Caravan Stability

[Gafferbill]

Rob......... I refer you to a previous topic on this subject in March

http://www.practicalcaravan.com/newforums/fm_messages.asp?FO=13&FM=439702
You will find links to video clips and research done at Bath University that should help.

 

[ProfJohnL]

john l

Where do you get your information re the levelling of the caravan, declare your source, because it is in direct conflict with the information that i have.

1/ the Bailey handbook clearly states the van should be level, or slightly nose down.

Are you saying Bailey is in error?

2/ The ALKO handbook clearly states the van should be level or slightly nose down.

Are you saying ALKO are incorrect also?

Hello Ray,

I have no 'source' as such but it is the result of a logical progression.

All current manufactures and chassis manufacturers know that the EU have specified the height limits to the centre of the tow ball (350 to 420mm for saloon cars) and will have designed their products to accommodate that range. Therefore if a car presents a towball within the EU specification and the attached caravan is nose up then the attitude is one that is acceptable to the caravan manufacturer.

It is perfectly possible for Bailey and Alko to both expect a level or nose down attitude because they will have designed their units to have that characteristic. Thus if one of their units exhibits a nose up attitude, then it is a matter that needs further investigation, and it will almost certainly be the tow vehicle that is none conforming.

 

[ProfJohnL]

I'd check wheel balance and nose weight and get weight low down and near to axle if this has not already been done.

If the roof box is not mounted on the car roof centre line move it and it could halp moving it towards the back of the car. Too far forward and the box may cause air turbulance to build between the car and van.

In theory JohnL's advice about ball tow ball heaight may be correct. In Practice a nose high largish trailer or caravan is a recipe for problems. Have always found slightly nose high lends to a skittish towing experience.

As for speed, Rob mentions that he has towed in France. So it is would be wise to have his outfit as stable as possible. If he tows in France again with this outfit he may well find occasions where he is legally above the UK limits.

Re the regular sniping at speed and the following point

"Firstly there is never a legitimate reason to exceed the speed limit - not even for overtaking"

If you drive to that way of thinking your driving standards are somewhat suspect.

Euro,

I stand by that statement and I challenge you to explain how speeding during an overtaking or any other manoeuvre is ever justifiable.

If you would need to speed to complete the manoeuvre then it is not appropriate to consider the action.

Anyone who considers themselves above the law and free to break speed limits (in any country) has suspect driving standards.

Please note I am not equating speeding as necessarily being unsafe, just illegal.

 

[Guest]

In reply to JohnL's challenge.

Firstly if you have to have it explained then you are a really cause for serious concern on the road.

Any perceptive aware experenced driver will realise that despite the greatest of driving skill, forward planning or driving care they can't control what other road users do or what might happen on a road. If the unexpeced presents itself speed may be the only option to prevent an accident for yourself or other road users around you.

Something rolling into the road, an obstacle that needs avoiding with other traffic around you. Or the recent event on a UK road where a car hit the bending armco barrier caused by a heavy impact by the car on the other side of a dual carriageway. Two cars that were behind the VW that the armco hit accelerated out of its way to the inside lane and prevented cars on the inside lane being in a multi car pile up.

There are many scenario's where a burst of speed can save a life and prevent an accident. I've had a few in nearly forty years on the road, and know of many other drivers who've had to put a foot down to save themselves from some dopy half awake idiot doing something daft.

It is quite simple, would you "crash and burn" to stay within the law. Or do you take the praise from the law for a burst of speed and avoiding a life threatening sittuation not of your making to save yourself or others.

 

[Lutz]

No matter how powerful the towcar, acceleration will suffer due to the weight of the caravan being towed behind. The performance of the average family car towing a caravan is unlikely to be adequate to allow the outfit to accelerate away from the hazard. Besides, unless the caravan is fitted with an electronic stabiliser, it is also unlikely that one can take avoiding action without the outfit becoming unstable in such a critical situation. In other words, even if the outfit may be stable in a straight line at 80mph, it will probably not be stable when negotiating something like an 'Elk Test'. For most purposes, braking is therefore the only option available to the caravanner when faced with a sudden emergency.

 

[Guest]

Lutz I never realised that caravanners always drove with a van hitched to the car!

Recently we were overtaking a line of lorries approaching the end of a dual carriagway when another smaller lorry pulled out from a farm track. We were left in a difficult position with a car travelling to close to our van with a line of vehicles behind it. Foot down was the only safe option. I believe my wife took the correct action for our safety, the lorries on the inside lane and the vehicles behind us.

With over 300hp we can still pull away quite quickly whatever Lutz might think.

The only really valid part of your post Lutz is re an "Elk Test" scenario. If presented with a scenario where a little extra speed allows you to straight line out of trouble rather than take swerving action when towing that may cause more of a stability problem.

I don't believe that you will get these sittuations every day solo driving or when towing. But JohnL who regularly uses 'NEVER' when mentioning exceeding a speed limit is completely out of touch with good safe driver aware road craft.

I hope that most drivers towing rarely get presented with a dangerous sittuation.

To regularly post that there is NEVER a time when exceeding a speed limit is acceptable is WRONG. That goes for Solo or when Towing.

 

[xtrailman]

Quote of John l post

" Hello Ray,

I have no 'source' as such but it is the result of a logical progression.

All current manufactures and chassis manufacturers know that the EU have specified the height limits to the centre of the tow ball (350 to 420mm for saloon cars) and will have designed their products to accommodate that range. Therefore if a car presents a towball within the EU specification and the attached caravan is nose up then the attitude is one that is acceptable to the caravan manufacturer.

It is perfectly possible for Bailey and Alko to both expect a level or nose down attitude because they will have designed their units to have that characteristic. Thus if one of their units exhibits a nose up attitude, then it is a matter that needs further investigation, and it will almost certainly be the tow vehicle that is none conforming."

So john, you have no source to contradict my post, but you rubbish it anyway?

It is logical to tow level or nose down, as per the manufactures advise i would of thought?

 

[ShadySadie]

Towing with the nose high I felt that the caravan was trying to lift the back of a friends Mitsubishi. Tow ball dropped lower it was like it was a very different and much tamer relaxed drive.

As for speed and stability, on many multi lane roads especially in traffic, other vehicles drivers can't always see obstacles or problems ahead. A little extra speed at the correct moment can prevent trouble for yourself and other drivers.

Heavy braking in traffic or swerving is not always the safe or best option.

 

[Gafferbill]

The aerodynamics of a towed caravan are such that the front will tend to sit down as speed increases and increase the noseweight on the towing hitch.

These are points worth remembering when discussing such precise nose weights and heights

 

[Glenn_5132962]

Bringing this post back on track to help Rob!!

You say you have towed the same unstable van with 2 different towcars & got the same results? That means the van is the problem. If you've checked the obvious such as loading distribution to give you a noseweight just below the limit for your car or hitch (whichever is the lower) & you do not have heavy items at the extreme back or front causing a "dumbell" effect - the tyre pressures are correct etc. My guess is that the van is faulty. I would be checking for play in the wheel bearings, and that the brakes not binding etc. It could be that a prevous owner has damaged the axle (bent it) etc. Look at the tyres for uneven wear. If all of this doesnt get a result I would trade it in for another one. No point going on holiday to relax if the journey home is a white knuckle ride.

 

[Lutz]

Lutz I never realised that caravanners always drove with a van hitched to the car!

Recently we were overtaking a line of lorries approaching the end of a dual carriagway when another smaller lorry pulled out from a farm track. We were left in a difficult position with a car travelling to close to our van with a line of vehicles behind it. Foot down was the only safe option. I believe my wife took the correct action for our safety, the lorries on the inside lane and the vehicles behind us.

With over 300hp we can still pull away quite quickly whatever Lutz might think.

The only really valid part of your post Lutz is re an "Elk Test" scenario. If presented with a scenario where a little extra speed allows you to straight line out of trouble rather than take swerving action when towing that may cause more of a stability problem.

I don't believe that you will get these sittuations every day solo driving or when towing. But JohnL who regularly uses 'NEVER' when mentioning exceeding a speed limit is completely out of touch with good safe driver aware road craft.

I hope that most drivers towing rarely get presented with a dangerous sittuation.

To regularly post that there is NEVER a time when exceeding a speed limit is acceptable is WRONG. That goes for Solo or when Towing.

I think it should have been clear that I was referring to towing a caravan and not the solo condition although I think you will agree that very few of us have 300hp at our disposal. In such a case, accelerating may not be adequate to get out of trouble.

 

[Lutz]

The aerodynamics of a towed caravan are such that the front will tend to sit down as speed increases and increase the noseweight on the towing hitch.

These are points worth remembering when discussing such precise nose weights and heights

Actually, the opposite is true. Noseweight decreases with speed due to the aerodynamic centre of the caravan being so much higher than the axle.

 

[Lutz]

70kg higher MTPLM shouldn't make such a difference between a stable and an unstable outfit. The fact that the layout of the two caravans in question is different suggests that the new one is not well balanced between left and right hand wheel load (probably due to the change in layout). Stability can suffer if the left hand side carries significantly more than the right, or vice versa. It may be worth checking wheel load on a weighbridge, not just the axle load or total weight.

 

[ProfJohnL]

Quote of John l post

" Hello Ray,

I have no 'source' as such but it is the result of a logical progression.

All current manufactures and chassis manufacturers know that the EU have specified the height limits to the centre of the tow ball (350 to 420mm for saloon cars) and will have designed their products to accommodate that range. Therefore if a car presents a towball within the EU specification and the attached caravan is nose up then the attitude is one that is acceptable to the caravan manufacturer.

It is perfectly possible for Bailey and Alko to both expect a level or nose down attitude because they will have designed their units to have that characteristic. Thus if one of their units exhibits a nose up attitude, then it is a matter that needs further investigation, and it will almost certainly be the tow vehicle that is none conforming."

So john, you have no source to contradict my post, but you rubbish it anyway?

It is logical to tow level or nose down, as per the manufactures advise i would of thought?

Ray,

I most certainly have not rubbished your comment or the fact that both Bailey and Alko expect a level or nose down tow. If that is how they have designed their product to conform with the EU regs then so be it.

But why is it logical to tow with the nose down or level or more to the point why is it illogical to tow with the nose up?

There are many camping trailers that are very nose up.

 

[ProfJohnL]

Hello Euro,

Please reference any official document from the police or Govt departments or the IAM, ROSPA or any other official body where speeding by members of the public is condoned or authorised under any circumstances.

If you find yourself in a situation that you think needs speeding to correct it then you should not have placed yourself in that position in the first place.

 

[Guest]

The 'need' to go over a limit is never likely to be an every day regular thing, this constant theme that one will 'NEVER' have a legitimate reason to exceed a speed limit is pie in the sky thinking and advice.

"If you find yourself in a situation that you think needs speeding to correct it then you should not have placed yourself in that position in the first place"

That statement has to be one of the very worst I've ever seen on this forum. No safety or police driving expert in any country would ever deny that the very best of drivers will find their safest of driving practices compromised by another driver or an event beyond their control.

With John's line of thought the driver who hit the armco barrier that bent and twisted out in to his lane due to the high speed impact from another vehicle on the other side of the dual carrigeway should never have been in the lane he was in! He should have known that another vehicle was going to crash in to the armco. Some other drivers who avoided the wrecked car by accelerating out of the way of others should not have been praised by a following police who witnessed the accident. They should've been prosecuted for breaking speed limits and given driver training as they had positioned themselves in the wrong place at the wrong time according to the JohnL rules of driving book.

*******'s

JohnL you may consider yourself a safe driver, with your level of reasoning I hope I am never around you when something goes wrong on the road.

 

[Lutz]

While John L is correct in theory that speed limits must never be exceeded under any circumstances, in practice who is going to check speed exactly at the moment as the driver is accelerating to take avoiding action? The driver will be too pre-occupied with the hazard to give his speed much thought and the chances of being caught by the police just at that instant is pretty remote. The only conceivable problem that one could run into were if the accelerating action were unsuccessful and an accident occurred nevertheless. If the insurance company were able to prove that one exceeded the speed limit at the time of the accident, they could refuse to settle any claim, at least in full.

 

[ShadySadie]

Good drivers react in an instant.

On the A303 near the Weyhill / Andover exit. Passing trucks on lng bend as I was clearing the leading truck to the side. I then saw a large obstacle in my lane, I'd seen a car pull out very close behind my caravan and realised in my position I blocked the truck drivers view of the obstacle ahead in my lane. In split second action aware of traffic around me. I went over 60mph to clear the truck fully and move to the left lane to avoid what turned out to be a very large industrial 3 piece ladder. I hit the hazard light button which is wrong on the move. The car driver got the hint and managed to get in behind me in front of the truck. A large ladder about 5 metres long with a buckled section sticking up at radiator height.

Car behind me should not have been so close to the rear of my outfit, HGV truck to the side with others behind where could I go?

BI and Lutz are both correct, you can not plan driving for a freaky one off. The lorry driver was not happy with my manouvre or the car behind me. Shaken by the close call I pulled in to the next lay by to call the police. The truck pulled in behind me and the driver came and said sorry for his actions (Air horn basting and flashing lights) and thanked me. He had not seen the ladder.

I've seen a coach crowd a caravan on the M4. Coming up so very close to the back of the caravan that it made it snake. With traffic to the inside the frightened caravanner pulled away from the idiot coach driver after the coach kept coming right up to the back of his van.

How was the caravanner to know that an idiot would come and all but push him up the road?

When the coach kept coming back at him after each snaking episode should he seriously have risked an accident?

Or was pulling away to a little over 65mph and getting out of the idiots way not the safest wisest option?

We reported the coach driver to his company and the police.

Rare incidents mean it is very important that our outfits are always stable.

 

[xtrailman]

Shady lady

That's a good post, on both counts.

Dave

I've been playing the bailey stability game, its quite good.

Its a same that different lengths and layouts can't be used.

Yaw appears to be reduced by placing weight in the middle of the van rather than on opposite sides.

Also it seems to contradict itself with the comments about the nose weight. Still its worth playing.

 

[Ianofwilts]

Rob,

Lots of good advice from the others. But in theory if the van weight is within the capacity of the tow car then there must be a simple solution to the problem. My experience with van at nearly 95% of the tow car is the stability is far better if the unit travels level not nose up or down. Nose weight is better heavier without exceeding cars limit. Of course storage also very important.

I would suggest a long winded approach but we are talking safety. Tow the van empty to comfirm the unit is stable without your possesions as it should be nose heavy, then try loading standard permanent kit stored as normal. I have then found with heavier items i.e. awning, suitcases and other stuff in differing positions around the axle its quite easy to load for stability. Its almost impossible to place everything over the axle and low down its a case of trial and error without driving stupidly I think you'll soon sort things out. A thing I think many people forget particularly with a car not 4 x 4 is just how easy it is to exceed your max weight with everything we carry these days. The weight quoted for my van did not include micro wave and aircon unit and they soon eat into your payload and also affact stability to some extent.

 

[extrucker1]

hi rob, what is the distance from your rear wheels to the tow ball? ive found the longer the distance the more exagerated any movment from straight ahead is felt through caravan swaying. allso the ruts in the road can sometimes give you a feeling of a snake. just a thought. raymond h.

 

[eckiew]

Getting back to Rob's post about stability. The centre of gravity dictates the balance of a caravan and can be adjusted when the van is static by the nose weight with the van at the towing height when connected to the towing vehicle. The reason that it is recommended to tow with a slight 'nose down' attitude or level automatically puts the centre of gravity forward of the axle, not the axle tube but a line between the centre of the stub axles. A 'nose up' attitude will put the centre of gravity behind the axle line and reduce the nose weight but this can be acceptable with correct loading of the van. Unfortunately the centre of gravity alters every second that the van is being towed so in some respect internal loading can be trial and error.I believe that Rob's problem may be loading across the van and he could check this by finding the centre of the roof and and the centre of the floor and suspend a plumb bob from the roof (inside) to the floor when the van is loaded to check if it matches the centre of the floor this is with the van connected to the car and checking from the outside. If the result,is ok then I thing the running gear needs to be checked i.e. suspension,toe in,damaged axle and possibly a drop test of the chassis to accertain that is not out of line. But I hope its a bit of loading adjustment.

A message to all the expert drivers,

I have inspected hundreds of accident damaged vehicles professionally and the funny thing is that the faster they had been travlling before impact the more damage was evident after the collision.

The answer to the question 'what action were you taking immediatly before the impact' 'I had my foot hard on the brake' sounds better than 'I had the throttle flat to the floor'

Alex

 

[ProfJohnL]

Hello Alexander,

There is some truth to your explanation about the action of the attitude of a caravan and the relative position of the CoG, there is a flaw.

It is the position of the CoG that generates the nose load. Now if the caravan is set up to create the necessary nose load with the caravan hitched, then the CoG is still forward of the axleline even in the nose up attitude.

 

[Guest]

" I have inspected hundreds of accident damaged vehicles professionally and the funny thing is that the faster they had been travlling before impact the more damage was evident after the collision.

The answer to the question 'what action were you taking immediatly before the impact' 'I had my foot hard on the brake' sounds better than 'I had the throttle flat to the floor' "

I do wonder bout some of the posts on this forum!

For alexander the 'Professional'

I don't think anyone has suggested foot to the floor or fantastic speed. The difference between using a little extra speed at the correct time for a brief extricate from trouble momet can be the difference between the number of vehicles you have examined and the potential numbers that you could have examined if drivers had not avoided those rare but difficult driving moments that could have lead to an impact!

Or are you suggesting in your professional opinion that more of us just crash rather than use good natural instinct and driving skill to avoid problems caused by others

I guess the extra work would benefit you and your colleagues

 

[eckiew]

Hello Alexander,

There is some truth to your explanation about the action of the attitude of a caravan and the relative position of the CoG, there is a flaw.

It is the position of the CoG that generates the nose load. Now if the caravan is set up to create the necessary nose load with the caravan hitched, then the CoG is still forward of the axleline even in the nose up attitude.

Hi John

Yes I am aware of that and I should have added that the van should be loaded as necessary in front of the axle line to give the correct noseweight even with a 'nose up' attitude. I would like to add that rapid acceleration will decrease the nose weight and hard braking will increase the noseweight