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'd like to dredge this topic back up, to discuss something I've been thinking about, that I'm not sure we took into consideration before, in all the models discussed before.
There seems to have been some 'disagreement' in this discussion previously, about whether or not the Hensley truly is 'locked' in a straight position (from the trailer's standpoint), or if its completely free to pivot, but strictly pivot through the arc/angle that the Hensley allows.
After some thought, I'd like to submit, that perhaps BOTH are true. Stressor was of the firm belief that there was indeed a 'lock' from the trailer's perpective, where as many others disagreed with such. It is my belief, that perhaps BOTH are correct. I'm not really able to put together the illustrations like others have, so I'll try to put it into words. Here goes..
Look closely at the video clip several posts back, where someone put a camera above a Hensley, when it was travelling down the road. This is the one that shows the Hensley going through its entire path of pivoting, when going down the road. Watch this video closely, a couple of times. After doing such, is when I came to a realization.
Notice, that the part of the Hensley affixed to the trailer (orange head), when it does pivot, it has to pivot through an ARC. And, notice that when the trailer/Hensley is in a straight line, its in the BOTTOM of this arc, such that in order to pivot either way, it has to move UP the arc in either direction, if you will.
Maybe one way to think of it, is to picture your truck and trailer suspended vertically by a crane or whatever, with the trailer hanging down below the truck. Gravity represents the same force pulling back on the trailer, that is normally pulling back on it when towing. Friction, air resistance provide this force when towing.
NOw, think of this dangling trailer, and you try to push it either way to make it pivot. In order for it to pivot, it would have to move up the arc the Hensley forces it to pivot through, hence it'd have to overcome the force pulling it back (gravity). Bottom line: It would NOT move/pivot. It would basically be LOCKED, from the trailer side. Thats exactly what Stressor(Milt) was trying to suggest.
Now, think about the truck pulling a trailer, and realize that there is tension/pulling between the truck and the trailer, similar to the way gravity pulled on it if suspended vertical like I just mentioned. It is this very 'pulling'/tension, that makes it almost impossible for the trailer to induce any pivoting. In order for the trailer to pivot, it has to move up the arc I mentioned above. As long as the truck is pulling the trailer, there is a TON of force the trailer would have to over come, in order to move up this arc. Hence, it cannot move up the arc, and the trailer CANNOT induce any pivoting. Basically, the Hensley is using the wind/friction resistance that a trailer has, to force it to stay in the straight position
Now, once the 'pulling' on the trailer goes away (as in, when braking and brake controller is not set aggressive enough), this whole effect goes away, and the Hensley pivots just like the previous models suggest - similar to a 5th wheel for first few degrees, getting more and more like a conventional TT the further it goes. Thats why its so crucial to have your brake controller set right, when using a Hensley, to get the full effect of the Hensley's design.
Anyway, I think in all our models/discussion before, maybe we did not take into account the fact that there is pulling/tension between the truck and the trailer/Hensley, which makes it nearly impossible for the trailer to induce any pivoting.
Thoughts? Ron Gratz, I'm sure you have a 3 page Physics model that may confirm or destroy my thoughts here, so go ahead - lay it on me. I'm ready. :)
There seems to have been some 'disagreement' in this discussion previously, about whether or not the Hensley truly is 'locked' in a straight position (from the trailer's standpoint), or if its completely free to pivot, but strictly pivot through the arc/angle that the Hensley allows.
After some thought, I'd like to submit, that perhaps BOTH are true. Stressor was of the firm belief that there was indeed a 'lock' from the trailer's perpective, where as many others disagreed with such. It is my belief, that perhaps BOTH are correct. I'm not really able to put together the illustrations like others have, so I'll try to put it into words. Here goes..
Look closely at the video clip several posts back, where someone put a camera above a Hensley, when it was travelling down the road. This is the one that shows the Hensley going through its entire path of pivoting, when going down the road. Watch this video closely, a couple of times. After doing such, is when I came to a realization.
Notice, that the part of the Hensley affixed to the trailer (orange head), when it does pivot, it has to pivot through an ARC. And, notice that when the trailer/Hensley is in a straight line, its in the BOTTOM of this arc, such that in order to pivot either way, it has to move UP the arc in either direction, if you will.
Maybe one way to think of it, is to picture your truck and trailer suspended vertically by a crane or whatever, with the trailer hanging down below the truck. Gravity represents the same force pulling back on the trailer, that is normally pulling back on it when towing. Friction, air resistance provide this force when towing.
NOw, think of this dangling trailer, and you try to push it either way to make it pivot. In order for it to pivot, it would have to move up the arc the Hensley forces it to pivot through, hence it'd have to overcome the force pulling it back (gravity). Bottom line: It would NOT move/pivot. It would basically be LOCKED, from the trailer side. Thats exactly what Stressor(Milt) was trying to suggest.
Now, think about the truck pulling a trailer, and realize that there is tension/pulling between the truck and the trailer, similar to the way gravity pulled on it if suspended vertical like I just mentioned. It is this very 'pulling'/tension, that makes it almost impossible for the trailer to induce any pivoting. In order for the trailer to pivot, it has to move up the arc I mentioned above. As long as the truck is pulling the trailer, there is a TON of force the trailer would have to over come, in order to move up this arc. Hence, it cannot move up the arc, and the trailer CANNOT induce any pivoting. Basically, the Hensley is using the wind/friction resistance that a trailer has, to force it to stay in the straight position
Now, once the 'pulling' on the trailer goes away (as in, when braking and brake controller is not set aggressive enough), this whole effect goes away, and the Hensley pivots just like the previous models suggest - similar to a 5th wheel for first few degrees, getting more and more like a conventional TT the further it goes. Thats why its so crucial to have your brake controller set right, when using a Hensley, to get the full effect of the Hensley's design.
Anyway, I think in all our models/discussion before, maybe we did not take into account the fact that there is pulling/tension between the truck and the trailer/Hensley, which makes it nearly impossible for the trailer to induce any pivoting.
Thoughts? Ron Gratz, I'm sure you have a 3 page Physics model that may confirm or destroy my thoughts here, so go ahead - lay it on me. I'm ready. :)
