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Old 09-22-2010, 11:10 AM   #71
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As I sit here at my dinette looking out the windows, I can see that there's a nice breeze today......but wait, I really can't SEE the breeze, what I'm observing are the EFFECTS of it.
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Old 09-22-2010, 12:06 PM   #72
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Normally I wouldn't respond to flamebait like the uninformed post I'm responding to, but after reflecting for a day, I think I need to reply in detail. I have a policy now of ignoring this author's posts, but when someone tries to make you look like an idiot before others and you no longer care what they think, but you care what everyone else reading thinks, you have little choice but to grab the troll by the horns.

My apologies mods, if you feel this is unnecessary - it is in response to an unnecessarily offensive and rude post.

Quote:
Originally Posted by 2airishuman View Post
1. i see no evidence of 'some knowledge of holes' rather i c HOLES in the knowledge
First, you quote me and change the words in my quote. Why?

Second, I do not have the "HOLES in knowledge" you suspect. I wanted to be an accident investigator, so I went to college and studied forensic anthropology and structural engineering with a specialty in automotive structure and behavior. I was heavily biased towards failure analysis and data capture. That's my academic qualification in this field. What is your relevant qualification, or are you a LAYMAN?

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Originally Posted by 2airishuman View Post
2. w/d doesn't provide LIFT at the hitch

(??? if the coupler is LEFT OPEN and w/d bars tensioned, what happens AT THE BALL/CUP???)
Weight distribution provides lift at the hitch. It leverages the hitch against the receiver to raise the receiver, which moves load forward. This is basic physics and I am surprised you do not grasp this.

Imagine, if you will, a truck with an 80# bag of cement in the bed, which deflects the rear suspension downward by 1/2". You put a bar in the receiver and you lift it up with enough force to restore the suspension to level. This is the equivalent of moving the 80# bag to a point load-neutral to both axles.

That is a lift on the receiver, which, if the receiver is solidly coupled to the hitch, is a lift working about the axis of the hitch pivot point. This is the ENTIRE PRINCIPLE upon which this type of weight distribution works.

Imagine further that you have a Y fork sticking out of your receiver, and you place your head on the ball, spread your legs out, and lift until you have equalized the weight of your head pressing on the ball. This recreates what the trailer and WD hitch are doing. The trailer has its wheels (feet) as the fulcrum, the hitch as the load, and the arms pushing up as the leverage. Obviously this is not ideal, as the leverage arms are relatively shorter than the line from the hitch pivot point to the road contact point - a ratio of maybe 10:1.

Now, I know you can argue abut which is the fulcrum - it's semantics, but I visualize the trailer as pivoting upon its' axles, so that is my standard. It's also the standard that MIRA uses. I did my internship there.

So, yes, WD provides a lift at the receiver that is a leverage of the receiver against the A-frame. If the bars are sprung and pulling down, what is the opposing force?

Quote:
Originally Posted by 2airishuman View Post
3. there is no evidence that stiffness of the tv suspension is passed on 2 the trailer...

in fact there is evidence that this does NOT happen.

http://www.airforums.com/forums/f238...tch-53341.html
I read the thread with glee. This is really at the core of my training.

One, the data collection was incorrect. They measured the wrong thing.

Movement is not what bends a frame. Deflection and internal stress bend frames. Accelerometers can only detect the overall movement of the frame, and with a 0.2s sample rate, a measly 5 samples per second, there is a failure to measure anything but the lowest frequencies of movement. The peak stresses come in transients at a much higher frequencies than the 2.5Hz maximum capture frequency they used. What should they have done?

Attached surface stress monitors to the frame, with a sample rate of at least 800 samples/second, allowing capture of frequencies up to 400Hz. I'm sure the resonance of the ENTIRE TRAILER is somewhere around 0.5Hz, but the stresses that will affect the A-frame will be extreme, transient and somewhere in the order of 50-100Hz, based on my experience taking these kinds of measurement.

Further, the conclusions drawn in that thread were not reasonably derived from the completely inadequate and incorrectly collected data. There was no detail given of the route, no testing of response at different, even known frequencies of input, no measurement of deflections or load, nothing. The experiment isn't even repeatable.

Quote:
Originally Posted by 2airishuman View Post
4. IF softer were better for the trailer then FLOPPY would seem to be ideal...

define soft in either qualitative OR quantitative terms...
If you say so.

If hardness were not an issue for comfort alone, it affects vehicle handling. Why would manufacturers spend hundreds of millions of dollars tuning and testing ever more advanced suspension systems? Because both front and rear road inputs affect handling.

Further, in this discussion, it is a distortion for you to act as if "softness" is a simple suspension issue. Perceived softness is a lack of response at any frequency. However, chassis can tolerate certain frequency inputs very well and others poorly because they're closer to the natural resonant frequency of the vehicle. Suspension is therefore tuned to provide damping at specific lower frequency ranges. "Harder" suspension filters the inputs at only the lowest input frequencies. Generally, the larger the vehicle, the lower its' chassis resonant frequencies, and the harder the suspension can be whilst still giving the same perceived smoothness of ride, because of absorption, rejection and our relative insensitivity to some frequencies that do not transfer well due to our own natural frequencies as coupled to the seat.

Quote:
Originally Posted by 2airishuman View Post
5. gibberish. w/d doesn't KNOW where the 'mid range' of suspension is for the trailer OR the tow vehicle...
Your argument is fallacious. WD "knows" what you program it to know by the selection of bar and the link you choose. There is more and less ideal programming, sure, but the WD is PROGRAMMABLE by selection and setting, to respond to your particular requirements - if configured CORRECTLY. This is not a claim that it can magically remove load, though you portray it as such with great mischief.

Quote:
Originally Posted by 2airishuman View Post
6. it's not about REAR axle handling, it's about REloading the steering axle.
If the two axles were decoupled, this would be correct. Unfortunately, they ARE coupled, and it is not possible to increase load on the forward wheels without changing the load on the rear axles. Load affects axle handling, regardless of location.

Quote:
Originally Posted by 2airishuman View Post
7. UNloading the front end doesn't "soften" the front axle, it reduces grip/traction/control at the tire/roadway.
UNloading the front axle "softens" the front axle in a number of ways.

First, it reduces load, which raises the frequencies the wheel is trying to transmit to the chassis, but lowering their intensity. As previously discussed, first these frequencies are harder to transfer so are more readily absorbed by the suspension. However, with lighter loading, tire deformation reduces so this is a "win some, lose some" point.

Second, the softening is RELATIVE. The front and rear suspension are tuned to work well together. However, differentially loading the front and rear axles (or left and right, which is why we have sway bars) changes the effective tuning of the two suspension systems so the heavier-loaded suspension becomes stiffer and the lighter loaded suspension becomes softer, in terms of handling input.

Quote:
Originally Posted by 2airishuman View Post
8. SWAY like w/d and bar function has been explained in DETAIL and by some really smart/qualified folks already...

in OTHER threads...
"This is the place where brilliant minds assemble to pool ignorance with questionable logic in order to reach absurd conclusions."

Quote:
Originally Posted by 2airishuman View Post
encouraging folks to WASTE keystrokes doing it all over again is disrespecting their (and others) previous efforts...

purely 4 self entertainment.

cheers
2air'
I don't double-space all my posts, use poor sentence structure, or say things I think are IMPORTANT in CAPS, except in parody posts like this one.

IF you feel the need for further education feel free to respond, preferably in private where the gentle reader of this forum need not be troubled by this petty, meaningless squabble. It's a shame, you have such great knowledge of Airstreams, but you feel the need to post slams like knowledge is a competitive sport, and sometimes you try to slam someone in an area where they have degree-level academic and practical expertise.

PS: please send details of your qualifications first, so I know how much weight to put on your LAYMAN'S opinion.
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Old 09-22-2010, 12:06 PM   #73
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Andy,

I have some bad news for you.

You cannot base a fact on experience or observation no matter over how long a period you do it. What you have done is come up with an hypothesis of what seems most likely to you and defined that to be a fact. That is the best you can do until you have used sound accepted engineering and scientific practices to prove your hypothesis to be correct. You have not shown us that you have done this is any manner.

More than one person, involved in the design and manufacturing of hitches and associated equipment has either stated (or been quoted as saying) things that make your hypothesis of lighter bars for heavier tow vehicles not only incorrect, but improper use of their equipment. I believe it is a very safe assumption that these people have either done or seen the drawings and calculations involve in these hitch system's design.

This is not the only subject on which you recommend that people not follow manufacturer's recommendations, but instead rely on your recommendations.

Your attempts to establish yourself as the ultimate authority may well have unforeseen consequences. You have a business and when you post on these forums as a vendor, you are speaking as a representative of that business.

I know of one thread when it is stated that you recommended WD bars rated at less that the trailers published tongue weight. One of those bars ultimately broke in two. Luckily it happened entering a parking lot and not on a big pothole in the interstate.

Are you willing to find yourself holding the bag, when something catastrophic happens and the manufacturer says his equipment was not used properly and your business was the one who recommended it.

I am a firm believer in reading the manual that comes with a piece of equipment and then following it and knowing that if I do something contradictory to it I am on my own.

As I see it, you are taking it on yourself to tell your customers and the members of this forum to use what you recommend not what the manufacturers recommend. Keep in mind that when you post things on a forum as a vendor, that it will be considered as an opinion of your business not you as an individual.

My posting in regard to this is to further my belief that the procedures and directions that come from the manufacturer of a piece of equipment, are the only ones to follow, until something else is PROVEN to be better or safer.

Regards,
Ken
Ken.

No matter what, you will disagree.

That's your privilege.

What I can and cannot do, I think, is my choice, based on facts, education and experiences. I do many things, that today, some say, "you can't do that".

Airstream said that twice, in 1969, to me and my bosses. They were proven wrong, and what I did, still stands today, some 41 years later.

No, I am not an engineer or even perhaps an expert. But I do have many years of experience, that I share for the comfort and safety of many owners, who usually express appreciation.

Other than that, no comment.

Andy
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Old 09-22-2010, 12:44 PM   #74
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<<Mod Mode>>

The OP's original question was in regards to A-Frame deflection and ways to adjust the level for accuracy. While most here recognize the bread and depth of knowledge contained in this group the thread needs to return to "On Topic Status" and not digress into a diatribe on hitches.

With that being said, kindly respect that this gamana's thread and respond accordingly.

Thanks,

Kevin
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Old 09-22-2010, 01:17 PM   #75
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The A-frame appears to not be bent. It has some deflection under load. This appears to be a healthy amount of deflection.
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Old 09-22-2010, 02:00 PM   #76
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Lets get back to something we can all agree on.... like politics or religion!
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Old 09-22-2010, 02:08 PM   #77
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Lets get back to something we can all agree on.... like politics or religion!
Or, how about Hawaii??

Andy
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Old 09-22-2010, 02:40 PM   #78
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Well, this thread sure turned out to be interesting. I'm certainly not an expert, but my recent experience tells me that my TV, AS, and wife all appreciated the "softened" ride I provided to my Airstream on our last 3,600 mile trip. See my post #19 in this thread. Thanks again, Andy.
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Old 09-22-2010, 03:16 PM   #79
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I appreciate Andy's remarks as well. With so much misunderstanding and so many opinions about weight distribution, as it may relate to the op's bent frame and many other structural concerns, it is good to hear the voice of extensive experience in repairing these problems.

It is also good to have Sean Woodruff weigh in, and I would like to hear more of what he has learned, and probably continues to learn.

Less valuable are those who have it all figured out, and post mostly to prevent further discussion.

Doug
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Old 09-22-2010, 03:30 PM   #80
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I think I'm biased towards Andy's answer in this case too.

Quite simply, when someone works on something and sees the failures that happen, I'll tend to listen to what they're saying in terms of what usually goes wrong.

For all the theory talk, that trailer has a slight bend that I have seen on every longer AS I've looked at, and it doesn't indicate any kind of immediate failure - though it may be indicative of poor design, poor hitch configuration, PO damage, or an oddity of manufacture, or a UFO may have bumped into it one night.

Our 'streams do make us worry so!
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Old 09-22-2010, 03:43 PM   #81
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Quote:
Originally Posted by dkottum View Post
I appreciate Andy's remarks as well. With so much misunderstanding and so many opinions about weight distribution, as it may relate to the op's bent frame and many other structural concerns, it is good to hear the voice of extensive experience in repairing these problems.

It is also good to have Sean Woodruff weigh in, and I would like to hear more of what he has learned, and probably continues to learn.

Less valuable are those who have it all figured out, and post mostly to prevent further discussion.

Doug

Hi Doug,

I don't disagree with Andy's stance on light bars. However, if a light bar does not bring the front axle back to near its unloaded weight I do disagree with using a light bar. I've sold, or been responsible for selling, over 14,000 hitches in my career and haven't had even one problem with this methodology.

There is also the dirty little sway issue that is coloring his recommendation. The hitch he sells requires bar deflection, through lighter bars, for it to perform. The hitch I manufacture does not require anything from the weight distribution to eliminate the sway so I tend to use weight distribution bars for weight distribution and not sway control.

My "official" stance on the subject is... use the lightest bar that will adequately distribute tongue weight to the front axle of the tow vehicle. If the trailer tongue cannot handle the loads that are required to adequately distribute enough tongue weight, it is a TRAILER DESIGN problem and not a hitch or tow vehicle problem.

As an engineer I would NEVER expect my product to require user intervention, outside of what is reasonably expected, in order for it to not fail (or bend). Using light bars that do not distribute enough tongue weight to the front axle of the tow vehicle, as a solution to the bending of the tongue, is outside of what I would consider to be "reasonably expected."
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Old 09-22-2010, 03:50 PM   #82
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Hi Doug,

I don't disagree with Andy's stance on light bars. However, if a light bar does not bring the front axle back to near its unloaded weight I do disagree with using a light bar. I've sold, or been responsible for selling, over 14,000 hitches in my career and haven't had even one problem with this methodology.

As an engineer I would NEVER expect my product to require user intervention, outside of what is reasonably expected, in order for it to not fail (or bend). Using light bars that do not distribute enough tongue weight to the front axle of the tow vehicle, as a solution to the bending of the tongue, is outside of what I would consider to be "reasonably expected."
Sean.

You and I are really saying the same things, but using different words.

Using lighter bars, on a truck, does not require them to shift all the tongue weight, since the truck is designed to carry, some of the weight. That's the difference between a truck and a car.

Andy
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Old 09-22-2010, 03:51 PM   #83
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Sean,

How much strain is relieved from the trailer frame by using lighter bars? Is it a linear or log function? (For everyone else, does using 500 lb bars instead of 1000 lb bars halve or quarter the load on the frame?)

Also, if lengthening the bars to increase leverage reduces load, how far can that reasonably be achieved?
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Old 09-22-2010, 04:07 PM   #84
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generally it seems we have two camps. one camp knows what works in use and the other knows why things work. usually the 'truth' lies somewhere in the middle. there are just too many variables for one system to do it all best.

this reminds me of when my different doctors give different orders that seem to be in the interest of their specialty.

one thing we can agree on (i think) is that there are a large amount of conditions that can be encountered and not completely solved with one setup.

from what i've seen in my limited experience, is that airstreams appear to flex more than trailers with bigger frames.

as for snapping a lower rated weight distribution bar, i myself would rather snap a bar than twist a truck or trailer encountering a steep angle such as a driveway. the bar is the cheapest thing to fix. other than I95 in NYC i don't think a bar would snap on the highway. from what i've read here, the issues seem to happen in driveways, severe turns and backing into camp sites.

i am highly uneducated but i do read and listen well :-)
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