<span class="highlight">Caravan</span> Rollovers

Doug, that's an amazing piece of video. That 'van is well built, usually they explode when they hit the deck on their side.

The video shows a classic example of poor 'van design by way of weight distribution though. The axle is dead central, the overhang behind the axle is enormous, and I'll wager the van was loaded with too much weight in the tail, acting as a huge pendulum.

All that's needed then, is speed (overtaking) to accelerate the tailwag - and once it starts whipping, there's very little you can do to control it, no matter how good your vehicle control skills are.
A tailwag nearly always ends in disaster.

The way to avoid it, is to load heavy items forward of the axle, pick a van design that has the axle/s moved rearwards from the centre (this makes only a small difference to towbar weight), and utilise heavy wall or low profile tyres on the van to reduce rim sideways movement in relation to the road.

Having a tow vehicle that is adequate weight is also pretty important. There's a lot of people towing vans that are too big for their tow vehicles.

I once saw an amazing set of caravan skid marks, back around 1981, on the downhill run to the Phillips River bridge on the South Coastal Hwy, West of Ravensthorpe.

The river is in a huge valley and the highway runs steeply downhill for about a kilometre each side of the bridge.
This set of caravan broadside skid marks started about halfway down the hill, and went back and forth across the whole width of the highway, for more than half a kilometre!

He/she managed to recover and pull out of the tailwag near the bottom of the hill, where the skid marks reduced in intensity and eventually straightened up.

I reckon there would have been a substantial change of underwear somewhere up the road, right after that performance!

Cheers, Ron.

Thanks Ron, yes the Axle is in the center , also note it's a single axle , for a van of that size it should have been a tandem, and as we both know and agree set back from center, another advantage is the further back the axles are it makes reversing easier.

For those who like mathematics and physics, here's an interesting link.

You may need to change your java security in your java control panel to add the page to a whitelist.

If you use the Next and Previous buttons to access different demonstrations, each page will have to be added to the whitelist.

Cheers

I hasten to add that the maths are beyond me but after reading the Collyn Rivers links that Nomadic Navara posted, playing with the parameters and moving the square block to simulate a swerving tug is interesting.Well, for me anyway :-)

Doug, what I find interesting in that dashcam video is how ambitious the tug driver was. I'm presuming the truck was sitting on his 100 limiter, so how fast was the tug/van going? And I'd suggest the van also outweighed the tug.

G'day Zippo
It's makes no difference as to the speed of the truck, as an ex truckie I got to learn that if they have a truck in front they have to overtake it.....regardless.

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Yes Doug, so it seems.

Having driven all sorts and sizes of vehicles over some fifty years (but only towed vans for a matter of weeks) I still hold firmly to the view that there needs to be a licence class (or endorsement) for towing vans.

And having seen some of the antics of people trying to reverse common box trailers, maybe they should be included in an endorsement.

Back to FollowUp 1 - "The video shows a classic example of poor 'van design by way of weight distribution though. The axle is dead central, the overhang behind the axle is enormous, and I'll wager the van was loaded with too much weight in the tail, acting as a huge pendulum."

The position of the axle is not arbitrary. If you shift it back willy-nilly you will throw too much weight on the coupling. Take another look at the video and note the side windows. The size of them indicates that there is no kitchen along the side. It will be a front kitchen van. Front kitchen vans need the axle in the centre so the ball weight is within limits. This is a classic example of why you should not have large weights at the ends of the vans.

Vans with weight concentrated at the ends have lower critical speeds than those with the weight concentrated in the centre (centre kitchen.) The critical speed of the van is the speed where if you are travelling at that speed or faster you will not be able to control the van if it becomes upset. Long heavy vans may feel stable as they are hard to make snake due to the large yaw inertia of their heavy ends. These vans may feel stable but they are not really. If you are travelling above the critical speed you will be in strife if the something upsets your van. One of the problems with the large vans is no one knows what the critical speed is, no one has tested Oz vans like they have the European vans. Some suspect that the critical speed of large vans is well below the posted speed limits. This is borne out with the number of roll overs where the driver states something like "I don't know what happened, everything was travelling smoothly when suddenly things got out of hand. I don't know what happened."

That video demonstrates what happens when the critical speed is exceeded. There is no chance of holding it. Things are perfectly "stable" until something like the bow wave of a large truck upsets the rig.

Nomadic Navara.
I see you are trying to explain all about critical speed for towing Vans , I think this link explains all about critical speeds, and when not to overtake and ...when not to overtake

LINK

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Good God, Doug! - That video reminds me of the late Thursday afternoon before the Easter Holidays, on any major highway leading out of a capital city in Australia!! [;-)

Cheers, Ron.

"And having seen some of the antics of people trying to reverse common box trailers, maybe they should be included in an endorsement"
Think you might find that if you can back a 6by4 trailer Ok you can back most things.
Dave.

David, I must admit to having anything from a wry smile to almost falling down LMAO at some reversing efforts I have seen. I can back caravans and trailers (box and car). My concern is those who can't, but are still allowed to drag them all over the countryside. Surely a licence test and endorsement would make for a better place for all of us.

Yes Ron, I think you got it right mate , Easter on the Albany Hwy.

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