Very serious Snaking whilst overtaking.

[keith_374224129]

After 30 years of pulling caravans around the country I now have this major problem. First off the van is a 2006 Eldiss Typhoon the car is a Mercedes E320 estate and the hitch is a Winterhoff 3000. Two weeks ago on the way two cornwall M5 @2am.

started to overtake two lorries which were doing approx 58mph.

when level with the first lorry it started ! not just a little wagg as we all come to expect but a major two lane experience as though stabilization was nil, luckily trafic was minimal and no accident was caused. I pull of the motor and did a complete check of hitch nose wieght loading etc. Is it the cars length,

or self leveling system, anyone else had this trouble ??

 

[CliveV]

Only time I have had a problem overtaking a convoy of Lorries. So it may be that it is the two Lorries that exacerbate the problem.

It seems to me that the "bow wave" of displaced air is manageable with a single lorry but can be very unpredictable with a series of vehicles.

I have often thought I would love to see a wind-tunnel test with smoke streams to see what can actually happen.

I am now VERY wary of overtaking a series of large vehicles when towing. I have noticed that even coaches when passing Lorries sway noticeably when having passed one then about to pass the next. Is the air "bow wave" being sucked in behind the first lorry then blasted out again as the lorry behind pushes along?

 

[Kanga_374224132]

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[Kanga_374224132]

spelling still carp then Clive

 

[Kanga_374224132]

Are you dickslexic Clive

 

[Davidventura_374224135]

you got your wording wrong there Clive, it should read you were born an ar**hole

 

[CliveV]

Whatever I was born - I have achieved a lot and have set certain standards.

Thing of which you are entirely devoid and have no understanding.

You are just like a gnat bite on a summers day. A minor irritation that will be fogotten in the morning.

 

[Lutz]

Returning to sanity and the topic in question, assuming you had everything set up correctly (noseweight, load distribution, tyre pressures, etc.) this was probably one of those cases where the forces created by the bow wave of the lorries were just too great for the stabiliser to be able to cope with. (Frictional stabilisers only have limited resistance to swaying movements. Once this threshold limit is exceeded, they can help no more).

In the case of such an incident, there's only one solution, take the foot off the accelerator and, if necessary, also apply moderate braking.

As a preventative measure, there are electronic stabiliser systems, either included as an additional feature of the car's ESP system (where fitted) or as a retrofit hang-on unit available for caravans. These electronic systems do not have the shortcoming of finite anti-sway performance that frictional stabilisers suffer from. (This does not mean that frictional stabilisers, like the AlKo or Winterhoff, don't provide any protection, though. In fact, the 2 systems complement each other ideally.)

 

[JohnI.Stephen]

So what would have caused these 'forces'? Keith does not suggest that the weather was particularly bad?

Finally; as a parent of 4, I have learnt that if a child throws a tantrum the worst thing is to give them attention. Just ignore it and they soon learn the lesson. Please apply in this forum!

 

[Litespeed]

As a note when overtaking a group / convoy of lorries I find it helps to decelerate just before you begin the overtaking manouvre then apply gentle acceleration whilst overtaking. It gives the same effect as towing up a hill, you very rarely get a snake on then either.

 

[CliveV]

So what would have caused these 'forces'? Keith does not suggest that the weather was particularly bad?

Finally; as a parent of 4, I have learnt that if a child throws a tantrum the worst thing is to give them attention. Just ignore it and they soon learn the lesson. Please apply in this forum!

You are right of course - I accept that responding is a flaw in my character - but the truth is I just like verbally outmanouvering them as they really are not very bright.

Bit like throwing a stick for a dog - they always want you to do it again.

And i like throwing the stick.

Apologies to all if you find it annoying.

 

[keith_374224129]

Returning to sanity and the topic in question, assuming you had everything set up correctly (noseweight, load distribution, tyre pressures, etc.) this was probably one of those cases where the forces created by the bow wave of the lorries were just too great for the stabiliser to be able to cope with. (Frictional stabilisers only have limited resistance to swaying movements. Once this threshold limit is exceeded, they can help no more).

In the case of such an incident, there's only one solution, take the foot off the accelerator and, if necessary, also apply moderate braking.

As a preventative measure, there are electronic stabiliser systems, either included as an additional feature of the car's ESP system (where fitted) or as a retrofit hang-on unit available for caravans. These electronic systems do not have the shortcoming of finite anti-sway performance that frictional stabilisers suffer from. (This does not mean that frictional stabilisers, like the AlKo or Winterhoff, don't provide any protection, though. In fact, the 2 systems complement each other ideally.)

Thanks for your comments,would you have any trade names for this electroic stablization or possible contact ? I will try anything to save the wife putting her head in a pillow every time I try to pass another vehicle.

 

[Paul_5064559]

Keith,

No one has mentioned tyres?

I suppose that these we all OK and at correct pressures...

Secondly, was one of the overtaken vehicles a car transporter?

I have heard of and experinced myself extreme stability problems when attemping to overtake these.

regards

 

[ProfJohnL]

This is a tricky subject. As many contributors have pointed out the air flow around one lorry can be complex enough but the combined effects of several lorries will be very complex, and may be the cause of Kieth's difficulty.

Air distuurbance is well recognised as a major hazard by airports. The minimal interval between landing succssesive aircarft is largely determined by the time it takes for the air disturbance from the first aircraft to fall to an acceptable level, before allowing the next craft to land. The bigger the craft the bigger the disturbace.

The issue of caravan stability has been well argued previously, and the general concensus is that care must be taken whne loading the outfit, the outfit must be in good road worth condition (tyres, brakes, suspension etc. Even with all the aformentioned criteria correctly managed, an outfit can still become unstable - due to drivers habits, and probably the most important of which is speed.

If an outfit starts to become unstable, then it is being towed too fast. Solution - reduce speed. For that reason I do not subscribe to Lightspeeds suggestion of acclerating out of trouble, it seems that you could easiliy be accelerating into an even bigger problem.

For keith it seems that 58mph plus is just too fast for those conditions.

 

[Lutz]

Keith, electronic stabilisers on towcars are part of their ESP (or DSC or whatever the manufacturers call it) system, where fitted, and cannot be retrofitted. However, not all ESP systems include the stabiliser feature as well. The following vehicles are examples which have the more sophisticated ESP with trailer stabiliser (the list may not be complete as new models are constantly being added):

BMW X3 and X5

Vauxhall Vectra (with optional factory fitted 'Towing Pack')

VW Passat

Merc E-, S- & M-Class

Al-Ko are planning to offer an electronic stabiliser system for caravans under the name ATC (Al-Ko Trailer Control). Here's the press release (unfortunately, all in German) Al-Ko Trailer Control.

This is basically the same as the

 

[Lutz]

Whoops, I was too fast at the 'submit' key, so here's the rest of the text:

This is basically the same as the LEAS unit which is already available and which I've got on my caravan.

An even more sophisticated system has been developed by Knott Brakes. This not only automatically applies the caravan brakes as soon as an impending snake is sensed but it also controls the pressure applied to the towball stabiliser pads at the same time.

 

[jon_5090857]

Hi Keith

I too was traveling to cornwall overnight on the 18th of september and had to slow down to 45 to 50 mph due to snaking after we had passed Bristol due to quite windy conditions it was quite strange as some parts of the M5 and A30 were ok but others we were blown about quite a bit. Lorrys were overtaking me and it could be quite hairy as i do only 60mph on the motorway whilst towing it made a very long journey from lincolnshire a lot longer 10 hours in total.

Jon