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 Post subject: Jacknife
PostPosted: Thu Dec 21, 2006 14:29 
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A question for you truckers. What makes a truck jacknife - especially on a fairly easy bit of the A14 like the one I had to divert round this week?


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PostPosted: Fri Dec 22, 2006 21:46 
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normally a car cutting us up and hitting the brakes leaving us with the choice of ploughing into them, moving over (as if that is possible) or slamming the anchors on which, depending on the load, can cause a jack-knife

this is reality, not a cheap dig ar non truckers

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 Post subject:
PostPosted: Fri Dec 22, 2006 22:05 
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scanny77 wrote:
normally a car cutting us up and hitting the brakes leaving us with the choice of ploughing into them, moving over (as if that is possible) or slamming the anchors on which, depending on the load, can cause a jack-knife

this is reality, not a cheap dig ar non truckers


Yeah, but there is Hope isnt there?

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PostPosted: Fri Dec 22, 2006 22:10 
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there is indeed but i suspect education would be more effective

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 Post subject: Re: Jacknife
PostPosted: Fri Dec 22, 2006 23:47 
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semitone wrote:
A question for you truckers. What makes a truck jacknife - especially on a fairly easy bit of the A14 like the one I had to divert round this week?


Good question, it’s usually caused by sudden heavy braking. However, on the one occasion I have been unfortunate enough to suffer a jacknife, it was caused by poor maintenance.

The air brakes on a truck rely on pressure to keep them off. This is a safety measure as theoretically if you have no air pressure you can’t move. Unfortunately in my case, an air tank became disengaged from the unit when I was travelling at 50MPH and the sudden loss of pressure caused the brakes to engage fully. This is not an experience I would care to repeat, as soon as your brakes are locked on like this you are effectively a passenger in a very dangerous environment with no control whatsoever. I was very fortunate that no-one else was involved in my accident – apart from the laundrette!


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 Post subject:
PostPosted: Wed Jan 03, 2007 05:50 
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We have trailer spikes over here. This is a column mounted lever which puts air to the trailer only. You would imagine that this would make the truck easier to pull straight in the event of a jackknife. It sort of helps if the roads are dry and clear, but I have had the trailer come around on me a few times in snow or ice and it only makes it worse.

the main cause of jackknife is loss of traction on the drive axle which allows it to go sideways with the weight of the trailer. The main reason this happens is, as stated before, heavy braking. The main reason for this is someone doing something stupid within the trucks "danger zone" and the main reason for that is lack of thought.

When you see the far end of a 53' trailer overtaking the 244" tractor unit you know you are in trouble! Trouble is, anyone within that 53' sweep is in the cart, too.

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PostPosted: Wed Mar 12, 2008 16:30 
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Exactly right bobthedog "A loss of traction on the drive axle of the unit sending the unit sideways and the weight of the trailer straight on"
I know this because I have 2 brand new Iveco Stralis 6x2 with serious safety faults so much so we took them off the road in November 2007 and we continue to fight Iveco for them to realise a serious loss of traction as we have on both our vehicles is a serious condition.
Phil


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 Post subject: Re: Jacknife
PostPosted: Sun Apr 27, 2008 13:32 
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To correct a couple of notions here......
A jacknife is nearly always caused by driver error and rarely defects with trucks or the actions of other road users. ( i do accept that a very small minority have been caused by mechanical defect and unusual or rare acts by others before you start shouting) Most are caused by neglect of drivers, inexperience, incompetence and ignorance. Some are avoidable and are avoided by the experienced. Driving too close with little reaction time is a regular cause, driving too quick for the conditions and nature of road is also a cause, falling asleep has also accounted for a significant number. The mechanical action resulting has already been explained but is not the cause.


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