Ron Gratz
full time RVer
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Joined: 12/27/2003
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willald wrote:Can we all agree with this, now? Ron? Don? Tim? Milt? ![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/biggrin.gif "biggrin")
Will
Will,
I cannot agree on this for all of the reasons I stated many pages back. And, right now, I'm too tired to go through all of that again.
Maybe tomorrow ----
Ron
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Ron Gratz
full time RVer
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Joined: 12/27/2003
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Stressor wrote:I meant to tell you, the struts can only be in compression, either less or more compression. There is absolutely no way to put one in tension, as it is a two part assembly, and simply falls apart.
Milt,
It's unfortunate that you didn't tell all of us this when you were demonstrating how the HA responds to a large tension force as a simulation of a strut force which can only be compression.
Now are we supposed to believe that the HA also "locks up" when subjected to a large pushing load?????????
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TeryT
Scottsdale AZ
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ZZZZZZzzzzzz Somebody wake me when it's all figured out!
Mighty 4Runner Sport V8 4x4 - over 200k
Hensley Hitch
McKesh Mirrors, Geolandar G015 Tires
Hopkins Insight Brake Controller
Tranny: Hayden Cooler/Fan & CyberDyne Gauge
Mobil 1 Full Synthetic fluids everywhere!
Rockwood 2502 Ultralight TT (3600 lb. dry)!
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willald
NC
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Ron Gratz wrote:willald wrote:Can we all agree with this, now? Ron? Don? Tim? Milt?
Will
Will,
I cannot agree on this for all of the reasons I stated many pages back. And, right now, I'm too tired to go through all of that again.
Maybe tomorrow ----
Ron
Awwwww, man!!! Just when I thought we finally had everyone on board, and in agreement!! Gotta be a party pooper, don't you, Ron? ![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/smile.gif "smile") J/K
Guess we're back to having to build a model, that can illustrate this point so clearly, even Ron won't be able to disagree with it any more..
Will
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TeryT
Scottsdale AZ
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Model MODEL MODEL! WE WANT MODEL!!
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TnAnFLA
Nokomis FL
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Joined: 02/18/2005
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Tim wrote:In order to be compression only they would have to be designed as a bushing or sleeve.
Yep, and that's exactly what it is. The forward, inner threaded part of the strut assembly slides into the aft tube that is attached to the A-frame. If you take the strut off, the threaded piece will fall right out if you don't hold the two pieces together. When you tighten the locknut, the nut's action on the threads pushes the inner piece towards the hitch head and the nut pushes aft on the outer tube/A-frame, placint the assembly under compression.
Ron wrote:In order to have the struts in compression, in the absence of any external forces on the hitch head or A-frame, you must have the coupler pushing rearward on the ball and the ball pushing forward on the coupler. This will cause the A-frame channels to be in tension.
During towing, the wind and tire drag forces will cause tension in the A-frame channels rearward of the strut attachments. Some of this drag force will be reacted by a decrease of compression in the struts and some of it will be reacted by an increase of tension in the A-frame channels between the strut attachment points and the ball coupler. The amount of drag reacted by struts versus A-frame channels will depend on their relative axial stiffness. The increased tension in the A-frame will increase the rearward force on the ball.
Thinking about it Ron, that's exactly right. Struts in commpression, A-frame (including the coupler) under tension. Which has me thinking about this (always a dangerous proposition): With everything hooked up, the struts and upper hitch head essentially become a new "A-frame" with a virtual apex forward of the coupler. This apex is the point around which the TT would want to pivot when a lateral force is applied if there were no linkage assembly. At the same time there is also another "virtual " A-frame delineated by the two forward linkage bearings (on the lower unit) with it's own virtual pivot point somewhere forward. And since this is the part that attaches to the TV, the forces on it are the ones felt on the TV.
What makes this second, virtual A-Frame different is that the "coupler" location is not in a fixed position, but rather is determined by the position of the four bar linkage, and the apex of the "A-frame" is laterally fixed in line with the stinger/receiver..
I'm obviously sort of rambling here, but this way of looking at the hitch might help explain why it appears "locked" in place from the trailer side. It might be (I haven't qiuite worked it out yet) that when a lateral force is applied to the trailer, the movement of the "virtual coupler ends up providing a counter force to hold the trailer in line. Similar to the way the compressive and tensioning forces work on the strut/TT A-frame assembly.
All in all, I think I've given myself a headache thinking about this, so I'm taking a break.
Andy
31' Itasca Impulse
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drfife
Dallas, Texas, USA
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Ron:
Have you studied a Hensley hitch in person? I think you would benefit to see how it is engineered and functions if you did.
Look around the campground for a trailer with a Hensley. I can just about promise you that the owner would let you look at it and play with it to your hearts content.
Russell
'12 GMC Sierra 3500HD SRW
'13 Excel Winslow 34IKE
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TeryT
Scottsdale AZ
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Who will build a model?
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tluxon
Kirkland, WA
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TeryT wrote:Who will build a model? What do you want the model to show? What parts of a real system would it include and which parts should be excluded?
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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willald
NC
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tluxon wrote:TeryT wrote:Who will build a model? What do you want the model to show? What parts of a real system would it include and which parts should be excluded?
Tim
Well, I think now, Tim, we need a model that illustrates what we were talking about before, comparing it to a swingset. Something, that illustrates that when a Hensley has tension/'pulling' on it, the trailer is in essence practically locked from pivoting, because it has to move forward and overcome the pulling force on the Hensley, in order to swing either direction.
I think this is the only point, where there is some disagreement - Ron just will not accept, that this effect the Hensley has, actually exists.
I mentioned several posts ago, a model that would illustrate this perfectly (although it would be a lot of work to build). It goes something like this:
We'd need to find a way to mount/fix a Hensley Stinger and hitch vertically, to something very solid, with the Stinger and Hensley pointing down. Then, we'd need to fashion a make-shift A frame, perhaps with a few pieces of 2x4s. We would attach the make-shift A frame to the Hensley, similar to the way a Hensley attaches to a trailer's A frame (using the struts). Then, we'd need to attach a heavy weight of some kind to the 2x4 A-frame (I had suggested an anvil..LOL), to simulate the pulling/tension on a Hensley.
Once we have all this in place (hahahaha!), all we'd have to do is try to push the A frame/weight side to side. You would find, that if it is a real heavy weight, it would be very difficult to pivot the A frame back and forth, because you'd have to overcome all the weight/gravity pulling down, since the Hensley's pivoting arc/path would make you in essence lift up the weight in order to pivot it either direction.
This is the point Ron refuses to believe - he thinks the pulling force on the Hensley makes no difference, and the force required to swing such, would be no different than what you'd experience on a conventional pendulum arrangement. It is NOT the same as a conventional pendulum arrangement, because the Hensley forces the trailer to be pulled closer to it, in order for it to swing either way. It would be like a pendulum arrangement, where the pendulum arm has linkage/mechanism in it, that makes the arm 'reel in'/get shorter, when swinging to either side.
Hensley's videos do not really illustrate/prove this, because they have the Hensley set up horizontally, without any tension/pulling between the simulated tow vehicle and trailer.
Tim, I believe you understand and accept the concept we're talking about. Can you think of another way to prove such to Ron? That seems to be the challenge here.
Will
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