a)an Expedition EL really isn't that 'soft' of a suspension
or
b).2 meters/second^2 (17 lbs) is actually a very substantial force when discussing 5" metal frames.
a)an Expedition EL really isn't that 'soft' of a suspension
or
b).2 meters/second^2 (17 lbs) is actually a very substantial force when discussing 5" metal frames.
Using accelerometers, I think, is a good idea. What they say then, must be converted into forces that momemtarially are applied to the A-frame.
Somewhere I think you said, something like 24000 ft/lbs of force, was applied to the A-frame.
I don't know about you, but I would not want to get hit with that kind of force.
If the forces are truly any where near that, and applied thousands of times to the A-frame, as when it's being towed, I then don't question why the fatigue failures are occuring.
Airstream says, a soft ride is necessary. I have said that for over 40 years. There are opinions that differ.
A rough ride and/or extensive impact forces, to me,will cause damages. Again, some blame the design.
I feel you are on to some answers, with more testing, and let the test results speak out.
Contrary to some, who challenge the currect designs, 30 and 40 year old Airstreams had the same fatigue problems, but were seldom towed with rugged tow vehicles, as opposed to today, where the vast majority of tow vehicles are heavy duty trucks. So the damages, obviously, are more pronounced, greater in numbers, today than in the past.
I am looking into our repair records regarding damages to the front ends, in the absence of the front hold down plate.
Perhaps, we could come up with an update kit, if indeed it would prove as an advantage.
Please keep up the excellent work, with your testing.
finalcutjoe ... Thanks. This is very interesting info, and as far as I know, something that hasn't ever been done before (or at least, never published). I wish we could enable you to test additional vehicles, to broaden the data set. It might be possible to draw more conclusions in that case.
But even if you were willing to lend out your setup for testing on other vehicles, it seems we'd need to run the exact same road and have the same trailer to get meaningful comparative results. Darn.
This hitch setup is about as rigid as you’re going to get. I’m a svelte 210lbs, and jumping up and down (with spring bars at MAX setting) on the orange head produces slight movement at best (but detectable on the accelerometer as slight aberrations in z-axis).
I waded into this experiment expecting to see numbers that would support the ‘overhitching’ and ‘too much vehicle’ theories. I’ve towed my 30’ Slide with a Dodge 3500 CTD, an experience that I would consider teeth rattling. My 2500 Suburban being only slightly less 'jarring', and the Expedition riding like a silver cloud (note: I intend to run our ‘track’ with the sensor in the different mules- I think quartile feedback with those numbers will give us a more understandable scale of the acceleration data)
At this point, the numbers don’t lie. The ‘harsh’ ride, that one feels inside a 'heavy-duty' tow vehicle, are NOT transferred to the trailer thru the ball and bars. Is it possible there are frequencies, oscillations, vibrations occurring that are harmful to the frame/shell of my ‘stream? Certainly. But I would wager, based on this feedback, that these forces are present whether driving a heavy-duty truck or a passenger vehicle- they’re inherent in over-the-road travel. There are those that would attempt to discredit my findings by citing my earlier misinterpretations of the data. Again, I’m not going to pretend to understand exactly ALL of what the data is trying to tell us-- It would be great if an engineer familiar with this could jump in here. (I’ve got all the data in excel, .csv, whatever is convenient for review and comment.)
But at this point- I feel very comfortable knowing that I’m towing my rig safely within manufacturer specifications- and at the same time not subjecting my 'stream to excessive abuse.
This is great info! We just bought a new(used) to us TV. 2003 Dodge 3500 CTD, 4x4, dually. We have a 31ft '72 AS. What load bars should we be using? We used 1000# when towing with our Excursion. Any help would be great.
The tests show huge weight impacts on the A-frame.
Those impacts cause the A-frame to flex.
Flexing of any metal, leads to fatigue.
Fatigue leads to cracks and failures.
You also claim a rough ride.
Flexing, and to what degree of the A-frame and it's effect on the bottom part of the front shell, can very easily be demostrated to the naked eye.
Use a fork kift, as we do, to move trailers in and out of our building, and lift the front of the trailer about 18 inches or so, above level.
Then, without letting the jack post hit the floor, drop the front end quickly, and observe the flexing, in the lower part of the shell.
If that doesn't cause long term problems, then I have wasted 43 plus years of my life, working on Airstreams.
Use Duallies, use 4 X 4's, use 1000 to 1400 pound bars, and you will keep service departments busy repairing front ends, guaranteed.
How do we know? Because we do a lot of that work, and then spend the time teaching the owner, what was wrong and how to fix the problem.
A very strange and interesting observation. Many of those customers, in time, come back for other services, none of which experienced a repeat problem with the front end, in spite of the fact that the trailer and tow vehicle, are the same as before.
What changed?
The rigidity was softened. That was it.
If that's not convincing information, then so be it.
To this day, Airstream says "soft ride". Do they take out pages of ads to say so, of course not.
It's overwelming, to read the insistance owners have of damaging their Airstreams, by over rigging, yet ignoring those that made the changes, and so reported, on this Forums, the improvements.
... (note: I intend to run our ‘track’ with the sensor in the different mules- I think quartile feedback with those numbers will give us a more understandable scale of the acceleration data)
At this point, the numbers don’t lie...[/I]
good idea fc' and u might try the track loop with the sensor INSIDE the stream too.
doesn't need to be done at the same time as the tow vehicle and if done on the SAME loop and conditions...
each tv/trailer combo would be interesting info...
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i agree there are low amplitude high frequency vibes being transmitted into the unit...
from the road via the tires/axles primarily and perhaps SOME via the hitch...
your data suggests NOT VERY MUCH via the hitch/a frame, ON YOUR 30 SLIDE...
i think ONE of the issues is this...
? is it better for a stream to move UP/DOWN somewhat level on all axles while connected (adequate w/d is needed here)...
? or is better for a stream to ROCK/roll like a teeter on soft sloppy w/d with loads shifting on the front/rear axles ??
following behind i've seen firm/flat units move very little UP/down,
while soft/sloppy units have rears that go WAY UP then way down...
where's that picture of plumber's crack?
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Quote:
Originally Posted by Maryw164
...What load bars should we be using?...
no offense mary but THIS thread is really about measuring forces and trying to make sense of the data.
it's NOT about how to set up any ONE rig (except maybe fc's rig)
so u might wanna START a thread on your needs and questions, or READ some of the 100s of threads on towing combos...
there are several folks here towing with 1 ton drw trucks who can offer help on tires, w/d bars, hitches and so on...
check out some of those threads in the tow vehicle/hitches section, good stuff is OUT there.
___________________
cheers
2air'
__________________ all of the true things that i am about to tell you are shameless lies. l.b.johnson
we are here on earth to fart around. don't let anybody tell you any different. k.v.
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