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
How the HA Reduces Lateral Loads Imposed by TT on TV
When external loading is imposed on the TT, via wind forces for example, some of the force is reacted by the TT's tires and some by the ball coupler. If the resultant external force on the TT acts forward of its tires, a clockwise moment will be imposed on the TT. If the resultant force acts behind the tires, a counterclockwise moment will be imposed. In the special case when the resultant force acts in line with the tire reactions, there will be no moment; all of the external force is reacted by the tires and there is no lateral load on the coupler.
The moment imposed on the TT by external forces can be countered in two ways:
1. By a lateral force acting at the coupler multiplied by the distance from coupler to TT axles and/or,
2. By a moment applied via the coupler (which the HA can provide, but a conventional hitch cannot).
With the HA, both moment and lateral force can be transmitted via the hitch. Since some of the moment acting on the TT can be countered by the moment transmitted via the hitch, the HA's lateral force does not have to be as large as it would be with a conventional hitch. The reduction in lateral force results from the effective increase in the TT's tongue length due to the forward projection of the virtual pivot point.
For example, consider a TT connected with a conventional hitch where the ball to TT axles distance is 20'. The actual moment arm is 20'. Now consider the same TT connected via a HA and assume the HA can project the VPP forward by 4'. The distance from the VPP to the TT axles has been increased to 24', so the virtual moment arm is 24'.
Now, for a given moment, the force decreases if the moment arm increases. Therefore, the force acting at the VPP is reduced to 20/24 = 83.3% of the force which would be imposed on the TV using the conventional hitch.
Now, it this makes it seem as though the hitch has caused the external force on the TT to be reduced, I must say that not even the Hensley Arrow can calm the wind. The amount of external force which is not being reacted at the coupler has been transferred to the TT's tires. For a given lateral load on a TT, as the distance from the TT axles to the pivot point (actual or virtual) increases, the TT's tires pick up more and more of the lateral load.
Ron
When external loading is imposed on the TT, via wind forces for example, some of the force is reacted by the TT's tires and some by the ball coupler. If the resultant external force on the TT acts forward of its tires, a clockwise moment will be imposed on the TT. If the resultant force acts behind the tires, a counterclockwise moment will be imposed. In the special case when the resultant force acts in line with the tire reactions, there will be no moment; all of the external force is reacted by the tires and there is no lateral load on the coupler.
The moment imposed on the TT by external forces can be countered in two ways:
1. By a lateral force acting at the coupler multiplied by the distance from coupler to TT axles and/or,
2. By a moment applied via the coupler (which the HA can provide, but a conventional hitch cannot).
With the HA, both moment and lateral force can be transmitted via the hitch. Since some of the moment acting on the TT can be countered by the moment transmitted via the hitch, the HA's lateral force does not have to be as large as it would be with a conventional hitch. The reduction in lateral force results from the effective increase in the TT's tongue length due to the forward projection of the virtual pivot point.
For example, consider a TT connected with a conventional hitch where the ball to TT axles distance is 20'. The actual moment arm is 20'. Now consider the same TT connected via a HA and assume the HA can project the VPP forward by 4'. The distance from the VPP to the TT axles has been increased to 24', so the virtual moment arm is 24'.
Now, for a given moment, the force decreases if the moment arm increases. Therefore, the force acting at the VPP is reduced to 20/24 = 83.3% of the force which would be imposed on the TV using the conventional hitch.
Now, it this makes it seem as though the hitch has caused the external force on the TT to be reduced, I must say that not even the Hensley Arrow can calm the wind. The amount of external force which is not being reacted at the coupler has been transferred to the TT's tires. For a given lateral load on a TT, as the distance from the TT axles to the pivot point (actual or virtual) increases, the TT's tires pick up more and more of the lateral load.
Ron
