towing response to letter in this months mag.by john helsby.

[mikepocknell]

mr.helsby asked doug about towing problems with his swift freestyle van.I had similar problems with a swift lifestyle van,a marquis special.I had,in the end to fit a traditional anti-snake bar to get it to tow sensibly.A problem i found, and i think mr helsby has the same chassis on his van,is that the van axle is set forward of the mid point along the chassis.this in my view,creates an in -built instability.
It took me a long time to get it right.balance.To the extent that could identify which vehicle i was overtaking would cause the most sway.
Unquestionably,it was car transporters,which i would say is caused by the air turbulence between the cars on the vehicle.
Incidentally,i sold the life style and bought a bailey pegasus rimini.towing now is chalk and cheese compared to the swift.lifestyle.
Anyone want to buy a snakemaster.?
my towcar is a volvo,xc70.Fantastic for towing and 4x4.
Regards,MIKE

 

[otherclive]

Mike
I would agree with you re the XC70 towing capability and if that car couldn't manage the Lifestyle I would think the basic van design is questionable especially since it now handles the bailey. That company have put a lot of work in with Bath University to better understand the dynamics of towing.

 

[colin-yorkshire1]

mr.helsby asked doug about towing problems with his swift freestyle van.I had similar problems with a swift lifestyle van,a marquis special.I had,in the end to fit a traditional anti-snake bar to get it to tow sensibly.A problem i found, and i think mr helsby has the same chassis on his van,is that the van axle is set forward of the mid point along the chassis.this in my view,creates an in -built instability.
It took me a long time to get it right.balance.To the extent that could identify which vehicle i was overtaking would cause the most sway.
Unquestionably,it was car transporters,which i would say is caused by the air turbulence between the cars on the vehicle.
Incidentally,i sold the life style and bought a bailey pegasus rimini.towing now is chalk and cheese compared to the swift.lifestyle.
Anyone want to buy a snakemaster.?
my towcar is a volvo,xc70.Fantastic for towing and 4x4.
Regards,MIKE

hi Mike, i think you may have stumbled on one of the most significant stability issues of the caravan industry ie, position of the axel in relation to the vans length, it is something i have been saying for years, yes with careful loading one can improve things but still the problem is there,
it comes about because manufacturers use a standard Alko chasiss based on weight, this can be shortend or lengthend via the ladder section behind the axel, and they base several vans on this one chasiss, the shorter ones tend to be more stable than the longer ones, as the position of the axel in relation to the van length moves further back, to compensate many of the vans have rear washrooms (this reduces the weight right at the back) with more of the equipment placed central (but still behind the axel).
we have (at the moment) a ranger 380 yes it is a small van but even towed with the lightest of cars is very stable, the axel is positioned some 18in forwards of the centerline I believe this helps, other vans in the range were the 400/ 420/ 440/460, all based on the same chasiss, all the others have rear washrooms exept the 440 (that had the end kitchen like the 380) stability does not seen too much of an issue exept for the 440/4 and this was a right pig to tow, same configuration as the 380 with the addition of a central bunk/diner the overall MTPLM was only 100kg more than the 380 but the axel was 2ft futher forwards.
this chalk and cheese senario you speak of mirrors my experience and new caravan buyers would do well to take notice

.

 

[RogerL]

The axle should be positioned where it gives an appropriate noseweight when the caravan is loaded - given that proviso it matters not whether it's in front of the mid-point or not as it's all dependent on the caravan layout and where the heavier (when laden) items are.
The real question should be:- is the noseweight acceptable when the caravan is loaded, assuming that things get put into obviously logical locations, food in fridge, bedding in bed boxes, clothes in wardrobe, etc.
There is a statutory minimum for noseweight of 4% of laden weight - best towing stability occurs when noseweight is as heavy as possible WITHOUT exceeding any limits of car, towbar or caravan hitch.

 

[colin-yorkshire1]

hi sorry roger have to disagree (again) the van or trailer should have the ability to be stable and conform to relevent weights and dimentions EMPTY without the need to load it first it should be in the design.
not every one carries a awning (35kg) for example to adjust the loading.
my van as above, has a noseweight empty of 100+kg with the spare wheel 2 bottles (full) and 110amp battery on board with all other standard equipment in place, now given this van is supposed to be a lightweight it makes one wonder, the 440 I spoke of in the same state has a noseweight of 60kg only difference position of axel.
when I joined the national speed boat club I did a weeks course on windermere part of the course was on trailer loading they had a computor program that mimics the effect on stability moving things around, it was remarkable just how much effect rear overhang has on stability given a trailer with a pre-determined load in place,

 

[RogerL]

Who mentioned awning? That doesn't come under "obvious logical location" that I referred to.

 

[ProfJohnL]

Hello Colin,

Whilst I agree in principal with your contention " the van or trailer should have the ability to be stable and conform to relevent weights and dimentions EMPTY"

The fact is that they don't, and in practice, as different tow vehicles have different tow ball nose loads, so "one size" will never fit all.

I reintroduce the point that it is up to the driver to ensure the outfit is roadworthy and legal, which means the driver must trim the car and trailer to bring it within limits.

The trailer manufacture cannot be expected to know what car each driver will be using, and it may fatally compromise the design and function of the trailer in trying to perfect the "empty" weights and balance.

 

[colin-yorkshire1]

hi John,
the point I was making was in reply to Rogers inference that the axel position has no effect on stability, I strongly believe this not to be the case both in theory and in practice through experience, using the empty van as a base line in which to make assesments on the best way to load it, a (empty van) should be inherantly stable and not have 12% of it's total weight on the nose if it has then there is a specific design flaw somewhere. for example while as you say it is true the driver towing the van is responsible for ensuring the outfit is legal and meets all the criteria it should not be necessary to remove basic items from there specific location ie battery gas bottles and spare wheel in order to make the van legal to tow, adding ballast to the rear may be a solution if the noseweight is too high, but this surely is not presumed normal and calculated into the basic empty van design,
while the owner has some scope with loading up to the maximum user payload it is often said the best way to load a van is low down and near the axel using heavy items like the awning (roger) to adjust the noseweight, fine but if the said axel is nearer the front on one model than another this must have an effect on the overall balance of the van under tow as would the position of basic equipment provided in the van,
I believe this area is where some get it wrong rogers comments that items should be stowed in there appropriate place irespective of the vans basic design is also wrong IMHO,
clothes in wardrobe, pans under cooker, food in fridge, items in overhead locker, bedding under bed or bunks, sounds reasonable unless all the equipment is on one side of the van or to the rear, then you have loading issues, to contend with when it comes to getting the noseweight and van balance correct,
if you do have the awning, poles, annex, bbq, chairs ect, to move around the floor then it may well be fine, but not everyone carries these, do they???

 

[ProfJohnL]

hi John,
................it should not be necessary to remove basic items from there specific location ie battery gas bottles and spare wheel in order to make the van legal to tow, adding ballast to the rear may be a solution if the noseweight is too high, but this surely is not presumed normal and calculated into the basic empty van design..........

Hello Colin,
It isn't necessary to remove basic items as you suggest, but it is necessary to ensure you obtain the correct towing configuration for the vehicle you are using, and as vehicle is not a constant, you cannot expect a trailer to be universally suited to all cars. I expect this and have no issue with providing ballast to trim the trailer in the form of water containers that can be filled as necessary. That is the approach I have used, and have reported on many previous occasions. (And for anyone who is shoked at this, were not going to debate the rights and wrongs of using water as balast and end loading)
As I pointed out above, the manufacture does not know what vehicle will be towing the trailer, perhapse it will be a 4x4 with a towball limit of 150kg, or perhaps it will be a small car with only a 50Kg limit (provided the maximum towed limit allows it)
Caravans are vrey rarely towed entirely empty, that is not a usual state, so generally the designer will expect there to be some user load which will be used to trim the trailer. With that assumption in mind, they may allow the empty nose weight of a caravan to creep up if it maximises the functional layout of the caravan.
Now I don't condone the practice of allowing the exworks nose weight to exceed the hitches limit (generally 100Kg) but it doesn't make the caravan unfit for purpose, as one of its prime purposes is to carry user load.

 

[RogerL]

Unless it's an Airstream, caravan hitches are limited to 100kg by both Alko and BPW.
Cars with towbar limits over 100kg are still limited to 100kg caravan noseweight unless it's an Airstream.

 

[colin-yorkshire1]

hi John,
................it should not be necessary to remove basic items from there specific location ie battery gas bottles and spare wheel in order to make the van legal to tow, adding ballast to the rear may be a solution if the noseweight is too high, but this surely is not presumed normal and calculated into the basic empty van design..........

Hello Colin,
It isn't necessary to remove basic items as you suggest, but it is necessary to ensure you obtain the correct towing configuration for the vehicle you are using, and as vehicle is not a constant, you cannot expect a trailer to be universally suited to all cars. I expect this and have no issue with providing ballast to trim the trailer in the form of water containers that can be filled as necessary. That is the approach I have used, and have reported on many previous occasions. (And for anyone who is shoked at this, were not going to debate the rights and wrongs of using water as balast and end loading)
As I pointed out above, the manufacture does not know what vehicle will be towing the trailer, perhapse it will be a 4x4 with a towball limit of 150kg, or perhaps it will be a small car with only a 50Kg limit (provided the maximum towed limit allows it)
Caravans are vrey rarely towed entirely empty, that is not a usual state, so generally the designer will expect there to be some user load which will be used to trim the trailer. With that assumption in mind, they may allow the empty nose weight of a caravan to creep up if it maximises the functional layout of the caravan.
Now I don't condone the practice of allowing the exworks nose weight to exceed the hitches limit (generally 100Kg) but it doesn't make the caravan unfit for purpose, as one of its prime purposes is to carry user load.

Yes John,
but a van say a 25footer with a MIRO of 1500kg and a user payload of 500kg you could be dam sure it won't be towed by a Mini!!.
yet a small ultra lightweight van that weighs less than 1000kg and advertised as being suitable for towing by the smallest of cars would have had a bit more thought into where basic equipment is placed, a battery box is expected to carry a battery and the gas cylinder in its place next to the regulator same with the spare tyre in the front box where it is designed to be carried. not to mention fridge water heater wardrobe all in front of the axel adding weight to the nose, the user payload of such vans is by definition small so by the time clothes have been stored (in wardrobe) food in fridge bedding under front bunks there is not a lot left to balance the nose by adding weight in the back,
yes it is possible (just) as I get the noseweight down in such a van from 102kg "empty" to 48kg "max for car 50kg" fully loaded but it requres the spare wheel to be removed and carried in the back with the ehu ect and nothing under the bunks or front box with only one light weight cylinder on board, (designed for two) this of course leaves no floor space while under tow and obviously one cannot get into the van,while loaded, if this is not a design flaw I dont know what is!!.
none of this however detracts from the OP's observation that the position of the Axel could affect stability given the problems of loading a van with rearward axel that is in fact ultra stable, I would tend to agree.

 

[RogerL]

500 kg payload ?
EN standards define a minimum payload based on the number of berths and internal caravan length - few caravans have payloads in excess of the minimum although a number can be upgraded a little.

 

[ProfJohnL]

Hello Colin,

I do absolutely agree the position of the axle will have a major effect on the stability of a trailer, Whilst you can look just at that one aspect of a caravan design, there are a mirriad other factors that affect stability also, so it is possible that some other aspects of the design may add or subtract from the packages overall stability.

Regardless of the design of a trailer it still does not detract from the drivers ultimate responsibility to ensure the outfit is road legal.

I have moved caravans in different states of loading, and I have never yet come across one that before towing on the roads I cannot trim either with the indigenous items in the caravan or the addition of some water ballast.

When approaching an unknown caravan I simply assume it will need some ballast so I carry the containers to to do it. It a question of being prepared.

 

[xtrailman]

Unless it's an Airstream, caravan hitches are limited to 100kg by both Alko and BPW.
Cars with towbar limits over 100kg are still limited to 100kg caravan noseweight unless it's an Airstream.

Not entirely correct.
Elddis use the BPW chassis with two hitch limits 100kg and 150kg, model dependant.

 

[Lutz]

500 kg payload ?
EN standards define a
minimum payload based on the number of berths and internal caravan
length - few caravans have payloads in excess of the minimum although a
number can be upgraded a little.

Which EN standard is that, Roger? I thought it was only an NCC guideline. Mine was a 1600kg, upgraded to an 1800kg, which now gives me over 400kg payload.

 

[RogerL]

500 kg payload ?
EN standards define a
minimum payload based on the number of berths and internal caravan
length - few caravans have payloads in excess of the minimum although a
number can be upgraded a little.

Which EN standard is that, Roger? I thought it was only an NCC guideline. Mine was a 1600kg, upgraded to an 1800kg, which now gives me over 400kg payload.

I should have said "few caravans on sale in the UK have payloads in excess of the minimum".

My understanding is that the EN standard (1645 ?) defines a minimum payload based on number of berths and internal caravan length - the NCC does indeed adopt the same minimum standard.

Any manufacturer can offer payloads in excess of the minimum - a number of European manufacturers do but mainstram British manufacturers use the minimum payload as their standard although they may offer a few kg upgrade. Airstream and Eterniti may be exceptions.

To achieve a 200kg increase in MTPLM then I presume a different axle/brakes/tyres assembly is used at production time? Mainstream British manufacturers can't/won't allow that sort of change.

 

[otherclive]

My S5 Bordeaux was upgraded from 210 kg to 250kg purely by issuing new certificate and tally plate. This was because the Vendee was on the same chassis etc and was a heavier MTPLM. One principal reason we have stuck with this van is its good payload, good length all in a sensible MTPLM of 1400kg. As van prices inexorably rose and equipment and weights increased we decided to spend our cash elsewhere.

 

[Lutz]

I should have said "few caravans on sale in the UK have payloads in excess of the minimum".

My understanding is that the EN standard (1645 ?) defines a minimum payload based on number of berths and internal caravan length - the NCC does indeed adopt the same minimum standard.

Any manufacturer can offer payloads in excess of the minimum - a number of European manufacturers do but mainstram British manufacturers use the minimum payload as their standard although they may offer a few kg upgrade. Airstream and Eterniti may be exceptions.

To achieve a 200kg increase in MTPLM then I presume a different axle/brakes/tyres assembly is used at production time? Mainstream British manufacturers can't/won't allow that sort of change.

You may be right, Roger, but EN 1645-1 and I know it covers what is and what is not included in the MIRO, but it is subtitled, 'Leisure Accommodation Vehicles - Caravans - Habitation Requirements relating to Health and Safety', so somehow doubt whether it includes minimum payload requirements, but as I have not been able to access the standard without purchasing a copy, I can't say for sure.
The upgrade of my caravan obviously involved fitting a different axle, but this was done at the time the caravan was built.

 

[emmerson]

As some of you may be aware, I tow with a Classic Range Rover, and my van of choice is my unique Royale Rangemaster, with a combined age of 55years, and outfit weight of 3,700kg. The Royale is 16ft body length, with the axle exactly in the middle. All of my previous Royales have been 14ft 9in, with the axle towards the rear.
The difference in towing stability between the vans is very noticeable, the smaller van being the most impressive, by far, of any van I've ever towed.The 16 footer is only average to good.
Common sense tells us that the longer the distance from the axle to the rear of the van, the greater the pendulum effect.Equally, the greater the distance from the towball to the axle, the more stable the van will be.
I toally agree that you should not have to rely on load position to create stability. It should be built in to the EMPTY van.
Also, any stabilizer should be used to enhance stability, not create it.