Really stop snaking forever

[DomDom]

Lutz

Appreciate your comments. Please consider this as well.

I have hydraulic disc brakes on the boat trailer (american import) which perform faultlessly. They are vastly superior to the cable actuated drums on the caravan. Yet still they are technically illegal, mainly because of the lack of attention the law gets in these areas. Seems to me like the dinosaurs in Westminster need to move into the 21st century before the rest of us can.

Canbus could easily be used and a common transmitter is another easy one. Just think back to when we all had points & condensors. The industry soon developed electronic ignition retrofit kits. Plus of course, if canbus were to be used there would be plenty of spare pins in the socket. the CAN could be used to trigger all the various road lighting functions which frees up about 7 pins.

The main thing to consider is that articulated lorries don't need stabilisers mostly due to the fact that the trailer brakes are directly linked to the brake pedal. There is also the fact that the trailer can weigh over 6 times the kerb weight of the tractive unit, something we are all told is bad in a caravan. I contend that it is only bad because of the prehistoric braking systems on caravans. If we had a decent and more "connected" system for braking then stabilisers would not really be so important.

Let's be honest, the larger single axle vans can weigh up to a tonne and a half and yet still legally rely upon one set of drum brakes to stop it (with a LOT of help from the tow car) That's not good in any language.

Plus of course, once we do get better braking systems which are more connected to the tow car, such stability devices as the sophisticated electronic ones we are starting to see now would simply become another module on the CAN BUS and therefore cost a lot less. We might even end up with ABS on our vans !!

This ATC system seems like good news to me, for now at least until we get type approval on some more modern brakes.

I guess for now I'll stick with the ALKO friction hitch despite the fact I have to clean the ball every time I've pulled the boat. Yes it's only 30 seconds with a rag and some thinners but still mildly irritating.

 

[colin-yorkshire]

RAY you may well be right about the 1300 and the 2004 type is better,

and yes old habits do die hard, it is just that the old habits still work and just as good as they ever did so why change them.

yes I could (if I wanted to) change the 1300 for a new 2004 type at a cost of

 

[Lutz]

It is simply not true that the caravan with drum brakes will stop "with a lot of help from the towcar". Even with drum brakes, the caravan is perfectly able to stop on its own without any help other than the relatively small force required to actuate the overrun.

You also talk about single axle caravans weighing up to a tonne and a half. Well mine is a single axle and weighs closer to two tonnes.

A can-bus system would be very difficult to put into practice because, unlike car manufacturers where the system can be specific, it would require industry-wide agreement for application on caravans, because all makes would have to be freely interchangeable. I cannot see such an agreement being achieved very quickly. Besides, unlike trucks where such industry-wide standards have existed for a long time, the caravan industry lobby is just too weak to push an agreement through.

 

[Gafferbill]

Caravan brake design or efficiency does not cause caravan snaking.

It is caused when lateral forces on the hitch point of the caravan, exceeds the towcars ability to resist these forces causing the rear tyres of the towcar to loose adhesion with the road surface.

This is felt by the driver as a rear steering effect and is usually of a reciprocating nature.

It is not possible for a snake to occur when the towcar is accelerating as the hitch is in tension and the lateral forces are resisted.

Alko's ATC prevents snaking by applying the caravan brakes to achieve this same tension.

Conversely when the towcar is on the overrun downhill, there is no tension and snaking is likely as these forces can flourish and magnify unchecked.

The design need to position the axle centrally to carry almost the entire weight of the caravan is what leads to the propensity of a caravan to snake.

Towcars are simply not designed to carry more of the caravans weight if the axle was placed more towards the rear of the caravan.

Such a design would create an outfit less likely to snake, as there would be more weight on the towcar's rear axle, increasing its adhesion to the road surface.

This effect is demonstrated by 5th wheel caravans towed by pick-up trucks which have been found to be more stable and less snake prone.

Stabilisers work by reducing these lateral forces as does correct loading of the caravan.

Putting heavy items in the rear or boot of the car helps to increase the towcar's rear axle adhesion as does having the correct tyre pressures on this axle.

For the above reasons, the heavier the towcar in relation to the caravan the less likely a snake.

The 85% rule has largely come about as a rough measure to achieve this

 

[xtrailman]

colin

I certainly wouldn't go out and buy an alko, if i already had the blade fitted, as you say not worth the money, nor will i go out and buy ATC, at

 

[DomDom]

It is simply not true that the caravan with drum brakes will stop "with a lot of help from the towcar". Even with drum brakes, the caravan is perfectly able to stop on its own without any help other than the relatively small force required to actuate the overrun.

You also talk about single axle caravans weighing up to a tonne and a half. Well mine is a single axle and weighs closer to two tonnes.

A can-bus system would be very difficult to put into practice because, unlike car manufacturers where the system can be specific, it would require industry-wide agreement for application on caravans, because all makes would have to be freely interchangeable. I cannot see such an agreement being achieved very quickly. Besides, unlike trucks where such industry-wide standards have existed for a long time, the caravan industry lobby is just too weak to push an agreement through.

Sorry, two tonnes on two tyres with drum brakes cannot ever come close to the stopping efficiency of even a large 4x4 on 4 tyres with disc brakes. What you say would defy the laws of physics.

Even if the drum brakes were as efficient as discs (which they are not) the van tyres would lose adhesion long before the tow car so thus the tow car is providing a fairly high level of stopping assistance.

I would concede that under most normal situations this is not an issue but the discussion was initially about stabilising systems and how they cope with extraordinary situations.

You also mention the caravan lobby not being large enough. well, from what I can make out (and I stand to be corrected) a large majority of european vans are built on one of two chassis designs. If both manufacturers were to develop a common "linked" braking system then car makers would all include the relevant facility on the canbus to cope with it, particularly those manufacturers who have models which are high profile tow cars. CANBUS is not rocket science contrary to popular belief and it basically works on a pair of copper wires which are terminated with 120 ohm resistors. Add in a rheostat on the brake pedal and the resultant digitised signal can be transmitted on the CANBUS to the caravan braking system. On a mass production basis I doubt it would add much more than 20 quid to the cost of a new car.

I would imagine that this new stability system is only the start of the process towards more intelligent braking systems. I for one certainly hope this sort of innovation is continued. Some might prefer the older systems and that is their prerogative. But given the choice of 2 identical vans,one built to 2009 spec and one built to 1970 spec (no hot water, no heating, no mains hookup etc) which would you choose? And therein you have the answer; people have always resisted change and I would agree when it is change for the sake of it, but when it is change for the better I wholeheartedly embrace it. Overrun drum brakes are the technology of the 1950's and it's time we moved on.

Stabilisers all have one goal which is to reduce or eliminate snaking but intelligent braking systems are already proven to remove a lot of instability issues BEFORE they arise. Otherwise companies like Land Rover, Mercedes, BMW etc would not fit ESP systems to their cars, ESP systems which rely heavily on things like ABS and electronically controlled braking systems. In other words, the technology already exists so it is only a case of implementing it. The time will come.

 

[DomDom]

Caravan brake design or efficiency does not cause caravan snaking.

It is caused when lateral forces on the hitch point of the caravan, exceeds the towcars ability to resist these forces causing the rear tyres of the towcar to loose adhesion with the road surface.

This is felt by the driver as a rear steering effect and is usually of a reciprocating nature.

It is not possible for a snake to occur when the towcar is accelerating as the hitch is in tension and the lateral forces are resisted.

Alko's ATC prevents snaking by applying the caravan brakes to achieve this same tension.

Conversely when the towcar is on the overrun downhill, there is no tension and snaking is likely as these forces can flourish and magnify unchecked.

The design need to position the axle centrally to carry almost the entire weight of the caravan is what leads to the propensity of a caravan to snake.

Towcars are simply not designed to carry more of the caravans weight if the axle was placed more towards the rear of the caravan.

Such a design would create an outfit less likely to snake, as there would be more weight on the towcar's rear axle, increasing its adhesion to the road surface.

This effect is demonstrated by 5th wheel caravans towed by pick-up trucks which have been found to be more stable and less snake prone.

Stabilisers work by reducing these lateral forces as does correct loading of the caravan.

Putting heavy items in the rear or boot of the car helps to increase the towcar's rear axle adhesion as does having the correct tyre pressures on this axle.

For the above reasons, the heavier the towcar in relation to the caravan the less likely a snake.

The 85% rule has largely come about as a rough measure to achieve this

Caravan brake design does not cause snaking, I agree. What it does do is provide (or fail to provide as it the case with overrun brakes) the most effective mechanism of dealing with a snake.

It is very possible for a snake to occur when the hitch is under tension. This is the situation almost every time when you consider that it happens at the higher speeds only, the car is pulling and the van is causing a drag with their lesser aerodynamic shape and running weight although I concede there would possibly be an exception when going down very steep hills, but they would have to be steep enough for the imaginary runaway caravan to be able to achieve a gravity assisted speed in excess of the speed which the tow car is travelling at. (possibly Shap on the M6 or similar) The ATC system simply increases this tension which helps sort out the problem.

Yes, more weight on the rear axle can help with tyre adhesion but it can also cause other undesirable effects like tow car instability if overdone. As you say, cars are not generally designed to have a lot of extra weight on the rear axle. All the more reason to make the caravan as intelligent as possible then.

As regards the 85% rule, how is it I manage to tow 3500KG's of trailer & boat with 2600KG's of Land Rover in a perfectly safe and stable manner? (it actually tows better than my caravan) That's about 135% which is perfectly safe and legal. Probably something to do with it having 3 axles, all with shock absorbers, hydraulic disc brakes and good quality tyres. Strangely, the one thing it doesn't have is a stabiliser.

 

[Lutz]

In reply to your response, Dominic, yes, disc brakes are usually more efficient than drum brakes, but at what a cost? For a start, it is almost impossible to implement disc brakes without a servo unit and hydraulic or air actuation. Secondly, because of the very high forces required to operate them (hence the need for a servo unit), disc brakes are not ideal for use as handbrakes, so one would probably still need drums for that purpose. As the caravan has no power of its own to operate the servo, this too would have to come from the car. All this would lead to prohibitive costs which are difficult to substantiate.

You are also correct in suggesting that can-bus systems are not rocket science, but that would require industry-wide agreement to ensure universal interchangeability. The two major caravan chassis manufacturers are diminutive compared with the size of volume car manufacturers so they would hardly be in a position to put very much pressure on them. As each car manufacturer can currently do his own thing as far as can-bus systems are concerned, it would require unification of systems throughout the industry before they can be applied to caravans, too. But which can-bus system would be adopted? That of Audi? of BMW? of Ford? I just can't see that they would be very willing or quick to agree to any change in their own existing systems.

What you are suggesting is technically feasible, no doubt, but I ask myself whether the shortcomings of current caravan braking systems that I do agree exist are so great as to warrant the degree of sophistication (and obviously cost) that this would involve.

Drums brakes on caravans do achieve surprisingly good braking results. Tests have shown that an car/caravan outfit does not necessarily have a significantly longer stopping distance than a solo vehicle. As long as caravans are limited to around 60mph (for stability rather than braking reasons) there really isn't the need for a quantum leap in improvement.

 

[DomDom]

Regarding the powe assistance I mentioned air previously. Very easy with an electric compressor and small reservoir. My LR Discovery has air suspension operated on this very principle. Also a lot of modern cars have handbrake mechanisms on disc calipers which seem to work well enough.

The CAN BUS bit I would agree on. But again, an add-on module could be common in terms of output signals. Let's face it, none of the car manufacturers make their own radios/Cd changers etc but they are interchangeable across some models. For example ny Land Rover navigation is identical to that in a Jaguar S Stype.

I'm not sure about caravan volume though. There must be millions on the road already which implies significant annual sales across europe. I really am only guessing at this though.

Shortcomings exist, that we both agree on. How large they are is the deciding factor. I see it that when a major player like ALKO start offering sophistcated electronic systems for stability as well as the traditional mechanical ones then there is a requirement. Cost??? well everything costs to a degree. I think the secret is minimising that cost rather than ignoring the requirement. But let's look at it in some rough detail. What would be required is an air compressor, a receiver, some valves & pipework, modifications to the actual brakes, a control box in the van, a signal transmitter in the car and to use a spare pin in the socket. In mass production (let's assume things like horseboxes & general trailers adopt it as well) what would this cost?

 

[Lutz]

Of course, an electric compressor on board the caravan could provide the power assistance necessary, but that alone is relatively expensive. Just consider AlKo's ATC costing around

 

[DomDom]

Lutz

agree with some of what you say. A compressor would cost but you might be surprised at the relatively low price. I have 2 onboard ones and the most expensive it the LR unit at about

 

[Gafferbill]

Dominic ...... I for one simply do not recognise the caravan braking problem you are concerned about.

The present design works well and statistically does not cause any road safety issues.

However before you tow your 3600kg boat again...

Please take note.........

The maximum trailer weight a Land Rover can tow is 3500kg

85% (or even 100%) rules are not "rules" but guidelines which have no substance in law. They are designed to ensure that the outfit will be stable (all other factors being equal). Exceeding this figure, whilst not illegal in itself, COULD lead to prosecution if the driver was stopped because of (say) instability or after an accident as there is a requirement on the driver to ensure the safety of his vehicle in the Construction and Use Regulations.

Usually a manufacturer will quote a tow weight which is far greater than the mass of the vehicle. Generally this is based on the total train weight (car + caravan) which can be started on a 12% gradient. Where this weight (or any other e.g. nose weight) is given as lower by the manufacturer the user ignores it at his peril. Insurance could well be void after an accident - worse, the illegal combination could cause the accident if the vehicle is unable to handle it.

Source

IAN WILLIS

http://www.uktow.com/towing capacity.asp#tab1

 

[Lutz]

I agree, Gafferbill. While I don't have any statistics to prove it, I am sure that instability is a far greater issue as a cause of accidents than inadequate braking performance.

 

[smiley]

ok a lot of technical and male guy talking here.

So bear with me I'm confused..

Q What does ATC stand for?

We used to have the old stabiliser bar but it was not good has we now have the new swan neck, this made us change our hitch.

We bought the new alko 3004 triple, that's what it was called.

It is different from the other hitch, which only had the hitch bar handle on one side and didn't stop pitching.

As I said before cost to buty

 

[Lutz]

ATC stands for AlKo Trailer Control and is an electronic stabiliser which acts on the caravan's brakes.

More information can be found under http://www.al-koatc.co.uk/

 

[smiley]

Good video.

But was it tested on our motorways in the left hand lane, hee hee

 

[Royston]

Hi george.h,

My caravan has a shipping length 7.266m, On my first trip out I experenced the same systems as you have described,Second trip re-arranged the internal load positions with no weights beyond the rear of the single axle, never had any problems since.

Royston

 

[Lutz]

So long as you got by without exceeding the noseweight limits, that's fair enough. However, sometimes it's unavoidable to put loads behind the axle.

 

[DomDom]

Dominic ...... I for one simply do not recognise the caravan braking problem you are concerned about.

The present design works well and statistically does not cause any road safety issues.

However before you tow your 3600kg boat again...

Please take note.........

The maximum trailer weight a Land Rover can tow is 3500kg

85% (or even 100%) rules are not "rules" but guidelines which have no substance in law. They are designed to ensure that the outfit will be stable (all other factors being equal). Exceeding this figure, whilst not illegal in itself, COULD lead to prosecution if the driver was stopped because of (say) instability or after an accident as there is a requirement on the driver to ensure the safety of his vehicle in the Construction and Use Regulations.

Usually a manufacturer will quote a tow weight which is far greater than the mass of the vehicle. Generally this is based on the total train weight (car + caravan) which can be started on a 12% gradient. Where this weight (or any other e.g. nose weight) is given as lower by the manufacturer the user ignores it at his peril. Insurance could well be void after an accident - worse, the illegal combination could cause the accident if the vehicle is unable to handle it.

Source

IAN WILLIS

http://www.uktow.com/towing capacity.asp#tab1

Please show me where I stated the boat was 3600KGS ? Read it properly and you'll find I wrote boat was 3500KGS and Land Rover was 2600KGS. the boat & trailer combi actually weighed in at 3487 kilos last time I weighed it at a public weighbridge so it's completely legal & safe.

 

[DomDom]

I agree, Gafferbill. While I don't have any statistics to prove it, I am sure that instability is a far greater issue as a cause of accidents than inadequate braking performance.

But despite this, you seem to be missing my point. I think we agree that instability is at its worst when the outfit is under compression (under braking) and if this were not true why does the new ALKO ATC system even exist? It serves to tension the rig when such action is required.

Therefore, a system of directly linking the braking to the towcar's brake pedal is the proper solution, not tinkering around the edges with ever increasing amounts of gizmos. None of these gizmos will ever give us the nice to have things like ABS and ESP either.

The only downside I can see as a valid argument is it would enable poor loading to be masked, and no amount of electronics can defy the laws of physics. However, I don't see too many drivers relying on ABS all the time as many doom-mongers predicted would happen.

Linked brakes, whether electric, air or hydraulic are commonplace in other parts of the world and this would not be the case if it were not an improvement. The evidence for me lies in the fact that my boat, on it's american trailer (with 3 disc braked axles) tows much better than my caravan on it's ALKO chassis.

If better brakes are a complete waste of time and money then I must be imagining the massive improvement I gained by fitting Brembo's to my LandRover. Should have spent the money on beer instead

 

[Lutz]

Dominic, you state: "I think we agree that instability is at its worst when the outfit is under compression (under braking)". I'm afraid I cannot agree to that statement without some reservations. Instability requires a sideways force to create a swaying motion. Such a sideways force is not necessary present when braking, certainly not when braking on a dry road surface and in a straight line.

You also say that your boat trailer tows better than your caravan. Of course it does. A boat trailer has a much lower frontal area and is less slab-sided than a caravan, so a boat trailer will always tow better than a caravan, regardless.

Nevertheless, any improvement in braking performance would be welcomed, but I just cannot see how linked braking can be introduced on cars in the foreseeable future, as such a system would require worldwide autoindustry agreement on the type of system to be adopted and I just cannot see that happening. The caravan lobby is much too weak to be able to push something like that through the might of the big car manufacturers. It would also require a common EU standard and that is just as unlikely.

 

[forestgump]

Dominic, you state: "I think we agree that instability is at its worst when the outfit is under compression (under braking)". I'm afraid I cannot agree to that statement without some reservations. Instability requires a sideways force to create a swaying motion. Such a sideways force is not necessary present when braking, certainly not when braking on a dry road surface and in a straight line.

You also say that your boat trailer tows better than your caravan. Of course it does. A boat trailer has a much lower frontal area and is less slab-sided than a caravan, so a boat trailer will always tow better than a caravan, regardless.

Nevertheless, any improvement in braking performance would be welcomed, but I just cannot see how linked braking can be introduced on cars in the foreseeable future, as such a system would require worldwide autoindustry agreement on the type of system to be adopted and I just cannot see that happening. The caravan lobby is much too weak to be able to push something like that through the might of the big car manufacturers. It would also require a common EU standard and that is just as unlikely.

may be a hydrolic coupling from car brake pipes to caravan ,same as hgv trailors but theye use air lines called suziys a quick hitch conector is all thats needed into brake system only a thought

 

[Gafferbill]

Dominic ...... I for one simply do not recognise the caravan braking problem you are concerned about.

The present design works well and statistically does not cause any road safety issues.

However before you tow your 3600kg boat again...

Please take note.........

The maximum trailer weight a Land Rover can tow is 3500kg

85% (or even 100%) rules are not "rules" but guidelines which have no substance in law. They are designed to ensure that the outfit will be stable (all other factors being equal). Exceeding this figure, whilst not illegal in itself, COULD lead to prosecution if the driver was stopped because of (say) instability or after an accident as there is a requirement on the driver to ensure the safety of his vehicle in the Construction and Use Regulations.

Usually a manufacturer will quote a tow weight which is far greater than the mass of the vehicle. Generally this is based on the total train weight (car + caravan) which can be started on a 12% gradient. Where this weight (or any other e.g. nose weight) is given as lower by the manufacturer the user ignores it at his peril. Insurance could well be void after an accident - worse, the illegal combination could cause the accident if the vehicle is unable to handle it.

Source

IAN WILLIS

http://www.uktow.com/towing capacity.asp#tab1

Yes Dominic... I realised my mistake as soon as I saw my post back in September...I read your post correctly...my finger hit the wrong key.... 5 and 6 are next to each other!!

However my post was to point out that towing your boat at 135% could result in a prosecution were you to have an accident as explained by the quote I gave by Ian Willis.

The vehicle may be legal but the driver may be acting illegally!

 

[ProfJohnL]

Hello Dean,

It is of course possible to engineer a hydraulic solution but as Lutz points out it would require a agreed standard for the pressure the volume movement of the fluid, and any control interface for BAS or other braking control systems.

Not to mention the potential for the loss or contamination of brake fluid when coupling and decoupling. The Risk assessments are frightening.

I'm sure one of the reasons trucks use air brakes for their trailers is there is no specialist working fluid to be lost or contaminated, just air, and I assume there is a common set of standards for couplings, and the relationship between pressure/Vacuum and the thrust on the brake shoes.

 

[Lutz]

Besides, at present, regulations don't provide for a linked braking system on trailers less than 3500kg, so it's not only a technical problem but also an administrative one. The law would have to be changed. In view of the fact that this would have to be coordinated throughout the EU, we all know how long it would take to get that through.