…
Sod me Lorn Trakta that one of the best explanations of this problem as i’ve ever seen, top stuff.
Applause
Juddian:
Sod me Lorn Trakta that one of the best explanations of this problem as i’ve ever seen, top stuff.Applause
Agreed
DrivingMissDaisy:
weeto:
Cruise control! and if you want to see the evidence i will tell you were to find it, were trucks ended up jackknifed which wast not caused by braking.
Oh just to add to this re a Brake induced jackknife, even VOSA has an official line on it!!You’re not wrong. Cruise control should NOT be used in slippery conditions. But before you pat yourself on the back you started this thread by declaring that many of the other factors that could result in a jackknife were nowt but myth when clearly the weight of opinion voiced by these experienced “know-alls” would suggest otherwise. Now why don’t you explain to all the “know-alls” how exactly cruise control can cause a jackknife? Know-all…
Unlike ABS, traction control won’t stop the drive axle losing enough traction to put a truck into a jackknife.
So while the cruise control is on, and you hit a bit of slippery road you may get away with not losing enough traction to put it in one, hit a lot of slippery stuff like black ice then you are going to be in trouble, don’t forget while all this is going on your trailer would still be pushing you if you were on a slight incline, drive axle a fraction out of line then momentum of the trailer would start pushing it further out of line until it hits the point of no return. (That scenario would not happen going uphill for obvious reasons!)
Now some drivers have said you could drive out of a jackknife, braking is a no no, even ABS won’t get you out of that one, only other option would be to feather more power on to catch back up with the trailer momentum and hope for the best.
Since the majority of drivers will drive on cruise at the maximum possible speed of the vehicle, you could not even try to use that option as you have no more speed to play with.
weeto:
DrivingMissDaisy:
weeto:
Cruise control! and if you want to see the evidence i will tell you were to find it, were trucks ended up jackknifed which wast not caused by braking.
Oh just to add to this re a Brake induced jackknife, even VOSA has an official line on it!!You’re not wrong. Cruise control should NOT be used in slippery conditions. But before you pat yourself on the back you started this thread by declaring that many of the other factors that could result in a jackknife were nowt but myth when clearly the weight of opinion voiced by these experienced “know-alls” would suggest otherwise. Now why don’t you explain to all the “know-alls” how exactly cruise control can cause a jackknife? Know-all…
Now some drivers have said you could drive out of a jackknife, braking is a no no, even ABS won’t get you out of that one, only other option would be to feather more power on to catch back up with the trailer momentum and hope for the best.
Wrong, not enough power available, or room, or time, its all over in an instant its not a slow motion happening.
The only possibility of snatching a hard lock up (even its the momentary lock up before ABS cuts in thats enough) braking jack knife back from disaster is to apply the trailer brakes ONLY to pull it back straight, but as far as i know no vehicle available here has had that facility since Scanias 110 days, and the likelihood of it working in practice in the on road event of such a panic stop is so remote as to be almost impssible.
If any one has a vehicle so equipped and was prepared to put it to the test though it would be an interesting experiment at MIRA or similar.
It would never reach production or get type approval again though, the driver’s not even allowed to control his own tag axle or gearbox in an increasing number of cases now, what hope he should have some input on the brakes.
My 1985 Scania 112 had a trailer brake. Very useful it was too. Used it routinely for slowing down when pulling 3rd party trailers. Easy way to find out which trailers had naff brakes.
How many drivers do a rolling brake check after coupling to a different trailer as soon as you get to about 10mph?
A few tips that some might find useful:
When going up the in/outside of standing or slow moving traffic always watch their front wheels. If you see them turning your way its an early indication of the driver’s intention. A good horn blast should stop them continuing, hopefully avoiding what happened to Rikki.
Stale green lights should always be expected to change - slow down on approach.
(I totally agree the amber phase isn’t long enough).
Juddian:
weeto:
DrivingMissDaisy:
weeto:
Cruise control! and if you want to see the evidence i will tell you were to find it, were trucks ended up jackknifed which wast not caused by braking.
Oh just to add to this re a Brake induced jackknife, even VOSA has an official line on it!!You’re not wrong. Cruise control should NOT be used in slippery conditions. But before you pat yourself on the back you started this thread by declaring that many of the other factors that could result in a jackknife were nowt but myth when clearly the weight of opinion voiced by these experienced “know-alls” would suggest otherwise. Now why don’t you explain to all the “know-alls” how exactly cruise control can cause a jackknife? Know-all…
Now some drivers have said you could drive out of a jackknife, braking is a no no, even ABS won’t get you out of that one, only other option would be to feather more power on to catch back up with the trailer momentum and hope for the best.
Wrong, not enough power available, or room, or time, its all over in an instant its not a slow motion happening.
The only possibility of snatching a hard lock up (even its the momentary lock up before ABS cuts in thats enough) braking jack knife back from disaster is to apply the trailer brakes ONLY to pull it back straight, but as far as i know no vehicle available here has had that facility since Scanias 110 days, and the likelihood of it working in practice in the on road event of such a panic stop is so remote as to be almost impssible.
If any one has a vehicle so equipped and was prepared to put it to the test though it would be an interesting experiment at MIRA or similar.
It would never reach production or get type approval again though, the driver’s not even allowed to control his own tag axle or gearbox in an increasing number of cases now, what hope he should have some input on the brakes.
Oh, that will work and do work, I’ve even had the trailer coming down the side of the truck when using it, they had them upto 112s as well. but since separate trailer brakes are now obsolete it is not an option, so not much point mentioning it is there!
And I did say they wouldn’t have enough power, because they are already flat out on cruise, but could have plenty of room on an empty 4 lane motorway!
@ Driver One.
Nice pic that, i drove a 112 regularly but can’t remember a trailer brake on it, mnd you me memory’s gone to pot anyway… 
Note you’ve got a rear tag (wasn’t double drive was it?), therefore you’re 5th wheel will have been slightly behind the drive axle, yes?
Now i’ve never driven a rear tagged tractor or double drive come to that, but i suspect they would be less susceptable to jack knife under harsh braking than a normal tractor, weight transfer should at least in theory see more weight applied in exactly the right point straight onto the drive axle and not putting so much bias towards the steering axle.
Would that be right or am i barking up the worng tree…again.
weeto:
Juddian:
weeto:
DrivingMissDaisy:
weeto:
Cruise control! and if you want to see the evidence i will tell you were to find it, were trucks ended up jackknifed which wast not caused by braking.
Oh just to add to this re a Brake induced jackknife, even VOSA has an official line on it!!You’re not wrong. Cruise control should NOT be used in slippery conditions. But before you pat yourself on the back you started this thread by declaring that many of the other factors that could result in a jackknife were nowt but myth when clearly the weight of opinion voiced by these experienced “know-alls” would suggest otherwise. Now why don’t you explain to all the “know-alls” how exactly cruise control can cause a jackknife? Know-all…
Now some drivers have said you could drive out of a jackknife, braking is a no no, even ABS won’t get you out of that one, only other option would be to feather more power on to catch back up with the trailer momentum and hope for the best.
Wrong, not enough power available, or room, or time, its all over in an instant its not a slow motion happening.
The only possibility of snatching a hard lock up (even its the momentary lock up before ABS cuts in thats enough) braking jack knife back from disaster is to apply the trailer brakes ONLY to pull it back straight, but as far as i know no vehicle available here has had that facility since Scanias 110 days, and the likelihood of it working in practice in the on road event of such a panic stop is so remote as to be almost impssible.
If any one has a vehicle so equipped and was prepared to put it to the test though it would be an interesting experiment at MIRA or similar.
It would never reach production or get type approval again though, the driver’s not even allowed to control his own tag axle or gearbox in an increasing number of cases now, what hope he should have some input on the brakes.Oh, that will work and do work, I’ve even had the trailer coming down the side of the truck when using it, they had them upto 112s as well. but since separate trailer brakes are now obsolete it is not an option, so not much point mentioning it is there!
Firstly Weeto, is there the remote possibility of being slightly less aggressive with your posts re ‘‘so not much point mentioning it is there!’’ , we’re trying to have a sensible discussion here and your sarky comments don’t exactly enthuse one to adding to the debate, though if you’d like to discuss this by yourself only just say and i for one will glady ■■■■ out.
How the hell do you get the trailer coming down the side of the tractor, you’d be using all three lanes of a standard motorway?
limeyphil:
Shoshaye:
Winseer:
If your trailer starts to swing around the side of you, then you floor the accelerator (in the dry and straight) and flick the trailer brake/handbrake to effectively “jerk the combination straight again”.If you’re going around a corner, it won’t work. If it’s icy it won’t work. If it’s wet, it might still not work.
There’s a reason of course that we have a yellow airline as well as a red one. You can drive it around on “only” the red, but I wouldn’t advise it. Shunters do it all the time, but even they run into the occasional bother come the rain and snow…
Are you for real?
Please enlighten me as to why we have a yellow airline,as well as a red one? you sound like a professional driver who i could learn a few things from. Flick the handbrake lol Wtf,i wouldn’t let you drive my dyson round the living room.It’s scary that some people don’t know basic things, Then naive people like Shoshaye try to take the mick out of someones obviously good advice, It’s the sort of thing that most drivers would already know.
Im far from naive,who in there right mind would flick the hand brake in a Jackknife situation! If you think this is good advice,i wish you the best when trying it out.
Weeto you said vosa explained it then you went on to put it on an earlyerpost,…Why dosent a jacknife happen when going up hill.Unless I have read you wrong I can not see where it says cruse control.
Juddian:
weeto:
Juddian:
weeto:
DrivingMissDaisy:
weeto:
Cruise control! and if you want to see the evidence i will tell you were to find it, were trucks ended up jackknifed which wast not caused by braking.
Oh just to add to this re a Brake induced jackknife, even VOSA has an official line on it!!You’re not wrong. Cruise control should NOT be used in slippery conditions. But before you pat yourself on the back you started this thread by declaring that many of the other factors that could result in a jackknife were nowt but myth when clearly the weight of opinion voiced by these experienced “know-alls” would suggest otherwise. Now why don’t you explain to all the “know-alls” how exactly cruise control can cause a jackknife? Know-all…
Now some drivers have said you could drive out of a jackknife, braking is a no no, even ABS won’t get you out of that one, only other option would be to feather more power on to catch back up with the trailer momentum and hope for the best.
Wrong, not enough power available, or room, or time, its all over in an instant its not a slow motion happening.
The only possibility of snatching a hard lock up (even its the momentary lock up before ABS cuts in thats enough) braking jack knife back from disaster is to apply the trailer brakes ONLY to pull it back straight, but as far as i know no vehicle available here has had that facility since Scanias 110 days, and the likelihood of it working in practice in the on road event of such a panic stop is so remote as to be almost impssible.
If any one has a vehicle so equipped and was prepared to put it to the test though it would be an interesting experiment at MIRA or similar.
It would never reach production or get type approval again though, the driver’s not even allowed to control his own tag axle or gearbox in an increasing number of cases now, what hope he should have some input on the brakes.Oh, that will work and do work, I’ve even had the trailer coming down the side of the truck when using it, they had them upto 112s as well. but since separate trailer brakes are now obsolete it is not an option, so not much point mentioning it is there!
Firstly Weeto, is there the remote possibility of being slightly less aggressive with your posts re ‘‘so not much point mentioning it is there!’’ , we’re trying to have a sensible discussion here and your sarky comments don’t exactly enthuse one to adding to the debate, though if you’d like to discuss this by yourself only just say and i for one will glady ■■■■ out.
How the hell do you get the trailer coming down the side of the tractor, you’d be using all three lanes of a standard motorway?
Didnt mean to be, just sayin not much point in mentioning something that would never be found in a modern truck, well not a UK one any way.
It was not a very big trailer, it was a 40 ft step frame flat twin axle trailer, on a wide stretch of the A75, using the trailer brake only, was a bit like the video with the girl in the middle of the road with the artic coming towards her as mentioned in an earlier post.
fuse:
Weeto you said vosa explained it then you went on to put it on an earlyerpost,…Why dosent a jacknife happen when going up hill.Unless I have read you wrong I can not see where it says cruse control.
Is that 2 questions, or 1 combined? are you refering to going uphill on cruise control on a slippery/icey suface?
Lorn trakta:
weeto:
Following on from another post, So, can some explain this myth? Since when on straight road will my artic jackknife if I break “to hard?”, seems to me there a lot of misinformed drivers out there telly stars included!
Modern trucks don’t jackknife on there own, I can only think of one major scenario were this is likely to happen, but hard braking? I don’t think so.To compile all the factors that can trigger a jacknife event could take forever, ABS EBS etc are braking stability enhancers, a revolving wheel being braked having more retardational effect than a wheel locked and skidding, these braking stability systems ARE NOT anti jacknife measures.
With an artic in motion many variables can come into play, individual tyre pressures, pairing up of different tyre makes, tread patterns & pairings, differently paired tread depths, air/ steel suspension compatibilities, suspension compression/ rebound activity during deceleration, brake components their balance and stage of wear, total carried load imposition and load position on the truck, individual axle/wheel loadings at point of and during deceleration, surface type, the weather/surface/tyre interaction, the degree and severity of surface gradients, undulations and any surface contaminations, the moment the trailers ‘pin’ delivers to the tractor a directional momentum poundage exceeding the drive axle surface adhesion poundage its possible for the trailer to simply overwhelm and ‘sweep’ the tractors rear end away to the direction offering the least resistance, if a tractor/trailer misalignment is caused, such as by deceleration or if the outfit wasn’t running laser light beam ‘straight lined’ at the point of initial deceleration, a jacknife can be invoked without touching the brakes at all, any and all these factors, all of them within road legal parameters of roadworthiness, and many others acting together or alternating by the part-second can bring misfortune.
Fate alone can deliver all that is neccassary to render, even the newest high-tec trucks and the best of drivers, unable to prevent a jacknife, every artic driver has the right to fear the worst of outcomes when forced to apply their brakes in an all out emergency ‘crash stop’ level application of brakes, to risk disaster for the sake of appeasing nothing more than an automaton set of lights, serving no purpose at the time, is not something that the hgv driver should ‘‘face a royal shafting for’’, as you put it in the ‘stopping distance’ thread, and there is a void, a massive void in the difference between ‘jumping’ a set of lights and being unable to bring an artic to a manifestly safe controlled halt at a set of lights, driving well under the speed limit will not guarentee that you can stop safely as fast as the lights can change, a blink of an eyelid seems to be the average time the ‘state’ allows you to safely stop, in all weathers, very realistic, I’ve had my group 1 since sept 1974, in all that time I’ve done mainly night yard shunting and night trunking, working arenas thankfully devoid of most of the ‘traps’ the state happily deploys nationwide and have not come to grief, drivers I know who have had many years of pan european, middle east and really out of the ordinary specialist stgo experience, whose driving skills, knowledge and experiences completely dwarf my own have been caught out by jacknifing, having a ‘■■■■ sure’ blind faith reliance in ABS as a guarantor against jacknifing seems to me to be a near perfect recipe for experiencing it.
^ This.
Although possibly with the ( hopeful ) reservation that those modern day ‘stability’ systems divert/time the outfit’s braking effort from the trailer forwards not the unit which would at least give the unlucky driver more of a chance.
Juddian:
@ Driver One.Now i’ve never driven a double drive come to that, but i suspect they would be less susceptable to jack knife under harsh braking than a normal tractor, weight transfer should at least in theory see more weight applied in exactly the right point straight onto the drive axle and not putting so much bias towards the steering axle.
Would that be right or am i barking up the worng tree…again.
That’s exactly the logic behind the old American idea of double drive units and unbraked steer axles which provided the best of all worlds situation of a 3 axle unit,which provides more contact at the road where it matters,with only weight transfer acting on the front of the trailer which puts weight onto the drive axles but without the effects of a braked steer axle causing the nose of the unit to dive thereby removing weight from the rear of the unit.
From what I remember, in the 80’s you was always hearing of jackknifes on the road especialy when wet, 90’s seemed to be rare as new vehicles were fitted with ABS, 2000 onward we are back to always hearing of jackknifing on nearly a daily basis only difference between the 90’s and now is cruise control is standard fitment now, early days it was a luxury optional extra!
@ Juddian (is this going to start a new trend instead of people constantly quoting long quotes?)
It was a tag axle making it a very short wheel base once lifted - very handy for reversing, but an uncomfortable ride when bob tailing.
To be honest i can’t remember the 5th wheel position, its 14 years ago now, but yes, I think you’re right, the pin just behind the drive axle.
I’m not happy with the pic(first ever appearance on TN) - it doesn’t look “right”. The valve was knackered and the tag axle used to creep down when driving with it up (which was most of the time as the work was light). In the pic it is neither up nor down.
Later I got into the habit of touching the switch from time to time.
She was a good strong truck and pulled well. Cruise control too - well Scania call it a hand throttle. 
weeto:
From what I remember, in the 80’s you was always hearing of jackknifes on the road especialy when wet, 90’s seemed to be rare as new vehicles were fitted with ABS, 2000 onward we are back to always hearing of jackknifing on nearly a daily basis only difference between the 90’s and now is cruise control is standard fitment now, early days it was a luxury optional extra!
We hear of JK’s a lot, but then any time an artic is seen stationary at anything other than arrow straight its jacknifed according to BBC traffic, especially in winter when an artic stuck with tractor at an angle which is quite normal is reported as JK’d.
I do wonder if a genuine full JK, which lets make no bones must be terrifying thing and one i hope not to experience, is as regular as we hear.
Used to see lorries running about and on tow with the rear quarter panels bent in, haven’t seen one like that for ages towed or not, seen far more simply bashed to hell from normal prangs and bridge strikes.
Carryfast:
Juddian:
That’s exactly the logic behind the old American idea of double drive units and unbraked steer axles which provided the best of all worlds situation of a 3 axle unit,which provides more contact at the road where it matters,with only weight transfer acting on the front of the trailer which puts weight onto the drive axles but without the effects of a braked steer axle causing the nose of the unit to dive thereby removing weight from the rear of the unit.
I’ve never experienced the effect at first hand, can’t be much good in practice cos in all the films i’ve seen the driver can’t possibly stop in half a mile but instead lays on the horn and drives straight through anything/anyone in the way…remember Omen where the poor woman had he eyes pecked out by Ravens……well she was winking with both eyes…yes i know thats in bad taste…
Seriously though i’m very unsure about that, an unbraked steering axle leading presumably to locked or locking drive axle(s) sounds to me like a recipe for disaster, be interesting to hear from our overseas contingent as to the system in practice.
Driveroneuk:
She was a good strong truck and pulled well. Cruise control too - well Scania call it a hand throttle.
Good motor indeed, drove the low cabbed 4 x 2 versions regularly, no rear shockers and the ride was, yes, shocking.
No computerised junk to go wrong though, bet there’s still a good few 2 and 3 series doing their stuff in other places and will be for many years to come.