Hensley Arrow: How does it REALLY work?

tluxon wrote:
For the most part you're right, Ed. However, since in the real world there are always tolerance gaps and wear on interfacing materials, I'm certain that there is a slight amount of play in the linkage, some units more than others.

The links pivot on double tapered roller bearings - two sets under the domed caps on the orange part - like the wheel bearings on a car or truck. As a result, the operative word in your statement above is "slight".

tluxon wrote:
This would allow some translation to occur without any rotation of the rear bar, resulting in no moment to be applied to the tires from the hitch.

Theoretically yes, but practically, it's nil.

tluxon wrote:
Besides, the rotational angle changes very little in the first inch or two of translation on each side of center anyway.

This is absolutely true.

tluxon wrote:
In addition, I'm having a hard time imagining what kind of forces outside of a broadside hit at the axles that could result in anything other than a moment on the CG of the TT. I've already shown above how a lateral force resulting from the moment of a TT results in a reactive COUNTER moment generated by the trans-rotation of the hitch linkage. We just don't know how much of a reactive moment the hitch CAN generate given its relatively minimal leverage and unknown compressive strength.

One of the more astounding testimonials on the Hensley website is from an owner who was involved in an accident where another vehicle lost control and rammed the TT at just about the axles. The TV and control of the TT were not affected in terms of directional stability. I find this hard to swallow, but that's what the fellow said.

tluxon wrote:
I think it might be more useful to identify specific hazardous conditions and analyze the various reactions using a HA. For example, if lateral slippage of the tires is a concern, pick a possible cause so we can start with those inputs.

Tim

Obviously icy conditions is one such hazard. The TT must have some traction in order for the hitch forces to be reacted. On the other hand, the problem would be worse (I presume from the calcs) with just about any other hitch.
The other hazard is what Hensley refers to as "over-driving" the TV. I take that to mean improper brake control on the TT, combined with carrying too much speed into a downhill corner. A sharp corner where one of the links has moved 'overcenter' would be much worse than a gradual corner. In the former case, "too much speed" wouldn't necessarily have to be a huge amount. It's the momentum thing...

A comment on the MIT reference. BINGO! Thanks for that. I note that some are looking for the short courses in Kinematics to be provided here. I know it was a long time ago (for me), but I can remember the name of the course..

Regards

Ed B