So let's get to the crux of the matter (and also the controversial bit): the suspension. In SA, almost all camping trailers have live axles on leaf springs. These typically only have around 100mm of suspension travel.The only common alternative is the Rubax axle, which has even less travel.
The Patrol has upwards of 200mm. Typically, the ride gets uncomfortably rough only when the suspension starts bottoming out. The result is that you can be driving along fairly comfortably on a bad road, while your trailer is busy destroying itself, and you don't even realize it. I found this out the hard way a while ago when I hooked the old Venter and went down to Dwesa on the wild coast for a family holiday. At one point I clearly saw the trailer's roof filling my side mirror.
So suspension here is independent by trailing arm. Big and powerful shocks are incorporated. However, the only way I could find to keep it up within a reasonable space was by using air springs.
At first, this seems like a risky option in an off-road trailer, and you are all seeing visions of Land Rovers on car transporters, but bear with me:
1) Usually, it is the control system that fails. My control system is really simple, consisting of a tube from each air spring to an air valve (like the one in a ca's rim), with an equalizing valve teed in between the two.
2) These air springs are commonly used by modern trucks and trailers throughout africa, and failures are quite uncommon. Certainly less frequent than with leaf springs on normal trailers.
3) This brings the advantage of making it very easy to level the trailer on a less-than-flat campsite: simply equalize pressure, shove the trailer to a level position, close the equalizing valve, drop the feet, un-fold the jockey-wheel, un-hitch the car and jack up the jockey wheel.
4) It also allows a very stable sleeping platform by reducing air pressure, and possibly the ability to change ride height and attitude in difficult terrain...
The only real risk is puncturing an air bag. To prevent this, the trailing arm is of a very wide section, with a solid, impenetrable base, and there is very little room between it and the wheel. The air springs are also small and light enough to carry one as a spare, and relatively easy to replace.
The trailing arm's inner swivel point is a bush fitted inside a 10mm thick plate welded into the chassis's main cross member, right at the strongest point:
The outside bush is in a strong bracket bolted to the outside of the drawbar tube:
Maximum droop is 250mm:
Minimum height (the spring will reduce this a little bit) is 100mm:
Thus the total travel is nearly 250mm:
With air-spring fitted:
In this view, the "control panel" is visible:
This will be hidden inside the mudguard when it's all finished.
Mag ons ons kenniskry met lekkerkry aanhoukry.