Hensley Arrow: How does it REALLY work?

sfdon wrote:
I mounted the frame brackets with u-bolts, installed the spring bars and installed the strut assemblies. I did not install the two 5/16" shear bolts into the frame brackets.

The shear bolts are little more than an indication that the frame brackets have shifted (thus shearing the bolts). They are purposely made of low grade steel for this reason. It's not a good idea to replace them with higher grade bolts because you're preventing the safety feature from working as designed.

sfdon wrote:
I approached the 90 degree turn and had no problem, but when I approached the stop sign at the intersection I heard a clunk coming from the hitch. I pulled over and found that the frame brackets had shifted rearward about a 1/2" on both sides.

I concluded the following:

The strut assemblies are in compression. Actually it is a very cleaver design, requiring no external tools.

When I applied the brakes going into the 90 degree turn, the instability of main hitch assembly under braking and turning conditions was enough to overload the struts, causing them to shift on the frame.

Nope. You may have overstressed the installation when you turned more than 85 degrees. That's one situation in which the frame brackets will shift.

sfdon wrote:
The clunking sound was the hitch assembly flopping around because of the loose struts.

My experience seems to substantiate what Ron and others have been saying.

There are a bunch of questions.

Instructions say to tighten u-bolt fasteners to 45 ft. lbs. What force on the struts would cause the brackets to slide on the frame?

You will find that the lug nuts on your wheels are in the same neighborhood. 45 ft # is a LOT of torque. You will probably get some localized deformation of the tongue - mine are rectangular and I've noted a little. The brackets sliding on the tongue are a last resort outcome. I've never experienced my brackets sliding, although I've heard the system clank from time to time. I'm not familiar with the special requirements of non-rectangular structural tongues.

sfdon wrote:
What is the shear strength of the (2) shear bolts, resulting in a total resisting force to prevent the sliding to occur?

It's very low - probably 35,000 psi or less.

sfdon wrote:
Finally, what event could occur that would cause the shear bolts to shear and the bracket to slide?

You've experienced (or caused) one such situation. Another might be the link collapse / hitting the stop phenomenon described on the previous pages.

sfdon wrote:
Question: is there any evidence that Hensley-Arrow monitors these treads and responds to them? I would hope they would be actively involved as I believe it would help their sales efforts.

You should call the Hensley service folks and discuss with them. What you experienced is not something I would expect. It sounds to me as though you may not have reached the 45 ' # of torque specified. Near the limit when the brackets were breaking loose at the specified torque, you might have noted some groaning or popping that would have alerted you to something being amiss. The fact that both brackets moved adds some logic to my suspicion about the installation.

From what we can tell, Hensley is selling all the Arrows they can make, so I wouldn't worry about it on that side. What you've experienced is out of the ordinary.

sfdon wrote:
Posting to follow on brake controllers with HA.

Lastly, as I wanted to install the HA myself, I knew that I was not going to lift up the 100# Main Hitch Assembly. I devised a hoist consisting of a collapsible saw horse on which I mounted a small boat winch. Not only did it work well, it is possible to take it with me on trips in case I have to or want to remove the main assembly. If you are interested, I can e:mail you photos.


Don

You might find it easier to use a floor jack. I jacked my hitch up, secured it with some blocks, lowered the coupler down onto the ball in the hitch with the TT tongue jack, locked the coupler on the hitch on and then raised the trailer to clear my blocking. As you know, the hitch normally "hangs" on the ball.

Overall, my hunch is that you're experiencing problems of an unsatisfactory installation. Under normal circumstances, the frame brackets will not move and generally, they shouldn't.