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Old 01-14-2022, 08:43 AM   #41
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Quote:
Originally Posted by uncle_bob View Post
Hi

You stated:

"If one has downward head tilt, then there is definitely an interaction between WD and sway control. No head tilt, no interaction....or maybe influence is a better word"

That is not correct.

The Hensley and Propride folks both calm to be "emulating" a 5th wheel via their mechanical magic. The 5th wheel is said to have total immunity to sway. It's all geometry in the horizontal plane. Vertical plane does not get into it.

This is talking about sway ( oscillation that puts you in the ditch) and not about porpoising (which is a completely different thing).

Bob
I don't think we are on the same page. I wasn't talking about PPP exclusively, only that when even maximum head tilt is in place, the spring bars are pretty much parallel to the ground. In that situation, there is little interaction between the WD tension and sway control.

With conventional hitches, there is some friction (not a lot really) which creates an interaction, but if there is a lot of head tilt, there is quite a bit of interaction on turns.

Some, like Reese dual cam, rides in a saddle and has a pretty decent on-center "lock position", IF the cam arm is adjusted for the load and the spring saddle rides perfectly centered on the cam. The more WD the better this on center lock is.

I wasn't talking about PPP at all as it relates to a fifth wheel.
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Old 01-14-2022, 10:56 AM   #42
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Quote:
Originally Posted by jcanavera View Post
One other thing to consider is dips in the road. If you have ever been driving and hit a dip in which the tow vehicle dips up and down, the forces applied will cause the trailer nose to dip which increases the forces being applied to the lift bars. As noted by others if you don't positively know the weight of the trailer, too light a bar may not be able to support the weight being applied as the nose pitches down. There have been cases of bars cracking or snapping.

I've hit some pretty bad dips (one for sure on I-94 in Indiana) that would raise you out of the drivers seat if you aren't belted in. With my hitch weight on my 30' slide out at over 1260 lbs, I'm happy to have the reserve in 1,400 lb bars to resist the downward forces applied by dips in the pavement.

Jack
I would be less concerned with the bars snapping or cracking and more concerned with the pressure placed on the bars and the Airstream frame by the raising of the front axel above the rear axel, leveraging the length of the truck from the front axel to the hitch head.

Mind you the AS model with a slide out may have a stronger/stiffer frame. I have compared the rivet density on Excella models with current models and there were definitely more rivets in the earlier models than you have today, which may explain the resilience of older models to frame stress and front end separation. With my new 1000# round tapered flexible bars, there is a bit more up-down movement than I had with the square stiff 1200# bars when driving on uneven roads, but there is also a lot less stress on the trailer front end. So I shouldn't be getting any more front end separation issues.
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Old 01-14-2022, 11:51 AM   #43
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Just as an aside from regular programming. Back in 2011, I had asked the Mothership for any pics of my 30' Classic NON-slide. They only had 2 pics of a 30' Slide Classic, but said they were exactly the same EXCEPT for the extra bracing in and around the slide itself. You can see that in the pic(s). Frame rails and A-frame are the same as a non-slide.

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Old 01-15-2022, 08:14 AM   #44
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Quote:
Originally Posted by dznf0g View Post
I don't think we are on the same page. I wasn't talking about PPP exclusively, only that when even maximum head tilt is in place, the spring bars are pretty much parallel to the ground. In that situation, there is little interaction between the WD tension and sway control.

With conventional hitches, there is some friction (not a lot really) which creates an interaction, but if there is a lot of head tilt, there is quite a bit of interaction on turns.

Some, like Reese dual cam, rides in a saddle and has a pretty decent on-center "lock position", IF the cam arm is adjusted for the load and the spring saddle rides perfectly centered on the cam. The more WD the better this on center lock is.

I wasn't talking about PPP at all as it relates to a fifth wheel.
Hi

What I said was that not all hitches have interaction between WD and AS.

What you came back with was:

"If one has downward head tilt, then there is definitely an interaction between WD and sway control. No head tilt, no interaction....or maybe influence is a better word"

The term used in your statement is "definitely". My point is (and has been) that there are hitch designs that do not have this interaction.

Bob
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Old 01-16-2022, 09:48 AM   #45
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Sean Woodruff advised me that it was OK to give dznf0g his email address so they could talk Engineer to Engineer.
Personally, I would like a dummied down version of their conversation so I can understand why Sean believes that that the 1400# bars will not put excess stress on the Airstream. I mentioned “popped” rivets to him and this was his response:

“Stiffness is directly proportional to the force applied. Stiffness is equal to the force divided by the deflection of the bar.

With a 3P hitch you control the force applied to adjust the stiffness of your bars through the jacks.

You can run them as stiff as you’d like regardless of the rating on the bar.”

I understand some of this, but mostly, NOT! The again, it took me five (5) years to finish high school.

Sean told me that he has tried to talk to Airstream Engineers, but they would never contact him back. Really!? Airstream doesn’t want to talk to ProPride. It seems to me like a great opportunity to combine intel between the two and be able to promote each other.

If I were Sean, I’d fly to Jackson Center. If I were Airsream, I’d fly to Holly, MI. But what do I know.
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Old 01-16-2022, 10:14 AM   #46
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Originally Posted by Spaggs View Post
Sean Woodruff advised me that it was OK to give dznf0g his email address so they could talk Engineer to Engineer.

Personally, I would like a dummied down version of their conversation so I can understand why Sean believes that that the 1400# bars will not put excess stress on the Airstream. I mentioned “popped” rivets to him and this was his response:



“Stiffness is directly proportional to the force applied. Stiffness is equal to the force divided by the deflection of the bar.



With a 3P hitch you control the force applied to adjust the stiffness of your bars through the jacks.



You can run them as stiff as you’d like regardless of the rating on the bar.”



I understand some of this, but mostly, NOT! The again, it took me five (5) years to finish high school.



Sean told me that he has tried to talk to Airstream Engineers, but they would never contact him back. Really!? Airstream doesn’t want to talk to ProPride. It seems to me like a great opportunity to combine intel between the two and be able to promote each other.



If I were Sean, I’d fly to Jackson Center. If I were Airsream, I’d fly to Holly, MI. But what do I know.
To be clear, I am not an engineer. My degrees and career were in applied technology with an OEM auto maker. I interacted with engineers relative to problem root cause identification and remedy.

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Old 01-16-2022, 10:28 AM   #47
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Quote:
Originally Posted by uncle_bob View Post
Hi



What I said was that not all hitches have interaction between WD and AS.



What you came back with was:



"If one has downward head tilt, then there is definitely an interaction between WD and sway control. No head tilt, no interaction....or maybe influence is a better word"



The term used in your statement is "definitely". My point is (and has been) that there are hitch designs that do not have this interaction.



Bob
And I stand by that. If the trunnions or front curved part of the bars are not perpendicular to the ground (rearward tilt), they swing in a vertical arc on turns, thus the interaction of changing (primarily directionally) wd and some (little) change in sway control by tensions and resulting friction.

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Old 01-17-2022, 08:01 AM   #48
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Quote:
Originally Posted by dznf0g View Post
And I stand by that. If the trunnions or front curved part of the bars are not perpendicular to the ground (rearward tilt), they swing in a vertical arc on turns, thus the interaction of changing (primarily directionally) wd and some (little) change in sway control by tensions and resulting friction.

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So, in layman’s terms, this translates into undue stress to the Airstream frame?

Please let us know what you find out from Sean. I, personally, would like to know his thinking regarding this stress and why he does not believe his 1400# bars will result in “popped” rivets.
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Old 01-17-2022, 08:36 AM   #49
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Originally Posted by Spaggs View Post
So, in layman’s terms, this translates into undue stress to the Airstream frame?

Please let us know what you find out from Sean. I, personally, would like to know his thinking regarding this stress and why he does not believe his 1400# bars will result in “popped” rivets.
Hi

First off, stress on the frame is something that happens in the vertical axis ( up and down). Sway is the trailer wagging back and forth in the horizontal axis (right to left). One is not the same as the other.

WD is what puts stress on the tongue of the trailer. To much WD is not going to do the trailer any good. With any spring, the amount of WD is a combination of the spring and the adjustment. You can adjust a light spring to do the same level of WD as a heavier spring. Until you run out of range on the adjustment ( chain, crank, whatever) they are doing the same thing.

The only reason to fret about spring size is to keep from running out of range on
the adjustments.

Real simple:

If I have a "thousand pound spring" and I deflect it 1", I get 1,000 pounds of force. If I have a "two thousand pound spring" and I deflect it 1" I get 2,000 points of force. Deflect either one half that distance and you get half the force. That's why you have adjustments.

Bob
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Old 01-17-2022, 09:31 AM   #50
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Originally Posted by uncle_bob View Post
Hi

First off, stress on the frame is something that happens in the vertical axis ( up and down). Sway is the trailer wagging back and forth in the horizontal axis (right to left). One is not the same as the other.

WD is what puts stress on the tongue of the trailer. To much WD is not going to do the trailer any good. With any spring, the amount of WD is a combination of the spring and the adjustment. You can adjust a light spring to do the same level of WD as a heavier spring. Until you run out of range on the adjustment ( chain, crank, whatever) they are doing the same thing.

The only reason to fret about spring size is to keep from running out of range on
the adjustments.

Real simple:

If I have a "thousand pound spring" and I deflect it 1", I get 1,000 pounds of force. If I have a "two thousand pound spring" and I deflect it 1" I get 2,000 points of force. Deflect either one half that distance and you get half the force. That's why you have adjustments.

Bob
Is this scenario correct:

1500# bar deflected 1/2 inch = 1000# force (just as example)
1000# bar deflected 1 inch = 1000# force (just as example)

If you go over a big dip, both bars temporarily deflect an additional 1/2 inch:

Now 1500# bar has an additional 1000# force for a total of 2000# (assumes deflection is linear)
Now 1000# bar has an additional 500# force for a total of 1500#

If correct, this would be the reason for the smaller bars in most cases.
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Old 01-18-2022, 07:55 AM   #51
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Originally Posted by Mikemdd View Post
Is this scenario correct:

1500# bar deflected 1/2 inch = 1000# force (just as example)
1000# bar deflected 1 inch = 1000# force (just as example)

If you go over a big dip, both bars temporarily deflect an additional 1/2 inch:

Now 1500# bar has an additional 1000# force for a total of 2000# (assumes deflection is linear)
Now 1000# bar has an additional 500# force for a total of 1500#

If correct, this would be the reason for the smaller bars in most cases.
Hi

If you watch how these things work, there is a bit of a pivot process involved as well. It's not quite as simple as that example. No matter what the springs, big dips will be "fun". That's why they all tell you to disconnect the springs before you pull into the campground or do other fancy maneuvers.

If the springs are near max, the pivot process is impaired. You then get something crazy happening with the "soft" springs. How much pivot is involved depends a *lot* on which hitch you have.

Is the 1000 pounds at 1" or at 12" or 24" .... they don't seem to ever talk about that side of it. One probably needs to know that to redesign the system on the fly.

Lots of variables.

Bob
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