Jason was a bag of laughs ... I've seen lots of engineers like that.
I'll store that one away for the next time the airbag V WDH argument raises its head.
Thanks for sharing, as they say.
Aus-Kiwi said
06:17 PM Sep 25, 2018
No weight in back of truck . A little loaded . Plus all the weight INFRONT of trailer axles . My guess tow bar weight is very high ??
Cupie said
08:21 PM Sep 25, 2018
Aus-Kiwi wrote:
No weight in back of truck . A little loaded . Plus all the weight INFRONT of trailer axles . My guess tow bar weight is very high ??
Yes there were a few things like that eg. The tow ball was tilted backwards rather than the recommended slight tilt forward. Of course that would have no influence on the outcome.
It would have been great if the hitch had been adjusted to pull the rear sag back to standard.
-- Edited by Cupie on Tuesday 25th of September 2018 08:22:18 PM
miroku12g said
08:05 AM Sep 26, 2018
Question !
I was told not to have any more than 30 psi in my airbags, they had 55 psi, anyone with different ideas on that please.
Cheers
Dave M
mezza56 said
08:12 AM Sep 26, 2018
great vid Aussie Paul
Dickodownunder said
09:34 AM Sep 26, 2018
Great accurate info in your link Paul, thank you.
I am constantly surprised that there are still members of the towing fraternity around that operate vehicles which WDH systems are either recommended or at the very least, not discouraged, and they still argue that they are not needed.
rockylizard said
09:55 AM Sep 26, 2018
Gday...
The video gives a good indication of the different application of air bags to rear suspension and the application of WDH. Each has their place - neither are perfect solutions.
It should be remembered that a WDH is most commonly used for long or heavy caravans. If your van is light, well-balanced, and has a light ball load, you probably don't need a WDH.
-- Edited by rockylizard on Wednesday 26th of September 2018 09:59:35 AM
yobarr said
10:35 AM Sep 26, 2018
Dickodownunder wrote:
Great accurate info in your link Paul, thank you.
I am constantly surprised that there are still members of the towing fraternity around that operate vehicles which WDH systems are either recommended or at the very least, not discouraged, and they still argue that they are not needed.
And I suggest that the only reason that manufacturers recommend WDHs is to cover their rears in the event of an accident involving their car? Furthermore,I believe that WDHs are terribly over rated,giving people a false sense of security when used to remedy a problem that would not exist if the car and the van had been matched appropriately from the outset. WDHs are used by many in an attempt to make a car carry loads that it never was designed to carry.Because I spent many months doing research,I can run 6800kg GCM,legal on all axles,with no WDH.Get a more suitable car,or a lighter van.Simple really.Cheers
Cupie said
10:42 AM Sep 26, 2018
rockylizard wrote:
Gday...
The video gives a good indication of the different application of air bags to rear suspension and the application of WDH. Each has their place - neither are perfect solutions.
It should be remembered that a WDH is most commonly used for long or heavy caravans. If your van is light, well-balanced, and has a light ball load, you probably don't need a WDH.
-- Edited by rockylizard on Wednesday 26th of September 2018 09:59:35 AM
Interesting that two of the three articles reflect the views of the same 'Expert' Philip Lord. If I were sufficiently interested I would seek a third opinion in the search for balance.
In the one titled How a WDH works, I noted the recommendation that only 50% of the rise in the front wheel arch (FALR) be achieved by the WDH adjustment. Looks like I might have fluked that one too. I have long pondered, in my ignorance, if I could recover 100% of the load reduction but fortunately put it in the Too Hard basket.
BTW my GQ Patrol AVM is 2.8ton v the Westport's ATM 2.34 so we got that right too. Sometimes its good to have an old banger and almost vintage van. Financially it was good too with new van & < 50,000km GQ was <$70,000, less than the price of an equivalent van of today perhaps.
-- Edited by Cupie on Wednesday 26th of September 2018 10:44:27 AM
rockylizard said
11:03 AM Sep 26, 2018
Gday...
Which links did ya click Cupie?
RVBooks author - Collyn Rivers - (yeah - as per Dickdownunder's recommendation - woodn't know nuffin)
Without a hitch author - Laura Gray (yeah - wot wood a woman know )
Caravancampingsales author - Philip Lord (yeah - wot would some man journo know)
Yep - three people all with similar opinions MUST be wrong.
Interestingly, they do NOT say do NOT use a WDH - just that a WDH is not the 100% solution to EVERY caravan/vehicle combination.
I think they each agree that a WDH has its applications - but it is not the panacea too many think.
Cheers - John
-- Edited by rockylizard on Wednesday 26th of September 2018 11:04:34 AM
Aus-Kiwi said
11:17 AM Sep 26, 2018
How about a decent tow vehicle ? Licence !! How about both ? Drive appropriately ! I found the WDH tends to push , understeer . But I was pushing way harder that I would on holidays etc . Wouldnt normally drive like that pushing limits ., I would use both .
-- Edited by Aus-Kiwi on Wednesday 26th of September 2018 11:19:37 AM
Cupie said
11:23 AM Sep 26, 2018
rockylizard wrote:
Gday...
Which links did ya click Cupie?
RVBooks author - Collyn Rivers - (yeah - as per Dickdownunder's recommendation - woodn't know nuffin)
Without a hitch author - Laura Gray (yeah - wot wood a woman know )
Caravancampingsales author - Philip Lord (yeah - wot would some man journo know)
Yep - three people all with similar opinions MUST be wrong.
Interestingly, they do NOT say do NOT use a WDH - just that a WDH is not the 100% solution to EVERY caravan/vehicle combination.
I think they each agree that a WDH has its applications - but it is not the panacea too many think.
Cheers - John
-- Edited by rockylizard on Wednesday 26th of September 2018 11:04:34 AM
The 'Ask an Expert' article .... in its first paragraph says ...
"So how do you know if you need one or not? We asked our expert tow tester Philip Lord for his advice."
The last article is attributed/written by Philip Lord.
Of course we all worship Collyn Rivers. His view is certainly to be valued.
Yes, I accept your interpretation of their views & didn't challenge that.
As to the sexist comments... your words not mine. I made no such comment.
Is it valid to imply 'here are three concurring views', ergo they MUST be correct. Indeed they might.
My last word on this topic ... bye.
Rod Mac said
04:30 PM Sep 26, 2018
Yep seen that video before, do not agree with them putting the load in front of the trailer axle, poor weight loading, demonstrated by the amount of weight coming off the front axle.
Rod Mac said
04:54 PM Sep 26, 2018
Hi I run my air bags at (old measurement) 20psi not towing and 50psi when towing, no problem as the instructions state a max of 60psi.
Tow vehicle is a 2016 Pajero, van is a tandem axle pop top with 200kg on the ball, no WDH used or fitted.
Vehicle sits near level and handles the load no problem ( van 2200kg loaded and off the ball)
Best check the make of bags and get correct info, not just someone with a verbal comment.
-- Edited by Rod Mac on Wednesday 26th of September 2018 04:55:50 PM
Dickodownunder said
07:24 PM Sep 26, 2018
We could all go on and on about the fores and against but, physics say that if you place a weight ( any weight ) behind the rear axle on a tow vehicle by means of a draw bar and tow bar fixture then that weight is going to cause weight to be removed from the FRONT axle.
It doesnt matter wether it is a lightly loaded well balanced caravan the simple matter is that if weight is applied to the tow vehicles suspension behind the c/l of the rear axle then weight WILL be removed from the steer when hooked up.
The front axle is the steer axle in almost all of the combinations we are dealing with in this discussion.
When weight is removed from a steer axle it may contribute towards the towing stability of the combination both with steering and braking.
Go for a walk around the next busy caravan park you may be in and ask each person if they have actually weighed their combination with attention to axle and drawbar weights and with attention to the weights on the steer axle both when hooked up and unhooked.
Most will look at you like you have two heads and for that reason alone in most cases it may be safer that they were using a WDH.
For those same people to be told that they dont need one could be extremely detrimental to their safe operation.
Please yourselves wether you use a WDH or not, really it is your individual choice but to blindly follow advice from an authors who can not state recognisable qualifications apart from whose agenda is to sell publications, and worse still suggest on a forum that a person with no experience should follow that advice is fraught with danger.
A newbie with a caravan and a tow vehicle should be checking all the parameters of safety and I personally take a video as linked by Paul in the OP is a basis and a start for far safer information than some who say that his vehicle is safe because he said so on a forum.
Every persons situation with loading, weights of vehicles, weights of caravans / trailers WILL be different.
No one will be able to apply well intended but not necessarily correct information and recommendations to ANOTHERS combination.
So to all the experts who find a need to pick posts that dont fit into their agenda to pieces then go ahead but I will adopt the same approach as Cupie above....
Bye!
wasn_me said
09:56 AM Sep 27, 2018
I believe one of the functions of the WDH has been missed in the video & following discussions.
I have 180 kg on my tow ball, Maybe 100 kg in the tug behind the axle.
That's 280 kg attempting to lift the steer wheels off the ground.
280 kg won't lift the steer wheels off the ground as there's more weight up front.
That's fine while I'm driving along a perfectly flat road. No different to sitting in the driveway at home.
However Australian roads are far from flat. If the combination drives into a creek culvert, that 280kg is going downwards at a great rate, while the steer axle is starting to lift as it comes out of the culvert. That 280 kg is multiplied greatly at the bottom of the culvert, assisting to lift the steer axle. Possibly to the stage of loosing steering momentarily.
This can happen on any undulating road, & this is where a WDH is essential to reduce that downward force.
yobarr said
10:31 AM Sep 27, 2018
wasn_me wrote:
I believe one of the functions of the WDH has been missed in the video & following discussions.
I have 180 kg on my tow ball, Maybe 100 kg in the tug behind the axle.
That's 280 kg attempting to lift the steer wheels off the ground.
280 kg won't lift the steer wheels off the ground as there's more weight up front.
That's fine while I'm driving along a perfectly flat road. No different to sitting in the driveway at home.
However Australian roads are far from flat. If the combination drives into a creek culvert, that 280kg is going downwards at a great rate, while the steer axle is starting to lift as it comes out of the culvert. That 280 kg is multiplied greatly at the bottom of the culvert, assisting to lift the steer axle. Possibly to the stage of loosing steering momentarily.
This can happen on any undulating road, & this is where a WDH is essential to reduce that downward force.
Hi Peter...interesting note,but full of misunderstandings,I believe.First if all,if you have 180kg TBW and another 100kg behind the back axle,there is no way that the full 100kg can be added to the TBW unless it also is centred directly over the towball.Lets assume that half that weight is applied to the towball and the rest to the cars rear axle....you now have 180kg plus 50kg effectively.This gives 230kg,but the weight removed from the front axle is nowhere near 230kg because the TBO,or distance from the rear axle of the car to the hitch point is significantly less than your wheelbase.TBO in BT50 is about 1200mm while wheelbase is 3220mm,which means that the wheelbase is about 2.7 times the TBO so the leverage effect is dramatically lower than you might think.230kg divided by 2.7 is only 85kg.Next is your comment about entering a creek bed.....there is no way known that any person with more than half a brain would use a WDH whilst crossing a creek culvert! All a WDH does is create what is effectively a stiff-arm from the front axle of the car,through the hitch point,to the vans axle group,so everything is fine and dandy when the whole rig is on a flat surface. However,can you imagine the massive forces applied to the drawbar, towbar and the cars chassis when one axle. .....any axle....drops below the level of the other two.And people wonder why their towbars,drawbars and chassis break! Spare me.
-- Edited by yobarr on Thursday 27th of September 2018 10:31:40 AM
Collyn Rivers said
05:57 PM Dec 2, 2018
The WDH was initially an Australian invention. Hayman Reese invented it in 1950 - but it mainly caught on initially in the USA.
In my opinion its use is virtually essential if you choose to tow a long and end-heavy caravan that weighs more than the tow vehicle. If one does, however, it is essential to know that it inherently reduces the rig's maximum 'cornering power' by about 25%. It is better by far to have a more balanced rig that has no need of a WDH.
The reason why is that a WDH transfers part of the imposed tow ball weight from the tow vehicle's rear tyres to restore part of that otherwise removed from the front tyres. This reduces their cornering power (i.e. increases their slip angle). The WDH does not (cannot), however, reduce lateral yaw forces imposed by yaw (sway) on those tyres now less able to resist them.
This can be partially corrected by increasing the tow vehicle's rear tyre pressures by 50 to 70 kPa and reducing the front tyres by 20-40 kPA. This will assist restore the desired margin of understeer required for stability. It also assists to only restore about 50% of the front axle loading.
I'd like to add (with respect) that some confusion is occurring in this thread by the occasional misunderstanding use of the term 'weight'. Weight is simply a force resulting as a result of gravity acting on mass. The WDH does not move mass (that needs an angle grinder and arc welder!) - it simply moves the downforce of weight.
In essence - if you are using a WDH be aware that it inherently reduces your maximum cornering power.
Collyn
Mike Harding said
07:54 PM Dec 2, 2018
Very good to see you here Collyn and I look forward to your knowledgeable contributions.
yobarr said
08:02 PM Dec 2, 2018
Mike Harding wrote:
Very good to see you here Collyn and I look forward to your knowledgeable contributions.
Like Mike,I am very happy to see Collyn here,as his wisdom and experience is unrivalled.Welcome Collyn!
Dickodownunder said
10:52 PM Dec 2, 2018
Collyn Rivers wrote:
In my opinion its use is virtually essential if you choose to tow a long and end-heavy caravan that weighs more than the tow vehicle. If one does, however, it is essential to know that it inherently reduces the rig's maximum 'cornering power' by about 25%. It is better by far to have a more balanced rig that has no need of a WDH.
The reason why is that a WDH transfers part of the imposed tow ball weight from the tow vehicle's rear tyres to restore part of that otherwise removed from the front tyres. This reduces their cornering power (i.e. increases their slip angle). The WDH does not (cannot), however, reduce lateral yaw forces imposed by yaw (sway) on those tyres now less able to resist them.
This can be partially corrected by increasing the tow vehicle's rear tyre pressures by 50 to 70 kPa and reducing the front tyres by 20-40 kPA. This will assist restore the desired margin of understeer required for stability. It also assists to only restore about 50% of the front axle loading.
I'd like to add (with respect) that some confusion is occurring in this thread by the occasional misunderstanding use of the term 'weight'. Weight is simply a force resulting as a result of gravity acting on mass. The WDH does not move mass (that needs an angle grinder and arc welder!) - it simply moves the downforce of weight.
In essence - if you are using a WDH be aware that it inherently reduces your maximum cornering power.
Collyn
Welcome to this forum Collyn
I actually had to watch the video again to ensure that I had not missed the exercise when the two gentlemen connected the WDH and weighed the axle groups.
The weight, or if you like, the gravity acting on mass, increased on the front axle and on the trailer axle as a direct result of the WDH being connected.
While I basically understand your fears of the effect on steering my thoughts are that the fact that removing the gravity acting on mass (weight) from the front wheels has more of a detrimental condition with steering than does the use of a WDH.
The fact that this gravity acting on mass (weight) is less on the steer wheels not only may induce dangerous understeer when towing a van or trailer but it will create a serious and potentially dangerous lack of braking on this axle.
This lack of braking would be a direct result of less traction or grip due to less weight (gravity acting on mass) on the steer tyres.
I have followed your comments Collyn on WDH use from other forums and I can't recall it being mentioned this loss of braking efficiency on the front axle.
I did not see where the two fellows in the video in Pauls link in the first post did any other modification with welders or any engineering equipment but the gravity acting on mass (weight) increased on the steer axle by merely connecting the WDH.
With respect Collyn I wonder how the figure of 25% steering loss was achieved in your tests as how I interpret it, the percentage of steering loss would have a few variables, the first of which would be actually what type (brand) of WDH was under test and what type of road surface.
For example the type of WDH that has a sway control in the form of a friction cone would display a different result that a standard WDH with no sway control.The WDH kits with sway control rams would be different again. A poorly serviced WDH without any sway control may change the percentage figure again due to nothing else but extra friction caused by lack of lubrication. And yet another type of WDH that has the spring bars ride in a saddle fitted to the caravan drawbar will offer more friction than the type with chains. The actual angle of the tapering drawbar in as much as a longer drawbar will offer less resistance to most of the WDH systems particularly the ones using friction bar mounts. An extended drawbar would have a different result with friction on the bars and would offer less resistance when turning. This again could be variable depending on the engineering design of each system.
The very act of towing a pig trailer with a vehicle that has a towing pivot point behind the centre line of the rear axle will have a tendency to an increased understeer attitude when driving. The trailer will have a pushing effect on the tow vehicle.
My thoughts are that if there is a measured amount of steering loss of 25% with the use of a WDH there would be many a number of virtually non driveable combinations. I suggest that the loss of braking on the front axle when not using a WDH would be of as much or more concern to any authority that may be assessing safety.
Again, with respect I become disturbed when anyone suggests on an open forum the advice to alter the tyre pressures to an advised figure which may very easily fall outside the specifications of the tyre and / or the vehicle manufacturer.
From what I have understood a lot of your research is from British point of view but I think the second sentence of your post pretty much covers a good proportion of Aussie vehicles and caravans and that is that they are long, generally unbalanced and towed by a vehicle that will be close to, if not lighter than the caravan.
To all those who still may be with me in reading this post I ask that you go up read my first post above where I said about anyone going and talking to people with vans and the majority of them have no clue what their weights are. If these same people are using a WDH and then read on an open forum that there are some who recommend not using them and they decide to blindly follow that advice my thoughts are that this may be fraught with danger.
In that post above I also said
"We could all go on and on about the fores and against but, physics say that if you place a weight ( any weight ) behind the rear axle on a tow vehicle by means of a draw bar and tow bar fixture then that weight is going to cause weight to be removed from the FRONT axle.
It doesnt matter wether it is a lightly loaded well balanced caravan the simple matter is that if weight is applied to the tow vehicles suspension behind the c/l of the rear axle then weight WILL be removed from the steer when hooked up.
The front axle is the steer axle in almost all of the combinations we are dealing with in this discussion.
When weight is removed from a steer axle it may contribute towards the towing stability of the combination both with steering and braking."
With regard to this topic we probably should all be using a fifth wheel combination vehicles and caravans but while authorities permit what the majority of vanners are doing out there with respect to weights of vehicles and vans, the use of any devices to make the combination safer can only be a bonus and I might add that even if all our combinations were fifth wheelers then there would still be people who will blindly (or deliberately)overload their combination.
-- Edited by Dickodownunder on Sunday 2nd of December 2018 11:08:21 PM
-- Edited by Dickodownunder on Monday 3rd of December 2018 01:17:56 AM
Collyn Rivers said
11:08 AM Dec 3, 2018
Dickodownunder
I normally no longer respond to posts such as this except provide evidence (to suggest) that if my background was good enough to design and test most of the equipment used in this very area during my years with Vauxhall Bedford Research as a Test Engineer it is probably overkill for this forum. Here is that evidence. Scroll down and you will find a pic of me plus that proof.
I normally no longer respond to posts such as this except provide evidence (to suggest) that if my background was good enough to design and test most of the equipment used in this very area during my years with Vauxhall Bedford Research as a Test Engineer it is probably overkill for this forum. Here is that evidence. Scroll down and you will find a pic of me plus that proof.
It must have been a interesting and challenging time in your career and I am sure we are all amazed how technology has advanced in the last 60 years or so.
Cheers
Collyn Rivers said
11:54 AM Dec 3, 2018
One series of posts on this thread confuses understeer (a required condition for stability) with oversteer throughout. Possibly others may spot it too.
Increasing pressure in the rear tyres assists to restore the otherwise loss of required understeer when a caravan is hitched up.
If people seriously believe weight alone is critical over steered wheels consider how a Harley Davidson trike with two heavy men could possibly go other than in a straight line. It's a lot to do with relative (front/rear slip angles)
Note also that a rubber tyre does not follow the normal laws of Coloumb friction. The grip is partly friction and partly molecular.
The query re 'approximately 25% loss in cornering power' is deduced from SAE J2807. This Recommendation is now followed by all US tow vehicle makers plus the top three Japanese.
The actual loss is related to the percentage of WDH load restoration and the maximum g level at which there is no loss of understeer. At 100% as typically used in Australia that limit is 0.3 g. As 50% it is 0.4 g.
Re friction mechanisms - all suffer from the same failing: their extent of friction remains constant - but the forces they address increase with the square of the rig's speed. At anything over 80 km/h their effect is down to about 1%/. Dual-cam is all - or literally nothing when the yaw forces overwhelm the sprung cam action.
For those who are unaware of how I work - I have a few minor concepts of my own but primarily summarise the work of the few true experts in this area. They are thus not 'Collyn's theories. The source documents are available but some are very costly, in techo-talk and a mass of mathematics. I attempt to turn them into readable English. As in all such work, all theory is backed by very thorough (and sometime border-line dangerous testing.
I have almost completed my own text in this area and hope to publish it next year. As with my own (newish) it is valid for Australia, USA and Canada.
For a UK view (that reflects UK/EU differences) see the excellent Caravan Chronicles website.
https://youtu.be/XBZu39pQ8Gg
Aussie Paul.
That tells the story very clearly.
WDH + Airbags -
Jason was a bag of laughs ... I've seen lots of engineers like that.
I'll store that one away for the next time the airbag V WDH argument raises its head.
Thanks for sharing, as they say.
Yes there were a few things like that eg. The tow ball was tilted backwards rather than the recommended slight tilt forward. Of course that would have no influence on the outcome.
It would have been great if the hitch had been adjusted to pull the rear sag back to standard.
-- Edited by Cupie on Tuesday 25th of September 2018 08:22:18 PM
I was told not to have any more than 30 psi in my airbags, they had 55 psi, anyone with different ideas on that please.
Cheers
Dave M
great vid Aussie Paul
I am constantly surprised that there are still members of the towing fraternity around that operate vehicles which WDH systems are either recommended or at the very least, not discouraged, and they still argue that they are not needed.
Gday...
The video gives a good indication of the different application of air bags to rear suspension and the application of WDH. Each has their place - neither are perfect solutions.
It should be remembered that a WDH is most commonly used for long or heavy caravans. If your van is light, well-balanced, and has a light ball load, you probably don't need a WDH.
A read through this site is worthwhile as well -
https://www.rvbooks.com.au/page/how-a-weight-distributing-hitch-works/
or praps this - http://www.withoutahitch.com.au/caravan/ask-expert-need-weight-distribution-hitch/
or this praps - https://www.caravancampingsales.com.au/editorial/details/are-load-levellers-a-waste-of-time-56620/
Cheers - John
-- Edited by rockylizard on Wednesday 26th of September 2018 09:59:35 AM
And I suggest that the only reason that manufacturers recommend WDHs is to cover their rears in the event of an accident involving their car? Furthermore,I believe that WDHs are terribly over rated,giving people a false sense of security when used to remedy a problem that would not exist if the car and the van had been matched appropriately from the outset. WDHs are used by many in an attempt to make a car carry loads that it never was designed to carry.Because I spent many months doing research,I can run 6800kg GCM,legal on all axles,with no WDH.Get a more suitable car,or a lighter van.Simple really.Cheers
Interesting that two of the three articles reflect the views of the same 'Expert' Philip Lord. If I were sufficiently interested I would seek a third opinion in the search for balance.
In the one titled How a WDH works, I noted the recommendation that only 50% of the rise in the front wheel arch (FALR) be achieved by the WDH adjustment. Looks like I might have fluked that one too. I have long pondered, in my ignorance, if I could recover 100% of the load reduction but fortunately put it in the Too Hard basket.
BTW my GQ Patrol AVM is 2.8ton v the Westport's ATM 2.34 so we got that right too. Sometimes its good to have an old banger and almost vintage van. Financially it was good too with new van & < 50,000km GQ was <$70,000, less than the price of an equivalent van of today perhaps.
-- Edited by Cupie on Wednesday 26th of September 2018 10:44:27 AM
Gday...
Which links did ya click Cupie?
RVBooks author - Collyn Rivers - (yeah - as per Dickdownunder's recommendation - woodn't know nuffin)
Without a hitch author - Laura Gray (yeah - wot wood a woman know
)
Caravancampingsales author - Philip Lord (yeah - wot would some man journo know)
Yep - three people all with similar opinions MUST be wrong.
Interestingly, they do NOT say do NOT use a WDH - just that a WDH is not the 100% solution to EVERY caravan/vehicle combination.
I think they each agree that a WDH has its applications - but it is not the panacea too many think.
Cheers - John
-- Edited by rockylizard on Wednesday 26th of September 2018 11:04:34 AM
How about a decent tow vehicle ? Licence !! How about both ? Drive appropriately ! I found the WDH tends to push , understeer . But I was pushing way harder that I would on holidays etc . Wouldnt normally drive like that pushing limits ., I would use both .
-- Edited by Aus-Kiwi on Wednesday 26th of September 2018 11:19:37 AM
The 'Ask an Expert' article .... in its first paragraph says ...
"So how do you know if you need one or not? We asked our expert tow tester Philip Lord for his advice."
The last article is attributed/written by Philip Lord.
Of course we all worship Collyn Rivers. His view is certainly to be valued.
Yes, I accept your interpretation of their views & didn't challenge that.
As to the sexist comments... your words not mine. I made no such comment.
Is it valid to imply 'here are three concurring views', ergo they MUST be correct. Indeed they might.
My last word on this topic ... bye.
Yep seen that video before, do not agree with them putting the load in front of the trailer axle, poor weight loading, demonstrated by the amount of weight coming off the front axle.
Hi I run my air bags at (old measurement) 20psi not towing and 50psi when towing, no problem as the instructions state a max of 60psi.
Tow vehicle is a 2016 Pajero, van is a tandem axle pop top with 200kg on the ball, no WDH used or fitted.
Vehicle sits near level and handles the load no problem ( van 2200kg loaded and off the ball)
Best check the make of bags and get correct info, not just someone with a verbal comment.
-- Edited by Rod Mac on Wednesday 26th of September 2018 04:55:50 PM
It doesnt matter wether it is a lightly loaded well balanced caravan the simple matter is that if weight is applied to the tow vehicles suspension behind the c/l of the rear axle then weight WILL be removed from the steer when hooked up.
The front axle is the steer axle in almost all of the combinations we are dealing with in this discussion.
When weight is removed from a steer axle it may contribute towards the towing stability of the combination both with steering and braking.
Go for a walk around the next busy caravan park you may be in and ask each person if they have actually weighed their combination with attention to axle and drawbar weights and with attention to the weights on the steer axle both when hooked up and unhooked.
Most will look at you like you have two heads and for that reason alone in most cases it may be safer that they were using a WDH.
For those same people to be told that they dont need one could be extremely detrimental to their safe operation.
Please yourselves wether you use a WDH or not, really it is your individual choice but to blindly follow advice from an authors who can not state recognisable qualifications apart from whose agenda is to sell publications, and worse still suggest on a forum that a person with no experience should follow that advice is fraught with danger.
A newbie with a caravan and a tow vehicle should be checking all the parameters of safety and I personally take a video as linked by Paul in the OP is a basis and a start for far safer information than some who say that his vehicle is safe because he said so on a forum.
Every persons situation with loading, weights of vehicles, weights of caravans / trailers WILL be different.
No one will be able to apply well intended but not necessarily correct information and recommendations to ANOTHERS combination.
So to all the experts who find a need to pick posts that dont fit into their agenda to pieces then go ahead but I will adopt the same approach as Cupie above....
Bye!
I believe one of the functions of the WDH has been missed in the video & following discussions.
I have 180 kg on my tow ball, Maybe 100 kg in the tug behind the axle.
That's 280 kg attempting to lift the steer wheels off the ground.
280 kg won't lift the steer wheels off the ground as there's more weight up front.
That's fine while I'm driving along a perfectly flat road. No different to sitting in the driveway at home.
However Australian roads are far from flat. If the combination drives into a creek culvert, that 280kg is going downwards at a great rate, while the steer axle is starting to lift as it comes out of the culvert. That 280 kg is multiplied greatly at the bottom of the culvert, assisting to lift the steer axle. Possibly to the stage of loosing steering momentarily.
This can happen on any undulating road, & this is where a WDH is essential to reduce that downward force.
Hi Peter...interesting note,but full of misunderstandings,I believe.First if all,if you have 180kg TBW and another 100kg behind the back axle,there is no way that the full 100kg can be added to the TBW unless it also is centred directly over the towball.Lets assume that half that weight is applied to the towball and the rest to the cars rear axle....you now have 180kg plus 50kg effectively.This gives 230kg,but the weight removed from the front axle is nowhere near 230kg because the TBO,or distance from the rear axle of the car to the hitch point is significantly less than your wheelbase.TBO in BT50 is about 1200mm while wheelbase is 3220mm,which means that the wheelbase is about 2.7 times the TBO so the leverage effect is dramatically lower than you might think.230kg divided by 2.7 is only 85kg.Next is your comment about entering a creek bed.....there is no way known that any person with more than half a brain would use a WDH whilst crossing a creek culvert! All a WDH does is create what is effectively a stiff-arm from the front axle of the car,through the hitch point,to the vans axle group,so everything is fine and dandy when the whole rig is on a flat surface. However,can you imagine the massive forces applied to the drawbar, towbar and the cars chassis when one axle. .....any axle....drops below the level of the other two.And people wonder why their towbars,drawbars and chassis break! Spare me.
-- Edited by yobarr on Thursday 27th of September 2018 10:31:40 AM
The WDH was initially an Australian invention. Hayman Reese invented it in 1950 - but it mainly caught on initially in the USA.
In my opinion its use is virtually essential if you choose to tow a long and end-heavy caravan that weighs more than the tow vehicle. If one does, however, it is essential to know that it inherently reduces the rig's maximum 'cornering power' by about 25%. It is better by far to have a more balanced rig that has no need of a WDH.
The reason why is that a WDH transfers part of the imposed tow ball weight from the tow vehicle's rear tyres to restore part of that otherwise removed from the front tyres. This reduces their cornering power (i.e. increases their slip angle). The WDH does not (cannot), however, reduce lateral yaw forces imposed by yaw (sway) on those tyres now less able to resist them.
This can be partially corrected by increasing the tow vehicle's rear tyre pressures by 50 to 70 kPa and reducing the front tyres by 20-40 kPA. This will assist restore the desired margin of understeer required for stability. It also assists to only restore about 50% of the front axle loading.
I'd like to add (with respect) that some confusion is occurring in this thread by the occasional misunderstanding use of the term 'weight'. Weight is simply a force resulting as a result of gravity acting on mass. The WDH does not move mass (that needs an angle grinder and arc welder!) - it simply moves the downforce of weight.
In essence - if you are using a WDH be aware that it inherently reduces your maximum cornering power.
Collyn
Very good to see you here Collyn and I look forward to your knowledgeable contributions.
Like Mike,I am very happy to see Collyn here,as his wisdom and experience is unrivalled.Welcome Collyn!
Welcome to this forum Collyn
I actually had to watch the video again to ensure that I had not missed the exercise when the two gentlemen connected the WDH and weighed the axle groups.
The weight, or if you like, the gravity acting on mass, increased on the front axle and on the trailer axle as a direct result of the WDH being connected.
While I basically understand your fears of the effect on steering my thoughts are that the fact that removing the gravity acting on mass (weight) from the front wheels has more of a detrimental condition with steering than does the use of a WDH.
The fact that this gravity acting on mass (weight) is less on the steer wheels not only may induce dangerous understeer when towing a van or trailer but it will create a serious and potentially dangerous lack of braking on this axle.
This lack of braking would be a direct result of less traction or grip due to less weight (gravity acting on mass) on the steer tyres.
I have followed your comments Collyn on WDH use from other forums and I can't recall it being mentioned this loss of braking efficiency on the front axle.
I did not see where the two fellows in the video in Pauls link in the first post did any other modification with welders or any engineering equipment but the gravity acting on mass (weight) increased on the steer axle by merely connecting the WDH.
With respect Collyn I wonder how the figure of 25% steering loss was achieved in your tests as how I interpret it, the percentage of steering loss would have a few variables, the first of which would be actually what type (brand) of WDH was under test and what type of road surface.
For example the type of WDH that has a sway control in the form of a friction cone would display a different result that a standard WDH with no sway control.The WDH kits with sway control rams would be different again. A poorly serviced WDH without any sway control may change the percentage figure again due to nothing else but extra friction caused by lack of lubrication. And yet another type of WDH that has the spring bars ride in a saddle fitted to the caravan drawbar will offer more friction than the type with chains. The actual angle of the tapering drawbar in as much as a longer drawbar will offer less resistance to most of the WDH systems particularly the ones using friction bar mounts. An extended drawbar would have a different result with friction on the bars and would offer less resistance when turning. This again could be variable depending on the engineering design of each system.
The very act of towing a pig trailer with a vehicle that has a towing pivot point behind the centre line of the rear axle will have a tendency to an increased understeer attitude when driving. The trailer will have a pushing effect on the tow vehicle.
My thoughts are that if there is a measured amount of steering loss of 25% with the use of a WDH there would be many a number of virtually non driveable combinations. I suggest that the loss of braking on the front axle when not using a WDH would be of as much or more concern to any authority that may be assessing safety.
Again, with respect I become disturbed when anyone suggests on an open forum the advice to alter the tyre pressures to an advised figure which may very easily fall outside the specifications of the tyre and / or the vehicle manufacturer.
From what I have understood a lot of your research is from British point of view but I think the second sentence of your post pretty much covers a good proportion of Aussie vehicles and caravans and that is that they are long, generally unbalanced and towed by a vehicle that will be close to, if not lighter than the caravan.
Cheers Collyn and once again, welcome.
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To all those who still may be with me in reading this post I ask that you go up read my first post above where I said about anyone going and talking to people with vans and the majority of them have no clue what their weights are. If these same people are using a WDH and then read on an open forum that there are some who recommend not using them and they decide to blindly follow that advice my thoughts are that this may be fraught with danger.
In that post above I also said
"We could all go on and on about the fores and against but, physics say that if you place a weight ( any weight ) behind the rear axle on a tow vehicle by means of a draw bar and tow bar fixture then that weight is going to cause weight to be removed from the FRONT axle.
It doesnt matter wether it is a lightly loaded well balanced caravan the simple matter is that if weight is applied to the tow vehicles suspension behind the c/l of the rear axle then weight WILL be removed from the steer when hooked up.
The front axle is the steer axle in almost all of the combinations we are dealing with in this discussion.
When weight is removed from a steer axle it may contribute towards the towing stability of the combination both with steering and braking."
With regard to this topic we probably should all be using a fifth wheel combination vehicles and caravans but while authorities permit what the majority of vanners are doing out there with respect to weights of vehicles and vans, the use of any devices to make the combination safer can only be a bonus and I might add that even if all our combinations were fifth wheelers then there would still be people who will blindly (or deliberately)overload their combination.
-- Edited by Dickodownunder on Sunday 2nd of December 2018 11:08:21 PM
-- Edited by Dickodownunder on Monday 3rd of December 2018 01:17:56 AM
I normally no longer respond to posts such as this except provide evidence (to suggest) that if my background was good enough to design and test most of the equipment used in this very area during my years with Vauxhall Bedford Research as a Test Engineer it is probably overkill for this forum. Here is that evidence. Scroll down and you will find a pic of me plus that proof.
vauxpedianet.uk2sitebuilder.com/vauxhall---chaul-end-engineering-research-test-centre
Collyn
Good morning Collyn
No real need for you to respond.
Thank you for the informative link.
It must have been a interesting and challenging time in your career and I am sure we are all amazed how technology has advanced in the last 60 years or so.
Cheers
One series of posts on this thread confuses understeer (a required condition for stability) with oversteer throughout. Possibly others may spot it too.
Increasing pressure in the rear tyres assists to restore the otherwise loss of required understeer when a caravan is hitched up.
If people seriously believe weight alone is critical over steered wheels consider how a Harley Davidson trike with two heavy men could possibly go other than in a straight line. It's a lot to do with relative (front/rear slip angles)
Note also that a rubber tyre does not follow the normal laws of Coloumb friction. The grip is partly friction and partly molecular.
The query re 'approximately 25% loss in cornering power' is deduced from SAE J2807. This Recommendation is now followed by all US tow vehicle makers plus the top three Japanese.
The actual loss is related to the percentage of WDH load restoration and the maximum g level at which there is no loss of understeer. At 100% as typically used in Australia that limit is 0.3 g. As 50% it is 0.4 g.
Re friction mechanisms - all suffer from the same failing: their extent of friction remains constant - but the forces they address increase with the square of the rig's speed. At anything over 80 km/h their effect is down to about 1%/. Dual-cam is all - or literally nothing when the yaw forces overwhelm the sprung cam action.
For those who are unaware of how I work - I have a few minor concepts of my own but primarily summarise the work of the few true experts in this area. They are thus not 'Collyn's theories. The source documents are available but some are very costly, in techo-talk and a mass of mathematics. I attempt to turn them into readable English. As in all such work, all theory is backed by very thorough (and sometime border-line dangerous testing.
I have almost completed my own text in this area and hope to publish it next year. As with my own (newish) it is valid for Australia, USA and Canada.
For a UK view (that reflects UK/EU differences) see the excellent Caravan Chronicles website.
Collyn