Out of control sway

[pteck]

Originally Posted by cazual6

Understood. I already know what works. I'm just trying to see what else I can do. Maybe what I want can't be done.

You might be surprised to hear I was able to successfully use a bike rack off the back of a 23D. With a tandem and a toddler bike.

IMO, putting bikes there is doable, in moderation. And you absolutely must have enough counterweight loaded near the hitch to ensure 10-15% weight at hitch distribution.

You can achieve stability so long as you have that.

Durability of the shell/setup is a whole other question in my mind.

[dkottum]

More bad advice.

You cannot stabilize an unstable trailer by adding counterbalance to excessive weight on the back. If sway begins with overweight too far out front and rear, it will be even more difficult to control.

If you have done this, you were not successful, you were lucky. This is a really bad idea, your Airstream Owners Manual warns against it.

[Tom_T]

Originally Posted by Alumineer

Take your time to read this thesis before you do a bunch of experimenting.

Basically, it's all been done before and the theory is clear and well understood. The operative principles of trailer sway elimination are:
- keep your loads close to the center of the trailer
- keep your tongue weight in a reasonable range
- keep your speed down.

But, you seem to be bent on pushing the envelope on all three fronts. Good luck with that. If I was your wife I'd whack you over the head with the bicycles until you stopped.

I disagree that the OP is pushing the envelope on those 3.

Because the OP has not weighed his HW - there is still no direct evidence that his HW is low, other than presumptions of same by others on here based on his sway issue, which could've been due to many other factors.

I would bet that the HW was within 10-15% - even with the bikes on back, once he does weigh it, since the LP tanks & WD/SC hitch alone would counteract it, & AS allows some bikes carried on the rear.

He has stated that he kept his speed down, & a bike rack & 2-4 bikes are allowed per his AS manual (I don't recall if it said 2, 3 or 4 bikes).

While useful to some extent, this Grad School Thesis paper involves some significant differences from USA/N.American trailers & tow vehicle & their WD/SC hitches.

1st, is that our WD hitches aren't used in the UK/Euro area, because they were outlawed in most of the area back in the 1960's in a protectionist move by their major trailer chassis maker when they were approached by a US WD hitch maker/inventor suggesting that they strengthen their frames to be able to use WD hitches & build bigger/better trailers (search for the story if you're interested. Therefore....

2nd - All UK/Euro trailers are (still) built smaller, lighter & narrower, than are most US/NA trailers - so they have different dynamics than those here. And more significantly ....

3rd - All UK/Euro trailers - including the ones in this paper's study - are towed on a bare ball & using other types of less effective sway control than we use here in the US/NA.

However, there was a similar & more detailed study done for US-DOT in the late 1960's or early 70's on the subject & other matters relevant to towing, which I've seen on the net. Unfortunately, that bookmark & pdf download is on my old "dead" laptop, so I'll leave that to your own devices to find it (it may have involved CanAm's Andy T's Dad IIRC).
.

Also, what pteck is saying above, is to use counter-weighting at the front of the trailer to maintain the the HW at 10-15% ot GTW - NOT as a dynamic counterbalance as dkottom took his comment.

While it makes sense to do that if you're rear weight inside or outside the trailer box/frame (e.g.: rear bathrooms, queen & king size beds with storage under them, all that stuff we put in our trailers' "trunk"/storage area back there) is causing it to be less that 10-15% - the better solution is to keep the rear weight less than where counter-weighting is needed.

In many cases, the addition of big LP tanks, battery boxes, power jacks, WD/SC hitches, etc. to the A-frames, tends to put the HW at more than 10-15% - so counter-weighting at the rear isn't necessarily a bad idea, bringing the HW back within 10-15%, & perhaps helping with the TV's HW & Rear Axle Wt. limits.

In our case, our factory dry 2680# & 275" HW 1960 Avion T20 (dry/empty/no options I assume) - went to 542# (per my Sherline), due to the addition of 2x 30# LP tanks, Tekonsha RF Brake Controller mounted on a 15"x18"x3/32" steel plate (for clearance), & the 160# Hensley Cub + the change from the factory 20 gal aluminum pressure fresh water tank to a 27-30 gal. poly tank, pump & battery/box at the front of the trailer/dinette. So clearly putting +/- 200# at the rear of my trailer will still leave me at 342# & within 10-15% HW (assuming a 100% counter-weight effect).

So there are cases where counter-weighting will work to a positive benefit.
.

AS & all of the other trailer mfgrs. are "breaking the rules" laid out by the writer of the thesis above, by placing bathrooms & tanks, storage bins & trunks etc., beds & furniture etc., at the far rear of their trailers - as well as making trailers with huge long rear overhangs.

So to assume it's inherently dangerous to add a properly designed for trailer use & appropriately secured/stabilized bike rack at a position on the rear of the trailer, which is loaded within the limits of the rack & trailer's mfgr's. documentation for same - is just not correct.

Many of you wouldn't give a second thought to adding a non-mfgr. or non-mfgr.-recommended aftermarket item to your cars or trucks, but some here will call foul for using a non-AS or non-AS-recommended bike rack - even when the OP has stated that he has or will attend to all of the weight & stabilization parameters of the AS.

AS has a vested interest in only recommending their racks & accessories, called profit - as well as the cost/time limitations on testing each & every rack or accessory available out there. Instead, the recommend theirs & 1 or 2 others (maybe), & the owner is left to match the parameters of those items design.

For example, Porsche has a whole line of their accessories for the Cayenne which we are looking at for our TV, but that doesn't mean that I can't safely use my Yakima Swing Daddy bike rack on it's hitch, nor other non-Porsche roof rack mounted bike, ski, surfboard racks or cargo boxes on its roof either.

If your AS is under warranty & you want to play it safe, then by all means make your choice to only use AS products, but don't assume that other products can also be safely used. If an AS/Fiamma hitch is allowed to carry 2, 3 or 4 bikes per AS, then another type/brand can likewise safely do so, as long as it is properly mounted & stabilized to perform in the same way.

I wonder how many AS buyers out there would suddenly dump their current favorite WD/SC hitch, if AS/Thor were to suddenly strike a deal with Hensley &/or PP to ONLY recommend that hitch for use on their trailers? Would we suddenly have a whole new crop of Hensley/PP devotees? .... or would we see most folks sticking with other hitch choices? I suspect the latter.

So don't unjustly harrang the OP for using another bike rack, but instead just offer the parameters to to make it safe, because there is nothing inherently unsafe about using another non-AS bike rack to carry the same number of bikes.

If anything, perhaps the AS/Fiamma bike racks are not all that great nor strongly made, because at least one photo erlier in this thread showed that the AS recommended Fiamma bike rack BROKE & FAILED while carrying bikes! And yet that is completely ignored by the disciples of them for some reason.
.

Lastly, as to the dynamic loading & whether counter-balancing weights would be effective or now in damping any natural sway - there are high rise building around which are using dynamic counter-balance systems to dampen, counteract & eliminate seismic (earthquake) movement.

While that sort of computerized dynamic system is beyond application to our trailers, it is likewise not absolutely correct to say that there can be no counter-balancing effect at all by careful placement of what is stowed inside, on top of & outside/behind our trailers.

Pilots also have to do weight & balance calculations & adjust loads & placement accordingly, in order to keep their aircraft in balance & controllable in 3-axes. Certainly we can do so in 2-axes.

Most of you out there do strategically place cargo in your trailers, without them becoming a Lucy "Long Long Trailer" disaster, so this should be no different if done properly.

Keep Cool in the Heat & Cheers!
Tom
///////

[OTRA15]

Well said, Doug, once again.

One is reminded of the Mr. Magoo cartoons, as most folks do not seem to appreciate all the nuances of this overloading/sway issue, as reviewed extensively in this and other threads.

pteck, the Quebec Roll-over thread linked in Post #154 here, once again, is worth a read.

Originally Posted by dkottum

More bad advice.

You cannot stabilize an unstable trailer by adding counterbalance to excessive weight on the back. If sway begins with overweight too far out front and rear, it will be even more difficult to control.

If you have done this, you were not successful, you were lucky. This is a really bad idea, your Airstream Owners Manual warns against it.

[PKI]

All designs are a compromise. The engineer pushes the configuration and specifications to achieve the best result for the customer's requirements and budget. What is left over is safety margin. When you start using it, you reduce the safety of your rig.

Counter weight is a poor approach, as in a dynamic event it adds moment forces that must be controlled. Some is required, to get the gear aboard, but it needs to stay as close to the axles as possible. Using counterbalance weight to solve either a bumper or a tongue overweight condition uses up a lot of safety margin.

C6 you say you know what works. Suspect that you need to test your configuration with a tire failure, strong variable wind conditions, and an emergency lane change. Actually, please do not. Leave the bikes at home or buy a truck and put them in the bed.

It is hard to believe that anyone, that believes the thoughts in your signature tag lines are valid, would continue with this effort.

Please, reconsider your analysis. Pat

[xrvr]

I tightened the screw about a quarter turn. The handle I tighten about as tight as I can get it. I think the instructions say until the threads disappear.

[Rocinante]

Hate to be negative but I worry that the famous last words of a recipient on the next "Darwin Awards" show may be, "I'm gonna do what I'm gonna do."

[cazual6]

Tom, it's becoming harder to be optimistic about this thread, but as I said in the beginning, I'm gonna appreciate the good, the bad and the ugly advices because to me, it just means they care.

When you said everyone does some sort of balance to counterweight the balance, why is my attempt any different. When we load our AS or TV we keep in our mind how the weight is distributed, I'm doing the same thing. My weight is gonna be heavier in the back, so I will put more weight in the front, and advices from other add an equipment to help if not enough, hench swaybar, cutting the bike shank to bring it closer, tie down sway control.

I was watching the military channel about a RoRo boat, and guess what, they also deal with weight distribution to make it balance and have additional equipment to help it remain balance should it not become balance or if outside forces such as waves, wind etc.

I will be going on a cruise, same thing the ship has to balance the fuel and load throughout the ship.

As for scenario such as a tire blow out, alien invasion, the infinite possibilities, etc anyone of any failure can cause a catastrophic event regardless of setup.

Just because it works doesn't mean I'm lucky. With that kind of mentally, driving to work and coming home, just because you made it that day doesn't mean your lucky.

I already know the negatives, it has been expressed here. That is why I am asking for advice to making it as safe as possible.

Please consider what you say before you post. I appreciate the few of you have stuck with me.

[OTRA15]

The primary reason for the difficulty you are having to be optimistic, is that you still do not seem to understand the basic concepts of physics involved, and everyone else keeps trying to open your eyes and get you to take off your blinders. (IMO)

That is why this thread reminds me so much of Mr. Magoo.

Originally Posted by cazual6

. . . My weight is gonna be heavier in the back, so I will put more weight in the front,
. . .

Do you understand that this increases the chance of sway? To add more weight far from the trailer's center of gravity, just makes it want to sway more not less !!!

There are two dynamics at work here, and they are independent of each other:

1. fore-and-aft weight distribution -- up-and-down basically, no side-to-side component;

2. side-to-side rotational forces.

It is this second component which is the important sway-related factor. If you could stow, right in the center of the trailer, those same bikes and the added front gen, you would NOT be increasing its propensity to sway. But when you move these weights fore and aft, you are in essence creating two levers (or pendulums) each hinged at the same center of gravity, which want to rotate left and right each time the trailer bounces left and right. [all the time basically]

When all the rotational forces harmonize, that is when sway occurs. [tow vehicle bouncing L/R, trailer bouncing L/R, road bumps and crown undulates causing L/R reaction in both vehicles, tire blows out, wind from left hits tow vehicle, while wind from right hits trailer, . . . and on and on . . . tow vehicle swerves to avoid pothole, pedestrian, another car, obstruction, etc., . . . driver over-corrects to all of the above .. another L/R force is introduced . . . ]

Get it?

This is way more complicated and nuanced than simply weighing the trailer and its tongue weight etc., as you seem to be thinking.

You seem to think that weight distribution is ONLY an up-or-down consideration.

It is NOT that simple.

Many people have tried to explain this so many times . . . in this thread, and in the Quebec roll-over thread, with little success apparently . . .

. . . Out of breath again . . .

Good luck.

PS -- There is one and only one basic problem here IMO:

Stubbornness

__________________________________________________ _____
"Everyone is entitled to be stupid, but some abuse the privilege." (as you said . . . )

[OTRA15]

This one is close enough! Click on link at top of frame to open a new window, which permits full screen volume control, etc..

Or click on Play button in middle of frame to stay here:

"Road hog, that fool barely missed me!

https://www.youtube.com/watch?v=ghZqAHhNibY

[mojo]

Keep plugging away Casual, many here wear a belt and suspenders.
http://www.engineersedge.com/calcula...ht-balance.htm

[A W Warn]

Originally Posted by cazual6

>> snip>>
My weight is gonna be heavier in the back, so I will put more weight in the front, and advices from other add an equipment to help if not enough, hench swaybar, cutting the bike shank to bring it closer, tie down sway control.
<< snip<<

Of all of these things you mentioned, the only one that will help solve your problem is to cut the bike rack shank to "bring it closer".

IMO:

Changing placement payload weight on a trailer should be done for two purposes.
(1) to adjust the vertical load on the trailer axles.
(2) to adjust the vertical weight load on the tow vehicle hitch receiver.

When weight is added to a trailer behind the trailer's normal length (adding a hitch, bike carrier, luggage carrier, or anything else) essentially lengthens the trailer. It changes how the trailer reacts in a rotational left to right horizontal direction (yaw or sway)

If you insist on making the trailer longer by adding length and/or weight to the rear, beyond the normal length of the trailer, there are two ways to overcome the problem that has been create.
(1) move the axles toward the rear of the trailer
(2) make the trailer tongue longer in the front

Another thought about one of your "solutions":
If you "hench" the sway bar resistance tighter than normal you might cause a different type of problem if weather conditions change. When towing through rain the resistance on a friction type sway bar can overcome the traction the tires have on the road. On the instructions I have read for this type sway bar says to loosen the device when it rains. If you do that, then you have lost what you gained by your "solution".

[OTRA15]

Originally Posted by mojo

Keep plugging away Casual, many here wear a belt and suspenders.
http://www.engineersedge.com/calcula...ht-balance.htm

Your link has NO information about rotational sway problems, just up and down weight distribution.

A similarly myopic reaction to the mobile weapons system being discussed here. (IMO)

[OTRA15]

Originally Posted by A W Warn

Of all of these things you mentioned, the only one that will help solve your problem is to cut the bike rack shank to "bring it closer".
. . .

I believe he already did that, or considered it.

And thank you for referencing the concept of Yaw regarding rotational forces involved in sway issues. Here is a basic overview:

https://en.wikipedia.org/wiki/Yaw_(rotation)

Edit -- that link will not work right -- you have to add a ")" to the end of the URL after trying it. Or click on the blue suggested link in Wikipedia's error message.

PS -- Jack Canavera's Post #22 in the Quebec roll-over thread also discusses Yaw:

http://www.airforums.com/forums/f48/...ec-153984.html

[mojo]

Originally Posted by OTRA15

Your link has NO information about rotational sway problems, just up and down weight distribution.

The same myopic reaction to the mobile weapons system being discussed here. (IMO)

You're absolutely right, Mr. Magoo.

[PKI]

Maybe ... this is a process.

Bicycles are problematic to transport, because they have peddles and handlebars that stick out. However, folks fly with them. They do a partial disassembly and pack them in a cardboard or plastic carrier. Talk to your local bike shop. That would get them inside the coach so they are not carried in the ends. Your kids can learn how to assemble and disassemble their bikes and that will grow their mechanical abilities. There are hazards here too, as with the handlebars not being tightened properly, but not if you are committed to make it work.

Alternatively, folks have built simple wooden structures that fit in the aisle of the trailer to hold and secure the bikes. Would organize the bikes when outside as well. Bet those folks would offer input if you started a how-to thread.

Rig stability can be improved by shortening the tow vehicle overhang, the distance from the ball to the rear axle, to the minimum possible. That means you do the same thing you did to the bike rack shank.

The strength of your tow vehicle receiver is also a factor. If it can flex, it will, and the more it flexes the more it adds to instability.

The tires on the tow vehicle are another opportunity to improve stability. The less tire side wall, as with a low profile tire, and the stiffer the side wall, as with a light truck or run flat tire, the less flexibility there is in the wheel to road connection. Some consideration to contact patch, grip, and wet weather traction should be in the implementation as well. Don't forget the tire inflation pressure. You can make changes when your existing tires need replacement.

Coach tires should be the safest and most reliable to reduce the possibility of an unplanned excursion. Not sure of the value of the TPMS in the range of investments you might make, but knowing you have a low tire or one overheating is valuable information. There are TPMS systems for less than $200. Maybe not the first investment, but it likely should be on the list.

There are other tweaks that may help, and helpful folks may be able to pass them along. The important point is that you consider and understand the impact on stability that these suggestions offer. That gives you a better feel for the dynamics of towing.

The best thing that you can do is drive slow. From a general perspective, 65 mph is a transition point for a well balanced rig. Every thing that erodes the stability of the rig reduces that transition point. Consider droping your max speed to 50 or 55 mph. It sounds stodgy and is certainly a pain when rolling up I5, but it is one thing that saves you money and improves the safety of your RV travels. It is a bit less stressful as well.

I understand you are having a problem with assimilating the load distribution variables and their impact. Maybe .... take your kids to the playground and put them on a see-saw. It's easy to push them up and down. That is vertical balance, like for and aft loading your trailer with the single axle as a pivot point. Now, take the kids over to the merry-go-round. Have them stand in the middle, if it is one of those flat disk types. See how easy it is to start and stop the rotation. Now have them move to the outside and see what difference that makes. It's similar to the moment arm force that is created by loading a coach in the ends. Maybe that won't help, but at least the kids will have some fun and that is what this RV thing is all about.

We really just want you to succeed.

Travel safe. Pat

[OTRA15]

Originally Posted by PKI

. . .
I understand you are having a problem with assimilating the load distribution variables and their impact. Maybe .... take your kids to the playground and put them on a see-saw. It's easy to push them up and down. That is vertical balance, like for and aft loading your trailer with the single axle as a pivot point. Now, take the kids over to the merry-go-round. Have them stand in the middle, if it is one of those flat disk types. See how easy it is to start and stop the rotation. Now have them move to the outside and see what difference that makes. It's similar to the moment arm force that is created by loading a coach in the ends. Maybe that won't help, but at least the kids will have some fun and that is what this RV thing is all about.

We really just want you to succeed.

Travel safe. Pat

Thank you for this excellent suggestion!

For a further illustration of out-of-control sway, have the children hold on to a vertical something (to keep them from flying off the merry-go-round), and then spin the thing so fast they can no longer hold on, and go flying off . . .

Something like out-of-control sway . . .

Obviously this is a joke of a suggestion, and one should not actually try it, but the concept does illustrate the way that sway -- yaw -- can go out-of-control in a heartbeat, as Jack Canavera pointed out in the Quebec Roll-over Post #22 just referenced.

[xrvr]

Originally Posted by A W Warn

Of all of these things you mentioned, the only one that will help solve your problem is to cut the bike rack shank to "bring it closer".

IMO:

Changing placement payload weight on a trailer should be done for two purposes.
(1) to adjust the vertical load on the trailer axles.
(2) to adjust the vertical weight load on the tow vehicle hitch receiver.

When weight is added to a trailer behind the trailer's normal length (adding a hitch, bike carrier, luggage carrier, or anything else) essentially lengthens the trailer. It changes how the trailer reacts in a rotational left to right horizontal direction (yaw or sway)

If you insist on making the trailer longer by adding length and/or weight to the rear, beyond the normal length of the trailer, there are two ways to overcome the problem that has been create.
(1) move the axles toward the rear of the trailer
(2) make the trailer tongue longer in the front

Another thought about one of your "solutions":
If you "hench" the sway bar resistance tighter than normal you might cause a different type of problem if weather conditions change. When towing through rain the resistance on a friction type sway bar can overcome the traction the tires have on the road. On the instructions I have read for this type sway bar says to loosen the device when it rains. If you do that, then you have lost what you gained by your "solution".

That warning applies to all friction sc. Equilizer type WD hitches, etc. not just the separate ones. Your Reese, Equilizer etc hitches all keep the trailer from returning to straight with the truck in slippery conditions.

[cazual6]

Before all this happened, one thing I never noticed with the AS was sway during high winds and trucks passing me by. One of the things I know about AS are they are very aerodynamic.

The rain scenario is one I didn't think about. Never really thought it because never been traveling in the rain.

The interior bike stand, whether DIY or store bought is something I would consider too if this idea of mine won't work.

My kids bike are the cheapy bike that are not mean to be taken apart. However my wife's and I are. I considered taking it apart, but I think the fork will damage the floor. I am very interested in learning more about those interior bike mounts if anyone cares to share.

I've been reading up on sway, from this thread and online. I have been watching videos of setup and learn as much as I can.

The insight about beyond weight loads such as making the trailer is something I have not considered and will look into.

The weight distribution and the "swing" analogy is great. But as mentioned in the past posts, putting the gens in the front to act as a counter weight wasn't a good idea.

After reading as much as I can, I believe the weight distribution is one of the keys I have solved. The dynamics of a single axel and making the trailer longer requires more thought.

Having the sway control will compensate to a degree. After all that is what they are designed for. I realize my problem doesn't stop there though, that is why I haven't rushed through with my road test.

[markdoane]

Here is a good discussion of yaw inertia that you will find interesting.

Caravan Dynamics