I'm building an offroad trailer, the thread is on another forum but I figured I'd double-post this part in case it can be of inspiration to anyone else here.

All the hardware was about $40 from Tractor Supply, all the dimensional steel and plastics are salvaged from my empire of dirt.



Made some parts:



All the parts for the vehicle side. The outer tube is 1 3/4" 0.120" wall DOM, the inner is something like 1.32" OD and 1" ID. Bushings are delrin turned on a lathe.



And the trailer side. This uses '95 pickup rear leaf spring bushings that fit inside 1 3/4" DOM after turning them down a tiny bit in the lathe.



The vehicle side gets assembled - the bolt clamps on the steel sleeve inside the bushing, so the bolt can be torqued down tight and all the swiveling happens with the bushings.



The longitudinal axis does rotate on the bolt, so the nut is welded on solid. That does make this part non-serviceable, but I can make another pretty quick if I need to replace it. There is a grease fitting to keep it lubricated. This uses the same 3" spacing as my ball hitch tongue, so it can be swapped in if needed.



The two assemblies are married with a removeable 7/8" pin. The vehicle side can be unbolted and placed on a different drop/rise hitch mount (or flipped upside down), and the trailer side can be flipped to ride under the tongue, with these options I can configure the trailer to tow level behind different vehicles.



How strong is this? I can start with estimating each axis, since I'm using standard fasteners and can look up their properties.

Horizontal axis: 1" Grade 8 bolt in single shear: 0.606in^2 * 150,000 psi * 60% = 54,450lbs

Vertical axis 7/8" SAE 1020 pin in double shear: 0.601in^2 * 55,100psi * 120% = 39,738lbs

Longitudinal Axis:1" Grade 8 bolt in tension: 0.606in^2 * 150,000 psi = 90,900lbs

In all reality, something else will fail before those numbers. I mean, a 2" hitch mount only uses a 5/8" pin so that's pretty much guaranteed to be the fuse before these fasteners. I suspect the weakest link is the trailer side of the vertical axis, with the tube welded to the bolt head. I did reinforce it with a second layer of steel and there's ~10" of blazing hot weld mating it all together so I'm pretty comfortable with it... I think it'll be fine unless I try to snatch a semi out a snowbank off the back of the trailer. Maybe I'll go hook it to a tree and see how much I can stretch my kinetic rope out as a proof test.