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
Who said this thread was only for the engineers? First we have a marketing guy and now we have a psychologist and both of them have postulated rational theories about the physics of the HA. Milt's reference to a HA-coupled trailer acting, or not acting, like a pendulum opens up some of the "contentious stuff" I alluded to a few posts back.
If one could vertically hang a semi trailer or a 5er or a PullRite-coupled trailer from its pin, the trailer could be made to swing like a pendulum about the pin. A vertically suspended trailer coupled with a conventional hitch could be made to swing like a pendulum about the ball. And, a vertically suspended trailer coupled with a Hensley Arrow could be made to swing like a pendulum about its VPP. Other than a small amount of friction, there is nothing inherent in the pinned or ball connectors which would prevent the oscillations. The same is true for the HA's 4-bar linkage.
If this sounds outrageous, consider that there are clocks, especially mantle clocks, in which the pendulum is suspended from a 4-bar linkage which is governed by the same physics as is the HA. These clocks use the 4-bar linkage to effectively increase the length of the pendulum. The objective is to achieve a one second or a one-half second period with a much shorter physical pendulum length. The 4-bar linkage in a clock is not "rigid" and does not resist the swinging of the pendulum. The same is true for the HA's linkage.
The HA's linkage does not provide a "rigid" connection at any angle, zero or otherwise. A heavier trailer and larger frontal area could cause a greater longitudinal "pulling" force on the linkage. However, the HA's linkage does not generate a moment in response to a longitudinal force. It only generates a moment in response to a lateral force. When the TV and TT are moving straight ahead it is the lateral force on the TT tires which prevents the TT from moving side to side. The HA only controls how lateral loading from the TT can affect the TV.
Ron
If one could vertically hang a semi trailer or a 5er or a PullRite-coupled trailer from its pin, the trailer could be made to swing like a pendulum about the pin. A vertically suspended trailer coupled with a conventional hitch could be made to swing like a pendulum about the ball. And, a vertically suspended trailer coupled with a Hensley Arrow could be made to swing like a pendulum about its VPP. Other than a small amount of friction, there is nothing inherent in the pinned or ball connectors which would prevent the oscillations. The same is true for the HA's 4-bar linkage.
If this sounds outrageous, consider that there are clocks, especially mantle clocks, in which the pendulum is suspended from a 4-bar linkage which is governed by the same physics as is the HA. These clocks use the 4-bar linkage to effectively increase the length of the pendulum. The objective is to achieve a one second or a one-half second period with a much shorter physical pendulum length. The 4-bar linkage in a clock is not "rigid" and does not resist the swinging of the pendulum. The same is true for the HA's linkage.
The HA's linkage does not provide a "rigid" connection at any angle, zero or otherwise. A heavier trailer and larger frontal area could cause a greater longitudinal "pulling" force on the linkage. However, the HA's linkage does not generate a moment in response to a longitudinal force. It only generates a moment in response to a lateral force. When the TV and TT are moving straight ahead it is the lateral force on the TT tires which prevents the TT from moving side to side. The HA only controls how lateral loading from the TT can affect the TV.
Ron
