Weight Distribution Bars

If you are considering redistributing the weight, make sure you don't placed it back too far behind the axle because then you are creating a serious instability problem. Much has been written on forums about the "pendulum effect" of poor weight distribution, (Collyn Rivers comes to mind). Redistributed weight should be put above the axle not at the extremities of the van, front or back.
WBS

Yes We had those bars. Only I do not recall them being called WBS. They were a funny shape and a bit like a stretched question mark. And they work. I experimented with a friends pair and it was very noticable at the very first corner so I got some.

That was a few decades back when we towed our Chesney wind up with the family sedan. No big heavy suspension work for towing or anything like that. Just the bars that twisted down on the "A" frame and effectively up on the rear of the car. But note that I had less than around 50 kg on the towbar. I could just lift it. And I moved weight around in the car to keep it around that weight.

And I could easily drive at 80+ MPH. Yeah Fast hey Bloody idiot hey. Hoon and should be off the road. Say or think what yopu wish but please note that it worked. The steering was excellent and very responsive and the whole lot travelled welll.

This is the advice I got from a bloke by the name of Doug Chivas. And it was solid and useful experience not some formula dreamed up by an engineer. But knowledge built on experience.

So I always chuckle when I hear figures like 200 kg. I wouldn't dare do that. Even with the 100 series. I can feel the steering get light just thinking about it. Simple physics and no computer to work that out. I don't care what the so called specialists say about it. It felt good and safe.

Take it as you wish but I believe those bars do help. They wont solve fully light steering, or the rear being low and or headlights blinding people even on low beam (dont you just hate that). Nor will it solve bad steering. But it will transfer some weight. Not a lot but some. They will help.

Phil

Phil
WBS is his name!!!!!!!!!!!!! Not the bars.

I like the mental imagery though, of a pendulum effect being" Collyn Rivers" swinging back and forward.


Driving on the road at 80mph I reckon deserves you being renamed,
"Lucky Phil"

The situation of it being good and feeling safe is just a feeling and doesn't indicate a level of safety. Collyn Rivers spoke of the possibility of all being well until it suddenly isn't. Then it gets interesting.

The Concorde felt good at take off too, however the situation did change.

Good on you picking something to have a go at me.

Now to my real point. Why so much weight these days?

Phil

Hey ROSS. I missed that bit about his name.

I meant WDS.

Phil

Phil, you ask " Why so much weight these days?"

From what I have noticed the tow ball weights are getting lighter, not heavier. Way back when a large van was one with a body length of 18' (5.5 m) it was established that vans with a ball weight of 10% were more stable than ones with a lighter tow ball percentage weight. Back then there were no vans with front or rear kitchens to speak of. When you construct longer vans the yaw inertia increases and you need heavier ball weights to achieve the same stability.

The yanks with their large vans work on ball weights of well over 10%. Some over there recommend 15 - 25% ball weights.

The European vans can get away with 5 - 7% ball weights. That is achieved by employing better dynamically designed vans. You will note that their van designs concentrate the weight to the middle. They don't have rear bumper bars, their spare tyres are mounted under the middle, the front boots are smaller and the list goes on.

While our manufacturers continue to design and build vans with poor dynamic weight distribution we should be loading our vans to have a ball weight of over 10%. Mine is 250kg on a all up weight of 2,000 kg. I am quite happy to have that amount of ball weight.

Thanks Peter.

Luckily we don't have any intentions of towing.

Phil

The pendulum effect is exacty what I was talking about when I say fundametally unstable.
This is why the pig trailer is all but extinct in heavy transport, replaced by much more stable dog or fifth wheel trailers.

Yeh what the yanks do is another thing all together.....over there they allow all sorts of things on the road that would not even be considered here...and they do some realy strange things with trucks too....heavy rigids with trainer wheels out the back and semi trailers with an axle in the middle... go figure.

The yanks also in generaly drive bigger vehicles and tow with bigger vehicles....even their very close equavalent of our Hilux...the Tacoma.....is longer, wider and heavier..not by a lot but by some.

The reason remans why people put sooo much weight on their balls....( hmmm...:)..there is a parelell there).....this is an attempt to compensate for a van that is either badly designed or badly loaded.
I remain gob smacked at how far caravan design has not come in the last 30 years.

Yes and then there is the tendancy for people to add significant weight at both ends of the van after manufacture.....just about every aftermarket add on is heavy and either fitted on the drawbar or one an aftermarket rear bumper.

No wonder people have problems.

Now an interesting thing.
If you look at the towing capacities of most modern vehicles..and in particular the permissable ball weights compared to the towing capacity.

There are a lot of people will find themselves, illegal and overloaded on their rear axle even though thay are as much as 2/3 of the towing capacity.

Actually a couple of the high towing capacity utes have very low permissable ball weights...down arround 5%.

It may have a 3.5 tonne towing capacity but unless it is towing a dog trailer ( 4 wleel self streering trailer) the practical towing capacity will be under 2 tonnes.

cheers

Quote "The "heavy Hayman Reeces types" won't effect your GVM enough to worry about."

Adding any weight does not affect your GVM. GVM is a technical term defined in the motor traffic regulations. It is defined in the ADRs as:

"GROSS VEHICLE MASS (GVM) - the maximum laden mass of a motor vehicle as specified by the Manufacturer‘."

Adding any weight on the tow bar will ad to the total weight of of your tow vehicle. However it will not add much weight to the rear axle as the van will if you don't use WDH. The chart below is an actual demonstration recorded by Caravan World technical editor Tom Olthoff at a Melbourne caravan show..

You will note that the 220 kg ball weight added 360 kg to the loading on the rear axle. The extra 130 kg comes from the weight removed from the front wheels when the van is coupled without WDH.

If you are not using WDH with your van then you should allow for that increased axle loading. Nissan calculates this for their vehicles. If you have any other vehicle you have to work it out yourself if you don't employ WDH.

I have to agree with you Pop, he has been keeping up to date on suspension design since his GM research engineer days in the 1950s and has paid a lot of attention to caravan dynamics for the last twenty years.

This is an extract from a post he wrote on another forum yesterday.
-----------------------------------------------------------------------------------
Any trailer towed via an overhung hitch has an inherent tendency to yaw. It is an unstable device that can, within limits, be rendered less unstable to an acceptable level.

There are two main approaches.

Australia
To have such substantial tow ball mass that a very large disturbing force is required to introduce yaw. This is effective - until one needs to swerve very strongly (to say avoid a head-on accident). Or subject to a sudden strong gust of wind.

This (in my opinion) the more potentially dangerous form as the huge front end mass commonly causes the rig to feel ultra-stable until a high disturbing force occurs whilst travelling at speed.

USA
This is much as above but changes in 2015 when long-delayed legislation includes obligatory and rigid stability testing. The allowable trailer mass is also specific to the tow vehicle and takes into account hitch overhang. (Technically it is the radius of gyration divided by the hitch overhang.) The standard requires the tow vehicle to maintain understeer up to 0.4 G.

Much of the above standard is based on the sources that I have quoted in other related threads.

EU
The EU approach is to totally accept that the 'van will sway but, by centralised low mass design, to substantially reduce its effects Tow ball mass is typically much lower than in USA and Australia and the inevitable but less dangerous yaw (as forces are far lower) is dissipated as heat via friction mechanisms or restrained by sprung cam mechanisms. The ESC is seen only as a further aid. WDHs are hardly ever required or used.
-------------------------------------------------------------------------------------------
Our huge tow ball weights are a primary reason why it is very common for a driver to say the van felt so stable --- until it suddenly jack knifed.

Note the .4 G understeer requirement for the tow car in the US. The usual way to make a car understeer or oversteer is to transfer more weight to the outside wheel in a corner via stiffer springs or sway bars. Almost all cars are designed to understeer. By stiffening the rear suspension of an overloaded tow car, you are making it more likely to oversteer (i.e swing the rear end out first in a corner). That is the last thing you want with a swinging front heavy caravan on the back.

Joe, a little advice if I may as I have gone down this line myself.
I have an onroad single axle van which I have modified with independant coil spring suspension and while not a dedicated "offroad" van like yours it's pretty close in size, weight and ride height.
I've also modified and strengthened my chassis so the drawbar is like yours and 6" deep.
I had an older "classic" trunnion style Hayman Reese WDH and I found that with the deeper van chassis that clearance was an issue as the arms angle downward from the adjustable height towhitch to the caravan drawbar.
I also wanted to incorporate some type of sway control and for me the stand out in active sway control is Hayman Reese's dual cam sway control which is an active type of sway control which resists sway from the onset rather than reacting to it like the friction type sway controls work.
I won't go into electronic sway control except to say it's something I will have fitted later to act basically as a last line of defence.
If as you say you are looking at a WDH I would suggest you buy the "standard" series round bar type ones as these run under the drawbar and are designed to use with 6" deep van chassis as the pic below shows.



This next pic shows just how close the "classic" style series runs to the drawbar and this is on only a 4" deep chassis.



The link to the ebay seller gives an approximate price they sell for.
Hayman Reese 6" drawbar WDH

The benefit of buying this system is that if you wish you can add the dual cam sway control at a later stage if you wish.
If you were to buy the "classic" trunnion style WDH you may find it very difficult to fit the dual cam sway control due to the angle of the arms and their possible interference with a 6" deep van chassis.
I hope this gives you some food for thought.
Regards Andrew.