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
willald wrote:
Milt (Stressor) argues that the 4 bar linkage, in actual, practical use on the Hensley, basically prevents any pivoting AT ALL from the trailer's perspective, and from the trailer's standpoint, everything is locked in line, like a straight truck. Based on how us Hensley owners have observed our rigs behave, its very easy to believe this.
Will, I'm still waiting for Milt to explain how a 4-bar linkage, whose links are connected via bearings, can be rigid ("locked up")when the hitch is aligned straight ahead, but be free to move otherwise.
Perhaps the linkage utilizes magic bearings which sense the articulation angle and "lock up" at zero angle but "free wheel" at non-zero angles. Or, perhaps, a magic diagonal brace materializes at zero angle to convert the 4-bar linkage into two rigid triangles. And, the brace then vanishes at non-zero angles. If it ain't magic, what is it?
The HA does not, and does not need to, "lock up" at any angle. It works because it is able to transfer both force and moment between the TT and TV via the two side links of the 4-bar linkage. A conventional ball coupler can only transfer force. It is the HA's moment transfer capability that is the key to how it works. It is that capability which effectively projects the pivot point forward. In doing so, the magnitude of the lateral force is reduced, and its point of application is moved closer to the TV's rear axle. The end result is that the "steering moment" imposed by the TT on the TV is significantly reduced.
Lateral instability is a threshold exceedence phenomenon - hence the name "instability". The HA enhances the TV/TT stability so that "sway" does not occur for a wide range of TV/TT combinations operating under a wide range of conditions.
Ron
