Hensley Arrow: How does it REALLY work?
There have been several discussions on this hitch that have become somewhat 'controversial'. I am NOT trying to stir this controversy/bashing back up. Instead, I'd like to see a good, intelligent di...
Forum Discussion
These two pictures were taken to demonstrate to non-Hensley owners what the word rigid and one way means in actual practice. It seems clear that it is difficult to gain an understanding of the operation of the hitch through the use of graph paper and popsicle sticks, although it is an entertaining theoretical endeavor. A Hensley is an application of a rocker-rocker 4 bar linkage, not one of the innumerable possible designs of a 4 bar linkage. With that in mind, let us proceed...
The hitch is connected via the stinger to an F-250 pickup reciever rated at 1500/15,000 pounds. The travel trailer end of the hitch is free floating, attached only via the two links. The wires attached to the strut pin on the right hand side are attached to a black willow tree, 24 inches in diameter, through a MAASDAM POW-R-PULL rated at 4000 pounds and a recovery strap rated at 15,000 pounds.
The come-along is under tension sufficient to pull the 3/4 inch strut clevis pin into the shape of a banana, rendering it useless. When the vehicle recovery strap is plucked, it emits a tone which is reminescent of one of the keys on the far left of a piano keyboard.
This is intended to simulate a side load on the travel trailer end that is approximately what would be experienced if a large elephant was leaning on the rear four feet of the travel trailer.
In actual operation, the rear of the hitch is attached to the travel trailer by a hitch ball connector, and prevented from moving side to side by two struts. This is nice, but as you can see, the linkage works just fine without being attached to anything.
What this proves:
The linkage from the TT to the TV is as rigid as a 2x2 inch steel bar is rigid. During a towing operation, the travel trailer and the tow vehicle move as one rigidly connected unit from the travel trailer end of the rig. Any forces applied to the travel trailer are applied to the TV receiver through a steel bar, more or less any effects related to leverage, flexing sidewalls, aerodynamics, or the like.
Note that the front linkage has not moved, and that the rear linkage has not moved. No pivoting has occurred anywhere. All of the very considerable forces being applied in this demonstration are being felt at the TV receiver, and transmitted to the TV frame and other components.
Close observation will indicate that all of the play has been taken out of the receivers, both the one on the TT end and the one on the TV end, and that the hitch has attempted to line up the linkage with the direction of the pull. Again, no pivoting has occurred. In actual operation, this play is limited by the operation of the struts on the TT end. The linkage is locked to inputs from the travel trailer end.
The much loved virtual pivot point can only be seen from the drivers seat of the vehicle, (use binoculars, it is out there somewhere).
Where does it actually pivot? Like anything else, if you look for where it bends, that is the actual pivot point. When towing ahead, it bends at the hitch when the tow vehicle initiates a turn, and not at all if the travel trailer initiates a turn. No Sway. :B
