Foremost Chieftain R

If you had the opportunity to visit superk-technic in the past you should already have read something about Foremost Canada built from LEGO Technic. The company is specialized in equipment for oil & gas, mining, construction and waterwell markets, but the part that interests me the most is their off-road tracked and wheeled vehicles creations.

The Chieftain is a 4 tracks articulated off highway vehicle. The “R” series is fitted with large rubber track (864mm) allowing a very low ground pressure in harsh environment. It is an 11m vehicle equipped with a 375bhp Caterpillar engine, a 13,6t payload and can be equipped with a lot of equipment on its rear deck.

The version I built here is the one equipped with an aerial lift. Unfortunately there is only few photos of the real machine and no video available online, but you can find general information ont the Chieftain R through Foremost website:

The MOC :

The MOC is a reproduction of the real machine; it is composed of two chassis mounted on large tracks and linked together by the central articulation.


All images are available on FlickR.

Ground clearance is not too bad with a height of 3 studs (can be push up to 4 studs but it could weaken the chassis and articulation.


Forward chassis/part

The forward chassis contains the battery and motors for steering and propulsion.
Steering is actuated by two mini linear actuators working together.
The propulsion is powered by a singlemotor, runs through the articulation thank to a universal joint. Both pair of track is equipped with a differential to accommodate the turns.
Surprisingly, the maneuverability is excellent but the gears used in the propulsion have a tendency to crack during turns on rough surfaces.

See also  Wheel Loader and Wheel Dozer


Rear chassis/part

The rear chassis accommodates all element related to operation of the aerial lift.
There are 4 outriggers made of mini linear actuators just powerful enough to lift the whole chassis of the ground.
The superstructure is mounted on a large (motorized) turntable that supports the mast.


Main mast is actuated by a pair of large linear actuator. They are a bit too short to allow a real 0-90 degree range of movement, but this issue will no longer be with the long linear actuator (15-23) released with the mighty Liebherr R9800 (yes I ordered 4 of them).

The second part of the mast is mounted on a special articulation I’m particularly proud of that allows a full 180 degree movement and is actuated by a single linear actuator.


At the extremity of the mas is suspended the pod. No special mention.


Motor & power

There is 6 LEGO Technic Power Functions motors used in this MOC controlled by Two SBrick Bluetooth modules and powered by a single rechargeable battery :
SBrick 1 (forward):
– Steering (1 PF-M motor)
– Propulsion of all 4 tracks (1 PF-L motor)
SBrick 2 (rear):
– Outriggers (PF-M motor)
– Superstructure rotation (PF-M motor)
– Main mast erection (PF-M motor)
– Secondary mast operation (PF-M motor)

Thank you for reading !