tluxon
Kirkland, WA
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Milt, the burden of proof isn't on us. Hensley doesn't claim that the hitch is ever locked - just that it is effectively locked. You still haven't explained how your real world demonstration with a real hitch proves that the hitch is locked. And where does "4-bar theory" say what kinds of force vectors lock it up? All a 4-bar linkage is are linkages with pivot points that are not restrained.
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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jdwhittaker
York, SC
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Stressor wrote:...thanks for asserting that this is not locked, however, the photograph is real...
Milt,
I haven't said that your picture isn't real, but it doesn't prove that the HA is locked. It is under a great load, but not locked. If we hook another come along to the other side of your HA and pull perpendicular to the first I'm sure that the HA will move.
Stressor wrote:...You have made an assertion that the trailer tires add to stability, and I have pointed out that this is not necessary and that the Hensley Arrow is not dependent on trailer tires to prevent sway. It is not, and as you can see in this picture, it is solidly locked up to input from the trailer end. The trailer tires are not attached....
There clearly are no trailer tires in your picture, however the force that you are putting on the hitch isn't sway force, so no trailer tires are necessary.
Stressor wrote: I do not argue that tandem axles are sway preventives in themselves, but simply state that the Hensley Arrow does not need them to prevent sway, and that any such assertions are not credible without proof. The tandem axles do not need to be attached, as demonstrated above, and below. The hitch would operate as stated in Hensley literature if clamped in a vise.
Did you see the video of the HA moving freely with it mounted in a receiver? Similar to being clamped in a vise, no? Loading the HA as you have done is in no way locking it, but it does make it harder to move (trans-rotate).
![[image]](http://home.ripway.com/2005-1/238631/Folder%20Name/Hensleytext006.JPG)
Do you get royalties each time your picture is shown on the internet?![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/wink.gif "wink") Try not to get too stressed over all of this...
Lastly I own a Hensley Arrow, had it for about 3 months, made an 800 mile trip to the Outer Banks with it, it works as well as everybody claims, and I wouldn't tow without it again.
Dave
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BurbMan
Indianapolis, IN
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Joined: 09/20/2001
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Scroll down quickly through this series of photos takes with high speed film, and you'll notice that the hitch doesn't move, therefore it must be locked to the TT.
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Ron Gratz
full time RVer
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Stressor wrote:
This picture proves, real world, inarguably, that the Hensley hitch locks up from the travel trailer end.
And I'm sure anyone who believes that also will believe that a simple door hinge also is a Rigid One Way Hinge.
![[image]](http://www.geocities.com/trailerphysics/hensleylock1.bmp)
Quote:All forces from the trailer are applied to the hitch head by pushing the struts
Milt, I've asked this before; but, I must ask it again -- Are you aware that your TT is coupled to your hitch via a ball coupler in addition to the two struts? Forces from the TT are applied to the TT in two ways:
1. via both lateral and longitudinal forces at the ball coupler, and
2. via tension (not "pushing" as you assert) forces in the struts. I doubt that the struts are designed to transmit any significant amount of "pushing".
The largest portion of lateral load on the hitch is transmitted via the ball coupler. The struts simply are not at an angle which allows their axial loads to have any appreciable lateral component.
Quote: and the photograph proves, by simulating a 4000 pound push on the left strut connection by a 4000 pound pull on the right connection, that the hitch is locked up, and that it will be destroyed before it unlocks.
The photograph proves nothing. However, the photo does indicate that you were very "fortuitous" in finding just the right angle at which to pull. Anyone with a HA can debunk your "proof". You are just hoping that no one will go to the trouble to do it.
As the following "supporting diagram" shows, if the cable is angled so its force vector passes through the VPP there is no net moment which would cause the linkage to shift. Lack of movement does not prove the hitch is "locked". Lack of movement simply shows that all forces acting on the linkage are passing through the VPP. Remember Tim's bicycle wheel analogy? You can't make a wheel turn by applying a force vector which passes through the pivot point.
![[image]](http://www.geocities.com/trailerphysics/RowH.bmp)
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AO_hitech
SF Bay Area
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Joined: 08/09/2004
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Stressor wrote:
This picture proves, real world, inarguably, that the Hensley hitch locks up from the travel trailer end.
Okay, I'm new here. I can't see how that picture shows anything. If I do the same thing to a standard WD hitch and connect the come-along to where the WD bars attach I'll get the same results. So, how is that showing the HA locks up from the TT perspective?
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Stressor
Whitefish Bay, Wisconsin
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Joined: 05/29/2001
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Gee, what a breeze. ![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/biggrin.gif "biggrin")
Hensley says:
The secret of the Hensley Arrow rests in its patented converging linkage design. The Arrow allows movement on the ball in every direction except side-to-side. Side-to-side movement is forced to go through the linkage system which is one directional. From the trailer side, the linkage is solid. Pivoting by the linkage must be initiated through the tow vehicle. The system's design is inherently stable. Best of all, it functions mechanically, without the use of friction so it exhibits consistent and predictable behavior regardless of changes in weather or road conditions.
This is exactly what Hensley said. From the trailer side, the linkage is solid. The Arrow allows movement on the ball in every direction except side-to-side. (It is actually locked up from the trailer end).
Once again, making assertions is not good enough from the perspective of the liberal scientific method, and I see a lot of assertions, but no alternatives, and no means of testing the assertions.
And once again, Ron trots out his red herring, stating that I was fortuitous in finding exactly the right angle. There is only one place the cable can be attached that duplicates the strut attachment. Once again, he fails to demonstrate how these forces might come about, or how they may be applied to the hitch except at the mechanical points of connection, which is where the cable is attached.
Tluxon trots out his red herring, how can a pull on one end of an iron bar be the same as a push on the other end of the iron bar. I don't know guy, but with a few decades and a calculator, somebody might figure it out.
JD Whittaker has still not figured out the meaning of a unidirectional device, and needs to go look at the video again, at the part where the trailer is shoved over and the hitch does not bend. JD, what you are referring to is the tow vehicle initiating a turn, and it can, because the hitch is not locked up from that end. As Hensley says, "Pivoting by the linkage must be initiated through the tow vehicle." (It is actually locked up from the trailer end).
I have the Hensley statement, the theory of 4 bar linkages, specifically as it relates to toggle point, and a picture of a 4000 pound come along demonstrating a locked up Hensley Arrow hitch in an easily and endlessly repeatable experiment.
Now show me yours.
Burbman, thanks for the film. I wish I had thought of that.
On edit, I forgot one of the assertions that needs to be dealt with. Hensley says the following under "Safety,"
The Arrow mechanically locks sway out and creates an inherently stable relationship between your trailer and tow vehicle.
I know how it does that. ![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/tongue.gif "tongue")
* This post was
edited 08/30/05 04:12pm by Stressor *
Milton Findley (and Kerene)
A small piece of my mind...
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Stressor
Whitefish Bay, Wisconsin
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AO_hitech wrote:Stressor wrote:
This picture proves, real world, inarguably, that the Hensley hitch locks up from the travel trailer end.
Okay, I'm new here. I can't see how that picture shows anything. If I do the same thing to a standard WD hitch and connect the come-along to where the WD bars attach I'll get the same results. So, how is that showing the HA locks up from the TT perspective?
AO,
Thanks for posting that wonderfully instructional picture. The cable is not attached at the same point as the weight distribution bars, those are what is flapping in the breeze out to the sides in the picture.
Go here if you will, and read what it says. You will be caught up in no time flat, the Hensley is really a simple device and virtually foolproof.
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tluxon
Kirkland, WA
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Milt, you've got to be careful about how literally you take marketing language such as that found on the Hensley website. Through the years they have changed their language dramatically.
In patent #4,722,542 that was linked to early in this thread, Hensley's patent attorney writes near the end,Quote: ..snip..
In use, the hitch assembly C couples the trailer A to the tow vehicle B such that the combination of the two is extremely stable at high speeds, even in the presence of gusty side winds or on uneven road surfaces. This derives from the fact that the effective pivot axis for the trailer, at least when it is aligned directly behind the tow vehicle B, is between the rear bumper 8 and the axis x for the rear wheels 6 of the vehicle B (FIG. 2), and not at the rear bumper 8 where the actual pivoting is accommodated. In this regard, the towing force is transmitted through the hitch bar 30 to the hitch box 34 and front pivot mount 36 and thence through the connecting links 50 to the rear pivot mount 56 to which the trailer A is connected at the hitch ball 58. Since the struts 60 prevent the trailer A from turning with respect to the rear pivot mount 56, that is rotating about a vertical axis at the hitch ball 58, the turning must be accommodated through the connecting links 50, the pins 40 and 52 of those links, and the bushings 46 and 54 in which the pins 40 and 52 fit. The bushings 46 and 52 are spaced such that the connecting links 50 converge and indeed if projected forwardly would meet along the centerline m of the tow vehicle B somewhat ahead of the rear bumper 8, but most likely behind the axis x for the rear wheels 6, assuming of course that the trailer A is aligned with the tow vehicle B, that is directly behind the tow vehicle B, as would occur while driving straight segments of highway. By displacing the pivot point forwardly, the tendency to sway or fishtail is significantly reduced. Actual tests of applicant's hitch assembly C have demonstrated a marked reduction in fishtailing. ..snip..
Hmmmmmm. Methinks that the marketing guys have significantly modified their talk despite the hitch remaining fundamentally the same.
Tim
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Ron Gratz
full time RVer
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Joined: 12/27/2003
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Stressor wrote:And once again, Ron trots out his red herring, stating that I was fortuitous in finding exactly the right angle. There is only one place the cable can be attached that duplicates the strut attachment.
Okay, let's ignore the fact that the ball coupler and both stuts are involved in the transfer of forces between TT and TV. Let's blindly assume that the tension in one strut can properly represent the load transfer. Then, the statement, "There is only one place the cable can be attached that duplicates the strut attachment.", is correct given the incorrect assumptions. But, the statement blindly ignores the fact that forces are vectors which have magnitude and direction. And to duplicate strut tension, you must properly duplicate the location of the attachment point, the magnitude of the force, AND THE DIRECTION of the force.
Milt either:
1. does not know what the "demonstration" cable angle was or,
2. he does know and is refusing to tell us.
The cable angle shown in the photo is about one half of what the correct strut angle should be. This "fortuitous", non-representative angle gives a force vector which passes through or very close to the VPP. If the cable were pulling at the correct angle for a properly connected TT, the tension vector would not pass through the "straight ahead" VPP location; and the rear unit would swing to the right. No wonder Milt repeatedly refuses to address questions about the cable angle.
Quote: Once again, he fails to demonstrate how these forces might come about, or how they may be applied to the hitch except at the mechanical points of connection, which is where the cable is attached.
Once again, Milt is unaware that his TT has a ball coupler.
Milt, I'm going to assume you're talking about the forces which are transferred between TT and TV. I's obvious that you do not know how these forces come about or you would not be attempting to model them the way you do.
First, some basics. That round, greasy, about 2" diameter object attached near the rear center of the upper hitch unit is the ball. And, there are two struts -- not just one. The TT A-frame has a ball coupler which connects the TT to the ball. When the struts are tensioned, and with no push or pull from the TT, the ball coupler is pushing forward on the ball and the struts are pulling rearward and outward on their pins. The ball coupler is under a forward "pre-load".
During straight-ahead towing, the TT exerts a rearward force on the ball/strut system. Some of this rearward "drag" is reacted by increased tension in the struts, some of it causes a reduction in the forward pre-load on the ball coupler. If the TT tries to yaw CCW (rear of TT swinging to the right), the tension in the right strut will decrease and the tension in the left strut will increase. This is what prevents the TT from pivoting on the ball.
As regards the resultant force acting on the HA's rear unit during an attempted yaw, a decrease of tension in the right strut combined with an increase of tension in the left strut results in an increased left force on the HA's rear unit. Simultaneously, the tension changes in the struts result in an increased right force of equal magnitude on the A-frame. This increased right force is transmitted through the A-frame to the ball coupler. The net lateral force on the HA's rear unit is zero. Also, the net longitudinal forces are zero. However, the increased forward force on the left side of the A-frame combined with a decreased forward force on the right side of the A-frame, results in a moment which resists the pivoting of the TT on the ball. This moment also must be transmitted via the HA's linkage to its front unit. You should be attempting to model the moment and not the strut tension. Your photos prove nothing.
How's that for a red herring?
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jdwhittaker
York, SC
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Joined: 06/01/2005
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apljb wrote:Wow, after reading that, I'm even more grateful that I bought a Hensley.
Seriously, this is a great thread and I'm trying hard to follow along.
John.
I have just one request, please can we make sure it gets wrapped up before page 18 ? ![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/awink.gif "awink")
Remember this post from page 6 of 38? Pretty funny huh?
Anyway I ran across this while looking for video of the hensley promo mock up. I thought that I saw it somewhere in this discussion, but it's SO BIG that I'm having trouble finding it, or maybe I saw it somewhere else. Can anybody help
Thanks,
Dave
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