Stressor
Whitefish Bay, Wisconsin
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Joined: 05/29/2001
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Willald,
I did not do the pin in on purpose, I just wanted first and foremost to prove what I said to myself, convincingly.
$4.91 at the nearest ACE hardware store got me back in business, as I was camping. It took a drift pin and a ball peen to knock it through the first hole. Previous screw ups on my part requiring the use of both tools made them readily available.
As for Tim's answer, it will probably start out: Stressor said... ![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/biggrin.gif "biggrin")
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Milton Findley (and Kerene)
A small piece of my mind...
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tluxon
Kirkland, WA
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Joined: 08/12/2001
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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
Tim -
wife Beverly & 2 boys who love camping
2002 K2500 Suburban 8.1L 4.10 Prodigy
2005 Sunnybrook 30FKS HP Dual Cam
Replaced 2000 Sunnybrook 26FK on 8/6/04
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tluxon
Kirkland, WA
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The pendulum analogy doesn't work very well because of the effect of gravity, especially as it pertains to a TT. I'd like to modify that analogy to make it more applicable.
Imagine that both the TV and TT have hockey pucks at the bottom of each tire (or a single large puck halfway between the centers of the two axles of each vehicle) and they are sitting on water-slickened ice. You would then see that you can't "turn" (pivot) either vehicle without the other one being forced to pivot as well. The difference is that the vehicle on the end of the hitch that has the long-long link does not pivot as far as the one on the short-long link when a bend at the hitch occurs. That's one of the reasons the TV is placed at that end of the HA. If the hitch were somehow reversed, a small turn of the TV would require a larger twist of the TT. This makes it impractical to arrange the hitch this way because it gives the TT greater "leverage" over the TV.
It's important to characterize something like this in order to understand the tendancies all the tires are being faced with. If you'll remember my "entertaining" model, you may or may not have noted that I had to twist each end bar in just a certain way in order to get it to "play" at all. Virtually any other direction of force results in no movement at all. Like it or not, playing with the model really does help one more fully appreciate the great advantage the TV has with a HA compared to a conventional hitch setup. I would suggest that we throw out the moment illustrations I presented because I'm not sure they properly characterize the complex translations that are required in order for a pivot to occur. Since the HA has no simple pivot point like a conventional hitch possesses, I think it would be extremely difficult to ever make a fair mathematical comparison between the two hitches.
Tim
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ttsr4us
Florida
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Joined: 10/17/2003
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I have read this with great interest. I am a Hensley owner and it taimed my sway problem which my Reese Dual Cam was unable to do. I am reaching some understandind about how this hitch works but am not quite there yet. One problem I have is that I am able to move the hitch from the TT-( Edit to read TV) end when I insert a bar into the hitch to unlock the drop down bar which prevents the hitch from moving when disconnected from the trailer. I can rotate it around quite freely buy pushing into the TV(should read TT) direction and applying a rotating force at the same time. So is this a force direction issue, ie tension rather than compression which would also explain why the brakes on the trailer have to be set correctly? Sorry to stir the pot but I have not seen this aspect discussed. (I may have missed it)
On Edit,
I got my TV TT,s mixed up. Really sorry guys.
* This post was
edited 06/07/05 10:49am by ttsr4us *
Brian and Esta
previously 2 Trailers and 2 Motorhomes, back in the trailer game.
GMC Sierra 3500HD 2WD, SLT Crew Short Bed. Duramax. 2014
Airstream 2016 Flying Cloud 30 RB with 2 a/c + Window Awnings
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Dakotahawk
Hudson, Wisconsin, USA
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This discusion of "projecting a pivot point it all bogus I think".
The issue is not wether a Hensley tow better (it definitly does) by why. The clue to why is not in projecting but in understanding the the design locks the pivot such that nothing the trailer does can make it pivot (no directional change from the towed vehicle (trailer) can pivot. Only pivot can happen from the front( the tower vehicle) End of story.
tom Marson
[email protected]
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tluxon
Kirkland, WA
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Dakotahawk wrote:...The clue to why is not in projecting but in understanding the the design locks the pivot such that nothing the trailer does can make it pivot (no directional change from the towed vehicle (trailer) can pivot. Only pivot can happen from the front( the tower vehicle) End of story. Not.
The only reason it is effectively "locked" is because you have tires on the ground. Put them on pucks on ice and you have a different story. Guaranteed.
Tim
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tluxon
Kirkland, WA
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ttsr4us wrote:...I can rotate it around quite freely buy pushing into the TV direction and applying a rotating force at the same time. So is this a force direction issue,...? Exactly! The force must be applied in a direction that complies with the tightly restricted elliptical-like path of the linkage in order to get it to move. Any other direction and/or combination will be met with incredible resistance, making many conclude that it is "locked" or rigid. It's not, but good luck ever getting a trailer to apply force and direction needed to pivot the hitch.
Brian, I believe you're the first Hensley owner to perceive the possibility of this behavior. You deserve some kind of award!
Tim
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bettered
UpCountry SC
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Joined: 07/26/2004
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ttsr4us:
I'm thinking you're pushing the head of the hitch in the direction of the TV and then TRANSLATING the black part of the hitch to the side. I suggest that you can't rotate it because of the linkage, but rather by translating it sideways, the linkage then forces the rotation. But of course with the TV attached, this is impossible, because you can't translate or rotate the hitch bar without moving the TV. And for those who haven't experienced this action, it's acheived with the hitch attached normally to the TT. The Orange part of the hitch is in this case immobile.
Ed B
BetterEd
DW + 2 grandkids + Mini Schnauzer
2005 Chev 3500 Crew D/A 6.6L LLY, 6 x 6 DRW, 3.73
Tru-Flow + Banks, 2005 Flagstaff 831FKSS
Hensley + Prodigy
"Genius may have its limitations...." E. Hubbard 1856 - 1915
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Stressor
Whitefish Bay, Wisconsin
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The only reason it is effectively "locked" is because you have tires on the ground. Put them on pucks on ice and you have a different story. Guaranteed.
Tim,
You are in no position to guarantee anything. The pictures clearly and absolutely demonstrate that the linkage works without tires on the ground.
It is locked up, there is no "effectively" locked up about it.
Your theory as you have developed it is in great trouble, and if you knew much about a 4 bar linkage, you would know how to lock one up, like this one is.
You would also be able to explain to the man how it works when the TT turns.
Tim said: "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."
The off center pulling force alone directly simulates an input from the travel trailer to the tow vehicle. The demonstration is real world, and supports my position on how the hitch works, so I believe it is safe to say that I had thought about it. The linkage is locked up, there ain't no translation, there is merely a lever from the TT direction. I have been watching engineers make fools of themselves for years.
Tim said: "Make light of it if you will - it's real whether you want to believe it or not."
I don't think that the audience clapping will revive Tinker Bell this time.
* This post was
edited 06/07/05 06:09am by Stressor *
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Stressor
Whitefish Bay, Wisconsin
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bettered wrote:ttsr4us:
I'm thinking you're pushing the head of the hitch in the direction of the TV and then TRANSLATING the black part of the hitch to the side. I suggest that you can't rotate it because of the linkage, but rather by translating it sideways, the linkage then forces the rotation. But of course with the TV attached, this is impossible, because you can't translate or rotate the hitch bar without moving the TV. And for those who haven't experienced this action, it's acheived with the hitch attached normally to the TT. The Orange part of the hitch is in this case immobile.
Ed B
This is true up until the linkage reaches 90 degrees, then it breaks over, see the link I posted after the pictures. The Hensley linkage only rotates about 160 degrees before running into itself.
All of the turns are through the linkage, and displacing the linkage changes the angular relationship between the truck and the travel trailer.
One more time, repeat after me, the hitch assemblies do not move relative to their attachment points on their respective vehicles. All movement occurs in the linkage.
Milt
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