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 could bend the whole hitch head on my conventional hitch nearly as well by pulling on it in the same manner that you pulled on one of your strut pins of your HA. These days, most engineers try to avoid costly damage by working through a problem theoretically (e.g. Verification testing) before putting actual configurations at risk.
You could've saved yourself a strut clevis pin by asking what might happen before actually hooking a come-along up to it. Better yet, if you had bothered to "entertain" yourself by running a popsicle stick model through its paces, you could've saved yourself a bit of hassle as well by observing the motion that is allowed. A little "playing" with the stick model would help you see that this 4-bar linkage will dictate by restriction the path a translation due to imposed forces will follow. The simple fact of the matter is that the linkage of the HA does NOT translate in such a direction that would accommodate the direction of the force you applied to it. Instead of applying an off-center pulling force alone, you would have to apply a twisting force at the rear link to simulate a trailer's swaying input to the hitch. This "twist" would serve to push at one side of the linkage while simultaneously pulling at the other. The catch is that the tow vehicle must translate as well, allowing the front link to pivot and traverse while the rear link twists in the opposite direction.
As for the virtual pivot point, go back a few pages and read again. It is never further forward than the single point each side link points toward. Re-read the link Ron provided early on that talks about instantaneous centers of rotation. Make light of it if you will - it's real whether you want to believe it or not.
Tim
You could've saved yourself a strut clevis pin by asking what might happen before actually hooking a come-along up to it. Better yet, if you had bothered to "entertain" yourself by running a popsicle stick model through its paces, you could've saved yourself a bit of hassle as well by observing the motion that is allowed. A little "playing" with the stick model would help you see that this 4-bar linkage will dictate by restriction the path a translation due to imposed forces will follow. The simple fact of the matter is that the linkage of the HA does NOT translate in such a direction that would accommodate the direction of the force you applied to it. Instead of applying an off-center pulling force alone, you would have to apply a twisting force at the rear link to simulate a trailer's swaying input to the hitch. This "twist" would serve to push at one side of the linkage while simultaneously pulling at the other. The catch is that the tow vehicle must translate as well, allowing the front link to pivot and traverse while the rear link twists in the opposite direction.
As for the virtual pivot point, go back a few pages and read again. It is never further forward than the single point each side link points toward. Re-read the link Ron provided early on that talks about instantaneous centers of rotation. Make light of it if you will - it's real whether you want to believe it or not.
Tim
