I checked it out. It obviously doesn't have the same potential for easy failure but you'd have to agree that if the bolt that holds the torsion bar to the hitch were to break the same conditions would exist.
Now I'm angry. Let's see if you come to the same conclusion.
First, let me describe the way the system works. A round tube torsion bar system does work well under normal circumstances.
The 2 x 2 solid steel bar that fits into the receiver on the tow vehicle is held in place with a hardened steel shaft with a spring pin passing through a hole in the end of it, holding it in place. That shaft becomes an extension of the vehicle as it is tied directly to the vehicle frame. I believe it was bent when the trailer nearly jackknifed.
The 2 5/16" ball is mounted to the new equalizing hitch, not the hardened steel shaft, as is normal for a non-equalized hitch.
The equalizing hitch is attached to the hardened shaft through the vertical shaft drilled with additional holes for height adjustment. A proper height is selected and proper shims are installed to make the ball tip slightly toward the trailer. This angle is important because it will change slightly when the torsion bars are put in tension.
The bars are put in tension by a cam device that snugs up the chains, transferring the load equally to the trailer and the tow vehicle. You are suppose to level out the trailer and tow vehicle and then apply tension to the bars by equally counting the number of links and setting the tension devices on both sides. 8 links produced no tension. 6 links was nearly impossible for me set. 7 was just right.
Each chain tensioner is fitted with a safety device that keeps the tensioner closed. These parts did not fail. The tensioner is fitted to the frame with a set screw. They supply different length screws for various frame widths. These clamps are snugged in place, but are mainly held by the spring tension pulling them straight down on the frame.
The objective is to make the trailer and tow vehicle a unified structure so that "porpoising" is minimized. The sway control comes from the round tube connection. The torsion bar has a diameter that is smaller than the tube it fits into. It is designed to move freely when not cocked in the opening by the tension provided by the chains. The rubbing of the round bar in it's receiving tube is what gives you sway control as that resistance is what makes the tube intentionally bind when needed.
There are many times that the tension drops and the round bar is free to move in its socket. It is held in place at this time, on this model, by a tapered, spring-loaded pin that allows you to push the round bar into place without pulling back on the pin.
That pin fits into a groove in the round bar that is designed to stay engaged with the groove, keeping it from falling out of the socket.
After a sleepless night I went back to the shop and made a closer inspection of the mechanism.
My first observation was that the pins were nowhere near as long as they could have been, based on the depth of the groove. Even so, they should have stayed in.
I then observed that the beveled face of the pin didn't line up with the locating grooves that are supposed to firmly position the pin.
If the beveled pin were allowed to rotate 180° the round bar would never stay in as it would simply push the pin back by sliding down its ramp. These pins didn't rotate 180°, they only rotated about 20-25°, enough for the pin to work its way out and disengage the safety device.
To check my hyphypothesis I used two metal plates with straight edges inserted all the way into the locating grooves. You can clearly see that they are not within any tolerances that I (or anyone else) would find acceptable.
This manufacturing flaw wasn't the total cause of the failure though. The springs installed to keep the pins in place are made of either very cheap or very thin spring steel. They offer little resistance to the pin being pushed out of place.
This is the last link in the failure. The top round bar is the one that fell out. The one that stayed in has a nice crisp edge while the one that fell out has a ramp-like edge that would definitely shorten the effective length of the pin.
In my opinion it was the cumulative manufacturing flaws that led to the torsion bar dropping out of its socket.
When the passenger side torsion was lost the torque of the remaining torsion bar put the trailer into a severe pull to the side that remained. It's indescribable how I felt at that moment as I've never encountered that effect before. Instead of diminishing sway the remaining bar was inducing it. Had I not applied the trailer brakes the trailer would have continued on its circular path clearly leading to a flip of either or both of the vehicles.
Does this qualify as negligence on the part of the manufacturer? I'm sure my insurance company will go after them to recover their costs. Is a retailer responsible for a product they sell? Keep in mind that this product is marketed and sold as a safety device. Is this an issue for NHSTA? Is that who would regulate this product or would this be a Product Safety issue?
I've heard from four people that they have observed round bar hitch failures, too.