Articulated Tractor

Articulated Tractor
modeled after an old Case tractor

This model was a fully functioning articulated tractor. It was powered by LEGO electric motors and pneumatics. I built this model (in 2001) in reponse to Steve Lane's challenge on LUGNET to create the most powerful truck or wheeled vehicle possible.

drive power: 4x 9V geared motors
transmission: 2-speed with neutral; shifting controlled by motor
drive gear ratios: low - 1:121.5, high - 1:40.5
drive: all wheels powered
steering: articulated chassis with two pneumatic cylinders
electric control: 4-channel RC prototype from HiTechnic
pneumatic power and control: hand compressor and switches
suspension: solid axles, but front axle was pendular
weight: close to 7 pounds (3.2 kg)

pulling weighted cart

the cart (from above)

pull test

pulling weighted cart

the cart (on side)

pull test

Pulling Power

I performed two pull tests with this model. One was to pull a weighted cart and the other was to determine the maximum tractive effort.

The model was able to pull a cart weighing 94.5 lb (42.9 kg). It moved very slowly, but it moved!

The tractive effort was determined by pulling a hanging weight connected by rope. This weight was suspended over the side of my desk by using a large plastic wheel. The maximum weight pulled in this set up was 6.5 pounds (2.95 kilograms). The gears strained and after just a bit, one of the 12-tooth bevel gears in the power gear train broke.

transmission iso

gear shift

transmission elev.

gear box


I built this simple transmission for a number of reasons. I didn't have the new (at the time) shifting parts - the ones that engage the dark gray 16-toothed gears. I wanted a transmission that could be shifted by a motor and remotely controlled. And I wanted a robust gear train capable of transmitting power from four geared 9V motors (and that's a lot of torque).

This transmission worked but was tricky to operate. Getting it to shift properly took some tweaking and operator finesse. In the end, it was too much trouble and took too much fiddling to keep it shifting properly.

This transmission also took up a lot of room inside the model. That's why there's a big, tan "lump" in the cab instead of a proper seat :-)

real, modern example

old one
The Real Tractor

I modeled my tractor after Case IH tractors. Their current line of large articulcated tractors is the STX Steiger 4WD series (on the left). My model is actually closer to the older series of tractors (on the right).

Thomas J. Avery 2001