Caravan detaching from tow car

[PhilLord]

Hi not a regular poster on this forum, but I thought I would share one of my neighbours experiences.

On their last outing with the van (2002 Lunar fixed end bunk 6 birth model), the van became detached from the tow car (BMW 5 series 2006 model). A very scary experience for my neighbour as the van snatched on the breakaway cable and then once this had snapped veered into the kerb and then bounced back into the rear of the car, making considerable damage to both car and caravan.
The car has a removable towbar and the van has an alko hitch. My neighbour never changed the towball after changing from his last van which was on a standard 'older' style hitch.
My neighbour says he was in a position where the car and caravan where in a v shape with the towball and hitch being the pivet point. So he was in a dip with the car pulling out of it and the van still dropping into it. He believes at this point unbeknown to him the hitch became detached from the tow ball. After this the road levelled out and he began to pick up speed with the hitch resting on top of the tow ball (again unbeknown to him). At approximately 50mph the hitch head fell off the tow ball and the incident occured.

My initial reaction was that he should have changed the towball when changing his caravan. This was backed up a caravan engineer who checked the tow ball after the incident. However, after research on the internet into this we are finding that the only towballs that need to be changed are on flange bolt on type towbars (like mine) and not swan neck and detachable (like my neighbours) as apparently they are fine with the both type of hitch heads.

Has anyone else had experience of this happening or has any alternative ideas as to why the incident took place. Understandably my neighbour is a bag of nerves now with regards to towing and as it stands will probably never use the van again. If we could put some technical reasoning behind why it happened and not that it was an 'act of god' then that might go some way to easing his fears.

Thanks for reading and feel free to add comments.

 

[ProfJohnL]

Hello Phil,

A detachment whilst towing is a very scary thing to happen. I hope your friend can get over the event.

Some caravan hitches are sensitive to the form of the swan neck and the ball. So he should double check he does have the right tow ball form for the type of hitch on the caravan.(Refer to the manufactures data plate for types and to the manufactures web sites for availability)

Worn components may contribute, but in general you would hear the and feel hitch rattling before the wear got to a point where the hitch could detach from the ball. Even with in head friction pads, if the pads wear away, it is unlikely for the metallic hitch to disengage.

Assuming both the ball and the hitch are within manufacturers tolerances, is It is actually very rare for hitch to detach from the ball if they have been correctly coupled. In most instances of detachment the coupling has not been fully completed before setting off.

Get your friend to check the operating instructions for his hitch.

 

[PhilLord]

Hi,

Thanks for the reply, im pretty sure the hitch components are in good working order as like you say you would hear the rattling and I assume that he had indeed connected the van to the car correctly. Therefore there must be some incompatability with the hitch and the tow ball. I thought that all tow balls had to be changed when changing for a standard (old style) hitch head to the Alko style but according to the internet on removable and swan neck bars you can keep the same ball.

Thanks,

Phil

 

[Red_Mick]

When I bought my first caravan, the salesman showed me how to use the Alko hitch. When I bought my second caravan, the salesman told me I had been doing it wrong.

I should do the tension first, then lock down the lever, I had been shown the opposite way initially.
I beleive the second one to be correct, but it goes to show that there are mistakes to be made.

 

[Sproket]

I changed my alko four years ago for a winterhoff ws3000 as it locks into place as soon as it is lowered onto the ball, only one handle to opperate not like two on the alko, but there lots out there who use both without any bother. the other thing with the winterhoff is that it will work on a normal towball as the head is not as big as the alko one's
http://www.winterhoff.de/Bilder/News/rwtuev-2004-engl.pdf

 

[MikeG2]

The Alko ball has a longer stem than standard allowing the stabilser head to rotate around the ball without coming into contact with the stem when the unit moves through a dip. Using the standard ball with an Alko hitch will seriously limit the amount of movement and in extreme situations it must be possible that the head will be levered off the ball.

 

[JTQ]

Some caravan hitches are sensitive to the form of the swan neck and the ball.

An interesting and worrying stetement re "snaw-necks" that I have never come across before.
Could you please tender more specific info as it is very worrying having used several swan neck units without any hint of this issue?

Pre the integrated stabiliser Al-Ko hitches I had a trailer jump off the hitch. I could have not put it on properly but I had by then a great deal of experience so feel that unlikely. After extensive investigation I found the ball was significantly worn and even where unworn it was only just within the DIN tolerance. Though I could not directly relate the wear to the failure I changed both the hitch and the ball, however finding a ball that was anything but marginal on size proved a long search. The ball I had the failure with had towed over 35 k miles and was an electro plated one, something I now avoid.
Since that incident I always ensure the jocky wheel can lift the vehicles rear end as part of the hitching routine.

 

[Dustydog]

I think I read somewhere that the latest MOT now includes the tow bar and electrics. If so I wonder if the test centre has to measure the tow ball tolerance?

 

[Gafferbill]

Since that incident I always ensure the jocky wheel can lift the vehicles rear end as part of the hitching routine.

.......very wise advice which I would also give.

The attachment point of a car to caravan is a mechanical device operated by a human.
It is well known in such circumstances that the human input is the weakest link (there is a pun in there somewhere!)
The jokey wheel test is a good way of checking the attachment has been done correctly.

 

[Parksy]

My test center ddn't measure the tow ball, apart from checking the electrics the tester had a good look around the mountings while the car was up on the lift and gave the ball a couple hefty tugs.
It's not unknown for the red/green indicator button on top of the Alko hitch to indicate that the towball is locked when in fact it is not and the tow hitch also makes a reassuring noise as if it is fully engaged, with the handle going down, which can be very deceptive.
I always do the same thing as JTQ and Bill before I engage the stabiliser, the jockey wheel wind down test will confirm that the tow hitch is properly engaged every time.

 

[ProfJohnL]

An interesting and worrying stetement re "snaw-necks" that I have never come across before.
Could you please tender more specific info as it is very worrying having used several swan neck units without any hint of this issue?

hello JTQ
My wife tells me I 'snaw'

. I dont belive her as I have never heard it

Perhaps I could have worded the statement better, The fact is that the Alko hitch requires a slightly different form of cut away under the main ball compared to the basic EU configuration. this is to allow the EU range of articulation without the hitch fouling on the ball support stem. This particularly affects the bolt on style balls, but if a swan neck was manufactured to the EU ball form the same limit to articulation would apply. This should not affect the ability to couple the trailer, but under towing the limit of articulation may be experienced, and I'm not sure what the consequence would be. To be fair, the majority of true swan necks shoudl be Alko compatible, but there is a chance that some makes may not be, so the advice to check is still sensible

 

[Lutz]

I'm a bit puzzled by the description of the failure in the original posting. It states that the towbar was removable. Typically, removable towbars are swan neck (there are a few exceptions) and I have never heard of a swan neck towbar not being compatible with an Alko coupling. This leads one to assume one of two possible causes. Either the caravan was not hitched up properly in the first place or the dimensions of the towbar were not according to the standards laid down. Now, if the neighbour is absolutely certain that he did everything correctly, it can only be the latter. If that is the case, I think he would stand a good chance of being able to claim against the manufacturer for compensation due to a design which did not comply with the regulations and therefore posed a real safety hazard.
For a towball to be out of tolerance would be more than unlikely. The tolerance is relatively large, -0.36mm on an overall 50mm diameter. Something would have to be seriously wrong and should have been obvious to the naked eye if the towball diameter was out of tolerance. It is absolutely impossible that wear of the towball could have caused the problem described so long as it meets the durability requirements as laid down in the regulations.

 

[colin-yorkshire1]

My test center ddn't measure the tow ball, apart from checking the electrics the tester had a good look around the mountings while the car was up on the lift and gave the ball a couple hefty tugs.
It's not unknown for the red/green indicator button on top of the Alko hitch to indicate that the towball is locked when in fact it is not and the tow hitch also makes a reassuring noise as if it is fully engaged, with the handle going down, which can be very deceptive.
I always do the same thing as JTQ and Bill before I engage the stabiliser, the jockey wheel wind down test will confirm that the tow hitch is properly engaged every time.

hi all, just had my car tested last week, the tester did the same as yours Parksy good tug on the ball ckecked the type approval plate on the bar and inspected the mountings, the 13pin plug was tested by his electronic gizmo and all was well. but no mention of the ball condition or diameter,

which leads me to two interesting points, that may be of interest to the OP,
ball size, many years ago trailer couplings were 2in and so were the balls, our first caravan had a 2in hitch, when the EU size 50mm balls and couplings came along there was a problem with the head couplings due to the different sizes, the car had a new towbar fitted and of course a 50mm ball but the coupling head was quite loose being 2in the difference being 0.8 of a mm the soution in those days was to cover the ball with tough plastic held around the neck with a elastic band and after covering the ball and plasic in grease attached the 2in coupling, this worked for a few years until we changed vans, the new one had the 50mm coupling fitted.
NOW I AM NOT SUGGESTING THAT ANYONE TRIES THIS. but mention it ONLY because it relates to ball size the difference was 0.8mm and within the possible wear diamentions of a old ball. that has been used a few years.
I am not sure of the current wear limits perhaps the Prof could tell us but a worn ball would make the coupling head loose in use and could lead to the trailer becoming detached as could fouling of the swan neck on acute angles "like on a ferry ramp or steep drive way" I have noticed re- the the Profs post that not all swan necks are the same angle on the neck part.this may also have a bearing on the alko coupling head.

the second point has to do with Parsky's comment on the head lock indicator some balls have a machined flat on the top "where the 50mm is stamped, while other are completely spherical woulld this have any bearing on the accurate reading of the indicator when locked or not ,as surely this difference in height would alter the reading.showing it as locked when infact it is not.
just a thought,
colin

 

[colin-yorkshire1]

For a towball to be out of tolerance would be more than unlikely. The tolerance is relatively large, -0.36mm on an overall 50mm diameter. Something would have to be seriously wrong and should have been obvious to the naked eye if the towball diameter was out of tolerance. It is absolutely impossible that wear of the towball could have caused the problem described so long as it meets the durability requirements as laid down in the regulations.

thanks Lutz that blows suggestion one out of the window

 

[Lutz]

Just to repeat my previous statement, wear of the towball can be excluded as a possible cause so long as the towbar meets the durability requirements of the regulations (from memory 6 million cycles on a shaker).

 

[ProfJohnL]

I have to say that the most likely scenario is the caravan was not hitched correctly.

 

[Trevormc]

I changed my hitch a couple of years back to an Alco one and it came with its new tow ball all painted black. After removing the paint it was then bolted to my Shocklink that fits to the towbar with 2 X 20mm? bars.

Now for the MOT. I always take off the Shocklink when not towing the caravan so my MOT earlier this year the ball was not tested. I will always keep taking the Shocklink off because to replace it at £300.00 plus is out of the question.

Trevor

 

[Sproket]

I changed my hitch a couple of years back to an Alco one and it came with its new tow ball all painted black. After removing the paint it was then bolted to my Shocklink that fits to the towbar with 2 X 20mm? bars.

Now for the MOT. I always take off the Shocklink when not towing the caravan so my MOT earlier this year the ball was not tested. I will always keep taking the Shocklink off because to replace it at £300.00 plus is out of the question.

Trevor

Trevor.
I use one of these with my shock link plus the two pins.
But when we get to where we are going off it comes, as they are now £400.00 + vat mine is only put on when needed to pull the van or the trailer.

 

[Lutz]

A word of warning regarding the use of a Shocklink (copied from the Dixon-Bate website):
Eu Approved Vehicles August 1994 on: Only fit the adapter plate after first checking with the towbar manufacturer that doing so will not invalidate the towbars’ approval

 

[PhilLord]

Hi all,

Some great answers and suggestions thank you all for your feedback. The towbar/towball was only fitted last year and is specifically designed for the bmw. I remember him commenting on how much it had cost compared to the last one he had fitted on his mondeo (previous car). Since being fitted it has only been used maybe four or five times on relatively smallish tows so it is still in 'like new condition' and not suffered from any wear and tear.

One interesting point that someone made on here is that you might think that you have hitched it up correctly but you havent. On my old fashioned hitch I have a red button that moves out when the two ball engages with the hitch. I also give the hitch a dam good shake and then wind the towball down until it lifts the back of the car up. So far 'touch wood' that has done me fine. My neighbour though is new to alko hitches and this was only the third time he had towed with it (fourth if you count picking it up from the seller). He bought the van privately and I am not sure what guidance (if any) he was given as to how the alko hitch is engaged correctly bythe seller.

In a strange sort of way, I think he would be pleased if it turned out to be his fault for not hitching the car to the caravan correctly, as it would give him some closure on the incident and he would know what had been the cause.

Cheers,

Phil

 

[Sproket]

A word of warning regarding the use of a Shocklink (copied from the Dixon-Bate website):
Eu Approved Vehicles August 1994 on: Only fit the adapter plate after first checking with the towbar manufacturer that doing so will not invalidate the towbars’ approval

Lutz
My V5 states that my truck is a light goods vehicle with a gvw of 2900kg.
Non M1 vehicles, light commercial vehicles and private imports from outside the EEC do not need Approved Towbars;
Taken from the link below. ????
http://www.ntta.co.uk/law/towbars/type_approval.aspx

 

[Raywood]

My feeling is the caravan was not hitched up correctly. After many years dealing with insurance claims I have seen only claims where this was the problem and one where a vey old hitch was involved and was probably defective.

 

[Trevormc]

Thanks for the price update Sprocket. I purchased mine from a Land Rover spares shop at cost price a number of years back.

Trevor

 

[Sproket]

No problem !
Have just greased mine & cleaned the ball ready for tomorrow

 

[Parksy]

........In a strange sort of way, I think he would be pleased if it turned out to be his fault for not hitching the car to the caravan correctly, as it would give him some closure on the incident and he would know what had been the cause.

Cheers,

Phil

There's a very high probability of the hitch not being engaged correctly, I've never read of a case where a correctly engaged Alko hitch (or any other type for that matter) has 'unlocked' itself for no apparent reason. When we see the unfortunate people who have motorway accidents whilst towing a caravan there are often pictures of the towing vehicle facing the wrong way, even upside down and with the caravan on top of the crash barrier, but the hitch has remained locked.
I've seen several forum topics on various caravan forums about caravan / towcar separation where it turned out that the Alko had failed to engage after giving the appearance of being engaged.
I've had a similar thing happen myself but with less serious consequences when I found after doing the jockey wheel wind down check that the hitch hadn't fully engaged and I'd suggest that the same thing happened to your neighbour.