Bike rack

[pcskier]

I believe that sway can be mitigated with proper loading. And I believe that the weight issue on the installed rear hitch can be mitigated with sound construction and welding.

As I posted earlier, the weak link, it appears to me, is the bike rack itself, bouncing up and down like it's on a spring. My concern would be the bike rack itself failing. The physics don't allow them to bounce that much when they are on the back of a car, as intended. The back of a car doesn't ratchet up and down nearly as much as the back of an AS does.

[Bluepost1]

Originally Posted by pcskier

I believe that sway can be mitigated with proper loading. And I believe that the weight issue on the installed rear hitch can be mitigated with sound construction and welding.

As I posted earlier, the weak link, it appears to me, is the bike rack itself, bouncing up and down like it's on a spring. My concern would be the bike rack itself failing. The physics don't allow them to bounce that much when they are on the back of a car, as intended. The back of a car doesn't ratchet up and down nearly as much as the back of an AS does.

I agree with you that the bounce on the actual rack would be the weak link. Acceptable? No, but compared to setting off a sway event a couple bikes down on the highway isn't likely to be life threatening....again not acceptable.

If it is a quality rack, properly loaded, I would have little concern. A cheap no brand Chinese brand would be a different story.

[jcl]

Originally Posted by Bluepost1

I agree with you that the bounce on the actual rack would be the weak link. Acceptable? No, but compared to setting off a sway event a couple bikes down on the highway isn't likely to be life threatening....again not acceptable.

If it is a quality rack, properly loaded, I would have little concern. A cheap no brand Chinese brand would be a different story.

If that quality rack is a Thule or Yakima, two that I have used, the manual instructs that they are not to be used on trailers. The issues are known and understood by the product designers. Cheap under-engineered racks may be the only option, but that opens up a different set of problems.

What can be done is to install a fore/aft strut at the top of the rack to stop movement of the rack when mounted in this type of environment.

[OTRA15]

PS to Posts #27 and #28.

[click on orange arrow to go to the last post in the Out of Control Sway thread where cazual6 is the OP]

Originally Posted by cazual6

Team,

I just reread this after someone posted something about wanting to put bikes in the back.

I can say it can be done. But, but, but be very cautions about it. Minimal weight is all I can say. I put only kids bike, less than 50lbs. For the most part, it is now just a flag pole holder.

It was interesting rereading the advices, challenges and lack of understanding of what I thought I knew, what people knew, and most of all experiences.

Having been in this forum for over a year now and have participated in many discussions and read tons of threads, what people know vs experiences don't always go hand in hand.

We all can agree on one thing: Safety first.

Another recently revived thread:

Originally Posted by OTRA15

. . .
PS -- Installing a bike rack that exceeds Airstream's design parameters, and "getting away with it" temporarily, is like cheating death in a game of Russian Roulette IMO. Sooner or later, you will pull the trigger when a chamber in the cylinder is not empty. Bam!
. . .

[OTRA15]

Originally Posted by Bougeois

. . .
All this was is to show an idea that I did and if anyone was thinking of doing something similar.
. . .

Have you read the various Rollover and Sway threads, as linked earlier, from start to finish? If not, you are not understanding the risks involved for you, your family, and everyone else on the road in the cross-hairs of your "mobile weapons system" IMO.

As requested please post when/where you are going to be towing, so we can stay out of the way.

Thanks,

Peter


PS -- See Russian Roulette comment in previous post.

[OTRA15]

Originally Posted by HowieE

. . .
While it is for 2 bikes I have carried 4 with it.
. . .

Your minimalist rack, mounted right at the bumper [with no rear bumper storage area on your heavy triple-axle 34' Airstream] probably comes close to conforming with Airstream's design parameters for the Fiamma rack IMO. [edit -- nice job in this regard!]






This installation should not be used as a blanket approval of all rear-mounted bike racks, especially those that involve a rear hitch assembly, behind the rear storage box, which cantilever the load way behind the rear axle of the trailer, where the forces are multiplied by the square of the increase of the distance back.

No need to "pull the wool over the eyes" of unsuspecting readers. The devil is in the details. Broad brush paint strokes can mask defective reasoning IMO.

Please see Russian Roulette PS in earlier post.

[OTRA15]

Originally Posted by jcl

If that quality rack is a Thule or Yakima, two that I have used, the manual instructs that they are not to be used on trailers. The issues are known and understood by the product designers.
. . .

Great observation, thanks!

[OTRA15]

FYI the other thread has a recent update from Andy of CanAm which clarifies his bike rack system:

http://www.airforums.com/forums/f295...rt-141188.html

[kscherzi]

About a year ago I was passed by a guy towing an Airstream with a full sized ATV hanging off the back of the trailer. I was so in shock I failed to take a photo.

[OTRA15]

The top photo in Post #45 is from the Quebec Rollover thread linked earlier. They had a huge storage box on the back of the AS which separated from the trailer during the rollover. It is a very long thread, but well worth reading for anyone who values his or her life IMO.

[HowieE]

[QUOTE=OTRA15;2110859]



which cantilever the load way behind the rear axle of the trailer, where the forces are multiplied by the square of the increase of the distance back.
/QUOTE]


I was under the impression that leverage was a linear thing not a function of the square of the distance. Yes weight and distance will effect the stability of a trailer. Trailers are designed tongue heavy, and can be towed safely as built, but do not include the weight of the gas bottles or any hitch used. 2 60 lbs. gas bottles and a 200 lbs HaHa hitch will not be overcome by 50 lbs. of bikes mounted rearward. Blaming a rollover on a bike rake is "tilting at windmills".



I have to say this rack system has been used with a Reese Dual cam. Reese Straight Line , and Andersen system. The only time any indication of sway was ever observed was while using the Reese dual cam system. After some investigation I realized the bars are not manufactured to reasonable tolerances and not always used in the same orientation as when the system was set up. That slight difference in length cause the bars to be additive to sway rather than decrease it. I would strongly suggest that everyone mark the hand of any bar system that has a cam function at the end of the bar when originally setting up the WD hitch.

[OTRA15]

Leverage is a linear thing, but when the weight at the end of the lever is accelerating, its effect is more like "squared" according to the increase in the radius IMO.

The above is obviously a lay person's understanding of the physics involved, but maybe this will illustrate things.

Hold a small dumbbell in your hand, and extend your arm out. Now raise the weight very slowly.

Then raise the weight at 100 MPH. Some difference!



The out of control sway happens when the weight cantilevered way out there is accelerating quickly sideways (mainly), with the rest of the rig harmonizing at the same time (tires, shocks, pivot at front hitch, tow vehicle tires, shocks, driver reaction (often wrong) etc..



Also, I said your hitch probably conforms to the AS design parameters.

"Your minimalist rack, mounted right at the bumper [with no rear bumper storage area on your heavy triple-axle 34' Airstream] probably comes close to conforming with Airstream's design parameters for the Fiamma rack IMO. [edit -- nice job in this regard!]"

Did you see that?

[HowieE]

Originally Posted by OTRA15

The out of control sway happens when the weight cantilevered way out there is accelerating quickly sideways (mainly), with the rest of the rig harmonizing at the same time (tires, shocks, pivot at front hitch, tow vehicle tires, shocks, driver reaction (often wrong) etc..

I don't think we can blame out of control sway solely on a cantilevered weigh on the rear of a trailer.


You have listed several of the factors involved with sway but you did not distinguish which ones are additive or subtractive to sway.



Tires, shocks, and WD hitch all have a friction coefficient and thus are subtractive to sway, they reduce momentum. So what can contribute to sway? Driver reaction is the biggest single additive factor. Reaction by definition has a time delay involved and thus is out of phase with the sway. This simple fact that it is out of phase, the drive is imparting energy through the steering wheel, causes it to be additive to the sway.


The driver action is the only source of energy going into the sway. That energy increases the sway to a greater extent than any system designed to reduce it.

[rewillia]

I've read all the post/threads here on this topic and even sent inquires to both Airstream and Fiamma about either strengthening of the Fiamma or replacing it to include installation of a horizontal cross-member and addition of a 2" hitch receiver at the rear bumper on my Classic and use of SOB bike rack, i.e. Thule.

My objective is to to transport two small frame size e-bikes which together weigh 122 lbs (ex-batteries) using a Thule Rack for them which weighs 45 lbs. (167 Lbs. combined)

My thinking at this point is that the crossmember and 2" receiver box would likely add say 100 lbs.so when welded in and along with the Thule rack and two ebikes would total something in the area of 267 lbs. vs the current set-up of the Fiamma Carry-Bike rack (told it weighs 28 lbs) and it's max. capacity of 72 lbs (100 lbs. total), a net increase of approx. 167 lbs.

Ok, I agree that's a somewhat "worrisome" amount of added weight but then I think about the JACK point of the trailer which is a good distance aft of the rear axle on my Classic and can't help to believe that if I were to limit the amount of weight I put in the bumper compartment storage as well as the cargo storage at the rear (under the head of the RQB including the floor tubs) then it becomes more of an offset as to where the weight is vs. overloading. I also agree that the dynamic forces upon the bikes/rack are a factor.

End result being - there is clearly no consensus on what can or cannot be done yet I plan to address this during a service appointment with Airstream in Jackson City next March and hopefully get in front of the right people to ask, i.e. Airstream engineering representatives.

Worthy to note that Airstream does not caution owners on the amount of weight that can be carried in the bumper storage or inside of the rear storage compartment and by default refer only to the trailers GVWR numbers.

Hell, I'd be willing to pull the rear belly pans and add (weld in) additional strengthening to the rear frame rails if that would help. I really want to haul those e-bikes on the trailer vs. inside of it or in/on my tow vehicle. In fact, Fiamma is now making racks for e-bikes only nothing yet on for Airstream.

[casarodante]

Having an extra receiver on the back of the trailer and just letting the bikes bounce up and down has always scared me. I used to have a hitch on the front of my truck and could see what they did.

But, I always thought if you could also attach the rack to the shell of the trailer for stability it would be much more like a part of the trailer. This was before Fiamma did it with theirs.

I am unsure how much I would like to do that on my trailer though.

I will be watching to see how the 'pioneers' do it.

[Froglips]

Originally Posted by rewillia

I've read all the post/threads here on this topic and even sent inquires to both Airstream and Fiamma about either strengthening of the Fiamma or replacing it to include installation of a horizontal cross-member and addition of a 2" hitch receiver at the rear bumper on my Classic and use of SOB bike rack, i.e. Thule.

My objective is to to transport two small frame size e-bikes which together weigh 122 lbs (ex-batteries) using a Thule Rack for them which weighs 45 lbs. (167 Lbs. combined)

My thinking at this point is that the crossmember and 2" receiver box would likely add say 100 lbs.so when welded in and along with the Thule rack and two ebikes would total something in the area of 267 lbs. vs the current set-up of the Fiamma Carry-Bike rack (told it weighs 28 lbs) and it's max. capacity of 72 lbs (100 lbs. total), a net increase of approx. 167 lbs.

Ok, I agree that's a somewhat "worrisome" amount of added weight but then I think about the JACK point of the trailer which is a good distance aft of the rear axle on my Classic and can't help to believe that if I were to limit the amount of weight I put in the bumper compartment storage as well as the cargo storage at the rear (under the head of the RQB including the floor tubs) then it becomes more of an offset as to where the weight is vs. overloading. I also agree that the dynamic forces upon the bikes/rack are a factor.

End result being - there is clearly no consensus on what can or cannot be done yet I plan to address this during a service appointment with Airstream in Jackson City next March and hopefully get in front of the right people to ask, i.e. Airstream engineering representatives.

Worthy to note that Airstream does not caution owners on the amount of weight that can be carried in the bumper storage or inside of the rear storage compartment and by default refer only to the trailers GVWR numbers.

Hell, I'd be willing to pull the rear belly pans and add (weld in) additional strengthening to the rear frame rails if that would help. I really want to haul those e-bikes on the trailer vs. inside of it or in/on my tow vehicle. In fact, Fiamma is now making racks for e-bikes only nothing yet on for Airstream.

I did exactly what you are proposing. Added a class 3 2" hitch with proper boxing and support. It will easily haul a 2500# trailer behind my 2019 Classic 30 RBT. I have a Haibike and a Pivot mountain bike. The Haibike is 47# with battery, the Pivot is 31#. I purchased a Thule T2 Pro XT 2 Hitch Bike Rack and a Thule T2 Pro XT 2 Add-on Bike Rack. This is a very heavy duty rack. With the Add-on rack, to be able to carry four bikes, it is nearly 100#.

My experience was very unpleasant. The significant additional weight, far behind the rear axles, removed several hundred pounds of tongue weight which created very dangerous sway issues. I eventually removed the Add-on rack which reduced the lever arm behind the axles but it remained an unstable situation. I have sold both Thule racks.

Pulling a 12' John boat behind the trailer causes no such issues.

[rewillia]

FWIW, I contacted Fiamma-USA and learned that they are now manufacturer their Carry-Bike style bike racks capable of transporting larger "fat tire" and heavier e-bikes for all types of RVs (excluding Airstream as unfortunately, and according to their representative, Airstream Inc. (Thor) has not thus far requested any such product for their line of trailers.)

They were able to help though and sold me one(1) of their new rail premium(s) which will serve to replace the existing two rails on our Fiamma Carry-Bike rack and permit us to transport one(1) of our heavier e-bikes (61 lbs) on our rack while not exceeding the rated max. capacity of 77 lbs.

Fiamma Part# is 98656M146, in the matching silver aluminum alloy with a wider track (to accept up to 4" width tires) and newer type wheel stop/strap support. Only exception being the end caps of the rail are black vs. the former red.