Ron Gratz
full time RVer
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Joined: 12/27/2003
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jdwhittaker wrote:Please note that with the HA for a left turn the front end of the TT moves to the left of the centerline created between the TV/TT combo.(opposite to that motion that is a result of sway) while driving straight, as my video and Tim's fig. 3 represent. Also note that with a conventional hitch for the same left turn the front end of the TT moves to the right of the same centerline created between the TV/TT combo(the same direction as the forces caused in sway).
The linkage in the HA is what causes turns to move in this way, and at the same time prevents sway.
Dave
Dave,
I'm not sure what your frame of reference is, but I think both TTs will move to the left in a left hand turn (unless you have an extremely long overhang). Since the HA's VPP is farther forward than is the conventional ball coupler, the HA's trailer will shift more toward the left than will the trailer with the conventional hitch.
Ron
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Ron Gratz
full time RVer
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Joined: 12/27/2003
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Guys,
This has been fun.
I'm going fishing for three weeks and don't know if I will find any internet access.
I'm sure you will have this all sorted out by the time I return.
Ron
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tluxon
Kirkland, WA
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Joined: 08/12/2001
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bettered wrote:tluxon wrote:In addition, I'm having a hard time imagining what kind of forces outside of a broadside hit at the axles that could result in anything other than a moment on the CG of the TT. I've already shown above how a lateral force resulting from the moment of a TT results in a reactive COUNTER moment generated by the trans-rotation of the hitch linkage. We just don't know how much of a reactive moment the hitch CAN generate given its relatively minimal leverage and unknown compressive strength.
One of the more astounding testimonials on the Hensley website is from an owner who was involved in an accident where another vehicle lost control and rammed the TT at just about the axles. The TV and control of the TT were not affected in terms of directional stability. I find this hard to swallow, but that's what the fellow said.
bettered wrote:Here's the 'astounding' testimonial direct from the Hensley web site that I referred to earlier...
"...we were involved in an accident after being hit by another car ... was in a spin hitting our trailer on the rear wheel, knocking the trailer up and the car going under a partial part of the rear of the trailer. My husband was able to control the rig and drive smooth: although shaken up, to the side of the freeway and bring us to a safe stop...
"I also feel very comfortable driving our rig and now share the "road-time" with my husband..."
"Sincerely,
"Mr. & Mrs. Glen Shelinbarger" Great example! Yes, any kind of broadside hit at the axles OR a sideslip of the tires could easily result in a moment that was NOT halfway between the axles or at the CG of the TT. This may in fact represent the most serious test of a hitch that was designed to negate typical sway. The Hensley clearly passed the test with flying colors in that case.
I'd like to comment on Mrs. Shelinbarger's last statement. To this date my wife has insisted that she doesn't want to tow our big trailer. She says if anything happened to me she just wouldn't use it if she had to tow it. Largely because of that and the fact that I have a LOT of experience and am very confident in the laws of physics, I have been very satisfied with the HP Dual Cam. However, if my wife ever even suggests towing the trailer herself, I wouldn't feel comfortable for her, me, or the family, without her using at least a Hensley. I know the Hensley isn't accident proof, but I suspect there are significantly fewer Hensley accidents per Hensleys used than any other kind of TT hitch with the possible exception of a Pullrite.
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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Joined: 08/12/2001
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Ron Gratz wrote:I'm going fishing for three weeks and don't know if I will find any internet access. Thanks for your many invaluable contributions. Have a great time!
Ron Gratz wrote:I'm sure you will have this all sorted out by the time I return. With over 240 posts, I sure wish I knew a manageable way to pull out all the highlights. Anybody got any ideas? I know this is easier said than done, but perhaps Will (since he started this enduring thread - ![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/grin.gif "grin") ) would be interested in pulling together the pertinent parts he found most helpful.
Tim
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bettered
UpCountry SC
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Joined: 07/26/2004
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I hate it Tim, but you've sort of set yourself up for this:
There's always www.hitchtrader.com........
If your wife isn't comfortable now, and something should happen to you, she's not going to go out and buy a Hensley just so that she can take on the challenge of the rig. Either you do it sooner, or it's not going to happen. You could spring for the $3k, install the Hensley, see what you think of it and then turn around and sell it on Hitchtrader if you decided you wanted to stay with the PR. While you might not get the full $3k, you probably could get almost $2500 for a "new" hitch and the new owner would probably spring for the $500 warrantee transfer.
Shipping the unit is a problem, cuz the main unit is HEAVY, but if you bought a new unit, you'd have the packaging from Hensley to re-use. To intall mine, I had to sit it on a box, let the coupler down on it and then close the coupler before I continued with the installation.
{I don't get a commission from Hensley, but I sure like my [used] hitch.)
Ed B.
Note: Due to invalid formatting, all formatting has been ignored.
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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bettered
UpCountry SC
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Joined: 07/26/2004
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I want to second the positive comments on Ron's contribution. He answered the questions about the ABCDE linkage professionally and clearly, something that I probably couldn't have done. Thanks Ron, and have a great vacation. You'll be missed.
Ed B
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Stressor
Whitefish Bay, Wisconsin
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Joined: 05/29/2001
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[quote=Ron Gratz][quote=Stressor]Can you tell me how this explanation differs in any way from this one?
[quote=Stressor][img]http://home.ripway.com/2005-1/238631/Folder%20Name/Hensley.JPG[/img]
[img]http://home.ripway.com/2005-1/238631/Folder%20Name/Hensley2.JPG[/img]
[img]http://home.ripway.com/2005-1/238631/Folder%20Name/Hensley3.JPG[/img]
Just curious. :B[/quote]
Milt,
You stated, "At any point along the lines A-C and A-B a set of points could be added as shown by D and E. These could be made flexible and become pivot points."
In my explanation, the extended links are A-C and B-E. There are no intermediate pivot points at D and E. The system A-C-B-A forms a rigid triangle -- the "A-frame" as I referred to it.
In your system, D-C-E-D forms a rigid triangle, but the 4-bar linkage A-D-E-B-A still allows A-B to translate and rotate relative to D-E.
In your second diagram, point C is the Virtual Pivot Point if the lines A-D-C and B-E-C are straight.
In your third diagram, point C is not the VPP. The VPP lies at the intersection of one straight line projected through A and D and another straight line projected through B and E. In your diagram, the VPP would lie to the left and rear of point C.
The location of the HA's VPP changes as the angle between TT and TV (same as the angle between D-E and A-B) changes. That's what makes the Hensley Arrow different from the PullRite. When the HA and PR are aligned straight ahead, the only significant difference in how they handle lateral loads from the TT is in how close their respective virtual or actual pivot point is to the TV's rear axle.
Ron[/quote]
The drawing demonstrates a locked up rocker-rocker 4 bar linkage, as it is from forces delivered from the travel trailer, and the last drawing shows it unlocked during a turn. C is of course, the VPP when towing straight ahead, after all, it is a projection of the linkage as drawn. I think that makes it equivalent myself.
When turning, the pivot point, or VPP, must necessarily move towards the hitch. Didn't you say for sharp turns it actually moves very close to the actual hitch? Within about 4 inches or less because of the length of the links"
Note: Due to invalid formatting, all formatting has been ignored.
Milton Findley (and Kerene)
A small piece of my mind...
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bettered
UpCountry SC
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Joined: 07/26/2004
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The HA does not lock in any position unless the side links interfere. It never locks in any other position as long as the hitch bar is in place. Ever.
Ed
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jdwhittaker
York, SC
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Joined: 06/01/2005
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Ron Gratz wrote:
Dave,
I'm not sure what your frame of reference is, but...
Ron, my statement was incorrect. Sorry
Have a good vacation.
Dave
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tluxon
Kirkland, WA
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Joined: 08/12/2001
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Stressor wrote:
The drawing demonstrates a locked up rocker-rocker 4 bar linkage, as it is from forces delivered from the travel trailer, and the last drawing shows it unlocked during a turn. C is of course, the VPP when towing straight ahead, after all, it is a projection of the linkage as drawn. I think that makes it equivalent myself.
When turning, the pivot point, or VPP, must necessarily move towards the hitch. Didn't you say for sharp turns it actually moves very close to the actual hitch? Within about 4 inches or less because of the length of the links" In the top picture, point C IS equivalent to the VPP. However, in the last picture, the VPP at the angulation you depicted should be shown where I've projected it in the following picture.
![[image]](http://home.comcast.net/~tbluxon/Milt-HensleyVPP.jpg)
As the rear bar translates and rotates to it's limit, the VPPs follow the path shown by the asterisks in the picture below. In order to reduce clutter, I have only shown enough VPPs to clearly show the "path" traced by the VPP as the rear bar progresses clockwise to its limit.
![[image]](http://home.comcast.net/~tbluxon/HensleyLink_InstCtr.jpg)
Look at the picture below and you will notice that the VPP of the side links when the rear bar reaches its clockwise limit is a fair bit behind the hitch.
![[image]](http://home.comcast.net/~tbluxon/HensleyLink_at_73deg.jpg)
When descending a steep hill with the trailer turned this sharply behind you, you should feel it there more than with a conventional hitch due to its longer lever on your TV.
Are we on the same page yet?
Tim
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![[image]](http://home.ripway.com/2005-1/238631/Folder%20Name/Hensley2.JPG)
![[image]](http://home.ripway.com/2005-1/238631/Folder%20Name/Hensley3.JPG)
