I did a mock caravan detach,this was done in my own back yard,I unhooked the van off the 4wd and used a 4wheel jack,the chains were crossed as supposed to be ,here's the test ,I lowered the jack as if the van had come off the4wd the first thing I noticed was as the van was being lowered the chains are lowering at the same time the van is,now the van A frame is on the ground sitting in the crossed chains witch are on the ground as well , ok the first thing to do is shorten the chains,witch i did ,the chains being at that length lower the a frame again the a frame sits in the crossed chains and don't touch the ground great that's what they are supposed to do ,ok then I hook the van onto the 4wd I do a turn test that's when this great theory of crossing chains becomes CRAP,when your chains are short enough to catch the van A frame you can't turn your vehicle in a manner where it is safe ,this theory does not work ,to have the chains so you can turn your vehicle will not stop your van a frame from hitting the ground,if you can explain to me how it can be done I would love to know.
I agree Lance - my Avan has 2 chains which when crossed whichever way you like still allow the A frame to hit the ground when given enough slack to turn. Many vans only have one chain so the problem is worse with them. If the same happened with a tandem wouldn't the same thing happen? So I'd imagine if the A frame detached, it would simply dig into the bitumen, snap the chains and then.........
Don't know if any of this will help , When connecting the van to tug , you must have at least one chain ( except where there is a breakaway systems used)which should hold the van off the ground. If over 2.5 tonnes , you must cross the vans safety chains UP and OVER the hitch. This will help A frame from striking ground should things go wrong. You may need to lengthen the chains to get it right..If only using one chain it must not be crossed or it will cause the unhitched van to veer to one side.,Shackles should be rated to handle the load being towed and done up only finger tight.
Only two States have a legal requirement for chains to be crossed when two chains are fitted. NSW & WA. And then it's only for vehicles registered in those States. Chees, Ozjohn.
-- Edited by ozjohn on Sunday 14th of April 2013 02:06:13 PM
__________________
Retired Engineer, Ex Park Owner & Caravan Consultant. Holden 2.8 Colorado - Roma Elegance 17'6" Pop Top. Location: Mornington Peninsula Vic.
herbie wrote:Don't know if any of this will help , When connecting the van to tug , you must have at least one chain ( except where there is a breakaway systems used)which should hold the van off the ground. If over 2.5 tonnes , you must cross the vans safety chains UP and OVER the hitch. This will help A frame from striking ground should things go wrong. You may need to lengthen the chains to get it right..If only using one chain it must not be crossed or it will cause the unhitched van to veer to one side.,Shackles should be rated to handle the load being towed and done up only finger tight.
I always cross my chains but under the hitch.
I assumed that the idea (but not tested by me) is that the crossed chains act as a cradle to catch the leading end of the A frame.
Have never seen or considered going up and over the hitch. Must give it a try ... I expect that I'll need to extend the chains somewhat. Need to think about the impact on turning etc too.
Although I've not tried it on my tandem axel van, I thought that the hitch won't go right down to the ground. I'll try that too & let you know.
Hi Every body, this is Banglabill and this is my first post.
The unthinkable happened to me over Easter, my caravan broke away from the Prado but the safety chains were attached and did hold it in position long enough for me to slow the vehicle with out using the foot brakes, I say that because I have the caravan brakes set to come on a second or so before the vehicle brakes come on in the Prado, (I use a redarc brake controler)
I do not have the chains crossed because as far as I can see apart from restricting your turning circle it does not make any difference to how they perform.The chains are rated as are the shackles.
What I believe saved me was I had welded a skid plate on the extreme front of the two A frame chassis rails, (under the tow hitch) and the chassis did hit the ground but because of the skid plate the chassis did not dig into the road like a plough.
so a couple of hours later the van was on the back of a tilt tray, and the only damage sustained to the van was a broken tow hitch which I replaced in 30mins by bolting on a new one (4 bolts)
Wow Banglabill, that must have been one very frightening experience. Welding a skid plate to the A frame is a great idea, shame it is not done when manufactured.
We have a breakaway system as well as the chains, I don't remember Les ever crossing them, but if the A frame were dropped off the tow bar, being a 4WD, it wouldn't hit the ground. The chains are loose enough to allow turning, but not long enough to drop to the ground. We have tried this with our trailer, and even have it happen once and it never touched the ground. I think I'd worry more the chains would break, than drag.
I guess it depends how high your tow assembly is off the ground. The chains on ours cross and are long enough to allow turning but then its quite high. We should do a test like you did Olley, don't really know if they would catch the tow-hitch.
I guess it depends how high your tow assembly is off the ground. The chains on ours cross and are long enough to allow turning but then its quite high. We should do a test like you did Olley, don't really know if they would catch the tow-hitch.
The part that anoy,s me is ,how can the a frame sit in the cradle when the chains are welded to the aframe they are lowering at the same time as the a frame, the theory does not work.it is a good test to try out, I hope a few people try this at home and let us know the result .
I guess it depends how high your tow assembly is off the ground. The chains on ours cross and are long enough to allow turning but then its quite high. We should do a test like you did Olley, don't really know if they would catch the tow-hitch.
I think that this is the only way it would work, having a very high tow hitch,I may be wrong overall.
Did all the tests sometime back and found that the as a safety measure the chains were next to useless, but required by NSW law which no one seems to know why, not ever the RMS which quote the rule book not any logic . The Skid plate is the best method to prevent a dig in, have seen them on car trailers and loging rigs in the bush
__________________
Pets are welcome but children must be leashed at all times
I did a mock caravan detach,this was done in my own back yard,I unhooked the van off the 4wd and used a 4wheel jack,the chains were crossed as supposed to be ,here's the test ,I lowered the jack as if the van had come off the4wd the first thing I noticed was as the van was being lowered the chains are lowering at the same time the van is,now the van A frame is on the ground sitting in the crossed chains witch are on the ground as well , ok the first thing to do is shorten the chains,witch i did ,the chains being at that length lower the a frame again the a frame sits in the crossed chains and don't touch the ground great that's what they are supposed to do ,ok then I hook the van onto the 4wd I do a turn test that's when this great theory of crossing chains becomes CRAP,when your chains are short enough to catch the van A frame you can't turn your vehicle in a manner where it is safe ,this theory does not work ,to have the chains so you can turn your vehicle will not stop your van a frame from hitting the ground,if you can explain to me how it can be done I would love to know.
To answer your question of how the van came of the tow bar is simple, the cast iron tow hitch on the van broke when I hit a dip in the road, I was travelling at the legal limit of 100km when I hit the bump, fortunatley the chains held the van but she did hit the road and was dragged a fair way, but as I have said there was a skid plate to stop the van digging in, and guess what it bloody well worked, I still have the van with no damage to it or the vehicle, but I did have to change my pants.
The van is an off roal Coromal that weighs in at 1.6 tonnes
I had dragged it all the way from Melbourne without a problem.
 Can i ask do you have any idea to what caused your van to come off the towbar. As i would be really interested to know the reason.
Kind Regards Herbie.
Why i asked you the question, to how your acident happened , as it was only last week i posted a post on here regarding nut's and bolts , under the heading of nut's and bolts.Was wondering if that may have contributed to your accident in anyway.
