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
I scratched together a quick sketch to help illustrate the difference between a Hensley and a conventional hitch and how they work with a trailer's moment, or twisting force. The source of this moment is not really important. It could be caused by a gust of wind or a quick lane change or a number of other things.
Assumptions:
All the lateral forces on the trailer combine together into a moment of 1000 Ft-Lb about the center of its axles.
The distance from the trailer coupler to the midpoint of the two axles = 20 feet. For reference, the axles of our Sunnybrook 30FKS are centered about 18-1/2 feet from the coupler.
To simplify the illustration, I've assumed that the trailer coupler is the same distance (67 inches chosen since Will had mentioned that he thought the VPP was about 20 inches behind the rear axle of his Excursion) from the rear axle of the tow vehicle with either hitch. I don't believe this is all that accurate, since a number of Hensley owners have said that the hitch adds about a foot or so to the overall length when compared to a conventional hitch.
There are other deficiencies in this sketch that don't perfectly reflect reality, but it should suffice for a general comparison.
Note that the trailer's moment converts to a slightly smaller lateral force (42 lb.) at the tow vehicle with the Hensley's VPP than with the conventional pivot point (50 lb.). However, the reacting moment of the TV is 4 TIMES as much with the long lever of a conventional hitch than it is with the much shorter lever created by the Hensley's VPP.
I think this could be taken a lot further, but this is good enough for me for now. Thoughts?
Tim
Assumptions:
All the lateral forces on the trailer combine together into a moment of 1000 Ft-Lb about the center of its axles.
The distance from the trailer coupler to the midpoint of the two axles = 20 feet. For reference, the axles of our Sunnybrook 30FKS are centered about 18-1/2 feet from the coupler.
To simplify the illustration, I've assumed that the trailer coupler is the same distance (67 inches chosen since Will had mentioned that he thought the VPP was about 20 inches behind the rear axle of his Excursion) from the rear axle of the tow vehicle with either hitch. I don't believe this is all that accurate, since a number of Hensley owners have said that the hitch adds about a foot or so to the overall length when compared to a conventional hitch.
There are other deficiencies in this sketch that don't perfectly reflect reality, but it should suffice for a general comparison.
Note that the trailer's moment converts to a slightly smaller lateral force (42 lb.) at the tow vehicle with the Hensley's VPP than with the conventional pivot point (50 lb.). However, the reacting moment of the TV is 4 TIMES as much with the long lever of a conventional hitch than it is with the much shorter lever created by the Hensley's VPP.
I think this could be taken a lot further, but this is good enough for me for now. Thoughts?
Tim
