I am certainly not questioning that, other than not just ATC, all its rudimentary "kin".
Even to an extent that just like other fundamental driving safety features that have come to the market, they be mandated on all new builds.
I think this needs a little more clarification,
Cruishally the threshold is not fixed value, in fact it is constantly changing becasue it's highly reliant on the driving and road conditions.
Elements such as a side wind or bow wave from a passing vehicle, it could be a change of direction or change of road surface, for example tram lines or a wet patch, any one or combination of these will lower the threshold.
But even more than the variability of the threshold point, it's actually two thresholds, and upper one that needs to be exceeded to initiate instability, and to bring the outfit under control the speed must brought down below the lower threshold point. The band between the threshold's is a range of speeds at which you or might not experience instability, but if you have instability you must bring your speed down below the lower threshold.
I cannot condone the concept of trying to accelerate out of a loss of control, as by increasing your speed you are adding kinetic energy to the outfit which can be converted in to a more severe instability action.
Parksy
Moderator
The closest that I've come to a bad snake when towing was last year travelling down the M5 southbound just past Gloucester.
The motorway was quiet, the road conditions were good and the car and caravan were correctly loaded.
I was passing a 7.5 tonne panel van in the middle lane at about 58mph, not a problem, but on this occasion a large Bentley saloon car came past in the third lane at what must have been at least 100mph.
Fortunately for us, I'd seen him blasting toward us and instinctively eased off just in time as he passed us, creating a massive bow wave of disturbed air which, coupled with that from the 7.5 tonner panel van, induced some quite severe instability in our unit.
I took my feet off everything to let the speed bleed off, and the panel van driver was alert to the situation and also backed off to give me some room.
Thankfully the bad wobble didn't develop into a full blown snake, but it was the most buttock clenching moment that I've had when towing.
I concur with the Prof, the instability threshold can change, sometimes quite dramatically when a speeding vehicle creates such a massive disturbance of air and slipstream.
If I hadn't seen the idiot high speed Bentley driver coming things could have been much worse.
The motorway was quiet, the road conditions were good and the car and caravan were correctly loaded.
I was passing a 7.5 tonne panel van in the middle lane at about 58mph, not a problem, but on this occasion a large Bentley saloon car came past in the third lane at what must have been at least 100mph.
Fortunately for us, I'd seen him blasting toward us and instinctively eased off just in time as he passed us, creating a massive bow wave of disturbed air which, coupled with that from the 7.5 tonner panel van, induced some quite severe instability in our unit.
I took my feet off everything to let the speed bleed off, and the panel van driver was alert to the situation and also backed off to give me some room.
Thankfully the bad wobble didn't develop into a full blown snake, but it was the most buttock clenching moment that I've had when towing.
I concur with the Prof, the instability threshold can change, sometimes quite dramatically when a speeding vehicle creates such a massive disturbance of air and slipstream.
If I hadn't seen the idiot high speed Bentley driver coming things could have been much worse.
That area of the M5 was notorious for tram lines and added to the above described by yourself does not help matters. That area was also where we had the bad snake.
It is true that the threshold speed will vary depending on prevailing conditions, but to allow comparison between different outfit configurations it is usually determined under ideal conditions such as a straight and level open road and calm weather conditions.
One should not confuse the threshold speed above which the outfit will not regain control of a snake without any active intervention and the speed at which a snake is induced in the first place. That speed can be significantly lower.
Under the conditions I've bold underlined, any outfit should be stable regardless of how badly matched or how badly loaded - and such a speed cannot be used as a safe speed to tow at as conditions are often far from perfect.
You are confusing the threshold speed with the speed at which instability may occur. Instability may be induced at speeds well below the threshold speed but this would not have any dire consequences as the outfit is capable of recovering from the snake without any active intervention.
Conversely, if nothing occurs to upset the equilibrium, the threshold speed may be exceeded without incident, but that is very risky.
If I recall correctly, the world speed record for towing a caravan stands at 149mph. Now that will definitely be way above the threshold speed for any outfit, so extreme care needed to be taken to ensure that nothing spoilt the prevailing ideal conditions. If anything untoward had happened it would have been well nigh impossible to avoid the worst.
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It is the responsibility of every driver to ensure their vehicle is safe and not likely to lose control under driving conditions without having to rely on non obligatory systems like friction couplings, or friction dampers, or ATC or similar systems.
None of these systems are presently considered to primary (like brakes )or secondary systems (like seat belts and anti lock braking systems) . They are third tier non essential aids - nice to have but must not be relied on to make an outfit drivable.
If your outfit has any of these, and for any reason you rely on these to keep your outfit under proper control during normal driving, then it suggests your outfit is not safe as required by the law.
An interesting take Prof. I never thought about a third tier non essential aid.
I never had ABS on my earlier cars. I was taught Cadence braking and even double de clutching.
Looking back an anti snaking device was at the top of the CC list of most wanted accessories. Not mandatory , maybe just a placebo?
But we were taught the skills that precluded the need for such devices.
So yes , I agree they were third tier as not supplied with the caravan, being considered non essential.
Ironically today ATC , anti snake devices have become standard fits . I wonder if anyone would buy a new car or caravan without these systems?
I never had ABS on my earlier cars. I was taught Cadence braking and even double de clutching.
Looking back an anti snaking device was at the top of the CC list of most wanted accessories. Not mandatory , maybe just a placebo?
But we were taught the skills that precluded the need for such devices.
So yes , I agree they were third tier as not supplied with the caravan, being considered non essential.
Ironically today ATC , anti snake devices have become standard fits . I wonder if anyone would buy a new car or caravan without these systems?
I agree Prof, our 2017 had no ATC and we didn't miss it, nor did we ever have the slightest wobble. They're an extra layer above your own safety checks/driving, that you don't want to come in to play but can help in an unseen situation. My take anyway. There's far too much reliance on auto this and that so people simply don't concentrate on safe driving. My grandfather used to say the safest car driver would be the one who drove a car with a spike pointing at his chest attached to the steering wheel!
There are so many factors that affect the behaviour of an outfit. Single or twin axle is just one. Most important is the polar moment of inertia of the caravan, but also the lateral compliance of the towcar’s rear suspension. One could go on and on with further criteria.
True, but that fails to cover those cases where "others" etc dictate how you drive, there are most definitely situations where even the most careful driver can face destabilising situations of any towed unit.
Not every road situation is within one's control.
An example, being forced to do effectively an "elk test", that potentially destabilises a caravan even at 50 mph, even to the best of matched unit and driver.
Consider these actual "real life" situations; where a loaded bike rack comes off an overtaking camper, scudding right close up into your path. Or a large scaffolding foot plate bounces off a lorry, again straight into your path.
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Ours without ATC was a Bailey Pegasus Verona towed by a Dacia Duster 4x4. Even an emergency elk test didn't invoke a wobble-as soon as the avoiding manoeuvre was complete the caravan simply followed the car. It did seem a perfectly matched outfit, though the old 109bhp petrol did need dropping through the gears on steep hills and motorway inclines to maintain good progress. 24mpg towing too. Not brilliant not towing-32!
And yet, its on straight and level roads I invariably see caravans whipping around like beachballs in a stiff wind.
These are issues of significant interest and critical examination in German caravan test, but do not even warrant a mention in a British 'Aren't the curtains nice' tests. They don't even measure the actual loads on the individual wheels of a caravan!
Yes, I think you have nicely captured the whole picture, indeed of this whole industry, its hangers on etc, over here.
I only categorised ATC etc as non essential becasue presently under UK law they are not required to be fitted "as standard" , and even if they it is fitted its not required to be used, and it can either accidentally or intentionally not set up. Its legal in the UK to have them fitted but not engaged hence not essential.
"A placebo is a sham substance or treatment which is designed to have no known therapeutic effect", so these devices cannot be classified in that way, as they can have a positive effect. But their action might only be tested if the driver looses control, which by rights they shouldn't.
Some manufacturers may offer caravans with ATC or its equivalent already fitted as part of its specification, but its definitely not a required "standard" on all trailers.
The problem with ATC etc is they actually can make a bad problem/attitude worse - see people convinced ABS makes their car stop 'faster' - it doesn't! ATC is not a panacea for a badly arranged rig.
We've all seen them - medium sized estate car, roof boxes, fully stacked to the roof with luggage in the back, 2 adults, 3 kids - and a bike carrier with all the tredders on the tailgate .
Towing a caravan far bigger but lighter than the car, the cars now nose up but down on its rear bump stops, (because the huge caravan has a pathetic 116kg payload and everything is carried in or on the car), the caravans now nose down.
I wonder why this arrangement is a bear to tow?
We've all seen them - medium sized estate car, roof boxes, fully stacked to the roof with luggage in the back, 2 adults, 3 kids - and a bike carrier with all the tredders on the tailgate .
Towing a caravan far bigger but lighter than the car, the cars now nose up but down on its rear bump stops, (because the huge caravan has a pathetic 116kg payload and everything is carried in or on the car), the caravans now nose down.
I wonder why this arrangement is a bear to tow?
Quite right, but AL-KO make no such claim nor I suspect were ever considering it as such.
If it was taming an inherently unstable unit it would be a nightmare to drive with the frequent application of the van's brakes, plus exceedingly short brake life, quite possibly burnt out on the first trip.
It seems to crop up quite often on forums that individuals comment in the vein, "it made no difference, would not specify it on a new van"; well then up till then they had been lucky, just as probably their seat belts had through their turn of luck been a total waste of money.
That situation will not necessarily continue, much will be down to luck, not necessarily uniquely to any skill or expertise.
Country lanes coming this Friday! But the ones I know quite well so that will be helpful. I will probably make some people miserable as some of those roads are narrow and have raised, concrete edge - so I suspect I will hit high 20-ties on the speedometer
I also bought bigger mirrors as the one I got with caravan (Milenco Aero) were bit hard to adjust and narrow. Now have XXL ones!
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Glad it went well. One trick to make Milenco mirrors easier to adjust is to disassemble the ball joint and if there is a injection moulding line slightly above the ball surface just very gently smooth it down with fine emery.Country lanes comming this Friday! But the ones I know quite well so that will be helpful. I will probably make some people miserable as some of those roads are narrow and have raised, concreate edge - so I suspect I will hit high 20-ties on speedometer
I also bought bigger mirrors as the one I got with caravan (Milenco Aero) were bit hard to adjust and narrow. Now have XXL ones!
Little update after next 600 miles. Caravan still in one piece.
Regarding country lanes, its 1:0 for them. I had to take very narrow turn. Now I have new side light!
Besides, I found driving with a caravan rather relaxing. Drove from Essex to South Wales, and except that I have to fill the tank in my thirsty CRV (18 mpg), otherwise I wouldn't make it, it was nice and slow - driving around 52-55 miles per hour. Everyone was overtaking me so I didn't need to pay so much attention on what is in front of me.
New, huge mirrors made a lot of difference, with previous one I had hard time to judge if I can change the lane, now its much, much easier.
Regarding country lanes, its 1:0 for them. I had to take very narrow turn. Now I have new side light!
Besides, I found driving with a caravan rather relaxing. Drove from Essex to South Wales, and except that I have to fill the tank in my thirsty CRV (18 mpg), otherwise I wouldn't make it, it was nice and slow - driving around 52-55 miles per hour. Everyone was overtaking me so I didn't need to pay so much attention on what is in front of me.
New, huge mirrors made a lot of difference, with previous one I had hard time to judge if I can change the lane, now its much, much easier.
Crikey someone with a car giving worse mpg than mine! Glad it went well.
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