As the OP could I say that I've never had a "snake". My wifes fear is of the sway that occurs when you pass artics which, hopefully, would be eliminated with the ATC. I always consider the van to be balanced so there is no inherent instability. We've just completed a 1000 mile, 2 day, tow across Europe with no problems other than the sway refered to above.
Paul,
I don't think you'll ever eliminate the sway, unless the caravan has the wheels right at the back. With the axle being in the centre, that's where the pivot point is. However, you can reassure your wife that the ATC would prevent thngs getting out of hand. It's a bit like having ABS and stability control on a car. It's there but hopefully you'll never need it.
Nigel.
I don't think you'll ever eliminate the sway, unless the caravan has the wheels right at the back. With the axle being in the centre, that's where the pivot point is. However, you can reassure your wife that the ATC would prevent thngs getting out of hand. It's a bit like having ABS and stability control on a car. It's there but hopefully you'll never need it.
Nigel.
Mmm . The OP asks a very valid question. Is ATC worth having?
Yes.
Would you buy a car today without ABS , ECS etc etc? No.
Any extra aid which can asssist in avoiding a problem on the road must be worthwhile.
I've had ATC for four years now and whilst I haven't actually felt it , in a violent way , I am sure on ocassions it has done it's job particularly in crosswinds.
Ask youself this. Back in the 70s we all went out and bought a Scott Stabiliser. Why? Because we wanted some extra insurance over and above Prof John's words of wisdom. There is nothing wrong with belts and braces but as John says don't use these extra aids as a "sort out your poor loading" issues.( My Words)
The more technology such as hitch stabilisers , ATC etc that can be introduced the safer we can all be.
Yes.
Would you buy a car today without ABS , ECS etc etc? No.
Any extra aid which can asssist in avoiding a problem on the road must be worthwhile.
I've had ATC for four years now and whilst I haven't actually felt it , in a violent way , I am sure on ocassions it has done it's job particularly in crosswinds.
Ask youself this. Back in the 70s we all went out and bought a Scott Stabiliser. Why? Because we wanted some extra insurance over and above Prof John's words of wisdom. There is nothing wrong with belts and braces but as John says don't use these extra aids as a "sort out your poor loading" issues.( My Words)
The more technology such as hitch stabilisers , ATC etc that can be introduced the safer we can all be.
Unlike ABS the Alko system is incapable of operating individual wheels, it can only operate both wheels simultaneously.
It is there fore essential that the braking system is correctly adjusted.
It is there fore essential that the braking system is correctly adjusted.
JohnMW said:
Hello John
Welcome to the forum, and an interesting post. I generally agree with your comments except the one i have extracted from your post.
There are plenty of outfits on the road that do oscillate at speeds below 60mph. even with maximum allowed nose weight. It may be self induced, or excited from an external force.but which ever its not safe to suggest that Max nose weight will give stability at 60mph. As ever good towing is about getting a range of factors under control and not focusing on just one.
I think you are confusing ATC with ABS. Both the working principle and the intent of the two systems are totally different. The intent of ABS is to reduce braking distance under less than optimal tyre grip conditions by automatic cadence braking. ATC on the other hand has nothing to do with reducing braking distance. It is only meant to prevent the caravan from swinging sideways due to instability. It will normally deploy well before the amplitude gets that big that the caravan would pull the back of the car sideways, too. Besides, it doesn't apply the caravan's brakes anywhere near fully so the tug should never be that strong anyway.
There's nothing "magical" about 60mph - each outfit has it's own critical speed above which any oscillation will increase, not die down - that critical speed can vary slightly trip-by-trip according to loading, etc.
All anyone can ever do to improve stability is move that critical speed upwards and then stay below it - the difficulty is that unless we spend years researching it, like Bath University, we don't actually know what that critical speed is.
All anyone can ever do to improve stability is move that critical speed upwards and then stay below it - the difficulty is that unless we spend years researching it, like Bath University, we don't actually know what that critical speed is.
Passive stabilisers such as those integrated in the hitch, raise the critical speed above which an outfit would not recover from instability without some sort of corrective intervention, but active systems such as ATC do not. However, they do the job where the passive systems leave off because they work even when the critical speed is exceeded. That's why they complement each other.
I've only just looked at this thread - how very interesting.
I must confess to being a luddite on this occasion. Caravanning since 1967 I have never had any stabilizer other than those fitted to the hitch as standard and have long held the view that stabilizers are a sticking plaster solution and generally just enable you to reach a higher speed before you get into trouble..
I have the same view on ATC, reinforced by the fairly poor standard of construction of many consumer level electronic packages - for example, what is the 'fail safe' mode ?. Brakes locked on or no action at all (when you are relying on some). Neither is attractive. Not having studied these devices, do they activate the caravan brake lights when operating ?
I am a firm believer in getting the outfit balanced and leveled correctly with a well matched tow car and driving to suit your experience and the circumstances.
I must confess to being a luddite on this occasion. Caravanning since 1967 I have never had any stabilizer other than those fitted to the hitch as standard and have long held the view that stabilizers are a sticking plaster solution and generally just enable you to reach a higher speed before you get into trouble..
I have the same view on ATC, reinforced by the fairly poor standard of construction of many consumer level electronic packages - for example, what is the 'fail safe' mode ?. Brakes locked on or no action at all (when you are relying on some). Neither is attractive. Not having studied these devices, do they activate the caravan brake lights when operating ?
I am a firm believer in getting the outfit balanced and leveled correctly with a well matched tow car and driving to suit your experience and the circumstances.
It's a bit like other passive safety features: ABS, ESP, airbags, lane change warning, emergency brake assist, etc. etc. Would you want to be without them too?
John - belately, UK manufacturers have been fitting dampers for some years now - although in some cases, not on their cheapest model.
Alko chassis have had mounting points for dampers for decades and they aren't expensive to retro-fit.
The whole point about ONLY applying the trailer brakers is the inherent tendency in doing that is to straighten the outfit.
Alko chassis have had mounting points for dampers for decades and they aren't expensive to retro-fit.
The whole point about ONLY applying the trailer brakers is the inherent tendency in doing that is to straighten the outfit.
I'd never consider a caravan without shock absorbers. Besides, they are even a legal requirement in Germany for anyone intending to tow at 100km/h. Because of the increased risk of instability one is limited to 80km/h without them.
A snake can occur even if the driver exercises best possible due care and attention. Unforeseeable situations can always occur no matter how careful you are. Another driver may be to blame, forcing one to take emergency avoiding action which can start a snake.
Light application of the car's brakes to assist recovery from instability, as you suggest, is exactly what ESP+ does.
A snake can occur even if the driver exercises best possible due care and attention. Unforeseeable situations can always occur no matter how careful you are. Another driver may be to blame, forcing one to take emergency avoiding action which can start a snake.
Light application of the car's brakes to assist recovery from instability, as you suggest, is exactly what ESP+ does.
JonMW,
Apart from the points other contributors have commented on in your post, I'm intrigued by your reference to "bouncing back from the tyre hysteresis"
What is your definition of hysteresis?
I await with interest your proposal to enhance trailer control.
Hysteresis cannot cause a tyre to bounce back, can you please be more specific?
Apart from the points other contributors have commented on in your post, I'm intrigued by your reference to "bouncing back from the tyre hysteresis"
What is your definition of hysteresis?
I await with interest your proposal to enhance trailer control.
Hysteresis cannot cause a tyre to bounce back, can you please be more specific?
HGVs have roof spoilers to reduce fuel consumption - the fact that HGV cabs and their trailers are very uniform in size and the front of the trailer is very close to the back of the cab makes that possible. The differences in airflow at the rear of cars, because of all their different shapes and sizes makes it pretty much a non-starter - they don't even build Volvos with vertical tailgates any more!
I have not come across any evidence that tyre bounce, or for that matter pitching, is in any way a major contributing factor to instability of a caravan fitted with shock absorbers. I therefore feel that shock absorbers are a vital first step. Only then is there any point in possible further development with a view to improving stability.
Additionally I insist all four wheels on the caravan are dynamically balanced.
I thought the whole point of ATC was to apply brakes on both sides, causing drag which then damped out the snake oscillation.
The Al-ko hitch does of course damp out pitching as well as yawing so it must be a safety contributing factor.
I thought the whole point of ATC was to apply brakes on both sides, causing drag which then damped out the snake oscillation.
The Al-ko hitch does of course damp out pitching as well as yawing so it must be a safety contributing factor.
Yes, the international industry standard ISO 11555-1 for integrated hitch stabilisers specifies a 350Nm resistance to yaw and 300Nm resistance to roll and pitch.
Lutz said:
Positioning of the pads affects the resistance in each axis - my understanding was that the Winterhoff had higher pitch resistance but zero roll resistance - compared to the Alko - both having similar yaw resistance.
I would have thought that renowned manufacturers such as AlKo and Winterhoff would design their hitch stabilisers around ISO 11555-1. It's not a legal requirement, but nevertheless a useful tool with which the industry, including the car industry can work.
I've read this whole topic, post by post,and the wonderful amount and scope of information provided by all the expert members who have posted here.
I can't help wondering however that if some folks exercised proper control of their right foot and used a little common sense then much of these modern "safety aids" might remain unused.
I can't help wondering however that if some folks exercised proper control of their right foot and used a little common sense then much of these modern "safety aids" might remain unused.
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