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
willald wrote:
Once we have all this in place (hahahaha!), all we'd have to do is try to push the A frame/weight side to side. You would find, that if it is a real heavy weight, it would be very difficult to pivot the A frame back and forth, because you'd have to overcome all the weight/gravity pulling down, since the Hensley's pivoting arc/path would make you in essence lift up the weight in order to pivot it either direction.
This is the point Ron refuses to believe - he thinks the pulling force on the Hensley makes no difference, and the force required to swing such, would be no different than what you'd experience on a conventional pendulum arrangement. It is NOT the same as a conventional pendulum arrangement, because the Hensley forces the trailer to be pulled closer to it, in order for it to swing either way. It would be like a pendulum arrangement, where the pendulum arm has linkage/mechanism in it, that makes the arm 'reel in'/get shorter, when swinging to either side.
Will,
You are mostly correct in principle; but you are greatly overestimating the magnitude of the weight/pull effect.
The "reel in" effect amounts to about 0.1" of forward movement of the ball for 1 degree of swing angle. This does not result in any appreciable resistance to swinging. The larger amounts of forward movement of the ball seen in the video are for swing angles which are much larger than those encountered at highway towing speeds; but even those larger forward movements, if they could be achieved at highway speeds, would not result in any appreciable resistance to swinging.
As far as regular pendulum versus 4-bar pendulum -- with either an ordinary pendulum or one supported by a 4-bar linkage, a very close approximation of the force required to swing the weight is given by:
Force = weight X tangent of angle of swing
For an angle of 1 degree, the tangent is about 0.017. So, if your test anvil weighs 100#, you will need to apply about 1.7# of force for each 1 degree of swing.
Please re-read this post if you want more details.
If you want to conduct a meaningful test, just reproduce Milt's test. But pull on the ball where the real force is applied; and pull at a few different angles which are not lined up to pass through the VPP.
Ron
