I chose to build an articulating vehicle because they are very efficient when it comes to turning, and require very little power to turn. It also makes adding 4wd fairly trivial when it comes to an electric drive train like mine. A pivot that only moves in one plane however concentrates a lot of stresses when the vehicle goes over rough terrain. A universal joint that allows complete freedom of movement would simply cause the vehicle to drop at the hinge point. What we need is something that acts as a hinge in one direction and can rotate on one side.

Here is a quick video of what I am talking about

To make this system work well has been a bit of a challenge, because I don't have access to any specialty equipment, and I am trying to make something that is reproducible by local people here in South Sudan.

What I have come up with is a hinge that rotates at the center, but the moment force actually transfers from one frame to another through bearing at the top and bottom. This makes the system very strong. I can get up and jump on the pivot point and notice no real deflection.

parts the make up the hinge are normal round tube. This is not actually round inside as it has a welded seam, so I use 1/2" water pipe as a bushing. It seams to work quite well, and when it wears out can be replaced for almost no cost.

The rotating part was made in a similar way. Two pieces of angle were cut to make a tube the right size to hold a larger water pipe which allows to metal pipe inside to rotate. a welded stud at the end allows a nut to lock the piece from pulling out.