3-Axis Coupler Idea (1 Viewer)

[ElPolloBlanco]

So I thought out a 3-axis coupler idea today, and wanted to run it by some other people before I committed to buying all the stuff for it. It goes like this from the truck to the trailer:

1. Clevis pin hitch in its standard orientation. This provides left and right movement.
2. A 5 inch long 2 inch .25 wall square tube with a .25 inch plate welded to one end. The plate has a hole with a 3/4 inch grade 8 bolt through it. Then a thrust bearing, then another square tube piece with a plate pinching the bearing together. This provides rotational movement. At the end of each tube are holes to allow a pin or bolt to be passed through to connect with clevis pin hitches.
3. Another clevis pin hitch , but turned 90 degrees. This allows for up and down movement.

I would probably use a bolt between 2 and 3 at the trailer side and a pin between 1 and 2 at the truck side.

I see this as somewhat similar to the Max Coupler design. Way cheaper than lock n roll or max coupler system. I plan on welding in a 2 inch receiver to the front of the trailer to fit either end of the setup through. I'd like to have y'all point out any potential flaws. I can't figure out the strength of the welds on the plates to the 2 inch tubes, but the bolt is something around 50,000 pounds in tensile and over 40,000 in shear, so I'm not worried about that pulling apart. I figure I can do this for under $100 as I already have the steel tube and plate. I'd just need the hitches at abut $40 each, bolt and hardware for less than $10, bearing is $5. With the plan to already have the 2 inch receiver on the trailer that cost doesn't factor in. If I decide to use a sealed thrust bearing, which I probably should, the price might get pushed over $100 a little.

So tear my plan apart. Better to do it here than have it tear itself apart doing 45 on a desert road.

 

[ntsqd]

I went as far down that road as buying a HF clevis hitch and playing around with it. I'm not a fan of having the pitch and the yaw pivot points very far apart, and the HF part at least was going to require it in order to get enough motion range. It is also difficult to design a simple to fabricate 'wrist' that fits within a 2" square tube. I've looked at this sort of thing for over a decade.

Messing around with the HF part convinced me to forget my previous bias against pintle hitches and learn what I could about them. The first significant thing that I learned is that very few make the OD of the lunette's torus big enough. There is a spec for that dimension and it is consistent across most all of the weight range. In realizing this I decided to buy some of those parts and see how they mated.
When the lunette's torus OD is big enough there isn't a whole lot of extra room in the opening of the pintle. I won't say that it completely quiets it down, but what noise it does make is nearly of no consequence.
Lack of a 'wrist' in the pintle hitch system caused me to design and fabricate this:

That is a common lunette ring that has the correct torus OD and to provide some sense of scale, those are 7" long 9/16" G8's. One of the flat washers between the nut and the plate is ginormous Belleville Washer and it is all that I want to do to rotate the lunette when on the end of a 3 foot long bar.

My frequently posted pic of it in use: