This might be of interest to anyone who uses a WDH
https://www.youtube.com/watch?v=09ydYbbONBw
yobarr said
08:11 PM May 27, 2023
JackoFJR wrote:
This might be of interest to anyone who uses a WDH
https://www.youtube.com/watch?v=09ydYbbONBw
Thanks Ron. This video has been around for some years now but the adoring fans of WDH units need to understand that the apparent increase in towball weight is simply a clamping force. The actual towball weight does not change.
More technically gifted persons (KJB?) may choose to explain the physics in detail, but members who dont understand would do well to access videos by John Cadogan where everything is explained clearly and simply.
But I wont hold me breath as some operators simply dont want to know. Cest la vie. Cheers
-- Edited by yobarr on Sunday 28th of May 2023 05:42:00 PM
Possum3 said
07:38 AM May 28, 2023
Sorry Chris, the WDH actually causes a lever wherein the rear axle is the fulcrum, it's action which transfers "weight" to front axles, doesn't increase GVM (Gross Vehicle Mass) of tug other than the carrying of extra weight from the WDH assembly itself.
yobarr said
08:06 AM May 28, 2023
Possum3 wrote:
Sorry Chris, the WDH actually causes a lever wherein the rear axle is the fulcrum, it's action which transfers "weight" to front axles, doesn't increase GVM (Gross Vehicle Mass) of tug other than the carrying of extra weight from the WDH assembly itself.
Hi Possum.Total mass of car (GVM if you like) decreases while total mass of trailer (ATM if you like) increases.
Weight is transferred from rear axle of car to front axle of car, and also to axle group of the trailer (van).
Percentage of weight transferred to each is dependent on many things, such as wheelbase of car, TBO (Towball overhang) and forward length of van. Towball weight remains constant.
Other variables play their part too, but Im off to work now so can't elaborate.
Perhaps I'll find time to give you a call next Friday or Saturday. Cheers
P.S The rear axle is not the fulcrum as a well-tightened WDH can actually lift the rear axle of a car off the ground.
-- Edited by yobarr on Sunday 28th of May 2023 10:28:31 AM
watsea said
05:56 PM May 28, 2023
If anyone is interested, in another similar thread on this forum, I did two postings with some information and some calculations using physics for an example vehicle and van, with and without a WDH.
i am sorry that I am not savvy enough with this forum to link those two posts into this post. Also I find it difficult to copy a whole post with attachments onto another post while using my iPad.
My other posts were in Techies' Corner, Weights and Measures, topic "WDH again"
times and dates as:
3.24 pm May 13, 2023
4.28 pm May 14, 2023
See some numbers to inform yourself.
Are We Lost said
08:35 PM May 28, 2023
Probably not so easy on a tablet, but for a PC browser ....
Go back to your post and click Permalink. The address bar now points to the specific post. Copy that URL and then type some words in your new post to describe the link. Highlight those words and click the link button (chain links). Paste the URL into the popup panel and choose for the target to open in new window.
-- Edited by Are We Lost on Sunday 28th of May 2023 08:37:06 PM
watsea said
10:11 PM May 28, 2023
Thanks Are We Lost. I tried the Permalink but got a bit lost.
Your link will help.
I will remember next time, if I feel inclined to copy a post.
I am hoping if people are interested that they will go to my posts for some more information where some physics has been used.
RAvanner said
03:26 PM Jan 13, 2024
Arriving late to this party and the real WDH party is always fun. The real party began sometime between 1978 to 1983 when an American engineer named Richard Klein wrote several papers not specifically about WDHs but in which he described their operation using several (five) static equations. The experiments that he reports also validate the equations for the impact of a WDH on the axle loads of a vehicle and caravan (pig trailer).
Hopefully it is accepted that the following occurs when a WDH is employed. That is that there is some addition to the front axle load, there is a reduction to the rear axle load and there is also an increase to the caravan axle load. The following table illustrates this. The table is one of around fifteen in situation weight checks conducted at Yarragon (Vic) West bound.
Front axle Rear axle Ball Load Van Axle Delta front Delta rear
Vehicle only 1160 kg 1300 kg
Vehicle with ball load 1020 kg 1760 kg -140 kg + 460 kg
Vehicle with BL and LL 1140 kg 1600 kg +120 kg -160 kg
Van BL 320 kg
GTM no LL 2420 kg
GTM LL 2460 kg + 40 kg
This particular weight check did report overload conditions as did ten others of the total fifteen checks conducted.
Unsurprisingly the sum of the reaction forces in all three configurations equals the total mass of the vehicle and caravan.
Before proceeding, recount Newton. For every action there is an equal and opposite reaction and Archimedes who is attributed with give me a fulcrum and a long enough lever and I will move the world Why these quotes? Because a WDH deals with forces and reactions which do not have to be co-linear and with moments, that is a force by a distance.
Here are some things that a WDH does or does not do, these are not in any priority order;
A WDH does not violate Newtons laws;
A WDH obeys the laws of statics in that the sum of the forces acting on the system is zero. Also, that the sum of the moments acting on the system is zero;
There is no movement of mass;
Reaction forces change because of where the weight distribution act on the caravan chassis and the resultant moments that this reaction generates;
The ball load dos not change;
The solution to Kleins equations requires that the ball load apparently increases. Again, in truth it does not change.
A WDH adds to the value of the reaction at the front axle after the application of the ball load has reduced the front axle reaction;
A WDH reduces the reaction at the rear axle;
A WDH increases the reaction at the caravan axles;
Under static conditions a ball load changes the stress within the chassis and or unitary body of the vehicle;
Similarly, a WDH under static conditions tends to reduce the stresses in the chassis or body of the vehicle;
Without the benefit of any analysis at all, it is not possible to quantify the stress changes or to guess that they are greater than what the vehicle manufacturer has designed for, or whether the stresses impinge on the fatigue limits which will have been considered;
A ball load reduces the understeer (gradient) and a WDH reduces the understeer (gradient) more. Or more correctly a WDH reduces the value of lateral acceleration at which the understeer gradient falls below zero. Richard Klein (mentioned above) was also involved in the formation of SAE J2708. This standard requires that vehicle and caravan systems maintain a positive understeer gradient up to a lateral acceleration value of 0.3 g (~2.94 m/sec/sec). But without analysis to assess what the impact maybe it is inappropriate to suggest that the understeer gradient has fallen below the 0.3 g value and that a WDH should not be used.
A WDH reduces the system critical speed, this the speed at which the damping of any oscillation falls below zero. Again, an analysis is required to make any assessment;
A WDH increases the damping ratio at 100 kph, which is desirable as this is close to the operating speeds that most caravanners seem to employ.
SAE J2807 recommends that approximately 50% of the reaction lost from the front axle when the ball load is applied is restored. The table above illustrates that 120 kg of the lost 140 kg is restored. A value of ~83%, which is greater than the recommended value.
SAE J2807 recommends that the value of the damping coefficient is 0.1 at 100 kph;
There is a whole Pandoras box of stuff related to the assessment of the value of the lateral stiffness of the tyres with varying loads as well, this is an input to the determination of the understeer gradient, damping and critical speed calculations.
Trusting that everyone has fun with this and stays safe throughout the year.
Bobdown said
05:10 PM Jan 13, 2024
Thanks Ron, my head hurts now.............
Are We Lost said
11:01 PM Jan 13, 2024
Chat GPT?
RAvanner said
09:39 AM Jan 14, 2024
No, not AI. Just some one who used to be an engineer.
dogbox said
10:11 AM Jan 14, 2024
Bobdown wrote:
Thanks Ron, my head hurts now.............
mine to!! but I ""think"" it says yobarr is on the right track
Gundog said
10:34 AM Jan 14, 2024
RAvanner wrote:
No, not AI. Just some one who used to be an engineer.
How do you extrapolate SAE J2807 as pertinate to the use and application of a WDH, considering J2807is about something different, "This document establishes minimum performance criteria at GCWR and calculation methodology to determine tow-vehicle TWR for passenger cars, multipurpose passenger vehicles, and trucks. This includes all vehicles up to 14000 pounds GVWR."
As a segment of testing, SAE used 1 type of WDH without sway control this cannot be considered as an alteration to the directions of the manufactures of weight distribution hitches.
As I am required to use a WDH under the direction of my vehicle manufacture requirement, and based on the instructions of genuine WDH it explains how to return FA back to origional height which would exceed 50% FALR, personally I have tried reducing FALR to 75% thus to ultimate result was lighter steering which could lead to understeer and braking, After upgrading my WDH to a different type, nowhere in the instructions is 50% FALR mentioned in the application and setup of the WDH. Even at this time I am considering upgrading to a WDH of the new design, even their instructions make no mention of 50% FALR
Brenda and Alan said
10:42 AM Jan 14, 2024
Ron
I see flaws in your argument.
You state that a WDH does not change the tow ball download.
If a WDH obeys the laws of physics then the WDH must reduce the loading that the drawbar of a caravan imposes on car. This is so because these laws tell us that the weight of the car can't increase or decrease unless the force of gravity or the cars mass is altered. neither of these things can be done by a WDH.
1st weighing car 2460 kgwt
2nd car 2460 kgw - tow ball load 320 kgwt - total 2780 kgwt
3rd car 2460 kgwt - tow ball load 280 kgwt - total 2740 kgwt
Yobarr
You still don't understand the difference between Mass ( the amount of material ) and weight ( force ). They are two entirely different things and are NOT interchangeable. As an example the amount of mass converted to energy in the Hiroshima atomic bomb was equivalent to the mass of a common paper clip, about 1 gm. Just think of the destruction of a 40 Kg change to the cars mass.
Alan
yobarr said
01:53 PM Jan 14, 2024
Brenda and Alan wrote:
Ron
I see flaws in your argument.
You state that a WDH does not change the tow ball download.
If a WDH obeys the laws of physics then the WDH must reduce the loading that the drawbar of a caravan imposes on car. This is so because these laws tell us that the weight of the car can't increase or decrease unless the force of gravity or the cars mass is altered. neither of these things can be done by a WDH.
1st weighing car 2460 kgwt
2nd car 2460 kgw - tow ball load 320 kgwt - total 2780 kgwt
3rd car 2460 kgwt - tow ball load 280 kgwt - total 2740 kgwt
Yobarr
You still don't understand the difference between Mass ( the amount of material ) and weight ( force ). They are two entirely different things and are NOT interchangeable. As an example the amount of mass converted to energy in the Hiroshima atomic bomb was equivalent to the mass of a common paper clip, about 1 gm. Just think of the destruction of a 40 Kg change to the cars mass.
Alan
Alan, do you not think that it is time to cease throwing your convoluted, incorrect and confusing 'theories' into every WDH thread that is created? All that your contributed rubbish does is thoroughly confuse everyday members who simply are trying to learn about WDHs.
The fact that a WDH is only ever used, whether mandated by manufacturers or not, in an attempt to make a car do things for which it never was designed has been extensively covered on this forum over some years, but still you waffle-on with your own theories, totally at odds with advice from many engineers, and indeed Hayman Reese themselves.
You are, of course, entitled to your opinion, no matter how wrong it is, but I despair the confusion you're causing among beginners, as well as the possible danger taking your advice would create.
Just in case you've forgotten, A WDH does NOT change towball weight.
Never has. Never will.
.. Cheers
P.S You will, of course, have noticed that this particular thread is almost a year old?
-- Edited by yobarr on Sunday 14th of January 2024 01:55:43 PM
Are We Lost said
05:04 PM Jan 14, 2024
RAvanner, sorry to be a bit critical of your first post (welcome to the forum), but it is very hard to read. There is a lot of information but it does not say much.
In the posted actual figures, the lack of commas to separate the measured items makes it hard to see what aligns with what. It appears there are 6 different column headings but none of the lines below have 6 figures. Then abbreviations are introduced .... does LL mean Load Leveller ... another name for WDH?
Half way through there is a statement
"A ball load reduces the understeer (gradient) and a WDH reduces the understeer (gradient) more."
I can't think of a scenario where adding ball load would reduce understeer. Understeer is a positive gradient. The second part is true .... a WDH reduces understeer.
Gundog mentioned that SAE J2807 is not relevant. Without reading it I don't want to comment on that. But I thought this part introduced something new that I have not seen in WDH discussions before.
"This standard requires that vehicle and caravan systems maintain a positive understeer gradient up to a lateral acceleration value of 0.3 g (~2.94 m/sec/sec). But without analysis to assess what the impact maybe it is inappropriate to suggest that the understeer gradient has fallen below the 0.3 g value and that a WDH should not be used."
I find the statement itself in a bit of conflict. It is saying understeer of up to 0.3 g is good, but then if less than 0.3 g, a WDH should not be used. So, what is a desirable (measureable) level of understeer to aim for?
Then ..
"SAE J2807 recommends that approximately 50% of the reaction lost from the front axle when the ball load is applied is restored"
That 50% is a common guideline, but there are too many variables for that to be definitive. If the back of the tow vehicle is already heavily loaded it will already be experiencing understeer, so the WDH should be adjusted differently from a lightly loaded vehicle. For example, my Ford Ranger, as with most utes, is fairly light in the rear end. It benefits from some weight in the back. So if a van is connected to it while empty, very little tension adjustment would be needed to reduce understeer to a reasonable level. Heavily laden, a very different situation.
RAvanner, could I tempt you to expand the discussion on the impacts of WDH on understeer, but put it in more practical terms and mimimise the engineering terms, so to make it more readable for those without an engineering background.
-- Edited by Are We Lost on Sunday 14th of January 2024 05:05:29 PM
Gundog said
06:35 PM Jan 14, 2024
Are We Lost wrote:
Then ..
"SAE J2807 recommends that approximately 50% of the reaction lost from the front axle when the ball load is applied is restored"
-- Edited by Are We Lost on Sunday 14th of January 2024 05:05:29 PM
AreWe Lost SAE J2807 does not recommend 50% FALR, however it does quote 50% along with 25% and 0% as testing controls when the WDH is used in testing.
Understeer (the opposite of fishtailing) is measured at three different levels of Front Axle Load Restoration (FALR), which is a calculation of how much the load on the front axle changes. It can sound complicated, but the procedures are designed so you can be assured your truck will not be steered by the weight of the trailer under typical driving conditions even while pulling the maximum tow weight.
Brenda and Alan said
10:00 PM Jan 14, 2024
Yobarr
The thread is a year old but, Ron's post is current. I think my post is relevant to Ron's post.
My comment on your confusion is also relevant.
Trying to explain physics to you is nigh on impossible as you seem to have no grasp of the principles and law involved in this discussion.
Go to a second hand book shop and get a high school physics text book the explains Newtons law of universal gravitation and his laws of motion.
After a good read you may just understand.
Alan
Brenda and Alan said
10:10 PM Jan 14, 2024
Things a WDH does not do.
1 Change GVM rating of car
2 Change GCM rating of car
3 Enable a car to do something it was not designed for. This is the realm of upgrades being done to said GVM and GCM by an engineer
Alan
Brenda and Alan said
08:33 AM Jan 15, 2024
A few more things a WDH can't do.
1 Change the force of gravity.
2 transfer matter ( mass ) between car and caravan.
3 Change the overall weight of a car or caravan. This is because of the two above points.
Alan
-- Edited by Brenda and Alan on Monday 15th of January 2024 08:36:51 AM
yobarr said
11:25 AM Jan 15, 2024
Brenda and Alan wrote:
A few more things a WDH can't do.
1 Change the force of gravity.
2 transfer matter ( mass ) between car and caravan.
3 Change the overall weight of a car or caravan. This is because of the two above points.
Alan
Alan, this is becoming somewhat tedious. Many times I have outlined howvto learn the effects of using a WDH, and again I will suggest that you attend a weighbridge with your fully loaded car and caravan, complete with the universal cure-it-all, but widely misunderstood, WDH, and conduct these exercises..
At this stage you should leave the WDH untensioned.
1) Weigh front wheels of car. Take weight then drive forward until both axles of car are on weighbridge.
2) Weigh car. Take weight, (GVM?) then deduct front axle weight from total weight of car. You now have rear axle weight. Drive forward until both car and van are on weighbridge.
3) Take weight of whole unit. (GCM). Deduct weight of car from GCM to get weight on van wheels. (GTM?)
You can double check this figure by moving car forward until only wheels of van are on weighbridge.
You now will have front axle weight, rear axle weight, weight on van wheels and total weight.
NOW reverse off weighbridge, or do a lap. Tension the beloved WDH as high as possible, simply for this exercise.
Again attend weighbridge.
1) Weigh front wheels of car. This will have increased. Take weight and drive forward until both axles of car are on weighbridge.
2) Weigh car. Take weight. (GVM?) This will have been reduced.
Now deduct front axle weight from total weight of car. This will give you your rear axle weight. This too will have reduced.
Drive forward until both car and van are on weighbridge.
3) Take weight of whole unit. (GCM). Surprisingly, this won't have changed.
Deduct weight of car from GCM to get weight on van wheels. (GTM?) This will have increased.
You can double check the van's axle weight by driving forward until only wheels of van are on weighbridge.
Weighbridge increments will sometimes cause these figures not to add-up exactly.
You now will have front axle weight (increased), total weight of car (decreased) ,rear axle weight (decreased), weight on van wheels (increased) and total weight of car and van (GCM), which won't have changed.
The increase in front axle weight, plus the increase in weight on van's wheels will match the reduction in weight on the car's rear axle.
Easy stuff! Cheers
P.S Now, in another post, you pointed out that a WDH does not change the GVM rating of a car, nor does it change the GCM rating of a car.
These seem to be pointless comments as I cannot recall it ever being claimed by anyone that these things occur?
You then claim that a WDH does not enable car to do things for which it was not designed.
This is demonstrably incorrect.
As an example an LC200 and any of the lightweight twin-cabs have NO chance of safely reaching their claimed 3500kg towing capacity without the use of a WDH, assuming a PIG trailer is being towed.
This clearly shows that a WDH is being used to in an effort to enable a car to do things for which it was not designed, and the fact that some manufacturers mandate the use of a WDH only reinforces this assertion.
Hopefully this is of some help to you, as clearly you are either confused or are simply being arguementative. Cheers.
How to waste a whole heap of money trying to make a car do things for which it was not designed.
Buy a bigger car or a smaller van. Simple stuff!
-- Edited by yobarr on Monday 15th of January 2024 11:26:39 AM
If it jumped off the towball, the chains appear too long?
Gundog said
05:25 PM Jan 15, 2024
yobarr wrote:
As an example an LC200 and any of the lightweight twin-cabs have NO chance of safely reaching their claimed 3500kg towing capacity without the use of a WDH, assuming a PIG trailer is being towed.
This clearly shows that a WDH is being used to in an effort to enable a car to do things for which it was not designed, and the fact that some manufacturers mandate the use of a WDH only reinforces this assertion.
-- Edited by yobarr on Monday 15th of January 2024 11:26:39 AM
Chris
The above 2 sentences would have to be the silliest ever written, the first assumes that every LC200 or Twin-cab claim to tow 3500kg with a wdh, many manufactures make no reference to the use of a WDH.
And the 2nd is the stupidest statement one can make, If a manufacture requires one to be used it is not trying to make it do things for whichit was not designed for. Proof is in the pudding, my Ranger id designed to tow 3000kg but a WDH is mandatory if the trailer is over 1800kg, my vehicle would be unsafe without one as the applied towball weight would create severe understeer as the load too much load would be removed from the front axle.
I think Ford engineers know more about design and safety that negates you misguided opinion, unless you can provide conclusive evidence to contradict them.
yobarr said
05:25 PM Jan 15, 2024
Craig1 wrote:
If it jumped off the towball, the chains appear too long?
Hi Craig, you are of course quite right, and this absolute waste of money was supplied and fitted by a so-called market leader in the WDH con-job industry.
Just get a bigger car or a smaller van, and stop playing with the lives of both your family members and other road users.
Again I will say that a WDH is used, or mandated, only by people or manufacturers that are trying to make a car do things for which that vehicle never was designed.
If safety is of ANY concern ALWAYS the weight on the wheels of the car should be AT LEAST 10% MORE than weight on the wheels of the van. Many experts in weights and dynamics suggest that this figure should actually be at least 30%, with one organisation even saying the figure should be 40%.
We must struggle on, but as Desiderata says:-
"Speak your truth quietly and clearly, and listen to others, even to the dull and the ignorant.They too have their story". Cheers
-- Edited by yobarr on Monday 15th of January 2024 05:30:05 PM
As an example an LC200 and any of the lightweight twin-cabs have NO chance of safely reaching their claimed 3500kg towing capacity without the use of a WDH, assuming a PIG trailer is being towed.
This clearly shows that a WDH is being used to in an effort to enable a car to do things for which it was not designed, and the fact that some manufacturers mandate the use of a WDH only reinforces this assertion.
Chris
The above 2 sentences would have to be the silliest ever written, the first assumes that every LC200 or Twin-cab claim to tow 3500kg with a wdh, many manufactures make no reference to the use of a WDH.
And the 2nd is the stupidest statement one can make, If a manufacture requires one to be used it is not trying to make it do things for whichit was not designed for. Proof is in the pudding, my Ranger id designed to tow 3000kg but a WDH is mandatory if the trailer is over 1800kg, my vehicle would be unsafe without one as the applied towball weight would create severe understeer as the load too much load would be removed from the front axle.
I think Ford engineers know more about design and safety that negates you misguided opinion, unless you can provide conclusive evidence to contradict them.
Hi Graham. My initial reaction was to totally ignore this post, as it seems that no matter how clearly and concisely I explain my stance, and the physics involved, you just do not, cannot, or will not understand.
Do you not understand that if your car was fit for purpose it would be able to tow 3000kg as a PIG trailer without needing a WDH.
Your admission that "If the trailer is over 1800kg my vehicle would be unsafe" says it all. Do you not understand that?
Should you need even more help with comprehension of the physics involved could I respectfully suggest that you study some/many of my posts made over the last 5 years as I'm about done talking to a brick wall.
Learning requires an open mind, an interest in learning, and an ability to comprehend supplied informatiin. Good luck.
Your weighbridge suggestions are of no help as they don't explain anything unless you accept that the weight of the tow vehicle and caravan is not altered in any way by the use of a WDH. This is basic high school physics that you still refuse to accept because it destroys your arguments.
This is the same Newtonian physics that NASA relies upon in all its space missions. You on the other hand dismiss it as rubbish.
Go get that text book I suggested and actually learn some physics.
Alan
Brenda and Alan said
07:18 PM Jan 15, 2024
yobarr wrote:
P.S Now, in another post, you pointed out that a WDH does not change the GVM rating of a car, nor does it change the GCM rating of a car.
These seem to be pointless comments as I cannot recall it ever being claimed by anyone that these things occur?
You then claim that a WDH does not enable car to do things for which it was not designed.
This is demonstrably incorrect.
As an example an LC200 and any of the lightweight twin-cabs have NO chance of safely reaching their claimed 3500kg towing capacity without the use of a WDH, assuming a PIG trailer is being towed.
-- Edited by yobarr on Monday 15th of January 2024 11:26:39 AM
The WDH does not enable the car to tow above its rated load, nor does it enable the car and van to be above their rated GVM and GCM. I think car manufactures would agree that their engineered ratings can comfortably handle the use of a WDH. After all they are aware that they exist and are used.
So a WDH does not enable a car to do things it is not designed to do as you so often suggest.
Alan
yobarr said
07:29 PM Jan 15, 2024
Brenda and Alan wrote:
Yobarr
Your weighbridge suggestions are of no help as they don't explain anything unless you accept that the weight of the tow vehicle and caravan is not altered in any way by the use of a WDH. This is basic high school physics that you still refuse to accept because it destroys your arguments.
This is the same Newtonian physics that NASA relies upon in all its space missions. You on the other hand dismiss it as rubbish.
Go get that text book I suggested and actually learn some physics.
Alan
Alan, could I respectfully suggest that instead of bleating and moaning that my weighbridge suggestions "don't explain anything" that you go ahead and do as I suggest. If you THEN continue to maintain that the weights of the tow vehicle and caravan are not changed in any way,I fear that you are a lost cause.
NEVER have I said that the TOTAL weight of the car and caravan has changed (been altered) in any way, but you seem to struggle to understand that the car is lighter and the van is heavier.
Just in case you've forgotten, a WDH DOES NOT change towball weight. Never has. Never will.
Your false and inaccurate assertions are of little concern to me, as ignorance is bliss, but I do despair that the rubbish that you sprout may negatively influence decisions made by members who simply are wanting to learn.
As I have said many times, if you stubbornly insist that you're correct you may wish to approach HR to advise them that, after 50 years manufacturing and marketing WDH systems, they still do not know what they're talking about.
But I fear that you will just keep posting your endless diatribe. Very sad.
P.S Are you sure that you're not simply being mischievous?
yobarr said
07:44 PM Jan 15, 2024
Brenda and Alan wrote:
yobarr wrote:
P.S Now, in another post, you pointed out that a WDH does not change the GVM rating of a car, nor does it change the GCM rating of a car.
These seem to be pointless comments as I cannot recall it ever being claimed by anyone that these things occur?
You then claim that a WDH does not enable car to do things for which it was not designed.
This is demonstrably incorrect.
As an example an LC200 and any of the lightweight twin-cabs have NO chance of safely reaching their claimed 3500kg towing capacity without the use of a WDH, assuming a PIG trailer is being towed.
The WDH does not enable the car to tow above its rated load, nor does it enable the car and van to be above their rated GVM and GCM. I think car manufactures would agree that their engineered ratings can comfortably handle the use of a WDH. After all they are aware that they exist and are used.
So a WDH does not enable a car to do things it is not designed to do as you so often suggest.
Alan
Not again? You conveniently forget to include the all-important word SAFELY .
If you have any idea of how tow ratings are issued you will understand that, when challenged, the universal "Out" for manufacturers is that their car can indeed tow the claimed weight, but only as a DOG trailer.
This all has been extensively covered and explained in the past, but you clearly are choosing to ignore this, and, quite frankly, I'm sick of trying to help you. Ignorance is bliss. Cheers
-- Edited by yobarr on Monday 15th of January 2024 10:17:30 PM
Your belief in spite of evidence to the contrary that the tow ball weight does not change leads you to the conclusion that the car gets lighter and the van heavier. This is in direct conflict with newtons law of universal gravitation and a simplified version his second law of motion.
You constantly fail to address this anomaly and blunder on regardless.
Just for once give us your new version of gravity to explain your belief.
Alan
PS I repeatedly try to explain the principles of physics involved in this discussion, but you continually use bluster and side tracking to avoid tackling the hard questions.
This might be of interest to anyone who uses a WDH
https://www.youtube.com/watch?v=09ydYbbONBw
Thanks Ron. This video has been around for some years now but the adoring fans of WDH units need to understand that the apparent increase in towball weight is simply a clamping force. The actual towball weight does not change.
More technically gifted persons (KJB?) may choose to explain the physics in detail, but members who dont understand would do well to access videos by John Cadogan where everything is explained clearly and simply.
But I wont hold me breath as some operators simply dont want to know. Cest la vie. Cheers
-- Edited by yobarr on Sunday 28th of May 2023 05:42:00 PM
Hi Possum.Total mass of car (GVM if you like) decreases while total mass of trailer (ATM if you like) increases.
Weight is transferred from rear axle of car to front axle of car, and also to axle group of the trailer (van).
Percentage of weight transferred to each is dependent on many things, such as wheelbase of car, TBO (Towball overhang) and forward length of van. Towball weight remains constant.
Other variables play their part too, but Im off to work now so can't elaborate.
Perhaps I'll find time to give you a call next Friday or Saturday. Cheers
P.S The rear axle is not the fulcrum as a well-tightened WDH can actually lift the rear axle of a car off the ground.
-- Edited by yobarr on Sunday 28th of May 2023 10:28:31 AM
If anyone is interested, in another similar thread on this forum, I did two postings with some information and some calculations using physics for an example vehicle and van, with and without a WDH.
i am sorry that I am not savvy enough with this forum to link those two posts into this post. Also I find it difficult to copy a whole post with attachments onto another post while using my iPad.
My other posts were in Techies' Corner, Weights and Measures, topic "WDH again"
times and dates as:
3.24 pm May 13, 2023
4.28 pm May 14, 2023
See some numbers to inform yourself.
Probably not so easy on a tablet, but for a PC browser ....
Go back to your post and click Permalink. The address bar now points to the specific post. Copy that URL and then type some words in your new post to describe the link. Highlight those words and click the link button (chain links). Paste the URL into the popup panel and choose for the target to open in new window.
Here is the specific post
Read on a little for the next.
-- Edited by Are We Lost on Sunday 28th of May 2023 08:37:06 PM
Your link will help.
I will remember next time, if I feel inclined to copy a post.
I am hoping if people are interested that they will go to my posts for some more information where some physics has been used.
Hopefully it is accepted that the following occurs when a WDH is employed. That is that there is some addition to the front axle load, there is a reduction to the rear axle load and there is also an increase to the caravan axle load. The following table illustrates this. The table is one of around fifteen in situation weight checks conducted at Yarragon (Vic) West bound.
Front axle Rear axle Ball Load Van Axle Delta front Delta rear
Vehicle only 1160 kg 1300 kg
Vehicle with ball load 1020 kg 1760 kg -140 kg + 460 kg
Vehicle with BL and LL 1140 kg 1600 kg +120 kg -160 kg
Van BL 320 kg
GTM no LL 2420 kg
GTM LL 2460 kg + 40 kg
This particular weight check did report overload conditions as did ten others of the total fifteen checks conducted.
Unsurprisingly the sum of the reaction forces in all three configurations equals the total mass of the vehicle and caravan.
Before proceeding, recount Newton. For every action there is an equal and opposite reaction and Archimedes who is attributed with give me a fulcrum and a long enough lever and I will move the world Why these quotes? Because a WDH deals with forces and reactions which do not have to be co-linear and with moments, that is a force by a distance.
Here are some things that a WDH does or does not do, these are not in any priority order;
A WDH does not violate Newtons laws;
A WDH obeys the laws of statics in that the sum of the forces acting on the system is zero. Also, that the sum of the moments acting on the system is zero;
There is no movement of mass;
Reaction forces change because of where the weight distribution act on the caravan chassis and the resultant moments that this reaction generates;
The ball load dos not change;
The solution to Kleins equations requires that the ball load apparently increases. Again, in truth it does not change.
A WDH adds to the value of the reaction at the front axle after the application of the ball load has reduced the front axle reaction;
A WDH reduces the reaction at the rear axle;
A WDH increases the reaction at the caravan axles;
Under static conditions a ball load changes the stress within the chassis and or unitary body of the vehicle;
Similarly, a WDH under static conditions tends to reduce the stresses in the chassis or body of the vehicle;
Without the benefit of any analysis at all, it is not possible to quantify the stress changes or to guess that they are greater than what the vehicle manufacturer has designed for, or whether the stresses impinge on the fatigue limits which will have been considered;
A ball load reduces the understeer (gradient) and a WDH reduces the understeer (gradient) more. Or more correctly a WDH reduces the value of lateral acceleration at which the understeer gradient falls below zero. Richard Klein (mentioned above) was also involved in the formation of SAE J2708. This standard requires that vehicle and caravan systems maintain a positive understeer gradient up to a lateral acceleration value of 0.3 g (~2.94 m/sec/sec). But without analysis to assess what the impact maybe it is inappropriate to suggest that the understeer gradient has fallen below the 0.3 g value and that a WDH should not be used.
A WDH reduces the system critical speed, this the speed at which the damping of any oscillation falls below zero. Again, an analysis is required to make any assessment;
A WDH increases the damping ratio at 100 kph, which is desirable as this is close to the operating speeds that most caravanners seem to employ.
SAE J2807 recommends that approximately 50% of the reaction lost from the front axle when the ball load is applied is restored. The table above illustrates that 120 kg of the lost 140 kg is restored. A value of ~83%, which is greater than the recommended value.
SAE J2807 recommends that the value of the damping coefficient is 0.1 at 100 kph;
There is a whole Pandoras box of stuff related to the assessment of the value of the lateral stiffness of the tyres with varying loads as well, this is an input to the determination of the understeer gradient, damping and critical speed calculations.
Trusting that everyone has fun with this and stays safe throughout the year.
Thanks Ron, my head hurts now.............
mine to!! but I ""think"" it says yobarr is on the right track
How do you extrapolate SAE J2807 as pertinate to the use and application of a WDH, considering J2807 is about something different, "This document establishes minimum performance criteria at GCWR and calculation methodology to determine tow-vehicle TWR for passenger cars, multipurpose passenger vehicles, and trucks. This includes all vehicles up to 14000 pounds GVWR."
As a segment of testing, SAE used 1 type of WDH without sway control this cannot be considered as an alteration to the directions of the manufactures of weight distribution hitches.
As I am required to use a WDH under the direction of my vehicle manufacture requirement, and based on the instructions of genuine WDH it explains how to return FA back to origional height which would exceed 50% FALR, personally I have tried reducing FALR to 75% thus to ultimate result was lighter steering which could lead to understeer and braking, After upgrading my WDH to a different type, nowhere in the instructions is 50% FALR mentioned in the application and setup of the WDH. Even at this time I am considering upgrading to a WDH of the new design, even their instructions make no mention of 50% FALR
Ron
I see flaws in your argument.
You state that a WDH does not change the tow ball download.
If a WDH obeys the laws of physics then the WDH must reduce the loading that the drawbar of a caravan imposes on car. This is so because these laws tell us that the weight of the car can't increase or decrease unless the force of gravity or the cars mass is altered. neither of these things can be done by a WDH.
1st weighing car 2460 kgwt
2nd car 2460 kgw - tow ball load 320 kgwt - total 2780 kgwt
3rd car 2460 kgwt - tow ball load 280 kgwt - total 2740 kgwt
Yobarr
You still don't understand the difference between Mass ( the amount of material ) and weight ( force ). They are two entirely different things and are NOT interchangeable. As an example the amount of mass converted to energy in the Hiroshima atomic bomb was equivalent to the mass of a common paper clip, about 1 gm. Just think of the destruction of a 40 Kg change to the cars mass.
Alan
Alan, do you not think that it is time to cease throwing your convoluted, incorrect and confusing 'theories' into every WDH thread that is created? All that your contributed rubbish does is thoroughly confuse everyday members who simply are trying to learn about WDHs.
The fact that a WDH is only ever used, whether mandated by manufacturers or not, in an attempt to make a car do things for which it never was designed has been extensively covered on this forum over some years, but still you waffle-on with your own theories, totally at odds with advice from many engineers, and indeed Hayman Reese themselves.
You are, of course, entitled to your opinion, no matter how wrong it is, but I despair the confusion you're causing among beginners, as well as the possible danger taking your advice would create.
Just in case you've forgotten, A WDH does NOT change towball weight.
Never has. Never will.
.. Cheers
P.S You will, of course, have noticed that this particular thread is almost a year old?
-- Edited by yobarr on Sunday 14th of January 2024 01:55:43 PM
RAvanner, sorry to be a bit critical of your first post (welcome to the forum), but it is very hard to read. There is a lot of information but it does not say much.
In the posted actual figures, the lack of commas to separate the measured items makes it hard to see what aligns with what. It appears there are 6 different column headings but none of the lines below have 6 figures. Then abbreviations are introduced .... does LL mean Load Leveller ... another name for WDH?
Half way through there is a statement
"A ball load reduces the understeer (gradient) and a WDH reduces the understeer (gradient) more."
I can't think of a scenario where adding ball load would reduce understeer. Understeer is a positive gradient. The second part is true .... a WDH reduces understeer.
Gundog mentioned that SAE J2807 is not relevant. Without reading it I don't want to comment on that. But I thought this part introduced something new that I have not seen in WDH discussions before.
"This standard requires that vehicle and caravan systems maintain a positive understeer gradient up to a lateral acceleration value of 0.3 g (~2.94 m/sec/sec). But without analysis to assess what the impact maybe it is inappropriate to suggest that the understeer gradient has fallen below the 0.3 g value and that a WDH should not be used."
I find the statement itself in a bit of conflict. It is saying understeer of up to 0.3 g is good, but then if less than 0.3 g, a WDH should not be used. So, what is a desirable (measureable) level of understeer to aim for?
Then ..
"SAE J2807 recommends that approximately 50% of the reaction lost from the front axle when the ball load is applied is restored"
That 50% is a common guideline, but there are too many variables for that to be definitive. If the back of the tow vehicle is already heavily loaded it will already be experiencing understeer, so the WDH should be adjusted differently from a lightly loaded vehicle. For example, my Ford Ranger, as with most utes, is fairly light in the rear end. It benefits from some weight in the back. So if a van is connected to it while empty, very little tension adjustment would be needed to reduce understeer to a reasonable level. Heavily laden, a very different situation.
RAvanner, could I tempt you to expand the discussion on the impacts of WDH on understeer, but put it in more practical terms and mimimise the engineering terms, so to make it more readable for those without an engineering background.
-- Edited by Are We Lost on Sunday 14th of January 2024 05:05:29 PM
AreWe Lost SAE J2807 does not recommend 50% FALR, however it does quote 50% along with 25% and 0% as testing controls when the WDH is used in testing.
Understeer (the opposite of fishtailing) is measured at three different levels of Front Axle Load Restoration (FALR), which is a calculation of how much the load on the front axle changes. It can sound complicated, but the procedures are designed so you can be assured your truck will not be steered by the weight of the trailer under typical driving conditions even while pulling the maximum tow weight.
Yobarr
The thread is a year old but, Ron's post is current. I think my post is relevant to Ron's post.
My comment on your confusion is also relevant.
Trying to explain physics to you is nigh on impossible as you seem to have no grasp of the principles and law involved in this discussion.
Go to a second hand book shop and get a high school physics text book the explains Newtons law of universal gravitation and his laws of motion.
After a good read you may just understand.
Alan
Things a WDH does not do.
1 Change GVM rating of car
2 Change GCM rating of car
3 Enable a car to do something it was not designed for. This is the realm of upgrades being done to said GVM and GCM by an engineer
Alan
A few more things a WDH can't do.
1 Change the force of gravity.
2 transfer matter ( mass ) between car and caravan.
3 Change the overall weight of a car or caravan. This is because of the two above points.
Alan
-- Edited by Brenda and Alan on Monday 15th of January 2024 08:36:51 AM
Alan, this is becoming somewhat tedious. Many times I have outlined howvto learn the effects of using a WDH, and again I will suggest that you attend a weighbridge with your fully loaded car and caravan, complete with the universal cure-it-all, but widely misunderstood, WDH, and conduct these exercises..
At this stage you should leave the WDH untensioned.
1) Weigh front wheels of car. Take weight then drive forward until both axles of car are on weighbridge.
2) Weigh car. Take weight, (GVM?) then deduct front axle weight from total weight of car. You now have rear axle weight. Drive forward until both car and van are on weighbridge.
3) Take weight of whole unit. (GCM). Deduct weight of car from GCM to get weight on van wheels. (GTM?)
You can double check this figure by moving car forward until only wheels of van are on weighbridge.
You now will have front axle weight, rear axle weight, weight on van wheels and total weight.
NOW reverse off weighbridge, or do a lap. Tension the beloved WDH as high as possible, simply for this exercise.
Again attend weighbridge.
1) Weigh front wheels of car. This will have increased. Take weight and drive forward until both axles of car are on weighbridge.
2) Weigh car. Take weight. (GVM?) This will have been reduced.
Now deduct front axle weight from total weight of car. This will give you your rear axle weight. This too will have reduced.
Drive forward until both car and van are on weighbridge.
3) Take weight of whole unit. (GCM). Surprisingly, this won't have changed.
Deduct weight of car from GCM to get weight on van wheels. (GTM?) This will have increased.
You can double check the van's axle weight by driving forward until only wheels of van are on weighbridge.
Weighbridge increments will sometimes cause these figures not to add-up exactly.
You now will have front axle weight (increased), total weight of car (decreased) ,rear axle weight (decreased), weight on van wheels (increased) and total weight of car and van (GCM), which won't have changed.
The increase in front axle weight, plus the increase in weight on van's wheels will match the reduction in weight on the car's rear axle.
Easy stuff! Cheers
P.S Now, in another post, you pointed out that a WDH does not change the GVM rating of a car, nor does it change the GCM rating of a car.
These seem to be pointless comments as I cannot recall it ever being claimed by anyone that these things occur?
You then claim that a WDH does not enable car to do things for which it was not designed.
This is demonstrably incorrect.
As an example an LC200 and any of the lightweight twin-cabs have NO chance of safely reaching their claimed 3500kg towing capacity without the use of a WDH, assuming a PIG trailer is being towed.
This clearly shows that a WDH is being used to in an effort to enable a car to do things for which it was not designed, and the fact that some manufacturers mandate the use of a WDH only reinforces this assertion.
Hopefully this is of some help to you, as clearly you are either confused or are simply being arguementative. Cheers.
How to waste a whole heap of money trying to make a car do things for which it was not designed.
Buy a bigger car or a smaller van. Simple stuff!
-- Edited by yobarr on Monday 15th of January 2024 11:26:39 AM
Hi Craig, you are of course quite right, and this absolute waste of money was supplied and fitted by a so-called market leader in the WDH con-job industry.
Just get a bigger car or a smaller van, and stop playing with the lives of both your family members and other road users.
Again I will say that a WDH is used, or mandated, only by people or manufacturers that are trying to make a car do things for which that vehicle never was designed.
If safety is of ANY concern ALWAYS the weight on the wheels of the car should be AT LEAST 10% MORE than weight on the wheels of the van. Many experts in weights and dynamics suggest that this figure should actually be at least 30%, with one organisation even saying the figure should be 40%.
We must struggle on, but as Desiderata says:-
"Speak your truth quietly and clearly, and listen to others, even to the dull and the ignorant.They too have their story". Cheers
-- Edited by yobarr on Monday 15th of January 2024 05:30:05 PM
Hi Graham. My initial reaction was to totally ignore this post, as it seems that no matter how clearly and concisely I explain my stance, and the physics involved, you just do not, cannot, or will not understand.
Do you not understand that if your car was fit for purpose it would be able to tow 3000kg as a PIG trailer without needing a WDH.
Your admission that "If the trailer is over 1800kg my vehicle would be unsafe" says it all. Do you not understand that?
Should you need even more help with comprehension of the physics involved could I respectfully suggest that you study some/many of my posts made over the last 5 years as I'm about done talking to a brick wall.
Learning requires an open mind, an interest in learning, and an ability to comprehend supplied informatiin. Good luck.
P.S Did the WDH cause this, I wonder?
Yobarr
Your weighbridge suggestions are of no help as they don't explain anything unless you accept that the weight of the tow vehicle and caravan is not altered in any way by the use of a WDH. This is basic high school physics that you still refuse to accept because it destroys your arguments.
This is the same Newtonian physics that NASA relies upon in all its space missions. You on the other hand dismiss it as rubbish.
Go get that text book I suggested and actually learn some physics.
Alan
The WDH does not enable the car to tow above its rated load, nor does it enable the car and van to be above their rated GVM and GCM. I think car manufactures would agree that their engineered ratings can comfortably handle the use of a WDH. After all they are aware that they exist and are used.
So a WDH does not enable a car to do things it is not designed to do as you so often suggest.
Alan
Alan, could I respectfully suggest that instead of bleating and moaning that my weighbridge suggestions "don't explain anything" that you go ahead and do as I suggest. If you THEN continue to maintain that the weights of the tow vehicle and caravan are not changed in any way,I fear that you are a lost cause.
NEVER have I said that the TOTAL weight of the car and caravan has changed (been altered) in any way, but you seem to struggle to understand that the car is lighter and the van is heavier.
Just in case you've forgotten, a WDH DOES NOT change towball weight. Never has. Never will.
Your false and inaccurate assertions are of little concern to me, as ignorance is bliss, but I do despair that the rubbish that you sprout may negatively influence decisions made by members who simply are wanting to learn.
As I have said many times, if you stubbornly insist that you're correct you may wish to approach HR to advise them that, after 50 years manufacturing and marketing WDH systems, they still do not know what they're talking about.
But I fear that you will just keep posting your endless diatribe. Very sad.
P.S Are you sure that you're not simply being mischievous?
Not again? You conveniently forget to include the all-important word SAFELY .
If you have any idea of how tow ratings are issued you will understand that, when challenged, the universal "Out" for manufacturers is that their car can indeed tow the claimed weight, but only as a DOG trailer.
This all has been extensively covered and explained in the past, but you clearly are choosing to ignore this, and, quite frankly, I'm sick of trying to help you. Ignorance is bliss. Cheers
-- Edited by yobarr on Monday 15th of January 2024 10:17:30 PM
Yobarr
Your belief in spite of evidence to the contrary that the tow ball weight does not change leads you to the conclusion that the car gets lighter and the van heavier. This is in direct conflict with newtons law of universal gravitation and a simplified version his second law of motion.
You constantly fail to address this anomaly and blunder on regardless.
Just for once give us your new version of gravity to explain your belief.
Alan
PS I repeatedly try to explain the principles of physics involved in this discussion, but you continually use bluster and side tracking to avoid tackling the hard questions.