Hensley Arrow Hitch Design Schematic
What is Special About the Hensley Hitch Design?
The majority of trailer owners think of a trailer hitch as a coupler that simply attaches to a ball. Typically, weight distribution bars are added and, finally, some sort of sway control device. This usually consists of friction or spring resistance of one form or another. So the first time they see a Hensley Arrow or Cub hitch, they assume that it contains the same basic elements: ball, coupler, springs, sway control device.
Comparing a Hensley Hitch to a traditional sway control hitch is akin to comparing a horse-drawn carriage to an automobile. People tend to look for the horse. It’s not there.
In the case of the Hensley Hitch, the “horse” is the ball. It has simply been removed from the equation. You’ll see in the photo below that the ball and coupler still exist, but they have been locked out. The trailer can no longer pivot on the ball. It pivots along the geometry of the linkage system. If you are of an engineering mindset, the Hensley Hitch design is based off of a 4-bar linkage system. For you true nerds out there, here’s a brief explanation from Wikepedia. If you truly have a thirst for knowledge and a desire to impress your friends around the campfire, simply Google “four bar linkage” and you’ll soon be a Hensley Hitch expert and we’ll probably have to hire you.
How does the Hensley Hitch impletment the 4-bar linkage system?
For those of you who just completed hours of research, you’ve probably realized that the 4-bar linkage system is all around us. Normally, it has a crank attached to it (think of those oil wells with the pump that looks like a giant steel bird). In our case, however, it’s a static system. We fix to points at the rear of the Hensley Hitch so that we limit their “degrees of freedom.” For you non-nerd types, that means we don’t let the rear two points move anywhere they like. Here’s a photo with the linkges overlaid:
So, class, if we refer to the drawing and our (now) vast knowledge of 4-bar linkage systems, we see four lines with four intersecting points. You will also notice that the two vertical lines aren’t parallel. So you get a trapezoid in the center. Points A and B are locked in place by the strut bars (the two black baars to the rear of the orange head). This keeps the points from moving, but allows the vertical lines to rotate about the points.
Points C and D are fullly free to to shift left and right while also allowing the vertical lines to rotate about the points. When you watch a Hensley Hitch in action, you’ll see the black “lower unit” shift side to side while the orange “upper unit” remains fixed. This geometry accomplishes three things:
- It creates a “single directional” tool that only allows the tow-vehicle to initiate the pivot.
- It “locks” the trailer in place so that it cannot pivot (or sway).
- It projects the pivot point 42″, or roughly over the rear axle of the tow vehicle (this is why it feels like a 5th wheel).
The Latest Hensley Hitch Design
The geometry mentioned above is unchangeable. The slightest change to any of those angles will result in a trailer that sways even more than a ball hitch or a tow-vehicle that cannot turn. Since we are the first company to implement this design into a functional trailer hitch, copycats abound. Any company that claims a “new and improved Hensley Hitch design” has simply changed the way it mounts, or the color, or some other cosmetic feature. While we are constantly developing new ways to mount the Hensley Hitch ourselves, as well as reducing weight, making hook-ups easier, etc., we must admit that all these are minor improvements over the original design. If you see a “new and improved” or “next generation” Hensley Hitch, simply take a look at the linkage system between the upper and lower unit. They are identical, though they may not be of the same quality.
Design Your Hensley Hitch
That being said, we do offer a variety of options to make your towing experience a better one. We have lighter Hensley Hitches for smaller trailers, Hensley Hitches with different sring bar options, and…well, that’s really it. Like I said, you can’t improve on established physics.
If you’d like to see which version of the Hensley Hitch design works best for your needs, check out our Build Your Hensley Hitch feature on the website.
Got questions? Comment on this post or call 1-800-410-6580.
Safe towing and we’ll be seeing you under the awning!
The biggest challenge I have had with the Hensley hitch is the swaying. Even with the nut tight on the swaying bar and leveling bars at the 2nd mark the wind can swaying the back of my F150 to where we have to drop the speed to 45 just to try and keep it under control. Trailer 33′ is level and truck with miner drop in back. Stinger has 2″ rise. Don’t know how to resolve this.
You may have too much weight taken off the back of the truck, George. Then any side force on the trailer will simply transfer through the truck, like it’s pushing the whole thing. Some trailers also tend to rock on the springs, which often looks like sway but is not. Give mike a call at 1-800-410-6580 ext. 121 if you need help.
I have been towing a 31 foot Airstream with the Hensley Hitch for the past 18 years and have only had sway once. It turns out there was a little bit of play in the strut bars. When I snugged them up the problem was gone. Other than that I drive with only one hand on the wheel and hardly notice that the trailer is there.
Al