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Burbman,
I remember seeing that picture of your damaged receiver some time ago. In all fairness to GM, either Hensley design does increase the amount of "twist" over that of standard designs. On the other hand, I haven't heard of any receiver tube failures besides this one GM design. Other GM designs work ok.
The receiver tube is basically analogous to the fulcrum I
spoke of earlier, and takes the full brunt of 4-link increased leverage. Besides the torn visible rear tube support, was there also another welded support behind it (to the front of the tube) that was completely torn loose?
A more accurate, but more complicated, analogy to the lever/fulcrum idea would be to consider the fulcrum location moves throughout the turning range. The fulcrum is almost at the far end of the short side of the lever when straight ahead, giving maximum leverage when straight, but more to the center when turned sharply. This variable ratio principle then mandates that an even smaller amount of unwanted play means a greater ratio of side-to-side slop in the link arms whenever the hitch is aimed straight ahead.
FWIW, I did measure a simulated 1/16 inch strut looseness to see how many turns of the coarse-threaded strut adjustment nut this represents. One sixteenth inch is equal to .0625 thousandths, so I combined a .025, a .020 and a .017 feeler gauge to comprise a total thickness of .062 (just .0005 shy of 1/16 inch). After I snugged against the thickness of the gauge pack, I was able to turn the strut adjustment nut about an additional 1/2 turn to the same snugness with no gap. My struts were once much looser than that after turning too sharp (U-ball) one time. I found the problem shortly when I made a brisk stop at a light and got the bump.
Other than that incident, I have
never gotten a bump, and that includes with an original faulty F-250 brake controller that did not set
any trailer brakes automatically. I had to manually operate it and often did not bother with TT brakes for slowspeed stops until I finally corrected the controller problem. In addition, on faster stops, I seldom manually led the trailer brakes with the faulty brake controller... still with no bump problem. Apparently leading with the trailer brakes is not necessary in every instance, although I would still definately recommend it for hard stops that may tilt the truck/trailer angle which may allow strut slack.
Wes
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jerem0621,
Interesting picture and story. It appears that only one side was torn in a tension incident.
The strut normally forces the head forward (and the ball into the TT coupler pocket) when properly adjusted, and the threaded strut rod just falls out of its tube when pulled straight ahead in mock tension by these pin holes. It is hard to imagine how this occurred.
Perhaps the head was somehow allowed to suddenly rotate by the rear strut pin coming out, and the strut rod, trapped by the tongue frame, twisted out of its pin mounting when the head rotated. One would think the strut pin boss would break off first, but the forward threaded strut rod end is solid steel otherwise.
Thanks.
Wes
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