Torsion-free mounting

When going over uneven ground, your vehicle's suspension will absorb much of the difference in surface height between the wheels. However, at some point the suspension movement will not be enough to compensate for the height difference. The weight of your vehicle will more likely than not result in some chassis-twist.

Many off-road vehicles are actually designed to allow chassis-twist. The Mercedes-Benz Unimog is a prime example of this. As the vehicle goes over very rough terrain, such that the vehicle's suspension cannot fully compensate, the weight of the vehicle will most likely cause the chassis to twist until one or more wheels make contact with the ground.

Let us consider this chassis twist. Assume your living cell is attached directly to the chassis in a rigid fashion - what will happen when your chassis twists? This twist will be transferred directly to your living cell. When driving over corrugations, which we will no doubt encounter in Africa, this twist can literally tear your living cell apart!

Countering this problem by making your body sufficiently strong to withstand this twist is not an ideal solution, as this will have the adverse affect of preventing your chassis from twisting sufficiently, thus reducing its off-road ability.

The ideal solution is to have a torsion-free mounting, which uses geometry to counteract the chassis twist.


Here you can see a diagram of the 3-point frame assembly used in the Unimog, which was used as the starting point for ours.

When any of the 4 chasss rails twist (green arrows), the fixed centre mounting holds the body in the middle while the front and rear mountings rotate, transmitting the force harmlessly away from the box, keeping it stable and allowing the chassis to twist freely beneath.

Here is the AutoCAD design of our mounting system:

Cad mounting

If you have AutoCAD, download the file here.

Following are some photographs of the build:
Rear chassis mounting

Rear chassis mounting attached

Chassis mounting - side


    1 .
    Good day, very interesting. Could you tell me what you used between the shaft and the mount. Is there some kind of special bush to prevent metal on metal?
    Christo - 8 Sep 2016, 15:41
    2 .
    Your central mount which appears to allow only the movement of the subframe on a transverse (or lateral) axis of the chassis. But since your forward (near cab) & the rear end pivoting trunnion mounts swing across the lateral axis, shouldn't the central mount allow a fore-aft (longitudinal) movement? Thanks for putting up detail plans of the mount.
    Himanshu - 21 Sep 2019, 11:13

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