Taking the bikes along

[reelfastgreg]

Originally Posted by AnnArborBob

This explanation of how the Fiamma rack works makes perfect sense. Basically, it maintains the integrity of the body/frame connection by placing the same amount of stress on the body AND frame simultaneously.

hard to believe that sheet metal screws will succeed in '...maintaining the integrity of the body/frame connection...'

i think this was added simply because the design of this bike carrier is not well thought out in the first place. the bolting to the frame would allow considerable fore/aft movement particularly from the perspective of the weight being held up high. so i suspect the arms were added to try and stabilize this movement as opposed to the above statement.

take a look at any bike rack from Yakima and you may be able to see the difference in what i am talking about.

[projector]

I took the risk in doing a receiver mount rack, very similar to gpt's. The rack is made by Swagman, it also screws to the receiver and doesn't move. Our axles are back more that usual on the trailer so the rear overhang is relatively very little, like a boat trailer. It almost looks like a 25' with the back cut down and makes for excessive tongue weight. I also did a rear spare tire carrier that I may remove after thinking more about it.

[perryg114]

Good luck on the long term reliability of that rig.

Perry

Originally Posted by JamuJoe

Nice job by the OP on a receiver mount. So much misunderstanding and misinformation on this topic, without clarity from Airstream. Monocoque vs semi-monocoque is a significant difference. Old chassis design vs newer models. No mystique to the overpriced Fiamma rack - it is clearly supported by the C beams and stabilized by attachment (with sheet metal screws) to the body. Airstream is simply negligent in not providing a receiver mount with clearly stated load capacity.

This Engineer took a different approach, extending the C beams by 12" with a "swim platform" on which I can carry a bike or other light cargo. Moving the bumper back 12" added crash protection to the rear end. 100 lbs on the tail decreased the tongue weight on my 2011 FC23FB from 14% to 13%. No noticeable change in towing characteristics in over 10,000 miles and all sorts of roads. Attachment 228814. No, the grandkids don't ride back there😉




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[JamuJoe]

Originally Posted by AnnArborBob

This explanation of how the Fiamma rack works makes perfect sense. Basically, it maintains the integrity of the body/frame connection by placing the same amount of stress on the body AND frame simultaneously.

Sorry, not correct. The braces attached to the shell will provide only a limited amount of lateral restraint. Look at the attachment of the braces at the rack frame. It rotates vertically on a little pin so as to not carry any vertical load. Not a bad design, but certainly dosen't reinforce body to chassis.


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[Mixter]

Originally Posted by JamuJoe

Sorry, not correct. The braces attached to the shell will provide only a limited amount of lateral restraint. Look at the attachment of the braces at the rack frame. It rotates vertically on a little pin so as to not carry any vertical load. Not a bad design, but certainly dosen't reinforce body to chassis.


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Yeah- that's exactly the conclusion I have come to in the last 24 hours....

Not sure I see the concept of providing torsional rigidity to the main frame rails either... There's definitely zero possibility of my frame rails twisting. The upper supports look to me, as an attachment point to just provide some stability to the upper part of the rack.... and not anything to do with a specifically engineered product to unify the shell and frame. Especially with #10 sheet metal screws in the the skin (even if 2 of them are into a rib)

Still watching for more comments and future conclusions

[reelfastgreg]

maybe some of our engineer posters can clarify this question:

with the AS bike rack, the bikes are carried quite high. with my Yakima rack, lower but about 8-10" further to the rear.

which assembly is likely to create a greater 'moment of force', higher or lower?

[SteveH]

Originally Posted by gpt

maybe some of our engineer posters can clarify this question:

with the AS bike rack, the bikes are carried quite high. with my Yakima rack, lower but about 8-10" further to the rear.

which assembly is likely to create a greater 'moment of force', higher or lower?

Higher or lower makes no difference, but farther to the rear would increase the force applied to the frame when the trailer hits bumps, assuming the same weight load.

[reelfastgreg]

Originally Posted by SteveH

Higher or lower makes no difference, but farther to the rear would increase the force applied to the frame when the trailer hits bumps, assuming the same weight load.

thanks Steve.

[jcl]

Having the CoG of the load higher does matter when you are considering longitudinal accelerations (braking, accelerating).

Having the CoG of the load further rearward matters when you are considering vertical accelerations (bouncing over bumps).

For both cases, having the load further away (in any direction) from the mounting point but without a brace allows relative motion in normal operation, and potentially introduces the issue of fatigue, even with small amplitude motion. Given that the older reports of separation refer to it happening over time (as I recall), I would look to reduce the relative movement of the two parts (trailer body and frame rails), and not just consider static loads on one or the other.

Jeff

[perryg114]

Whatever you put back there you don't want it moving around because this creates a hammering affect that amplifies the load. A bike on the back of the trailer is probably not going to cause a lot of problems. Two or three bouncing around back there might. I would not put anything I care about on the back of a trailer. I either put my bikes in the trailer leaning up against the couch or in the tow vehicle with the front wheels off. I have also put them in a large roof trunk mounted on the tow vehicle. Water in the rain will saturate every part of that bike when mounted on the back. The chances of it getting stolen or damaged in a rear end collision are there as well. You can buy suit cases to store bikes in and even take them on airplanes. You do have to be able to take them apart and put them back together again. I see rear car carriers as a short trip transportation method not full time like when traveling. I am not going to put a $2000 mountain bike outside in the weather.

Perry

[SteveH]

Originally Posted by jcl

Having the CoG of the load higher does matter when you are considering longitudinal accelerations (braking, accelerating).

Having the CoG of the load further rearward matters when you are considering vertical accelerations (bouncing over bumps).

For both cases, having the load further away (in any direction) from the mounting point but without a brace allows relative motion in normal operation, and potentially introduces the issue of fatigue, even with small amplitude motion. Given that the older reports of separation refer to it happening over time (as I recall), I would look to reduce the relative movement of the two parts (trailer body and frame rails), and not just consider static loads on one or the other.

Jeff

The longitudinal loads from braking and accelerating are insignificant compared to the vertical loads from the rear of the trailer bouncing over bumps in the road.

There's no way you can accelerate or decelerate at a rate great enough to stress the frame/body attachments, unless you had a head-on collision, and in that even the bike rack will be the least of your worries.

[jcl]

Originally Posted by SteveH

The longitudinal loads from braking and accelerating are insignificant compared to the vertical loads from the rear of the trailer bouncing over bumps in the road.

There's no way you can accelerate or decelerate at a rate great enough to stress the frame/body attachments, unless you had a head-on collision, and in that even the bike rack will be the least of your worries.

For the bike rack, you are focusing on the loads from a single event, and not on the small loads that create recurring movement and potentially fatigue. Are we concerned with potential separation happening on the first trip, or after some time?

In a more general sense, if fore and aft loads aren't important relative to vertical loads (and I agree that they are less), why would the last three receivers I installed all include specific instructions from the vehicle manufacturer with limits for the maximum ball extension (rearward from the pin) permitted, but also for the maximum rise and drop permitted? This is in relation to the strength of the mounting of the receiver to the vehicle structure. Both offsets produce a bending moment at the mounting of the receiver to the vehicle. But the rear offset only relates to vertical loads, and the rise/drop offset relates to horizontal loads. Are you suggesting that is that just a collision concern?

Jeff

[SteveH]

Originally Posted by jcl

For the bike rack, you are focusing on the loads from a single event, and not on the small loads that create recurring movement and potentially fatigue. Are we concerned with potential separation happening on the first trip, or after some time?

In a more general sense, if fore and aft loads aren't important relative to vertical loads (and I agree that they are less), why would the last three receivers I installed all include specific instructions from the vehicle manufacturer with limits for the maximum ball extension (rearward from the pin) permitted, but also for the maximum rise and drop permitted? This is in relation to the strength of the mounting of the receiver to the vehicle structure. Both offsets produce a bending moment at the mounting of the receiver to the vehicle. But the rear offset only relates to vertical loads, and the rise/drop offset relates to horizontal loads. Are you suggesting that is that just a collision concern?

Jeff

No, it's not a collision only concern, and your instructions stated above confirm my statement that the "farther to the rear would increase the force applied to the frame when the trailer hits bumps".

The same thing applies to a hitch ball mount, the farther away from the receiver, the greater the force applied from the tongue weight to the receiver when the tow vehicle hits bumps, and in reference to the max drop/rise, the greater these distances increase the torsional load on the receiver from the TRAILER, which is many thousands of times over the weight of a bike rack with bikes, put on the receiver when the tow vehicle stops and accelerates. The rack with bikes may be 100-150lbs, where a trailer could easily be many thousands of pounds. Not even close to a similar comparison.

[mefly2]

Originally Posted by AnnArborBob

We briefly considered a front mounted hitch rack for our bikes but decided that the exposure to the elements (e.g., rain, road grime & bugs) would not be good for the bikes so we opted for the enclosed storage in the truck bed. If you are just hauling some casual "beach cruisers" the front mount could work.

I like GPT's design, but we initially opted for AAB's use of the truck bed. After many years of beating my brain on the interior of the cab-high shell, we discontinued carrying our bikes in the truck bed and opted for an Eddie Bauer.

More to the point - may I might point out that for those with (as mentioned in earlier posts ... and including ourselves) $2,000 bikes, the back of the trailer is the last place that I would carry either of our bikes - and they are not carbon fiber! However, you are entitled to your position. I would suggest that the low pressure area at the rear of any vehicle or trailer is where all of the fine road grit gathers ... onto the bike's headset, rear cluster, chain ring, cables, etc. It is simply imprudent to put anything mechanical -that is lubricated with oil -into such a dusty environment ... (then think of the rain / water contamination as well) unless you clean the contaminants before use or tear down and re-lube frequently. A short blast to the exposed road crud at the rear of your AS is likely to cause your bikes to collect more contaminants than most folks would experience on their bikes in many ridden miles... or years of use..

However, had I not already sold our receiver bike mount, I would entertain the OP's possibility to carry an inexpensive knock around bike. YMMV

[Dave-Nancy]

We have a Yakima receiver rack that we use when not towing the trailer. The AS recommended rack is so solid and perfect for both our tandem and (when going to places with dirt trails) our two mountain bikes. I cannot imagine a better, safer arrangement. Dave

[Rorschach]

New forum member here (this is my first post).

I realize this is an old thread, but any updates from the OP on the longevity/affects of this setup using the Yakima?

I'm planning to do this as well.

Curt has a prefab setup that mounts much in the same fashion. I'm wondering if anyone has a report regarding that setup...

[Dave-Nancy]

We use the wonderful bike rack that Airstream recommends. We have two mountain bikes and a tandem, which we take on trips, depending on terrain and type of riding in the areas we are heading to. We also own a Yakima bike rack, which we use only when we are not using our Airstream. We are avid bicyclists.

We also thought about using our Yakima rack, before spending the $600 for the other. However, the Yakima has a narrow saddle for the bikes, no wheel rails, is very heavy, but seems well found, the way you are using it. However, we very much prefer the Italian, Airstream suggested, unit. We love it, mainly for the reason of stability for the bikes, and such quality attachments, It is very easy to use and does not require us to worry about having to invent methods of attachment. We very much appreciate the wheel rails, especially. The Yakima has no set way to support the wheels. We tend to scratch our heads, every time we attach our bikes to the Yakima.

Both work for us. Happy Camping and Riding, too.

[PeterDB]

We put two mountain bikes on the Fiamma, but I also mounted two Yakima Blockhead fork mounts on a board whose length is the width of the truck bed to carry bikes in the truck under the cap when we want to ride somewhere other than where we’re camping. While the mountain bikes are most versatile and there are often great trails where we generally camp there are also great roads that call for a road bike which, at least in our case, are significantly more expensive and thus putting them in the truck is a great option. I’m thinking of the Auferheide out of Westfir, Oregon or Route 7 from Bates campground to Sumpter, Oregon, or Route 67 into the Strawberry Mountains. These rides cry out for a road bike.

[Mollysdad]

I saw an ad for a bike carrier that mounts under the bolts for the electric jack. Two bars come up to the top of the jack, where they split and make a "V" to carry the bikes.
http://www.campingworld.com/shopping...-carrier/95634