Subframes: a technical challenge
Overland vehicles are designed for adventure and with few exceptions, the base vehicle chassis will twist when going over uneven terrain. Counterintuitively, this twist is beneficial from an off-road capability perspective as it helps to keep all wheels on the ground which improves traction.
Directly mounting a habitation box on a twisting chassis risks damaging the habitation box, which is usually much stiffer but relatively weak. Subframes are structures that mate the body of a habitation box to a truck's chassis.
There are three general options available to builders:
1. design a box and subframe that is strong enough to withstand the twist in the chassis and then mate the two using compliant mounts.
2. use a subframe including three or more pivots to allow for the full range of chassis twisting while transferring no torsional forces to the box. The design must be properly engineered to maintain stability and avoid point-loading the chassis.
3. a compromise between 1 & 2 where the stiffness of the chassis is carefully increased in addition to a subframe isolating the box from torsional forces. This can help reduce the total vehicle height in some cases.
How we help
In general, torsion-free subframes are poorly understood. Several publicly available subframes have flaws and overlook key considerations, and information on how to design subframes online is scarce, often incomplete, and sometimes even plain wrong.
Our approach is to choose the appropriate sub-frame architecture for your application and design a custom steel sub-frame based on your base vehicle and habitation box.
Our process is to:
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Perform a torsion test on your vehicle chassis
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model and stress-test any existing structures
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design a detailed subframe tailored for its intended application
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work with fabricators to have the subframe made to the intended specifications
Get in touch
Tell us about your project and find out if we can help.