Height has more to do with the "centre of gravity" with regards to rolling over.
Knight said
12:03 PM Aug 11, 2019
An interesting observation post is alongside a busy boat ramp where a majority of weekend fishermen struggle to launch and retrieve their boats, after battling the vehicle steering wheel to reverse down the boat ramp.
iana said
12:22 PM Aug 11, 2019
Maybe we should be fitting aerofoil wings to the back of our vans to keep it down at high speeds :), this thread is getting better every minute.
Do some think you can drive with van on the back like its not there ? From
my observation plenty do !! But its the vans fault ! Pfft Right !! Yea not just boat ramps . Some drive interstate and cant reverse park their van into position . So how did they drive 2 to 10,000 klrs to get there ??
Tony Bev said
12:59 PM Aug 11, 2019
I have just read the article, (by Collyn Rivers), put up by Peter (Peter n Margaret)
And it describes why the typical caravan independent suspension that is becoming fashionable, is about the worst choice available in terms of caravan stability.
There is certainly a need to improve the terrible leaf spring suspensions traditionally fitted to caravans, but independent suspension is not the way to address that, in my view. It is better addressed by using decent, longer travel leaf springs which are simple, rugged and cheap.
Independent suspension itself does nothing of value for a caravan. Problem is that those who have it love it but that is because they compare it to about the worst leaf spring designs available.
Cheers,
Peter
Aus-Kiwi said
03:56 PM Aug 11, 2019
Yes . Fitting shocks PROPERLY to leaf suspension also . Should be fitted but everythings built to price !!
SouthernComfort said
04:02 PM Aug 11, 2019
Knight wrote:
Colin Penrose wrote:
That is what I thought. If you have a lot of clearance underneath the wind can lift the van more easily ???
The greater the ground clearance the poorer the road holding worsening the higher the speed.
My view exactly. Higher ground clearance = higher overall height = higher centre of gravity = less stability. Entirely logical when you consider that F1 racing cars are the polar opposite, designed with minimal ground clearance and CG for maximum stability at hyper speeds and maneouvers.
Heavy full height o/r vans are about as aerodynamically inefficient as it gets. I reckon the only answer is to finely tune the load balance (vertical and horizontal) and travel at much lower speeds. Adding wings and other band aids (ESC excepted) will not compensate.
Aus-Kiwi said
04:36 PM Aug 11, 2019
Its not a race !! Sheesh !!
Peter_n_Margaret said
04:42 PM Aug 11, 2019
Aus-Kiwi wrote:
Yes . Fitting shocks PROPERLY to leaf suspension also . Should be fitted but everythings built to price !!
Dampers are a very valuable addition to leaf spring suspensions but are absolutely essential for coils, parabolic leaves and torsion bars which have zero self damping and will go "out of control" if the dampers fail and they are more likely to do so because of the much higher work load they have on those spring designs.
Cheers,
Peter
Whenarewethere said
05:41 PM Aug 11, 2019
iana wrote:
Maybe we should be fitting aerofoil wings to the back of our vans to keep it down at high speeds :), this thread is getting better every minute.
My relatives in Germany, their setup is frightening to put it mildly. I won't say how fast they drive other than over twice the fuel consumption than they ought to be using!
Peter_n_Margaret said
06:27 PM Aug 11, 2019
I have Dutch friends who have this 10m caravan (32feet?) and they tow it at speeds up to 130kph behind their Porsche. German built. Its total weight on the road is about 2.5T 10% ball weight? I don't think so!
There are some short videos clips on these & it would bring tears to your eyes to say the least! Land Rover have them as well.
Discovery Sports motorised tow bar:
https://m.youtube.com/watch?v=KTbJjZvq5jE
-- Edited by Whenarewethere on Sunday 11th of August 2019 08:20:21 PM
Long Weekend said
08:34 PM Aug 11, 2019
I note that the two dash cam examples shown in the rvbooks site mentioned by Tony Bev occurred during overtaking on straight and level roads. In both cases the sway begins just as they clear the vehicle on the left. Also, without knowing the actual make of the tow vehicle to me they look to be on the small size.
A roll over on the national news last week also occurred after overtaking.
Something to think about.
Murray
Noelpolar said
09:10 PM Aug 11, 2019
High clearance... is great... when you need to get under your van to do something. Independant suspension is great.... when you need to move forward or backwards whilst under your high clearance van doing something.
Towing a van at 130kph in Australia... well.... good luck with that says the roo, emu, eagle with a full belly etc.
-- Edited by Noelpolar on Sunday 11th of August 2019 09:11:18 PM
-- Edited by Noelpolar on Sunday 11th of August 2019 09:14:26 PM
yobarr said
07:57 AM Aug 12, 2019
Colin Penrose wrote:
Hi all. This is just my observation but I thought that I would put it out there. I have been taking an extra close look at all the caravan rollovers over the past year or two. I think all of them look like tandem off road vans of over 20 in length. Which brings me to think that there is either a problem with these huge heavy vans or a problem with the way they are being towed ???? The last one was obviously a very large van and once it started swaying the poor people had no hope stopping it. I dont Know the answer but I am just putting it out there. I pull a 16 pop top and so far I have never had a sway or anything untoward. I do always drive to the conditions but some of these rollovers seam to be on straight roads in good weather.
Just a thought to start, hopefully, a respectful discussion. Any useful suggestions for how to tow these very large vans.
Cheers Col
Hi Colin...you have received many and varied replies to your questions,but I have been sitting back in the hope that someone would mention axle-steer,which is present on all suspension types except the Coromal wish-bone system.Perhaps this post will provide food for thought? Cheers.
iana said
08:12 AM Aug 12, 2019
Well our van is 8.8 meters long, and has been made with, according to the experts on here, everything wrong. We have thousands of K's left to travel, but according to these posts we won't make it. But we travel slowly and rarely pass vehicles. Only done about 20,000km so far and it tows perfectly, never had a severe wobble, and any effect felt is from a side wind. So you had better say a prayer for us.
But speed and impatience I think are the dominating factors, followed by those who mount huge loads at the extremities.
I saw one that had so much on the back he had a crane mounted there as well, others three spares, water and fuel, they all passed me going flat out.
Knight said
08:47 AM Aug 12, 2019
I once had a Jaco single axle small caravan with leaf springs and had a double shock absorber each side kit fitted, it made a big difference, most noticeable driving over cattle grids but generally on imperfect road surfaces.
-- Edited by Knight on Monday 12th of August 2019 08:48:20 AM
Peter_n_Margaret said
09:25 AM Aug 12, 2019
iana wrote:
Only done about 20,000km so far and it tows perfectly, never had a severe wobble, and any effect felt is from a side wind.
That rarely understood by caravan owners is that their rig may feel ultra-stable in normal driving.
...... it tows perfectly, never had a severe wobble, and any effect felt is from a side wind.
I think most survivors of a van rollover say something along those lines.
Most of experts say that all combinations have a critical speed above which disaster is inevitable. As you say you do, driving slowly and not attempting overtaking at high speed is likely to be the best way to avoid finding out how fast is too fast.
Iza
8RAR Nasho said
10:15 AM Aug 12, 2019
In my humble opinion, many road accidents, including those involving caravans, are caused by stupidity which is manifested in many ways. The principle of driving within the limits dictated by experience, road conditions and vehicle capability seems to either be unrecognized or ignored by people sometimes, causing them to exceed one or all of the safety limitations. Towing a 12 month old caravan with ESC and sitting on what I consider to be a safe highway speed of 90kms/h we are often passed by other vehicles towing vans at what must be well over the speed limit, some of which appear to be too heavy for the towing vehicle. It's all very well to be charging along at high speed or with an overloaded van UNTIL something goes wrong and then it's usually too late, sometimes leading to tragedy. For instance, recently people were killed in a caravan rollover involving a 120 series Prado tow vehicle. 120 Prados have a maximum allowable towing capacity of 2.5 tonnes and weigh 2.6 tonnes, makes sense, so Prado plus van 5.1 tonnes max. The police collected everything from this particular accident and put it on a weighbridge. I live near where that accident occurred and I was told by a person who I believe knows the facts that the total weight was in excess of 7 tonnes and the driver now faces several very serious charges. Whether this was ignorance or blatant disobedience of the parameters, people lost their lives and others will probably never recover from a horrendous event.
When people talk about driving courses for caravan owners I believe those courses should focus on the technical aspects of loading the caravan safely, towing speeds, reading road conditions,the ratio of van to tow vehicle including the results of using weight distribution hitches as a band aid solution to an incorrectly set up rig, in other words, avoiding getting into trouble rather than getting out of it. Drivers who have never encountered an emergency situation can live in a dream world where they imagine they can skillfully operate their vehicle to save the day when, believe me, when the crap hits the fan it's a lot more difficult than they can ever imagine. The table below gives the time in minutes taken to cover distances in kms at 80,90,100 and 110ks/h. Sure, over a journey of 300ks you save an 27 minutes by travelling at 120ks/h instead of 90 BUT the exponential increase in danger level you would think would not be worth the risk. Still...............you see it. Anyway, food for thought.
Distance travelled Time to arrive 80ks Time to arrive 90ks Time to arrive 100ks Time to arrive 110ks
100 75.00 66.67 60.00 54.55
200 150.00 133.33 120.00 109.09
300 225.00 200.00 180.00 163.64
400 300.00 266.67 240.00 218.18
500 375.00 333.33 300.00 272.73
600 450.00 400.00 360.00 327.27
Jaahn said
01:37 PM Aug 12, 2019
Peter_n_Margaret wrote:
And it describes why the typical caravan independent suspension that is becoming fashionable, is about the worst choice available in terms of caravan stability.
There is certainly a need to improve the terrible leaf spring suspensions traditionally fitted to caravans, but independent suspension is not the way to address that, in my view. It is better addressed by using decent, longer travel leaf springs which are simple, rugged and cheap.
Independent suspension itself does nothing of value for a caravan. Problem is that those who have it love it but that is because they compare it to about the worst leaf spring designs available.
Cheers,Peter
Hi
I do agree with improved suspensions. Any quick read of suspension design will see that short stiff leaf springs with a big camber is not good. Just look at any leaf spring fitted under a ute or even light trucks will show that their springs are much better designed. The main spring eye is located at about same level as the designed axle height so the axle does minimal steering during suspension movement. This design feature seems to have been overlooked by all caravan manufacturers. Cost I guess to save $10 each !! But the fancy cupboard handle take a lot of time and planning. And shockies will help too under sudden dynamic movements. These two things could be the saviour when a truck goes past or similar provokation.
But the crap designed independent systems offered again seem to be designed by people who have never looked at the theory either. So they ride well on bumps ! Perhaps that is not all we expect from our cars and tugs so why buy them for your caravans.
Jaahn
SouthernComfort said
01:56 PM Aug 12, 2019
Noelpolar wrote:
High clearance... is great... when you need to get under your van to do something. Independant suspension is great.... when you need to move forward or backwards whilst under your high clearance van doing something.
Towing a van at 130kph in Australia... well.... good luck with that says the roo, emu, eagle with a full belly etc.
-- Edited by Noelpolar on Sunday 11th of August 2019 09:11:18 PM
-- Edited by Noelpolar on Sunday 11th of August 2019 09:14:26 PM
True. Can't compare European conditions with ours. Apart from the wildlife, Euro roads are much better surfaced, even in country areas. Fewer bumps or pot holes and the absence of soft shoulders also create less hazard. Also notice that most Euro vans (even full height ones) have a low centre of gravity, they're very low slung as well as lighter weight. The only times they can tow at 130kph plus is on motorways where keeping up with inherently fast traffic is a matter of survival. Still, I wouldn't want to tow at that speed. I've driven over there many times (not towing) and learnt quickly that on motorways your speed has to be increased to equal that of the next lane before you change, otherwise they're glued to your arse with headlights flashing in an instant. If towing I'd sooner stay planted in the inside lane! The other thing you never see in Europe is the likes of our ungainly high riding off-road vans.
Olive Oil said
02:22 PM Aug 12, 2019
SouthernComfort wrote: The other thing you never see in Europe is the likes of our ungainly high riding off-road vans.
Totally agree, on our 6 week UK trip all we saw were lots of ''Euro style caravans'' that most Australians call rubbish, (they're not).
They were overtaking us on the motorways doing 70mph.
Not a big heavy high riding caravan to be seen.
Knight said
03:50 PM Aug 12, 2019
A mate of mine had a 5.5 metre half cabin fishing boat on a dual axle trailer that he towed with a Ford Falcon Station Wagon. When driving at 80 KMH or over, which he avoided doing, the sway was noticeable from the trailer.
I had a different design 5.5 metre half cabin boat also on a dual axle trailer of similar weight that I towed with a Mitsubishi Pajero V6, and could travel interstate at the posted highway speed limits without any sign of swaying or other issue.
Obviously the weight difference between tow vehicle and trailer makes a big difference. In my opinion it is best to not tow to the maximum allowable weight.
The Falcon had a 2.3 tonne rated capacity and the Pajero 2.5 tonnes and both boat and trailer weighed 1.8 tonnes with fuel tank filled. But the Pajero weighed about 500 Kg more than the Falcon.
-- Edited by Knight on Monday 12th of August 2019 03:52:47 PM
-- Edited by Knight on Monday 12th of August 2019 03:53:45 PM
Height has more to do with the "centre of gravity" with regards to rolling over.
www.exploroz.com/Vehicle/Caravans/Caravan_Dynamics.aspx
my observation plenty do !! But its the vans fault ! Pfft Right !! Yea not just boat ramps . Some drive interstate and cant reverse park their van into position . So how did they drive 2 to 10,000 klrs to get there ??
I have just read the article, (by Collyn Rivers), put up by Peter (Peter n Margaret)
https://www.rvbooks.com.au/page/why-caravans-sway/
I take note (if I had read it correctly), that Collyn Rivers says that over 250 caravans overturned in the first six month of 2018
He then goes on to say that excess speed is always a major factor
I take this as coming from the horses mouth
It would still be handy to know, if certain brands/sizes/weights/heights of caravans, are more easily overturned
This may not be such a bad idea, as more speed would mean more down force, which would mean more fuel used, which may slow some people down
And it describes why the typical caravan independent suspension that is becoming fashionable, is about the worst choice available in terms of caravan stability.
There is certainly a need to improve the terrible leaf spring suspensions traditionally fitted to caravans, but independent suspension is not the way to address that, in my view. It is better addressed by using decent, longer travel leaf springs which are simple, rugged and cheap.
Independent suspension itself does nothing of value for a caravan. Problem is that those who have it love it but that is because they compare it to about the worst leaf spring designs available.
Cheers,
Peter
My view exactly. Higher ground clearance = higher overall height = higher centre of gravity = less stability. Entirely logical when you consider that F1 racing cars are the polar opposite, designed with minimal ground clearance and CG for maximum stability at hyper speeds and maneouvers.
Heavy full height o/r vans are about as aerodynamically inefficient as it gets. I reckon the only answer is to finely tune the load balance (vertical and horizontal) and travel at much lower speeds. Adding wings and other band aids (ESC excepted) will not compensate.
Dampers are a very valuable addition to leaf spring suspensions but are absolutely essential for coils, parabolic leaves and torsion bars which have zero self damping and will go "out of control" if the dampers fail and they are more likely to do so because of the much higher work load they have on those spring designs.
Cheers,
Peter
My relatives in Germany, their setup is frightening to put it mildly. I won't say how fast they drive other than over twice the fuel consumption than they ought to be using!
I have Dutch friends who have this 10m caravan (32feet?) and they tow it at speeds up to 130kph behind their Porsche.
German built. Its total weight on the road is about 2.5T
10% ball weight? I don't think so!
Cheers,
Peter
Where is his tow ball ?
Good question.
There is a button in the boot...
Cheers,
Peter
There are some short videos clips on these & it would bring tears to your eyes to say the least! Land Rover have them as well.
Discovery Sports motorised tow bar:
https://m.youtube.com/watch?v=KTbJjZvq5jE
-- Edited by Whenarewethere on Sunday 11th of August 2019 08:20:21 PM
A roll over on the national news last week also occurred after overtaking.
Something to think about.
Murray
High clearance... is great... when you need to get under your van to do something. Independant suspension is great.... when you need to move forward or backwards whilst under your high clearance van doing something.
Towing a van at 130kph in Australia... well.... good luck with that says the roo, emu, eagle with a full belly etc.
-- Edited by Noelpolar on Sunday 11th of August 2019 09:11:18 PM
-- Edited by Noelpolar on Sunday 11th of August 2019 09:14:26 PM
Hi Colin...you have received many and varied replies to your questions,but I have been sitting back in the hope that someone would mention axle-steer,which is present on all suspension types except the Coromal wish-bone system.Perhaps this post will provide food for thought? Cheers.
But speed and impatience I think are the dominating factors, followed by those who mount huge loads at the extremities.
I saw one that had so much on the back he had a crane mounted there as well, others three spares, water and fuel, they all passed me going flat out.
I once had a Jaco single axle small caravan with leaf springs and had a double shock absorber each side kit fitted, it made a big difference, most noticeable driving over cattle grids but generally on imperfect road surfaces.
-- Edited by Knight on Monday 12th of August 2019 08:48:20 AM
https://www.rvbooks.com.au/page/why-caravans-sway/
Cheers,
Peter
I think most survivors of a van rollover say something along those lines.
Most of experts say that all combinations have a critical speed above which disaster is inevitable. As you say you do, driving slowly and not attempting overtaking at high speed is likely to be the best way to avoid finding out how fast is too fast.
Iza
When people talk about driving courses for caravan owners I believe those courses should focus on the technical aspects of loading the caravan safely, towing speeds, reading road conditions,the ratio of van to tow vehicle including the results of using weight distribution hitches as a band aid solution to an incorrectly set up rig, in other words, avoiding getting into trouble rather than getting out of it. Drivers who have never encountered an emergency situation can live in a dream world where they imagine they can skillfully operate their vehicle to save the day when, believe me, when the crap hits the fan it's a lot more difficult than they can ever imagine. The table below gives the time in minutes taken to cover distances in kms at 80,90,100 and 110ks/h. Sure, over a journey of 300ks you save an 27 minutes by travelling at 120ks/h instead of 90 BUT the exponential increase in danger level you would think would not be worth the risk. Still...............you see it. Anyway, food for thought.
Distance travelled Time to arrive 80ks Time to arrive 90ks Time to arrive 100ks Time to arrive 110ks
100 75.00 66.67 60.00 54.55
200 150.00 133.33 120.00 109.09
300 225.00 200.00 180.00 163.64
400 300.00 266.67 240.00 218.18
500 375.00 333.33 300.00 272.73
600 450.00 400.00 360.00 327.27
Hi
I do agree with improved suspensions. Any quick read of suspension design will see that short stiff leaf springs with a big camber is not good. Just look at any leaf spring fitted under a ute or even light trucks will show that their springs are much better designed. The main spring eye is located at about same level as the designed axle height so the axle does minimal steering during suspension movement. This design feature seems to have been overlooked by all caravan manufacturers. Cost I guess to save $10 each !! But the fancy cupboard handle take a lot of time and planning. And shockies will help too under sudden dynamic movements. These two things could be the saviour when a truck goes past or similar provokation.
But the crap designed independent systems offered again seem to be designed by people who have never looked at the theory either. So they ride well on bumps ! Perhaps that is not all we expect from our cars and tugs so why buy them for your caravans.
Jaahn
True. Can't compare European conditions with ours. Apart from the wildlife, Euro roads are much better surfaced, even in country areas. Fewer bumps or pot holes and the absence of soft shoulders also create less hazard. Also notice that most Euro vans (even full height ones) have a low centre of gravity, they're very low slung as well as lighter weight. The only times they can tow at 130kph plus is on motorways where keeping up with inherently fast traffic is a matter of survival. Still, I wouldn't want to tow at that speed. I've driven over there many times (not towing) and learnt quickly that on motorways your speed has to be increased to equal that of the next lane before you change, otherwise they're glued to your arse with headlights flashing in an instant. If towing I'd sooner stay planted in the inside lane! The other thing you never see in Europe is the likes of our ungainly high riding off-road vans.
Totally agree, on our 6 week UK trip all we saw were lots of ''Euro style caravans'' that most Australians call rubbish, (they're not).
They were overtaking us on the motorways doing 70mph.
Not a big heavy high riding caravan to be seen.
A mate of mine had a 5.5 metre half cabin fishing boat on a dual axle trailer that he towed with a Ford Falcon Station Wagon. When driving at 80 KMH or over, which he avoided doing, the sway was noticeable from the trailer.
I had a different design 5.5 metre half cabin boat also on a dual axle trailer of similar weight that I towed with a Mitsubishi Pajero V6, and could travel interstate at the posted highway speed limits without any sign of swaying or other issue.
Obviously the weight difference between tow vehicle and trailer makes a big difference. In my opinion it is best to not tow to the maximum allowable weight.
The Falcon had a 2.3 tonne rated capacity and the Pajero 2.5 tonnes and both boat and trailer weighed 1.8 tonnes with fuel tank filled. But the Pajero weighed about 500 Kg more than the Falcon.
-- Edited by Knight on Monday 12th of August 2019 03:52:47 PM
-- Edited by Knight on Monday 12th of August 2019 03:53:45 PM