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 have followed this thread with keen interest as an HA owner of about 9 months with a rusty Mechanical Engineering degree that's 40 years old.
It's unfortunate that Mr. Gratz was recently forced to leave the discussion. It is apparent to me that he is an unusually capable engineer.
That said, the discussion went off track when the pictures of the 4 bar linkage were put up and the notion about "turning around the linkage" poked out of the weeds. This hypothesis is faulty and I'll explain why directly.
I recognized the confusion that erupted when Mr. Gratz was looking at the mechanism from the standpoint of the "black part" of the hitch, while others were focused on the "orange part." Much of this uncertainty and some confusion derives from one's point of view. Sitting on the back of the TV watching the Orange piece, one would see it move back and forth in turns. Sitting on the TT, one would see the black part move back and forth, while Mr. Orange was fixed, and stationary. Mr. Gratz has seen all of this but he has also looked at it from the standpoint of a bird flying over the hitch at the same speed of travel looking down. During turns, the bird has to fly a wavy path because of the Virtual Pivot Point phenomenon, which is not imaginary, it provides an explanation for the functionality of the linkage.
In the demonstration wmv, when the linkage is reversed, the pivot point used is the center of the horizontal bar in both cases. The bar pivots to and fro. The TT does this because it has effectively one fulcrum - it's 2, 4 or 6 wheels act as a single pivot point. The TV cannot approximate this motion unless its front wheels are scrubbed to and fro from side to side in a wide arc.
The idea of turning the linkage around doesn't work because the presumption then is that the TT is turning the vehicle, and we've already seen why that cannot happen. The friction between the 4 tires and the ground defines a fact that the tow vehicle cannot "pivot."
Much is made of the theoretical difference between a simple 4 bar linkage and the practical application. If there are no constraints on any of the links, we have merely a toy. A linkage becomes a mechanism only when one or more links are fixed to something.
It's unfortunate that Mr. Gratz was recently forced to leave the discussion. It is apparent to me that he is an unusually capable engineer.
That said, the discussion went off track when the pictures of the 4 bar linkage were put up and the notion about "turning around the linkage" poked out of the weeds. This hypothesis is faulty and I'll explain why directly.
I recognized the confusion that erupted when Mr. Gratz was looking at the mechanism from the standpoint of the "black part" of the hitch, while others were focused on the "orange part." Much of this uncertainty and some confusion derives from one's point of view. Sitting on the back of the TV watching the Orange piece, one would see it move back and forth in turns. Sitting on the TT, one would see the black part move back and forth, while Mr. Orange was fixed, and stationary. Mr. Gratz has seen all of this but he has also looked at it from the standpoint of a bird flying over the hitch at the same speed of travel looking down. During turns, the bird has to fly a wavy path because of the Virtual Pivot Point phenomenon, which is not imaginary, it provides an explanation for the functionality of the linkage.
In the demonstration wmv, when the linkage is reversed, the pivot point used is the center of the horizontal bar in both cases. The bar pivots to and fro. The TT does this because it has effectively one fulcrum - it's 2, 4 or 6 wheels act as a single pivot point. The TV cannot approximate this motion unless its front wheels are scrubbed to and fro from side to side in a wide arc.
The idea of turning the linkage around doesn't work because the presumption then is that the TT is turning the vehicle, and we've already seen why that cannot happen. The friction between the 4 tires and the ground defines a fact that the tow vehicle cannot "pivot."
Much is made of the theoretical difference between a simple 4 bar linkage and the practical application. If there are no constraints on any of the links, we have merely a toy. A linkage becomes a mechanism only when one or more links are fixed to something.
