Hensley Arrow: How does it REALLY work?

Tim wrote:
In order to be compression only they would have to be designed as a bushing or sleeve.

Yep, and that's exactly what it is. The forward, inner threaded part of the strut assembly slides into the aft tube that is attached to the A-frame. If you take the strut off, the threaded piece will fall right out if you don't hold the two pieces together. When you tighten the locknut, the nut's action on the threads pushes the inner piece towards the hitch head and the nut pushes aft on the outer tube/A-frame, placint the assembly under compression.

Ron wrote:
In order to have the struts in compression, in the absence of any external forces on the hitch head or A-frame, you must have the coupler pushing rearward on the ball and the ball pushing forward on the coupler. This will cause the A-frame channels to be in tension.

During towing, the wind and tire drag forces will cause tension in the A-frame channels rearward of the strut attachments. Some of this drag force will be reacted by a decrease of compression in the struts and some of it will be reacted by an increase of tension in the A-frame channels between the strut attachment points and the ball coupler. The amount of drag reacted by struts versus A-frame channels will depend on their relative axial stiffness. The increased tension in the A-frame will increase the rearward force on the ball.

Thinking about it Ron, that's exactly right. Struts in commpression, A-frame (including the coupler) under tension. Which has me thinking about this (always a dangerous proposition): With everything hooked up, the struts and upper hitch head essentially become a new "A-frame" with a virtual apex forward of the coupler. This apex is the point around which the TT would want to pivot when a lateral force is applied if there were no linkage assembly. At the same time there is also another "virtual " A-frame delineated by the two forward linkage bearings (on the lower unit) with it's own virtual pivot point somewhere forward. And since this is the part that attaches to the TV, the forces on it are the ones felt on the TV.

What makes this second, virtual A-Frame different is that the "coupler" location is not in a fixed position, but rather is determined by the position of the four bar linkage, and the apex of the "A-frame" is laterally fixed in line with the stinger/receiver..

I'm obviously sort of rambling here, but this way of looking at the hitch might help explain why it appears "locked" in place from the trailer side. It might be (I haven't qiuite worked it out yet) that when a lateral force is applied to the trailer, the movement of the "virtual coupler ends up providing a counter force to hold the trailer in line. Similar to the way the compressive and tensioning forces work on the strut/TT A-frame assembly.

All in all, I think I've given myself a headache thinking about this, so I'm taking a break.

Andy