Trailer Jacknifing

[davelow]

Hi,

As an emergency doctor I have noted of late an increase in the amount of drivers involved in accidents and roll over whilst towing their trailer,

On questioning 100% percent of them were not fatigued nor were under the influence of alcohol and their trailers were in good working order and properly loaded. Many stated that the last thing they remembered was the trailer swaying at the rear. They tried speeding up or slowing down but that did little to help before the trailer rolled/jackknifed.

Wondered if anyone had tips or bits of advice whilst towing?

(I have recently bought a trailer for the yak but do not have much experience towing yet)

Cheers,
Dave

[GoneFishn]

Have a read of this it may help.
http://auto.howstuffworks.com/auto-part ... /printable

[ELM]

I am assuming you are talking about cars jackknifing here;
While I agree with that article in regard to semi trailers and trucks with pig trailers and the final act of a car and trailer skidding in a jackknife is due to lack of traction. For a car/trailer and truck/dog trailer the lack of traction causing the skid and jackknife is different to just a breaking or cornering scenario in a lot of cases. I think this site is far better suited to cars and trailers; http://www.sherline.com/lmbook.htm

The reason a lot of cars with trailers jackknife comes down to poor weight displacement on the trailer which causes the trailer to fish tail. The act of a fish tailing trailer can then take away steering control causing the slide and ultimately a jackknife. When loading a trailer that is being towed by a car, you need to put the bulk of the weight slightly forward towards the tow point but with most of the weight being supported over the axle of the trailer. In other words while the trailer supports the bulk of the weight 2/3rd's to 3/4's of the weight, the car should also support 1/4 to 1/3 [edit] they suggest 12% to 15% [end edit] of the weight in fact 1/3 is probably to much.

With the trailer connected to the car, the trailer should never be canter levering the rear of the car away from the ground, nor should it it be forcing the rear of the car down at an extreme level.

Never have the rear of the trailer heavier than the front, this is the absolute worst way to load a trailer, better to have to much forward than back.

If you are struggling to lift a loaded trailer by the draw bar, you probably have to much weight forward on the trailer. If you can tip the trailer all the way to the tailgate, then pull it down with the weight coming forward before you hit center/level and then have sufficient weight that it takes some effort to hold but you can manage moving it up and down on your own, then it is fairly well balanced for towing.

Another thing that may cause fish tailing is a poor trailer design, a trailer with a longer draw bar will always tow better than one with a short draw bar.

[Edit again] Ow and forgot the other important fact, "SPEED". You have to tow at a sensible speed.

[PAINKILLER]

Firstly i think everyone should have to get a special licence on top of there car licence to toe a trailer.
Someone can go out and buy a boat/caravan and never towed before in there life travel at 100kph, this is potentially a death trap, the weight of a say family car and boat/ caravan is relative to a light truck licence and you have to get a licence for that.


With my experience of driving trucks with trailers and also my Nissan Navara with its max towing capacity 3000kg and a little more 500kg i would have to agree with ELM.
Weight and and where the load is placed would be the the biggest factor. For heavy trailers loads boats or caravans i have used an Electric Brake Controllers with the trailers but of course the trailers have to be fitted with electric brakes. I have found these far superior to hydraulic set ups for any heavy towing.
The EBC allows you to adjust the braking capacity of the brakes and it also has fully adjustable lag time meaning you can adjust the brakes instantly or slight delay and it has a brake over ride meaning you can brake from your trailer only.
But conditions or road, terrain, traffic and weather are also a factor . When a fully laden trailer is heading down a steep hill the trailers weight has the tendency to want to push the car along faster, any sudden braking be it for wildlife pot holes cars can result in the trailer trying to come around this is when a jack knife will generally happen when some one panics and brakes more. I saw this with my own eyes about 20 years ago when a smallish car was towing a big bastard bot to Bermagui on the Princess near Genoa. They were no one was coming the other way and the trees they hit were small.
A vehicle towing capacity is governed by the specs plate on the vehicle and a suitable tow bar which which should comply with this.
I have towed little light weight box trailers and Portable traffic light trailers which do not have any brakes not even hydraulic and only weigh about 50 kg and they bounce around on bumpy corrigated roads but have never had problems.

[paddlepop]

Justin


...lights can sometimes help.....

[dave68]

car trailers usuelly jacknife because the axles are centre of the body or the load is to far back when the vehicle gets to a cedrtain speed the back end of the car gets to light and looses tracktion if the trailer is made properly and loaded correctly this should noght happen unless you brake suddenly

[Digger]

Level-rides may help with boats and caravans.

Dig

[cruiser]

As stated above load weight and where its positioned can be a critical but also horses for cources ,make sure the tow vehicle up to the task as well,we tow a horse float with two neddys inside with a combined weight of about 2.5 tonnes with our troopy which also weighs 2 tonnes and touch wood we havent had any dramas and this is over a 15 year period
Speed can be another factor so always plan ahead and alow extra time for stopping

cheers cruiser

[Windknot]

I've only ever jackknifed a trailer once. I was towing my 16 foot centre console home from Narooma, behind my Falcon ute that I had at the time. It was pissing down rain and I was just on the outskirts of Sale (I think). I was travelling slightly above the speed limit, which I think was 80 kph and there was a 60 kph sign coming up, so I very lightly touched the brake. The next thing I felt the arse of the ute swing around. I distinctly remember seeing my boat pass by me as I was travelling along going nearly backwards. It certainly woke me up.

I was lucky. I just skidded along in the jackknifed position until I stopped. There were no other cars in the vicinity and luckily I remained on my side of the road. It was still very unsettling all the same.

I think my little episode was caused by the ute having a very light rear end (it was almost empty) and the fact that it was raining, making the road quite slick, causing me to lose traction. There may have even been something, like oil, on the road as well.

Mick

[kads]

as I am a truck driver, and have been driving heavy rigids for 5 odd years now, I will have to say the major reason for a car trailer to start fish tailing is .."LOADED WRONG"
Too much weight to the rear, and the rear axle of the car becomes light......too much weight to the front, and the rear axle of the car over loads.
Once a small sway starts, it will eventually turn into a wild fishtail.