Subframes


Subframes play a crucial role in the construction of any expedition vehicle, serving as the vital interface between the vehicle itself and the habitation module. These subframes must fulfill two critical and often contradictory functions: securely holding the habitation box to the vehicle while maintaining flexibility.

In the realm of large off-road vehicles, the ladder chassis design is commonly employed, consisting of two "C" section rails interconnected by cross members. Various components of the truck are then fastened to this underlying framework.

Due to its design, the ladder chassis possesses inherent flex and torsional twist capabilities. This flexibility serves as a secondary shock absorber, safeguarding the vehicle's components and augmenting axle articulation, thus enhancing the vehicle's off-road prowess.

However, if a rigid subframe is utilized without decoupling the habitation module from the torsional forces experienced during off-road usage, two significant issues arise.

Firstly, the habitation module acts as a "splint" on the chassis, restricting its articulation and, consequently, impeding its off-road performance.

Secondly, and of greater concern, these torsional forces are transmitted to the habitation module's structure. This imposes substantial loads on the module, leading to premature failure, ranging from minor issues like water ingress to major failures such as fractures that compromise its roadworthiness and safety.

To overcome these challenges, a dynamic fixing mechanism is essential between the vehicle's chassis and the subframe.

At Motorcraft, we offer two solutions: a rail-on-rail subframe and a four-point subframe. These advanced subframe designs provide the necessary flexibility to accommodate the vehicle's torsional movements while ensuring the habitation module remains securely attached. By employing our dynamic fixing systems, you can mitigate potential damage and maintain optimal off-road performance, while ensuring the long-term structural integrity and safety of your expedition vehicle.

Rail on Rail

Rail on Rail

This consists of two rails positioned on top of the chassis. These are rigidly fixed at the rear of the vehicle and then fastened at the front with spring bolts.

 

Advantages 

  • Cheaper to manufacture

  • Better load distribution onto the chassis

 

Disadvantages

  • Limited travel by spring bolts means a more rigid structure 

  • Reduces flex in the chassis and therefore articulation

  • corrosion between the rails due to debris ingress

Multi-point Torsion free

Four-point torsion-free

Our four-point torsion-free sub fame utilises three pivot points attached to the chassis rails at four positions. A pivot at the front and the rear of the chassis that is mounted longitudinally. The third is in the centre mounted laterally.

 

Advantages

  • Almost unlimited amounts of free movement

  • Ultimate off-road performance

 

Disadvantages

  • isolated load distribution 

  • expensive to manufacture

Please note that subframes for expedition vehicles are bespoke and tailored to each specific vehicle. At Motorcraft, we specialize in creating custom subframes that precisely match your vehicle's requirements. For a personalized quotation and to discuss your subframe needs, please contact our team. We are dedicated to delivering high-quality solutions that ensure the perfect fit and functionality for your expedition vehicle.