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Shootability
June 22, 2009, 20:35
I saw an accident and want to understand what happened.

I was heading south on I65 BHM to MOB and I saw an Excursion pulling a very long trailer - it looked brand new but not one of the really deluxe ones - in any event it started swaying - I thought this might not go so well and slowed back - it swayed back and forth the arc getting bigger each cycle and then jack knifed off to the right - everything flipped - the two passengers got out and dusted themselves off.

I could not really tell what happened but my guess was the guy was trying to slow to make an exit and it did not want to slow - it seemed to me if he had accelerated it would have pulled the unit back straight but braking may have made it worse.

Somebody out there know what makes these things setup an oscillation that is catastrophic? If it happens how do you recover. I have no experience with them but this was not the first time I have seen one jackknifed.

W.E.G.
June 22, 2009, 20:38
http://auto.howstuffworks.com/auto-parts/towing/vehicle-towing/maneuvers/how-to-avoid-jackknifing1.htm

Eric Bryant
June 22, 2009, 20:51
According to the reading I've done on the subject, there are at least five different causes of trailer sway (well, six, actual - but that last one is related to traveling backwards). It's a very complex phenomenon.

Most of what you see happening with light trucks and RVs is related to improper loading of the trailer, with the consequence of insufficient tongue weight. The problem gets worse as the ratio of trailer weight to tow vehicle weight increases. If this is combined with excessive vehicle speed and a "noise" input - side wind, big bump, etc. - trouble will occur.

Accelerating out of a sway condition is unlikely to work, as additional speed will typically make the oscillation worse. Gently applying the trailer's brakes via the brake controller's manual override can help. Hopefully, you can slow the vehicle down enough to end the oscillation before the combination gets out of control. Gently rolling off the throttle is wise, because the speed has to come down for the sway event to end. Trying to "ride it out" ain't too bright.

A lot of accidents happen because the driver doesn't realize that sway is occurring :eek: It might sound odd, but sometimes, it's difficult to detect sway via the seat-of-the-pants. Keeping an eye on the mirrors is a damn good idea.

Load the trailer right with 10-15% of the weight on the tongue (using weight distribution means on top of this doesn't hurt), and keep your speeds down. The bigger the trailer, the more quickly problems will occur. The latest crop of full-size trucks are almost all capable of traveling much faster than is advisable at max GCVW; just because you have 350 HP doesn't mean that it has to be used at all times!

Stranger
June 22, 2009, 20:59
I'm not sure how the linked helped, but okay. Jackknifing is a result of sway not a cause.

Because of the joint between tow-vehicle and trailer, sway always occurs to some extent. The hitch/joint allows the trailer to pivot in an uncontrolled manner. Because of this pivot, it is possible to start a rhythmic oscillation between the trailer and the tow vehicle. The only way to eliminate this sway is to make the vehicle and trailer behave as a straight unit (with no joint). If you can limit the unwanted oscillation, sway will be minimized.

There are a lot of sway control devices on the market. Most are basically friction devices that keep the joint from moving in an uncontrolled fashion. There are also electronic braking systems and special hitches that help control it as well.

Sway is a scary thing. Even pickups with little trailers can be flipped with bad oscillations. Unlike Eric, I have always been able to detect sway pretty damn quickly. It doesn't take long before the rig has a mind of its own trying to steer you into the dirt. The most important thing to do is to keep the steering wheel straight. Don't try to steer into the sway, or (for heaven's sake) let the thing steer itself.

Shootability
June 22, 2009, 21:37
Interesting stuff. It was mighty impressive and I am glad there were no apparent injuries.

hagar
June 22, 2009, 22:05
Did he have a decent hitch with a sway bar, and did he have an electric brake controller? I bet not, very few cars come standard with one.

Saw a guy pulling a huge pontoon boat, and it was swaying back and forth, all over the road. When I passed him, I looked at his hitch. Just a little $15 wallymart special. You need a serious hitch with tow and sway bars when you pull something like that.

L1A1rocker
June 22, 2009, 23:04
Originally posted by hagar
Did he have a decent hitch with a sway bar, and did he have an electric brake controller? I bet not, very few cars come standard with one.

Saw a guy pulling a huge pontoon boat, and it was swaying back and forth, all over the road. When I passed him, I looked at his hitch. Just a little $15 wallymart special. You need a serious hitch with tow and sway bars when you pull something like that.

The O.P. said that the tow vehicle was an Excursion so it most likely came with a trailer braking system (may not but I've never seen an Excursion that didn't). Of course it may not have been correctly adjusted.

You are absolutly correct though. There are far too many people that do not have the first clue on how to properly set up for towing, or do not care to invest in the money for the right set-up. Load distributing hitch and friction anti-sway bars a must for a travel trailer (if a real long or heavy trailer use two sway bars). And then you have to make sure to set up the load distributing hitch correctly.

I blame some of this on the big "Go RVing" campaign a few years ago promoting travel trailers. I think this put a lot of people on the road with no experiance and long trailers that skimped when it came to setting up the vehicle.

As an example my father had a real problem with a factory reciever hitch on his 3/4 ton suburbon. It was not a sway problem but a bouncing problem that seemed to eminate from the hitch point. After asking at several RV stores he finally got an answer. The problem was that the portion of the factory installed receiver hitch that "recieved" the hitch was only 6 inches long IIRC. It quite literly "flexed" up and down under load. The solution was to weld a couple of peaces of 1/2 x 4 inch steel flat bar from the hitch to the frame.

Anyhow I digress. Point is that there are people with the money to buy the toys but not the sense to use them responsibly.

John Culver
June 22, 2009, 23:18
New fords have sway control built into the truck, it can detect/correct some sway conditions.

Seen it demo'd and was rather impressed.

splattermatic
June 22, 2009, 23:21
buy a 5th wheel !
no swaying problems there.. oh, wait (you) don't own a pickup, that's gotta suck ...

oh well, buy everything that a dealer recomends, like sway bars, a hitch up to the task, have an electric brake box installed if not equipt, etc...
then there's proper tongue weight, load distribution, etc....

just like said above...

swaying sucks....

WannaFal
June 23, 2009, 07:03
My .02,
Sway can also be described as a situation where the towed is trying to pass the vehicle. This is why using the trailer braking helps, slows the trailer down. An effective anti-sway device uses balls, just like a hitch ball, on both trailer and vehicle/hitch and has a friction device between them. A rectangular bar that "slips" into a rectangular "tube" with an adjustment for more or less friction.
There is a ratio out there to determine how bad sway may be but I think the basic premise is that the longer the trailer, the worse its likely to be, add extra speed and problem gets worse.
Ive been towing a 35' trailer for 7 years with a long F350, and pop-ups before that, Ive never had any problems.
But I did see an accident once on I95, trailer was on its side (bottom towards me) vehicle was in front of trailer upside down. There was a man and woman and dog standing there looking at it. I told my wife the dog was looking up at the people thinking "WTF did you do!"

Dean P
June 23, 2009, 09:48
Rig it up like the pros, anything else is foolish.

Once upon a time, after I sold my lease trucks in cross country heavy hauling.

I thought I would try a soft job doing local delivery on a fuel transport 18 wheeler.
You know load up at Shell tank farms & deliver at their stations all over the metro area.
It was the same at Texaco, Exxon & Mobil.

Man that was neat I had a company credit card that let me go in & get 8000 gals of gas or diesel at any tank farm.

When I hired out, This bunch promised me the moon in wages & benifits.
College bennies for all my kids & the best of trucks to drive.

That was the buildup, now the let down was so bad.

To have the same truck to drive every day you better be at work by 3am every morning or you lost it.
Now if you are hungry maybe not so bad, but the tools that went with the truck was hard to get like quick couplings for the unloading hoses that don't leak.
Now you are paid per load that meant long hours in the seat, you might get in by 10pm at night
So that leaves about 5 hours to eat & sleep so you can get back to your truck before you lose it to another driver.
Now don't worry about logging the hours, you are allowed 80 hours per 7 days in local delivery. See you don't log loading & unloading hours.

Now the next trick is to survive the wet streets & roads running empty.
The tanker trailer is light, it is built light to haul the maxiam loads.
When driving down a wet road if you hit a bump the trailer will try to pass you.

So after 3 weeks of looking long & hard at the lying SOBs.
And finely seeing how much money was involved I told them where they could shove it.
And if they needed any help finding it I would be glad to help.

That outfit lasted a few more years after I left before they went belly up.

They must have found some hungry mother fuggers

And to this day I still get nervous when I get near a tanker truck.

smokingun45
June 23, 2009, 14:40
I'll bet my last nickel he did not have a functioning electric brake controller in that SUV. I would never, ever pull any of my heavy trailers without a functioning EBC.

flopshot
June 23, 2009, 15:03
i learned the hard way you can't tow a four wheel compressor over 35 mph after i watched it go from one mirror to the other. most sway problems seem to come from low tongue weight and can be exasperated by short wheelbase trailers. i've veto'd more than one hookup because a customer couldn't or wouldn't handle the weight on the hitch. the ones that want to argue get to play with my 2k lb hydraulic scale. on a 5000 lb machine they need 500 lb on the ball or it don't ride. they get pissed but so be it.

Shootability
June 23, 2009, 15:10
The scenario I had in my head for the poor guy was here is a guy on father's day weekend going out camping with the wife - they buy, borrow or rent a trailer and head off for a fun weekend on the first outing with the giant trailer - but they only got so far and no farther. Bad weekend had by all.

Texas Jaguar
June 23, 2009, 16:21
I've witnessed this phenomenom 3 times and experienced it once. Its my opinion that in 2 of those I witnessed and the one I was in the improper weight distribution in the trailer was the root cause.

My personal experienced was while riding in a 3/4 ton Chevy pickup pulling a 2 horse trailer loaded with survey equipment. Mostly bundles of 2 and 3 1/2 foot long wooden lathes. They were loaded hastily and all placed behind the axles of the trailer. Fortunately the driver recognized the situation before it got out of control and other than running off the road there were no other adverse effects. We redistribured the load forward in the trailer and experienced no further difficulties.

Eecessive weight behind the trailer axles will tend to amplify any sway induced by the actions of the driver or even by road conditions.

Uhaul warns its customers to place the bulk of the weight loaded into their trailers toward the front. Unfortunately some individuals don't want the weight put on the rear of their vehicle and assume Uhaul is trying to spare stress on their equipment by placing the weight on the customers vehicle instead of on the trailer axle(s). This assumption can cause them no end of grief in the long run.

As far as electric trailer brakes are concerned they are the neatest thing since sliced bread for stopping loaded trailers. Their presence or absence has little, if any, effect on a moving vehicle unless the driver applies the brakes in one manner or another. They were not a factor in any of the examples I witnessed to the best of my knowledge. All those vehicles were in a state of jack-knifing before the brakes were applied. In fact excessive braking may have agravaited the condition.

P.I. Staker
June 24, 2009, 01:59
What do ya'll think of hydraulic surge brakes on a trailer? Got them on a tent trailer that I pull behind my Dodge truck. I like 'em, but are there any hidden problems I should know about?

Czechsix
June 24, 2009, 02:14
Too small a tow vehicle, not enough tongue load.

Quick tip: Load the tongue heavy, that'll solve lots of issues. Of course, you've got to have the vehicle that's able to handle the weight too, otherwise that's tons of problems also. Best solution is just go fifth wheel, and learn how to load those.

flopshot
June 24, 2009, 07:39
Originally posted by P.I. Staker
What do ya'll think of hydraulic surge brakes on a trailer? Got them on a tent trailer that I pull behind my Dodge truck. I like 'em, but are there any hidden problems I should know about?

i don't think D.O.T. recognizes them for commercial applications. we have them on loader trailers and they work well.

cycle_rcr
June 24, 2009, 18:32
The surge brakes were on the 2 axle U-haul I used to move from Texas with.

If anyone rents from U-haul, they are well advised to make sure the surge brake has fluid, the tires have rubber, and the lights work. Damn those guys rent out some unmaintained crap.

JColdIron
June 26, 2009, 14:11
Originally posted by Czechsix
Too small a tow vehicle, not enough tongue load.

Quick tip: Load the tongue heavy, that'll solve lots of issues. Of course, you've got to have the vehicle that's able to handle the weight too, otherwise that's tons of problems also. Best solution is just go fifth wheel, and learn how to load those.

I had the same problem with my lifted Cherokee pulling a heavy two axle enclosed trailer. Soft suspension, underloaded tongue, and a passing 18 wheeler gave me the "deathwaggle" as it is known in some circles.

Slowing down, at least without a brake controller, is not the answer. You need to accelerate with a quick impulse to get the trailer to back in line. It is scary to do and counter intuitive but does work.

Bukaluka
June 27, 2009, 09:50
One thing not yet mentioned was improperly inflated tires. I had a small 4' x 6' open trailer that I pulled behind my Jeep. There was a profound sway induced when I went over 35 MPH while hauling some tree trash to the dump one day.

Pulled over and noticed that one tire was obviously under inflated causing the diameter of the tire to be less than the opposite side. I pulled into the nearest gas station, added air and problem solved.

Richard in PV