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Old 04-03-2016, 09:09 AM   #29
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I comment only as an interested bystander; I have no intention of adding anything to the back of my Airstream.

However, adding weight to the far end of a lever (for that is what the frame is, with the rear axle of the trailer as the fulcrum) is surely going to make that lever all the more effective. If the frame stays rigid then weight, magnified by the distance from the fulcrum and the bouncing effect from uneven roads, is going to lift the tongue of the trailer somewhat, which can't be good for stability at speed.

If the frame does flex, then you increase the possibility of it being separated from the shell.

Also, if you get into any kind of swaying situation, that sway is going to be magnified because you've increased the length of the trailer without adjusting the position of axle(s). More sway is going to be harder to get under control.

I've no evidence that these things would happen in a real-world situation, but from what I know about levers, I can't imagine the addition of 200lbs beyond the back of your Airstream is going to help anything.
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Old 04-03-2016, 09:25 AM   #30
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Originally Posted by BicycleStream View Post
We are having a 2" receiver hitch installed on the back of the new 28' trailer so we can carry our bikes and still get into the EB hatch. The dealer is doing the work (brand new trailer) and guarantees the work up to 200lbs. It is custom made tubing welded to the frame in very specific points (I double checked and it is AS approved). We should have the trailer in a couple weeks and I could post pictures if needed.
Anyone who condones this (200 lbs. hanging off the rear of the trailer) really does not understand how Airstreams are put together or towing dynamics. I don't care if it's a dealer who will "guarantee" his work or some misguided person at Airstream. This is a very bad idea and should be avoided!
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Old 04-03-2016, 09:33 AM   #31
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Opinions expressed here can sometimes be so entertaining and judgmental of the decisions made by others.
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Old 04-03-2016, 09:50 AM   #32
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The effect on hitch weight can be calculated. It is the weight at the rear times the distance to the center of the wheels divided by the distance from the center of the wheels to the hitch coupler. So, in most, if not all, cases, the effect on tongue weight is substantially less than the weight added at the rear.

The effect on stability could be calculated similarly, but you need to know the weight distribution of the trailer components behind and in front of the axles.

This is just my opinion, but I don't see either of these things being significant, and the idea that stability is affected by the airflow over the hitch framework is really out there. The most significant thing I can think of is the dynamic forces from the bike rack cantilevered from the hitch bouncing up and down putting significant loads on the bike rack and the hitch as well as the trailer. That is why the Fiamma rack, with its attachment to the skin of the trailer might be considered superior since it would eliminate the bouncing.

I had a front hitch on my F-150 which I used for a bike rack when traveling and to park the trailer at the house. I just put one on my 2500. I'll not be parking the 30' trailer at the house like I did my 25', but I'm loading up the bikes for the Keys trip.


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Old 04-03-2016, 09:58 AM   #33
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(I think) how much weight can be added should not be answered by one's opinion, but with fact. (not speaking to anyone above in particular)

Weighing the trailer, with the added weight on the rear, will provide the data regarding sway potential. If the trailer's tongue weight is less than 10%-15%, diminished because of weight added to the rear, something inside the trailer could be moved forward to counter balance, eliminating the problem.

Damage (separation/sag) caused by added weight is what I would be concerned about.
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Old 04-03-2016, 10:26 AM   #34
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I would argue that the proof is in the pud......

I have been using ours for close to two 3 years without a problem. Those frames are not as flimsy as you suggest.

On the other hand scaring the bejeebies out of you will get you running to Air Stream for " Their " product. The FIMA is screwed or riveted to the Skin. Tugging on it as the trailer bounces up and down.

I weigh 200 LBS and stand on the bumper regularly. The next time I will jump up and down on it to test your theory. I will let you know if I will bend.

Did my question to A W Warn bother you somehow? I don't know how many more caveats I could have put there to indicate I was actually asking the question because I don't have a theory and really don't know the answer - you may have assumed there was an answer behind the question and if so, you missed my point. Then again, I'm assuming your implication, and on and on that goes ... 😀
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Old 04-03-2016, 10:32 AM   #35
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Al - just checking to be sure I understand - let's say it's 200# on the bike rack, 7' behind the center of the wheels and 20' from there to the hitch ball. Are you saying that 70# gets lifted off the tongue (200*7/20=70)? I'm clearly not an engineer! Thanks.
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Old 04-03-2016, 10:44 AM   #36
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...snip...

Damage (separation/sag) caused by added weight is what I would be concerned about.

This is what I'm wondering about too. Even if I understand Al's formula (big if there) I don't think it addresses how much force the bikes on the hitch apply to the receiver installed on the rear frame of the trailer and how those forces change or are possibly amplified with up and down movement (bumps in road, etc.).
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Old 04-03-2016, 10:49 AM   #37
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Originally Posted by A W Warn View Post
Weighing the trailer, with the added weight on the rear, will provide the data regarding sway potential. If the trailer's tongue weight is less than 10%-15%, diminished because of weight added to the rear, something inside the trailer could be moved forward to counter balance, eliminating the problem.
Not entirely true. Airstream builds their trailers with the heavy appliances and storage tanks over or near the axles so that weight is not concentrated toward the ends. Putting heavy items at the ends to simply balance the trailer over its axles does not eliminate the the potential for out-of-control sway, but probably makes it worse.

The most stable condition is with heavy items over the axle, lighter items on the ends with at least 10% of the total on the hitch.
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Old 04-03-2016, 11:05 AM   #38
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Can't stand it, got to muddy the water. PJSEPSKI you can never go wrong on this Forum.

I would greatly enjoy hearing from those on the Forum whose opinion I appreciate and respect. AWCHIEF, PROTAGONIST, FRANKLYFRANK, DKOTTUM and A W WARN always bring real world experience to the table. Thank you.

The YouTube link showing the apparatus demonstrating loading and induced sway in a tow and towed vehicle combination was very informative. However, I question the setup suggesting whenever you back load a trailer, failure will soon follow.

Look carefully at that video you will notice that the trailer is a single axel. That axel is exactly halfway between the ball hitch and the rear of the trailer. Also note that the steering gear and the real axel separation of the tow vehicle is much less distance than the length from the ball to the real axel of the trailer.

This combination of givens already has doomed the apparatus to failure if the weight distribution is not perfect. But, that's the point. The apparatus is designed to elaborate a problem that can exist if you don't pay attention.

I suspect that each combination of tow and towed (combination) vehicles have unique conditions that must be taken into account when you load, balance and combine different loads throughout the entire combination vehicle.

Single axel, dual axel and even three axel rigs pulled by passenger cars, quarter ton, half ton, one ton and even two and one half ton vehicles are going to have a major impact on the stability of the over all rig in various conditions.

As far as the integrity of the frame of an Airstream travel trailer is concerned, I am inclined to agree with FRANKLYFRANK, who suggests that if the frame does not have a worst case engineered frame that cannot stand an additional 200 pounds of load on the rear end with out failure, it has no place on the public roads!

So this is where I put my neck out. I suggest that a properly engineered and designed attachment can be placed on the rear of an Airstream trailer that will allow no more than two-hundred pounds of additional loading (including the attachment) without any negative effects on anything. (But you must consider the entire combination vehicle, like a VW Beetle pulling a 31 foot Excella may have issues.)

Now the real important part. The combined weight of the lawyers and the insurance company will certainly exceed the recommended coefficient of drag of any design especially when combined with the negative square root of the distance from here to Mars which always screws up a good idea.

Happy Trails
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Old 04-03-2016, 11:29 AM   #39
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Yeah the frame/shell attachment can withstand 200 lbs dead weight. But put the 200 lbs at the end of a lever, then bounce it up and down along as roadways do, and you have much more than 200 lbs acting on the frame/shell attachment.

I don't think the frame would bend permanently either, I do think it will flex more than normal with this otherwise unsupported weight hanging out there. I think this flexing could eventually damage the frame/shell fasteners. That's what the Airstream repair shop owners have told us in this forum.

My greater immediate concern is about stability, especially of that dealer is talking about 200 lbs well behind the bumper. I've experienced sway trailering lumber, it happens and increases quickly, tow vehicle steering control is lost.

I don't understand the need to chance it; Airstream sells a rack that limits weight and holds and supports the bikes tightly against the shell, so does Can-Am Airstream in Ontario if you don't like Airstream.
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Old 04-03-2016, 11:51 AM   #40
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I'm not picking sides, but I wanted to point out that the waste tanks on my trailer are mounted to the frame at the very rear and the freshwater tank is ahead of the axles. If I leave home with full water, full propane and empty black and grey tanks, and return with empty water, less propane and full waste tanks, I've not only added more than 200 lbs to the rear of the trailer, but I've transferred that weight from ahead of the axles.
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Old 04-03-2016, 12:06 PM   #41
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Well yes, but your storage tanks are not behind the bumper, which makes a difference.
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Old 04-03-2016, 12:23 PM   #42
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Originally Posted by SteveSueMac View Post
Al - just checking to be sure I understand - let's say it's 200# on the bike rack, 7' behind the center of the wheels and 20' from there to the hitch ball. Are you saying that 70# gets lifted off the tongue (200*7/20=70)? I'm clearly not an engineer! Thanks.
Yes, that is what I am saying, but I was only addressing the concern for changing the hitch load. I can't comment on the concern for loads applied to the rear of the trailer, other than to say that I don't think the issue is the dead weight so much as it is the dynamic load induced by the trailer bouncing.

The bad roads we encountered on I-10 west of New Orleans had my trailer bouncing up and down and I suspect a couple of G's (maybe more) at the rear. That turns the 100# of bike weight into an oscillation between 200# up and 200# down that puts more stress on everything. This was happening at about a one second rate. So in an hour of driving, the rack, hitch and frame was flexed 3600 times. A previous thread on this subject described a failure of the hitch or bike rack that left the bikes skidding down the road. On the other hand, several on here have posted that they do it and have had no problems. As with most things on here, you read all the posts and make up your mind as to what best fits your situation. I have a bike rack in a receiver on the front of my TV. Others on here do he same thing. There have been posts claiming that it is illegal to block your headlights in some states. I can't confirm or deny that data. My point is that there are supporters and detractors of almost any approach to hauling bikes (and almost any other question that pops up on the forum.)

Al
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