wide. It contains no less than:

  • 5 turntables
  • 4 motors
  • 2 IR receivers
  • 1 batterypack
  • 2 pair of lights


Above is a close up on the steering mechanism. It was later changed a bit and the motor placed further down to make room for the batterypack.



Building “half-stud”

A few parts, and combination of parts, that enables you to build “half-stud”.



Lego triangles and Pythagorean triples

Usually Lego Technic models are based on square patterns of holes which in turn are based on the Lego length unit “1 stud”.

The problem is when you want to attach a leaning liftarm to your (square) construction, how do you find the correct holes to attach it to? Usually the leaning liftarm “almost” fits.


I translated the issue into a mathematical problem. The base is of course a right triangle with the condition that all sides must be an integer. The phenomenon is called Pythagorean triples. (google it). I found the following triples especially interesting for the context of Lego.


Then I realized that Lego also “supports” “half stud” constructions which also enable the following combinations:


Note that the numbers above corresponds to the length between the first and last hole in a liftarm. To translate the length into the number of holes of the liftarms you have to add one (1). Below you can see the examples of the variations.



The building process

Designing a complex Lego Technic model requires a lot of planning, thinking and building. I left my "dark ages" during the summer of 2010. Since then I have recurrent periods where I build a few hours every week. However, within those I periods, I find myself completely stuck. In this article I will give you my best tricks for fluent building!


Using Linear Actuators for Articulated Steering

There has been a debate on how to build proper articulated steering with the use of double linear actuators (LA). The problem is that the steering ”speed” will vary over the steering ”cycle” when only using a single LA. As a result, when using double LA:s, there will tensions, that might be large enough to engage the built in clutches in the LA:s. However, depending on how you choose your ”geometry”, this problem can be reduced. This video shows one example of a geometry that will work fairly well, using the mini LA:s. It has been tested in vehicle up to 70 cm / 2 kg.



Telehandler, v2

IMG_2650I was not really happy with the first version of my telehandler, the design was nice but it performed quite badly, especially the weak propulsion and poor suspension. For some reason the tires almost tore off the axles when it drove a meter or so and it looked like the suspension was really weak, which it wasn’t.

With the Grand Prix Racer (42000) set a new suspension system was introduced. I decided to have another go at building a Telehandler. I tried to keep the design as far as possible but reworked the entire chassis and used a PF L-motor for propulsion and the PF Servo for steering.

The improvements:

  • Stronger motor for propulsion
  • The chassis is two studs thinner
  • Completely reworked suspension
  • Almost twice as long telescopic boom

Here is a specific blog entry regarding the suspension.


  • 4WD, PF L-motor
  • 4 wheel steering, PF Servo Motor
  • Boom life, L-motor
  • Telescopic boom, M-motor
  • Bucket tilt, M-motor
  • Quick coupler
  • Pendular rear axle


I am really proud about how small but still robust I could make the chassis. In the picture you can see the entire chassis housing:

  • 2x PF L-motor
  • 1x PF M-motor
  • 1x PF Servo motor
  • 1x Battery Pack
  • 3x PF IR Receivers

However, It performed almost worse than the first version and I can’t get why. The tires do everything they can to rip apart which in turn affects the steering and propulsion. I am almost in doubt whether it is possible to build a 4 wheel driven and steered chassis with pendular suspension..

More pictures are available in the youtube clip.


Dump trailer


A model of a dump trailer designed to use with my Lego tractor.


Another autovalve

Not the best or most optimal, but might be useful in some scenarios.




The challenge

  • Incorporate 5 motorized and remote controlled functions in a 1:14.5 scale model.
  • Make the rear axle pendular while steered and driven

Video below.