I found one of the pictures of my towbar with it out of the car, there is showing all of the parts but I can't find it... but I went out and took some pictures of it in the car
the parts are as follows, going from the tongue back to where it mounts to the rear of the subframe, all of these bits are bolted together, and to the subframe
tongue
rear subframe rail mount
2 x rear mount load spreaders
2 x rear mount captive nut plates
forward subframe mount
2 x side forward mount plates
here's the picture out of the car, this is looking at the bottom of it, from the rear of the car, so imagine the car is on a hoist, and you're standing behind it
here's the tongue, I was given one of those nasty towbars that bolt through the boot floor, so I modified it and drilled holes in it.
here's the view from the rear, the red circled bolts go right through from the subframe, through the load spreaders and out the other side of the rear subframe rail mount. The purple circled bolts go into plates inside the subframe channel with nuts welded to them.
here's the view from the other side, nice thick angle, and any load on the rear rail of the subframe is taken by the spreaders behind those bolts circled in red. However, there isn't a lot of load on the rear of the subframe, the rear part is for side/side and up/down stability. You can see that I had to compromise a bit to fit around the hydrolastic, I would have liked to make the angle go all the way out to the side, but just couldn't without taking the subframe out of the car
this is where the forward part and the rear part join together, also circled in purple is the notch in the rear part to clear the hydro channels. I didn't originally have it there, and the hydro pipes cleared OK, but when I had it out I thought I'd notch it
here's the notch again
This is the drivers side forward mount plate. The bolt right at the front is through the strongest point of the subframe, where there are 3 pieces of metal together.
so there you go.... I made it in a few afternoons before dragging my little trailer to Sydney for MDU in 2005. All mounted to the subframe, and despite a few compromises, I reckon it'd pass an FEA test with flying colours
