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
Thank you for chipping in, Ron. You're absolutely correct about the direction of the force vector being critical. Thinking of the boy in "The Sword and the Stone", it wasn't how hard he pulled that got the sword out of the stone, it was the direction he applied the force.
If anyone has watched their Hensley in action they would note that it translates significantly from side to side on even very slight angulation between the TV and TT. If anything is done to keep it from translating through its restricted path of freedom, it will appear to be - for all intents and purposes - locked up. When either end of the hitch is securely attached to a fixed object (stationary vehicle), the linkage at that end is NOT free to move and all the other parts of the hitch will have to move differently to accommodate that restriction. When a TV/TT combination is at speed, however, the attachment at either end of the hitch is only anchored down as much as the rolling friction of the tires and the inertia of the vehicle force it to be. That's why I introduced the hockey puck on ice analogy. Given just the right amount of freedom (lack of anchoring) and the perfect direction and force of input (inertia or otherwise), the Hensley will allow an angle between the vehicles. When that degree of freedom (extremely low friction, etc.) is reached, it won't matter whether the TV or TT initiated the motion, the angle will still be generated, some of the required translation occuring at the TV end and some of it at the TT end. All the while there is no change in the angle of the tees formed by the TV and the "front bar" of the linkage and the TT and the "rear bar" of the linkage.
Another thing you can do to observe the interactions between each linkage "end bar" is to have someone drive straight slowly and then begin to initiate a turn. You will note that when the TV turns one way (translating the front bar tee), the front of the TT (rear bar tee) simultaneously moves off-center significantly to accommodate a change in angle between the TV and TT. If you remember the little video I linked to a few days ago, you will remember that it translated from rotational inputs on each of the "end bars", as long as the opposite end bar was given freedom to move. That is why I claimed that the hitch could be reversed (provided the necessary attachments could be made) and still allow the TV to turn the TT.
Tim
If anyone has watched their Hensley in action they would note that it translates significantly from side to side on even very slight angulation between the TV and TT. If anything is done to keep it from translating through its restricted path of freedom, it will appear to be - for all intents and purposes - locked up. When either end of the hitch is securely attached to a fixed object (stationary vehicle), the linkage at that end is NOT free to move and all the other parts of the hitch will have to move differently to accommodate that restriction. When a TV/TT combination is at speed, however, the attachment at either end of the hitch is only anchored down as much as the rolling friction of the tires and the inertia of the vehicle force it to be. That's why I introduced the hockey puck on ice analogy. Given just the right amount of freedom (lack of anchoring) and the perfect direction and force of input (inertia or otherwise), the Hensley will allow an angle between the vehicles. When that degree of freedom (extremely low friction, etc.) is reached, it won't matter whether the TV or TT initiated the motion, the angle will still be generated, some of the required translation occuring at the TV end and some of it at the TT end. All the while there is no change in the angle of the tees formed by the TV and the "front bar" of the linkage and the TT and the "rear bar" of the linkage.
Another thing you can do to observe the interactions between each linkage "end bar" is to have someone drive straight slowly and then begin to initiate a turn. You will note that when the TV turns one way (translating the front bar tee), the front of the TT (rear bar tee) simultaneously moves off-center significantly to accommodate a change in angle between the TV and TT. If you remember the little video I linked to a few days ago, you will remember that it translated from rotational inputs on each of the "end bars", as long as the opposite end bar was given freedom to move. That is why I claimed that the hitch could be reversed (provided the necessary attachments could be made) and still allow the TV to turn the TT.
Tim
