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Old 01-04-2012, 03:22 PM   #99
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Originally Posted by dznf0g View Post
Am I off base?
No. Neither is Redwood'. Threads wander around because of lack of intellectual discipline or we are seeking answers from every possible direction. It is the nature of brainwork. I agree overhitching is a vague term and maybe it can be better defined at some point. It is good to be reminded to focus.

Gene
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Old 01-04-2012, 03:26 PM   #100
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The coupler to ball connection, is totally flexible.

That flexibility is reduced when torsion bars are added.

Therefore the heavier the bar, the less flexing, as well as the lighter the bar, the more flexing.

The purpose of a load equalizing hitch,is exactly that. To "equalize the load".

It's purpose is not in any way, supposed to add to the spring rate of the trailer or tow vehicle, but it does alter the tow vehicle spring rate when excessive.

Basically, each rig is different, since different loading takes place as well as different tow vehicles.

Bottom line for the Airstream trailer, is a soft ride.

Anything that's done to reduce that soft ride, will have negative results.

Some of those are excessive rated tires, excessive tire pressures, excessive rated torsion axles, defective and/or bad rubber rods in torsion axles, excessive rated hitch torsion bars, and finally excessive rated tow vehicles.

Any one of those can and usually does cause trailer problems, that cost money to repair.

A combination of them causes problems too, but faster.

Many, many years of experience, very clearly demonstrates that, to this day.

Many owners, have posted here on the Forums, that when they lightened the bar ratings, things magically quit moving about the trailer when towed.

Is it a wonder then, why that happens?

Someone long ago, challenged the fact that the earth is not flat. I bet they caught all kinds of ridicule.

But, again, to each his own choices.

Andy
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Old 01-04-2012, 03:32 PM   #101
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Originally Posted by CrawfordGene View Post
No. Neither is Redwood'. Threads wander around because of lack of intellectual discipline or we are seeking answers from every possible direction. It is the nature of brainwork. I agree overhitching is a vague term and maybe it can be better defined at some point. It is good to be reminded to focus.

Gene
Gene.

Over hitching is usually defined as a hitch bar rating far in excess for the intended job.

As an example, 1200 pound rated bars for a Caravel that has a tongue weight of 350 pounds, towed by a dually or a 3/4 ton truck, or a truck with overload springs.

Maybe one of todays newer words is more apropriate, like "overkill".

Andy
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Old 01-04-2012, 06:30 PM   #102
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I think Red said it well in post #93. We've talked about this for a very long time under one subject heading "damage to AS while traveling" Then we continue to talk about overtrucking, overhitching, running gear balance, bad axles, etc. all in the same thread. There are so many dynamic inputs to the rig as it is going down the road that you can't combine all these thing into one coherent answer. I like this thread because it is about drilling down to ONE COMPONENT, analyzing how it works, the physics involved, how the component behaves with a particular input...then another. I think IF and when we gain consensus on understanding how this component applies forces to the AS, we can then more objectively predict what kind of damages are created by misapplication of that component and make better decisions about the component's use.

For example: I believe rivet popping from too much spring bar occurs only during high, slow stress loads during large angle deviations between trailer and TV frames. And I expect those pops to be in the very front of the AS. Perhaps only the center and side lower sections. Perhaps some front pano issues as well. Other pops, I believe to be harmonic vibration and shock load caused....running gear and bad axles respectively. I would expect those to show on the side walls, doors, rearward of the axles etc. All that is for, I assume later, discussions...this one has evolved into strictly a spring bar understanding discussion.

Am I off base?
No sir, you are standing right on the bag! You have have made several important points here about staying on the track of one phenomenon at a time. Isolating the question, drilling down to the narrow answer. It avoids so much confusion that occurs from mixing related, but not causal, factors.

You can see easily how people quickly mix several questions and phenomenon together.

I think the answer to Q1 (ride harshness vs. bar stiffness) can be answered with absolute clarity with one question:

Q: Does the trailer A-frame always move up when the rear TV body moves up, and does the trailer A-frame always move down when the rear TV body moves down?
A: YES, no matter what stiffness of bar is used.


Ergo, the bar stiffness is not controlling or changing the ride harshness or stiffness. It's really that simple. It's true because there is no compliance between the two platforms.

To show an example where that statement would not be true, use an Airsafe hitch. The answer when using an Airsafe would be "no, it does not always move." It might, or it might not, depending on what size unevenness was hitting the TV tire.

I do realize opinions will differ. But, I can't imagine what physical action could be taking place which would cause a "NO" answer to the question above.

On Q2 (stress on frame while traversing gullies and dips) it is easy to model the effect of the bars. You can make the bar so stiff that you will lift the rear wheels of the TV off the ground over the right size gully. At the other extreme you can make the bar so soft it doesn't hinder flex of the coupler-ball at all.

You can picture that with an infinite stiffness on the bar, the entire rig can be suspended between the front axle of the TV and the trailer axle, with the rear TV wheels off the ground. In this maximal condition, can the A-frame withstand this load? Well, maybe not if the TV is massive enough.

This condition would seem to be a serious thing to consider compared to the effects of Q1. My intuition would be that this could cause a wide variety of damages if it was this extreme. The A-frame clearly has some limits to its design strength. You can't pile unlimited load on it. Even with loads in the thousands of pounds range, the members will deflect or bend. Bending the horizontal members of a 28 foot trailer can't be a good thing.

I haven't looked directly at my rig traversing this kind of gully, so this is going to be what I want to see next. I don't think I have ever lifted the rear wheels off the ground, that much I am fairly sure of. Beyond that, I'd like to get a movie of it and study what is happening.
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Old 01-04-2012, 08:11 PM   #103
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Regarding "greasy parts", the Blue Ox hitch is also one of the "clean ones".
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Old 01-04-2012, 09:04 PM   #104
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"I think the answer to Q1 (ride harshness vs. bar stiffness) can be answered with absolute clarity with one question:

Q: Does the trailer A-frame always move up when the rear TV body moves up, and does the trailer A-frame always move down when the rear TV body moves down?
A: YES, no matter what stiffness of bar is used.


Ergo, the bar stiffness is not controlling or changing the ride harshness or stiffness. It's really that simple. It's true because there is no compliance between the two platforms.

To show an example where that statement would not be true, use an Airsafe hitch. The answer when using an Airsafe would be "no, it does not always move." It might, or it might not, depending on what size unevenness was hitting the TV tire.

I do realize opinions will differ. But, I can't imagine what physical action could be taking place which would cause a "NO" answer to the question above."

I can think of one other instance beside an Airsafe hitch. And when it occurs, you think," I hope those chains hold......!"
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Old 01-05-2012, 10:41 PM   #105
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Arguing about stiffness and compliance . . sounding like the Sex in an Airstream thread.

Redwoodguy, I may have missed this, but, IMO, it's always worthwhile to work from scale numbers to get an idea of what WDH's are doing, in and of themselves. If this has not been done then problems about "feel" (from steering inputs, etc) always seem a little off-base when anti-sway provisions of the hitch rigging are in play. More complicated questions about suspension interactions aren't helped by uncertainty (being able to replicate the same conditions consistently).

FinalCutJoe has one of the great threads around here on diagnosing hitch performance in one entitled Diminished Hensley Performance. I give it that appellation as the range of potential problems with hitch rigging is huge, larger than we first conceive. And the concerns are not trivial in any respect. While it isn't central to what is being covered in this thread, it may add to the decision tree of understanding how your TV-TT combination feels to you.

With that in mind I recommend a full set of scale weights, empty and loaded, on both your vehicles for your investigatory purposes if not already done (as example, an analysis in a set of posts starting here.)

Hypothetical conjectures, thought experiments, etc, are the pleasure of this -- the good, better, best arguments -- but without numbers we've cut ourselves off from solid ground.

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Old 01-05-2012, 11:16 PM   #106
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Originally Posted by REDNAX View Post

Hypothetical conjectures, thought experiments, etc, are the pleasure of this -- the good, better, best arguments -- but without numbers we've cut ourselves off from solid ground.
Hi Rednax,
You are right. Specific numbers are the only way to compute real answers when specific formulae are a known aspect of the solving the problem. I definitely agree with you.

Ok then. How would we use a set of real scale numbers to answer the question being entertained and dissected here? That question being, "Do 1000# bars on an EQ hitch create a harsher ride at the trailer than 600# bars when all other variables are equal?" I'll follow your lead! I love drilling down to specifics.
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Old 01-05-2012, 11:45 PM   #107
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Hi Rednax,
You are right. Specific numbers are the only way to compute real answers when specific formulae are a known aspect of the solving the problem. I definitely agree with you.

Ok then. How would we use a set of real scale numbers to answer the question being entertained and dissected here? That question being, "Do 1000# bars on an EQ hitch create a harsher ride at the trailer than 600# bars when all other variables are equal?" I'll follow your lead! I love drilling down to specifics.
The numbers, while it may answer some questions, doesn't really matter.

What does matter, is the stiffer the bars, the more shock is transfered to the trailer.

As an example, lets use railroad track for bars. Will they bend? Heck no. Then all of the forces from bumps etc, will be directly transfered to the trailer.

Now lets use broom sticks for bars. Skip the fact they we all know they will easily break. But, since they will easily flex, less forces will be directed to the trailer.

The real ideal situation, is for a hitch manufacturer, for that matter any hitch manufacturer to put up the money for in depth tested.

Folks, in plain english, THAT AIN'T GOING TO HAPPEN !!!

Why a person might ask??

Because they all love things just the way they are.

We invested time and money, to get the ball rolling, hoping that someone, anyone, would resume where we left off. That appears to be a dream that will never happen.

Clearly, however, our tests demstrated the the Equalizer bars, bent the least amount, from a given stress compared to others. That simply means that more round shock will transfer because of that bar stiffness.

There is no need to create any arguements regarding this subject, but there is, we think, a huge need to continue where we left off.

Someone..............anyone ???

Andy
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Old 01-06-2012, 12:01 AM   #108
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Thanks Rednax for getting me thinking about some real world data analysis. On this question I think it would be an ideal problem for some relatively simple instrumentation and data collection. Again, I am thinking out loud for an approach to this.

Since the question involves ride harshness, the most obvious instrument to apply first would be an accelerometer or tri-axial shock recorder. The latter being rather expensive, but the former might be as cheap as an $2 iPAD app. Ride harshness is exhibited as shocks in the 3-axis of movement. Higher G forces mean harsher ride. When the the rig traverses chuck holes and other road impediments, the harsher ride will generate spikes with higher G-force and or longer periods. It might be quite possible to simply graph a 5 minute ride over some course using first one bar, and then the other. (At the moment I realize that the two bars are not available for the same head, but that's a practical thing to be solved for the test).

I would imagine hard mounting the instrument in the front most part of the trailer. Then making a second pass with it mounted in the rear most part. If a visual analysis (on screen) didn't provide enough resolution, some tedious math could be applied to integrate the data.

I don't know the g-force range of an iPAD/iPhone accelerometer, but if that wouldn't work, there might be relatively inexpensive stand-alone units on offer somewhere. I know you can get a tri-axial recorder of industrial quality for about $800, but that's a bit steep for an experiment like this.

It sure would be cool to do though, wouldn't it? I think it would really put a nice foundation on the whole issue.

EDIT: Well - it looks like there are several apps for the Android. I have a Galaxy Tab, so I will see if I can find a cheap and useful app using the built-in accelerometer. I'm concerned if there is enough dynamic range in such a device, but we'll see!
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Old 01-06-2012, 12:32 AM   #109
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I just bought the Android app for $1,50 and it looks amazingly useful. 3axis graphing and storage. WOW.
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Old 01-06-2012, 06:49 AM   #110
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Scale Numbers

"Do 1000# bars on an EQ hitch create a harsher ride at the trailer than 600# bars when all other variables are equal?" I'll follow your lead! I love drilling down to specifics.

Measuring Forces at the Hitch

For an A-B-A comparison I'd think that getting the WDH set up according to formula would be first. Each bar set may call for some scale numbers that are different, but the adjustment tweaks ought to be the same each time, as well as being as close as possible.
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Old 01-06-2012, 09:36 AM   #111
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Ok, it looks like the accelerometer test was done 2 years ago, so I have no need to repeat that idea. The conclusion drawn by that test is precisely what was predicted in the thought experiment in this thread: ride harshness in the trailer is a function of the trailer suspension, not the hitch/TV.

Although his test measured used two different TV subjects, the use of two bar stiffnesses would yield the same conclusion. And that's because the bars do not form a compliance between the two platforms. In fact, there is ZERO compliance of any kind between the platforms in any solid coupled hitch, no matter if the bars are soft or stiff or totally rigid (visualize the compliance of a coil spring between tire and body).

In order to have compliance between two masses, each mass must be able to move independently of the other. The purpose of the compliant part (spring for example) is to store the energy transfer between one mass and the other. No storage of energy = no compliance!

The ball-coupler is solid - - therefore one part can not move without the other moving. Ergo, no compliance exists. If the body of the TV (ball) goes up - no matter how much or how little or how fast or how slow - the coupler will go up also. It must. No other choice is possible. And that will happen exactly so no matter if there are bars, light bars, totally stiff bars, or no bars at all. The function of WD bars is not to be a compliance between trailer and TV. The function is to provide lifting leverage of the TV. A side effect of that leverage is that the hinging of the ball-coupler becomes stiffened against flexing. The illusion here is that the hinging of ball-coupler is a suspension component. It is not.

REDNAX - - yes, I aim to get my rig on the scale as soon as I can find one and do it. Thanks.
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Old 01-06-2012, 09:40 AM   #112
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we have been discussing the stiffness of the bars of the Equilizer hitch and the damage they can cause. after I got the 98, (not foot) home I noticed that the A frame had a slight upward bend and there were cracks in the skin at the corner of both battery boxes not to mention the leaks.
On the A frame were holes where SOB of hitch had been installed.I believe it might been of the bar chain type. If this is true, there should have been sufficient flex to have prevented the cracks and bend in the A frame.
Just some thoughts, and from my experience. Now back to the discussion.
mike
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