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Old 04-03-2006, 01:37 PM   #71
Rivet Master
1975 29' Ambassador
Reno , Nevada
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airbags are like a pillar; wd is like a beam. You can "level" the load with airbags, but not "redistribute" the load the same way.
But its not really "a" beam; its 2 beams, overlapped, and strapped together ("sistered") at 2 points.
I'm thinking that one explanation is that my front axles are stiffer (in effect) than the rears...
Active suspensions are a bit more than just airbags. But even airbags can create load shifting to some degree by changing the attitude of the vehicle.

The beam idea should not be stretched to absurdity like getting into why a truss and a beam are different when the idea is to use a simple example that is common to both to illustrate a concept.

Your note on the heavy (and stiff) front end is typical of a lot of pickup trucks, especially diesels, and one reason why they often don't need weight distributing hitches, especially if they have a short rear overhang.

As for lifting a coupler off the ball - the only model I can envision so far is that the spring bars' attachment to the A frame don't allow them movement. When a load is applied they push forward on the ball and the pressure could be up and off riding over the ball towards your truck. A DC could aggravate this if the cams were set too far aft. Maybe.

its a puzzle.

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Old 04-08-2006, 09:24 AM   #72
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I wonder if Chuck's dual cam setup might have something to do with his coupler rise that he stated. I do not have that setup, but from the looks of it, the arms of the dual cam might be pushing up the front of the tongue. I would not think this would be a normal thing, but all these things may need to be considered. Looking forward to the results of your test Chuck.



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Old 04-10-2006, 07:43 PM   #73
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1960 24' Tradewind
santa barbara , California
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Hello to everone,

This is getting technical guys ,newtons theory and all .The tow vehical with heavy sprung suspension such as a 2500 hd chevy will utalize lighter spring bars say 500# this allows for the wanted deflection of the bars. My 68 travelall use the 750# bars ,it has the proper deflection .A 64 travelall towing an airstream with soft rear springs needed the 1000# bars to get the proper deflection. Without the wd sagged down ,level without the trailer .Wd installed , level .The angle of the hitch head leaning back to a point is crucial to the bars of proper rating to level the tow vehical and trailer.It was noted in this discussion about the bars almost touching the ground with the hitch head angled back as is specified in setting up the hitch. Each case will be different ,the hitch head in that application may be back alittle too much. If the ball height is correct on the tow vehical in relation to the coupler height ,with the proper bars tensioned the tow vehical and trailer should be level! If not the setup is incorrect . each application will not be the same and I know I have a travelall .The tension on the bars chained to the A frame under the proper tension will have a pulling down effect as others here have stated . azflycaster has clearly shown it with his test and photos.The reason there is available movement front to rear on each side of the A frame on the snapup brackets is so when you turn right or left the position of your bars will move towards the front or rear. The noise you hear with the reese dual cam snapping in and out when turning ,right? I dont see how the coupler could come up the ball though hmmm.... How about a picture of that .In the WD has a I agree the rear suspension of the VW T or expedition etc, they dont have regular rear springs complemented by airbags .The bags are the rear supension or rather air spring. It is the auto leveling system that I think would be affected .There are level sensors that monitor ride height . I can see that being a problem for sure .The VW T does not approve of any WD setup I believe do they?The last thing I would add is that when properly tensioned spring bars will have a (loaded) upward curve to them towards the A frame ,and if the bars touch the brackets up high and the bars show to much curvature they are too light in# ,need heavier bars . Trial and error to get it right.

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Old 04-10-2006, 08:06 PM   #74
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1960 24' Tradewind
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ME again
Sorry about that garbled sentance in my last post .Dont know how that happened. I forgot to say regarding the bar tension , the upward curvature should not be extreme ,just mild as in a tensioned set if the bars are correctly set up. Sounds like chuck needs lighter bars and it may look like he may not need them but he does . it wont move much and will be like a spring board if jumping on the tounge. It s how it act going down the road . If the truck and trailer seem to ride rough abnormally I agree the bars are too tight.

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Old 10-31-2007, 10:03 PM   #75
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This older thread was brought to my attention due to some questions I posed ["Misconceptions"] (thanks, 2Air).

FWIW, I agree with the premise that trailers need sway control, almost no matter the size. Over the past few months I have been more carefully studying trailers of every sort as we all drive along. It has been rare that, at highway speeds, that I do NOT see trailer sway on even the smallest trailer (short and low, heavy or light load, etc). Even down to portable welders on factory-provided trailers. I am seeing sway constantly.

I do not agree that "heavy truck" and "small trailer" in any way negate this. The comment was made that it was a good thing the Bambi owner had a Suburban. Better, I think, that he had a car pulling this trailer as it has a lower center of gravity, better handling, less rollover propensity, better braking and better power-to-weight ratio. He might not have gotten into the same problem at all. He needn't have fallen asleep to have caught a wheel off the pavement (this is why the highway departments ALWAYS warn of shoulders or medians being closed during construction), just a moment of inattention would have sufficed. I've watched a big rig roll onto its' side -- at city street speed -- because of a 4" curb. With a car the Bambi owner might not have had a problem at all.

Long wheelbase, first; low center of gravity, second. Trucks roll quite easily be they heavy duty (such as Class 8 tractors) or the light duty ones we drive. The light duty ones tend to have their center-of-gravity at/about the top of the transmission bellhousing. Stand outside your truck and measure that point, it is quite high. Recall that, once it starts to go over, that the momentum (height) makes it increasingly hard to stop.

Back to trailers in general: The cheap construction trailers with poor suspensions, and even more poor tires make me think that U-Haul has been right all along: Not for speeds above 45 mph! The only ones which I do not see sway are the small tandem axle dumps (expensive trailers of this type) where plenty of steel seems to provide a non-flexing chassis and decent axles/shock absorbers are doing their job. But I would still add some form of sway control. The "worst" offenders are stock haulers as, like many, I detest the idea of not treating animals well (even those headed to auction); a rollover here is emotionally painful.

Depending on the hitch (for a travel trailer) I still like the idea of balancing out the tongue load (as Andy/Inland RV Ctr points out): 2/3 onto the TV (50/50 FF to RR) and 1/3 back to the TT axles; kept at a constant rate, regardless of conditions (to the extent possible). If that can be achieved by even minor amounts of weight distribution then it would seem to be worth it. If the TV has a front/rear gross WD afterwards that more nearly approaches 50/50, then it would seem that handling is bettered, and the whole rig is better balanced.

And then the proper anti-sway control.

I probably missed something, or maybe made a generalization out of whack. But, just having gotten out of Interstate 35's heavy commercial traffic (and construction with closed shoulders AND medians simultaneously; after dark; three hours to go 126 miles in and then out of Dallas' evening Halloween rush hour), I was glad to have this thread to read and vent back to ordinary atmosperic pressure by an attempt at ordered thinking. Some mighty good stuff up above mine!

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