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Towing with a Peugeot 3008

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2 hours ago, Paul1957 said:

This is another report from the Bath University studies https://purehost.bath.ac.uk/ws/portalfiles/portal/147993632/JAUTO981.pdf A quick look in the reports suggests the tests were only done to 50 or 55 mph.

 

Interesting that they have shown, reasonably conclusively, that weight ratio is not a major issue in relation to minor oscillations during normal driving .

Pity that they seem to have completely ignored any stabilising effect of the sidewalls of the caravan.

Also a pity that the likes of ATC were not covered. 

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30 minutes ago, Stevan said:

Interesting that they have shown, reasonably conclusively, that weight ratio is not a major issue in relation to minor oscillations during normal driving .

Pity that they seem to have completely ignored any stabilising effect of the sidewalls of the caravan.

Also a pity that the likes of ATC were not covered. 

 

What is the stabilising effect of the sidewalls - or de-stabilising effect of the sidewalls?

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7 minutes ago, Black Grouse said:

 

What is the stabilising effect of the sidewalls - or de-stabilising effect of the sidewalls?

The caravan sidewall clearly affects stability because the driver can usually feel when the bow wave from an HGV or coach pushes against the sidewall of the caravan.  And any aerodynamic forces on such a large surface area when the caravan is at an angle to the car(when a snake is starting) must have an impact, good or bad, on stability.

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I always find that an up/down motion when towing is because the nose weight is wrong. A sway is because the lateral weight distribution is wrong.

 

Check the nose weight, and if at max permissible for the car (which it probably will be near or over as these nose weights for towbars seems to be coming down with every new car.)

 

If it is a sway, then depending on the layout of the van, check the distribution of stuff in the van normally in comparison to which side the kitchen is as this is a major weight which most manufacturers do not counter.

 

For our van which has dinette on one side and the kitchen the other I know that I pack the Dinette side a little more.

 

And why do manufacturers manufacture vans that are inherently unstable from side to side with weight distribution. They are unstable when empty, so if not packing correctly will become even worse. Seeing as the OP said he packs the van as light as possible, it is probable that it this inherent instability of an empty van that is the issue.

Edited by warrenb

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2 hours ago, Stevan said:

Interesting that they have shown, reasonably conclusively, that weight ratio is not a major issue in relation to minor oscillations during normal driving .

 

 

Speed has a much bigger effect to stability from minor oscillations.

 

But the study also shows that a major disturbance that will introduce significant Yaw such as a sudden change of direction in an emergency situation will only be recoverable if you have a sufficient weight advantage in the tow vehicle to control the yaw.

Just now, warrenb said:

And why do manufacturers manufacture vans that are inherently unstable from side to side with weight distribution. They are unstable when emty, so if not packing correctly will become even worse.

 

My caravan empty is very unstable, I thought I'd made a huge mistake when collecting it.

 

The noseweight with nothing in the front locker and just the battery fitted is 30kg. The bed, kitchen, battery, water tank, fridge, and longer front bed are all on the same side,

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11 minutes ago, logiclee said:

 

My caravan empty is very unstable, I thought I'd made a huge mistake when collecting it.

 

 

As did I, but after a few trips and a little jiggling with the load it is fine now.

I don't think we want to let the OP think he has made a major mistake when sometimes it is just a little experimentation that is required.

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2 hours ago, Stevan said:

The caravan sidewall clearly affects stability because the driver can usually feel when the bow wave from an HGV or coach pushes against the sidewall of the caravan.  And any aerodynamic forces on such a large surface area when the caravan is at an angle to the car(when a snake is starting) must have an impact, good or bad, on stability.

 

I agree it has an effect - I'd have thought detrimental though.

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14 minutes ago, warrenb said:

As did I, but after a few trips and a little jiggling with the load it is fine now.

I don't think we want to let the OP think he has made a major mistake when sometimes it is just a little experimentation that is required.

 

My van felt unstable when I collected it and the match then was 67% then. (Jeep Cherokee)

 

I've towed with it with cars since up to 97% loaded correctly and it's very stable. (Mondeo 3.0V6)

 

But does it feel stable is not the big issue with the 85%-100% recommended ratios. It's the ability of the tow vehicle to control the caravan is an unforeseen situation.  If the tow vehicle does not have the mass to dampen the yaw of the caravan in such situations then you will have an accident. 

It's just margins of safety.

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28 minutes ago, warrenb said:

As did I, but after a few trips and a little jiggling with the load it is fine now.

I don't think we want to let the OP think he has made a major mistake when sometimes it is just a little experimentation that is required.

 

The OP appears to have been banned. Maybe the powers that be didn't agree with his opinions.

Annotation 2019-09-11 175557.jpg

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32 minutes ago, logiclee said:

 

 

 

But the study also shows that a major disturbance that will introduce significant Yaw such as a sudden change of direction in an emergency situation will only be recoverable if you have a sufficient weight advantage in the tow vehicle to control the yaw.

 

 

Just where in the report does it actually say that?

 

7 minutes ago, Black Grouse said:

 

I agree it has an effect - I'd have thought detrimental though.

Back to the "I'd have thought" scenario! Exactly what we need to replace with facts.

 

4 minutes ago, logiclee said:

 

 

 

But does it feel stable is not the big issue with the 85%-100% recommended ratios. It's the ability of the tow vehicle to control the caravan is an unforeseen situation.  If the tow vehicle does not have the mass to dampen the yaw of the caravan in such situations then you will have an accident. 

 

That is a theory that has some logic to it, but just how much difference does it actually make? There have been plenty of accidents with heavy car and relatively light caravan spread across several lanes of motorway that suggest not much!

8 minutes ago, caravaningcapers said:

 

The OP appears to have been banned. Maybe the powers that be didn't agree with his opinions.

 

If that were the case there are a few of us who would have banned ages ago!

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7 minutes ago, Stevan said:

Back to the "I'd have thought" scenario! Exactly what we need to replace with facts.

 

 

No different to you suggesting the opposite with no evidence or facts.

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2 minutes ago, Black Grouse said:

 

No different to you suggesting the opposite with no evidence or facts.

My comment (which I admit could have been worded better) was made in the context of bemoaning the fact that they had not investigated this and that we were still short on facts. I have no problem with people producing facts to prove my thinking wrong. 

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Could quite simply be a matter of insufficient noseweight? Due to Baileys odd design of no front locker I’m wondering whether it’s difficult to achieve a sensible  noseweight without loading up the area between the front seats? Just a thought. 

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41 minutes ago, Stevan said:

Just where in the report does it actually say that?

 

 

 

The 2009 study was done it in conjunction with Bailey and the Caravan Club.

 

This was discussed widely at the time.

 

One of the conclusions was that yaw inertia increases with trailer mass and length which anyone with a decent understanding of physics will not be surprised at. So the heavier the trailer the more yaw inertia in an unforeseen situation, mechanical failure or emergency maneuver. 

The tow vehicle has to control this inertia, hence why the caravan club at the time reiterated it's 85-100% recommendations from that report.

 

Of course there are other contributory factors like real axle weight, rear overhang (Leverage), suspension, center of gravity, loading, wheelbase and road friction etc etc but that's why the 85-100% recommendation exists to give a margin of safety. 

 

Of course you can badly load a caravan at 85% and have an accident or have a badly maintained outfit at 85% and have an accident (How many blow outs do we see?) 

 

But as Scotty says "Ye cannae change the laws of physics” If the caravan exerts more force than your car can control then you have an accident.

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14 minutes ago, logiclee said:

 

 

 

One of the conclusions was that yaw inertia increases with trailer mass and length which anyone with a decent understanding of physics will not be surprised at. So the heavier the trailer the more yaw inertia in an unforeseen situation, mechanical failure or emergency maneuver. 

The tow vehicle has to control this inertia, hence why the caravan club at the time reiterated it's 85-100% recommendations from that report.

 

Of course there are other contributory factors like real axle weight, rear overhang (Leverage), suspension, center of gravity, loading, wheelbase and road friction etc etc but that's why the 85-100% recommendation exists to give a margin of safety. 

 

Of course you can badly load a caravan at 85% and have an accident or have a badly maintained outfit at 85% and have an accident (How many blow outs do we see?) 

 

 

I have a basic understanding of the physics and the mathematics involved, but I also have an understanding of risk analysis and risk management.

What perplexes me is that with so many variables involved, only some of which are properly understood, the numbers 85 and 100 can be plucked out of the air, quoted as though they had an empirical basis and then be used by so many people as though they represented a magic key to safe towing.

 

Yes, the mass of the towcar will have a bearing on its ability to control the yaw inertia of a swaying caravan, and its weight will have a bearing on how well its tyres can control the sideways forces generated by caravan wheels which are not pointing straight forwards. But, we have no real idea of the effect of other variables and these issues only come into play after a dangerous sway situation has started. To over emphasise the weight ratio figures  is akin to relying on the crumple zones in a car to provide security for the car occupants rather than focussing on driver ability and good brakes!

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7 minutes ago, Stevan said:

I have a basic understanding of the physics and the mathematics involved, but I also have an understanding of risk analysis and risk management.

What perplexes me is that with so many variables involved, only some of which are properly understood, the numbers 85 and 100 can be plucked out of the air, quoted as though they had an empirical basis and then be used by so many people as though they represented a magic key to safe towing.

 

Yes, the mass of the towcar will have a bearing on its ability to control the yaw inertia of a swaying caravan, and its weight will have a bearing on how well its tyres can control the sideways forces generated by caravan wheels which are not pointing straight forwards. But, we have no real idea of the effect of other variables and these issues only come into play after a dangerous sway situation has started. To over emphasise the weight ratio figures  is akin to relying on the crumple zones in a car to provide security for the car occupants rather than focussing on driver ability and good brakes!

 

The Germans apply lower speed limits to caravans over 100% so the UK's NCC Towing Ratio guidance isn't that far off the mark.

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5 hours ago, logiclee said:

My caravan empty is very unstable, I thought I'd made a huge mistake when collecting it.

 

Mine too, I’m reminded of this every time it goes in for a service, with my car unladen and the van largely empty it definitely doesn’t feel anywhere near as happy as when loaded. Being a Bailey it may be too light on the nose when empty and that’s what causes it.

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10 hours ago, FrankBullet said:

 

Mine too, I’m reminded of this every time it goes in for a service, with my car unladen and the van largely empty it definitely doesn’t feel anywhere near as happy as when loaded. Being a Bailey it may be too light on the nose when empty and that’s what causes it.

 

In general, it doesn't matter what the empty noseweight is, what matters is the laden noseweight - the one exception being when towing empty on delivery or for service/repair.

 

Sadly, we've allowed ourselves to be brain-washed to thinking that low noseweight percentages are ok when the reality of stability is that the higher the noseweight the better - car makers have no problem building versions with much higher noseweight limits to sell in Australia and North America where a 10% noseweight is regarded as minimum but European car buyers are content to accept the meagre limits we get here, the EU minimum of 4% often being all you get.

 

There is an urban myth that 5-7% is optimum - that's not optimum, that's all that's possible - 8-10% or more would be better, more stable, so 7% just isn't "optimum".

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9 minutes ago, Black Grouse said:

 

In general, it doesn't matter what the empty noseweight is, what matters is the laden noseweight - the one exception being when towing empty on delivery or for service/repair.

 

Sadly, we've allowed ourselves to be brain-washed to thinking that low noseweight percentages are ok when the reality of stability is that the higher the noseweight the better - car makers have no problem building versions with much higher noseweight limits to sell in Australia and North America where a 10% noseweight is regarded as minimum but European car buyers are content to accept the meagre limits we get here, the EU minimum of 4% often being all you get.

 

There is an urban myth that 5-7% is optimum - that's not optimum, that's all that's possible - 8-10% or more would be better, more stable, so 7% just isn't "optimum".

 

Not only car manufacturers. 

 

At 10% most family vans with an MTPLM of around 1500kg MTPLM would require a 150kg nose weight yet most UK vans will have a hitch rating of 100kg meaning even 7% is not achievable.

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42 minutes ago, Black Grouse said:

 

 

 

Sadly, we've allowed ourselves to be brain-washed to thinking that low noseweight percentages are ok when the reality of stability is that the higher the noseweight the better - car makers have no problem building versions with much higher noseweight limits to sell in Australia and North America where a 10% noseweight is regarded as minimum but European car buyers are content to accept the meagre limits we get here, the EU minimum of 4% often being all you get.

 

 

Very annoying! My car has an 80Kg noseweight limit shown in the handbook but a 2,000Kg towing limit (bang on 4%!).

The Australian and American spec versions have a limit of 150Kg! And even the towbar is rated at 150Kg.

So far as I am aware they have the same chassis and same self levelling rear suspension, but I am hesitant to use the extra 70Kg without being certain. 

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Australian and American noseweight and towing limits are determined differently to the way manufacturers do it in Europe so their figures aren't directly comparable.

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I have towed our caravans with 6 different cars and found the heavier and more power/torque the cars got the better they towed. The worst car was a Xsara Picasso 2.0 hdi, 90 hp, mass in service 1300 kg, caravan about 1100 kg when towed but MTPLM 1300 kg, so on paper the weights were ok. I only used it once since it felt as if the caravan was trying to push the car off the road so had to keep the speed down on the flat and it was slow up hills anyway due to lack of power/torque. Stability against snaking was not a problem since I was not going fast enough although it looks as if the studies only seem to be looking at snaking.

Edited by Paul1957

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24 minutes ago, Paul1957 said:

I have towed our caravans with 6 different cars and found the heavier and more power/torque the cars got the better they towed. The worst car was a Xsara Picasso 2.0 hdi, 90 hp, mass in service 1300 kg, caravan about 1100 kg when towed but MTPLM 1300 kg, so on paper the weights were ok. I only used it once since it felt as if the caravan was trying to push the car off the road so had to keep the speed down on the flat and it was slow up hills anyway due to lack of power/torque. Stability against snaking was not a problem since I was not going fast enough although it looks as if the studies only seem to be looking at snaking.

I have no doubt that, all other things being equal, a car with more weight, power and torque will provide a more comfortable and relaxed towing experience. Quite what effect this has on stability is contentious.

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32 minutes ago, Stevan said:

I have no doubt that, all other things being equal, a car with more weight, power and torque will provide a more comfortable and relaxed towing experience. Quite what effect this has on stability is contentious.

 

"more weight" isn't contentious - it will improve stability, all other things being equal - quantifying that improvement may be difficult, impossible even, but an improvement it will be.

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57 minutes ago, Paul1957 said:

The worst car was a Xsara Picasso 2.0 hdi, 90 hp, mass in service 1300 kg, caravan about 1100 kg when towed but MTPLM 1300 kg, so on paper the weights were ok.

 

You chose the lowest powered engine for your Picasso - the code RHY .   You could have had the RHZ which would have been the 110hp version producing 191lbs/ft against your 157lbs/ft.     Although yours is an early version of the present PSA DW family, many Citroen/Puegeot mechanics think it was better than the later 16-valve.

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