WDH

Are We Lost · Guru

WDH

Peter_n_Margaret · Senior Member

Brenda and Alan wrote:
[GM1m2divided by earths radius squared M1 the mass of earth m2 the mass of the car G the gravitational constant]
It can be clearly seen that the cars weight itself can't change.
Alan
_________________________________________________________________________________________________________________________________
Mass and weight are not the same.
The MASS does not change.
The WEIGHT certainly can and does.
Cheers,
Peter

Peter_n_Margaret · Senior Member

Here is another description.
If you apply a big G clamp onto the hitch over the tow ball and tighten it up, the force between the hitch and the tow ball will certainly be increased.
This is not an increase in WEIGHT or an increase in MASS, but it is certainly an increase in FORCE holding the 2 together.
I suggest that the effect of a WDH at the ball is similar. It has nothing to do with gravity and can not be measured on a weigh bridge. It could be measured with a load cell between the ball and the hitch.
Cheers,
Peter

-- Edited by Peter_n_Margaret on Thursday 25th of January 2024 03:37:33 PM

KJB · Guru

Spot on.....it so clear but some cannot or will not acknowledge it....

Are We Lost · Guru

Peter_n_Margaret wrote:
If you apply a big G clamp onto the hitch over the tow ball and tighten it up, the force between the hitch and the tow ball will certainly be increased.

The forces on both sides of a G clamp are equal. While it's true that the clamping pressure within the coupling/towball joint may be measured, the WDH generates more upwards force than downwards force and this difference is the hard part to measure. Without that difference, the coupling and vehicle rear end would not rise. So, you could measure the total clamping force but not the up/down opposing forces that create the clamping effect. They will vary as the tension changes and the coupling moves up and down. As you say, it can't be measured on a weigbridge either.

But we can see the result on the scales from each of the axles. Isn't that all that matters .... the measured weights of the axles on the weighbridge? Typically front, rear and van measured twice and reported in Kg. Plus towball load of course.

-- Edited by Are We Lost on Thursday 25th of January 2024 04:27:17 PM

Peter_n_Margaret · Senior Member

I did not suggest my example was a replication of a WDH. Its purpose was to change the direction of the thought processes expressed here.
The WDH is more like a spring loaded hinge. The spring is not equally spaced about the hinge pin. There is considerable extra load on the hinge pin. The hinge point in the case of the WDH is the ball. There is also extra load on the A frame via the chains, which is the other end of the spring.
The result that can be seen on the scales is NOT all that matters IMO as clearly many do not perceive the other significant forces involved.
I don't comprehend the extent of some of them at all.
Cheers,
Peter

Brenda and Alan · Guru

Are We Lost wrote:
. Once connected, the towball weight can't be measured on a weighbridge because it is internal to the workings of a WDH.

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But it is easily measured as weight or car alone minus weight of car hitched regardless if a WDH is used or not.
Alan

Brenda and Alan · Guru

Peter_n_Margaret wrote:
Brenda and Alan wrote:
[GM1m2divided by earths radius squared M1 the mass of earth m2 the mass of the car G the gravitational constant]
It can be clearly seen that the cars weight itself can't change.
Alan
_________________________________________________________________________________________________________________________________
Mass and weight are not the same.
The MASS does not change.
The WEIGHT certainly can and does.
Cheers,
Peter

Peter this is where the wooly thinking occurs. Where in Newtons equation is the actual weight of the car changeable.

The weight on the cars wheels is made up of two components, the weight of the car alone plus the weight imposed by the towbar of the van. any change in weight is due to a change in towbar weight.

Alan

Peter_n_Margaret · Senior Member

You can not use an equation about mass to argue about weight. That is "wooly thinking".
Cheers,
Peter

dogbox · Guru

Are We Lost wrote:

Dogbox, I think you may have missed the words "that the car itself exerts" from Alan's post. For explaining, he is referring to the car's weight when commected, and treating what the WDH tramsfers as a separate component of the weight measured. In this case, when the WDH is temsioned, the reading on the scales for the car will be less due to the negative component of the WDH. The component of "the car itself" does not change.
As I said in the previous post, I don't think anyone is disputing that.

-- Edited by Are We Lost on Thursday 25th of January 2024 03:24:22 PM

i think maybe you missed something, the component of the car is not the question it is the foot print of the car, the weight on the axles and the transferring of that weight by the use of leavers/fulcrums (wdh) to balance the unit. the weight of the car is defined by the weight on each axle it is the weight on each axle that will change when you try lifting the rear of car, the weight of car is transferred from rear axle of car to front axle of car and van axle(s) so weight of car (footprint)on weighbridge is reduce by the weight transferred to van which is not on weighbridge

if you put a couple of jacks under a car, an jack back wheels off ground the weight of the car does not change but the weight on rear axle does put some more jacks (fulcrums) under car the weight of car is still the same, but load on jacks reduced

Are We Lost · Guru

I don't understand where you think there is a misunderstanding other than choice of words and terminology.

Everyone is saying the same result occurs. Just different words and ways of explaining it. Whatever the rig weighed before, it will weigh the same afterwards ... but the scales will show the weights have moved around. The van wheels will read more weight than before .... 2 components .... the weight of the van (less towball) plus what was transferred from the car. The same principle for the car, which is what agreed with previously.

Nobody is saying anyrhing else.

-- Edited by Are We Lost on Thursday 25th of January 2024 06:25:24 PM

yobarr · Guru

Brenda and Alan wrote:
Peter_n_Margaret wrote:
Brenda and Alan wrote:
[GM1m2divided by earths radius squared M1 the mass of earth m2 the mass of the car G the gravitational constant]
It can be clearly seen that the cars weight itself can't change.
Alan
_________________________________________________________________________________________________________________________________
Mass and weight are not the same.
The MASS does not change.
The WEIGHT certainly can and does.
Cheers,
Peter

Peter this is where the wooly thinking occurs. Where in Newtons equation is the actual weight of the car changeable.
The weight on the cars wheels is made up of two components, the weight of the car alone plus the weight imposed by the towbar of the van. any change in weight is due to a change in towbar weight.
Alan

Alan, this is becoming sillier by the hour. How do you explain your "theory" when a WDH is tensioned so far that the car's rear wheels are completely OFF the ground? ( It can be done). Now the weight is on only the car's front axle and the van's axle group.

A WDH is effectively a stiff-arm from front axle of car through the hitch point, to van's axle group, and has NO EFFECT on towball weight. Never has,Never will. Spare me. Cheers (But not too many)

-- Edited by yobarr on Thursday 25th of January 2024 06:26:32 PM

Peter_n_Margaret · Senior Member

To say that a WDH has no effect on towball weight is misleading in the extreme because a WDH does have a significant effect on the forces on a towball to the extent that an excessively applied WDH could rip the towbar off a vehicle.

Cheers,

Peter

BarneyBDB · Senior Member

It seems to me that lighter than air flight is no longer possible as any force that opposes gravity cannot exist, or must be witchcraft....

yobarr · Guru

Peter_n_Margaret wrote:
To say that a WDH has no effect on towball weight is misleading in the extreme because a WDH does have a significant effect on the forces on a towball to the extent that an excessively applied WDH could rip the towbar off a vehicle.
Cheers,
Peter

Interesting assertion Peter. . Could you please detail your thoughts, as I have seen a WDH holding the rear wheels of a car completely off the ground, but the towbar remained secure.

If the rear wheels of the car are suspended in mid-air, how could any more tension be applied to "Rip the towbar off".

Please note that I'm not challenging your assertion, as generally you are a person who speaks a lot of sense, but I would be interested to hear your explanation. Cheers.

Peter_n_Margaret · Senior Member

Towing is not a static state and the forces involved can become very much larger when mobile, especially over undulating ground. Add to that, some vehicles have much less strength in the rear end than others which explains why some have much lower tow capacities and much lower ball weights than you would expect and some will not allow the use of a WDH.
Sometimes the weak link is the tow bar but more often I suggest the weak link is the structural strength of what it is attached to.
Exceed the specified limits at your peril.

ps... the design load capabilities for the approval of tow bars are:
Longitudinal (push and pull force) 1.5 x the rated tow capacity (= 5.25T for 3.5T tow capacity).
Vertical (up and down) and transverse (side to side) is half of the rated tow capacity (= 1.75T for 3.5T tow capacity).
Cheers,
Peter

Brenda and Alan · Guru

Peter_n_Margaret wrote:
You can not use an equation about mass to argue about weight. That is "wooly thinking".
Cheers,
Peter

Newtons equation of universal gravitation does precisely that. In the case of a mass on the surface of the earth the equation can be simplified to F=Ma.

Weight (force) equal its mass times the acceleration due to gravity. Again there is no wriggle room the force that a mass exerts downwards is chiselled in stone.

A 3000 Kg mass car will always weigh 3000Kg wt.

Alan

Peter_n_Margaret · Senior Member

Are you suggesting that applies to a moving situation like a van and tug passing through a sharp dip at 100kph?
Cheers,
Peter

dogbox · Guru

Brenda and Alan wrote:

Peter_n_Margaret wrote:
You can not use an equation about mass to argue about weight. That is "wooly thinking".
Cheers,
Peter
Newtons equation of universal gravitation does precisely that. In the case of a mass on the surface of the earth the equation can be simplified to F=Ma.
Weight (force) equal its mass times the acceleration due to gravity. Again there is no wriggle room the force that a mass exerts downwards is chiselled in stone.
A 3000 Kg mass car will always weigh 3000Kg wt.

Alan

QUOTE" Again there is no wriggle room the force that a mass exerts downwards is chiselled in stone."

what about the extra lift that is exerted upward by WDH, would that not balance the downward force and apply lift to rear of car?? thus transferring weight! go back to weighbridge example of weight car only on bridge with WDH applied then without WDH applied, the weight of car on bridge changes .....I wonder were that weight went?

the weight of the car is not the issue (the car and van become one) it is the weight on the axles that is being distributed with van attached by the use of a fulcrum.(WDH) to adjust weight distribution

when you apply a WDH you change(reduce) the load on the rear axle (lifting rear of car) but apply more pressure to tow ball (clamping effect no additional weight on towball) which removes weight from rear axle of car to front axle of car and the van. the gross weight remains the same but the weight on load point changes

Brenda and Alan · Guru

Peter_n_Margaret wrote:
Are you suggesting that applies to a moving situation like a van and tug passing through a sharp dip at 100kph?
Cheers,
Peter

Peter

Your question is irrelevant to a discussion of a weighbridge exercise. Hovever in answer. yes the equation holds true for any mass on the surface of the earth, but you have to add the forces generated by centripetal motion through the dip in your example.

Alan

Brenda and Alan · Guru

dogbox wrote:

what about the extra lift that is exerted upward by WDH, would that not balance the downward force and apply lift to rear of car?? thus transferring weight! go back to weighbridge example of weight car only on bridge with WDH applied then without WDH applied, the weight of car on bridge changes .....I wonder were that weight went?

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Dogbox
Can't you see it is precisely this upward force generated by the WDH that opposes the downward force from the tow bar. It does not balance it as it is not that high , but is does reduce the this downward force.
The weight of the car is the issue to me as Yobarr thinks the car exerts less force downwards and conversely the van exerts more downwards when WDH is tensioned. This is the only was he can rationalise his belief that towball weight remains unchanged
You ask where this reduction in weight goes to look at the vans wheels for your answer.
Alan

yobarr · Guru

Brenda and Alan wrote:

The weight of the car is the issue to me as Yobarr thinks the car exerts less force downwards and conversely the van exerts more downwards when WDH is tensioned. This is the only was he can rationalise his belief that towball weight remains unchanged
You ask where this reduction in weight goes to look at the vans wheels for your answer.
Alan

Oh Deary me, talk about being persistent, but wrong!

On the contrary, Yobarr does not THINK that the car exerts less force downwards, he KNOWS.

MANY times I had posted detailed information on the process that you could use to PROVE to yourself that fact, but still you float around in LaLa Land with your convoluted theories that have been shown to be wrong.

Although I had decided to give up on talking to a wall, the mention of my name got my attention.

AGAIN I will iterate that your misguided opinion is of little interest to me, but that I despair that newbies, and others keen to learn, will be negatively influenced by your theories, to their detriment.

Could I respectfully suggest that instead of constantly promoting mistruths, that you journey to the local weighbridge and conduct the exercise that I have selflessly outlined many times.

Somewhere I have all the figures from my own weighing exercise, which I have posted here previously on several occasions, showing that when the WDH was tensioned weight was removed from the car's rear axle and DISTRIBUTED to the car's front axle and to the van's axle group.

The total weight on the car's axles reduced, while the total weight on the van's axle group increased.

Strangely, the increase in front axle weight, plus the increase in van axle weight exactly matched the weight that was removed from the car's rear axle. Who woulda thought!

It also is of interest that you haven't developed some other convoluted theory that addresses weight changes that occur when a WDH is used to lift a car's rear axle COMPLETELY OFF the ground.

NOW try and convince the gullible that the car exerts the same downward force as it did before the WDH was tensioned. Yeah,right.

Greg 1 · Guru

As usual when this subject comes up, invariably it keeps going around in circles. At least just agree that if used correctly, a WDH does exactly what it says on the tin.

Are We Lost · Guru

Yes, please let's stop this never ending saga where words and meanings get misinterpreted, and next thing the thread gets closed. Apart from the inner workings of the forces involved, is anyone disagreeing with the resulting weights as per these hypothetical diagrams? Weights are just approximate as a guide.

Without bringing discussions on mass vs weight, newtons or kilograms, forces, moments or whatever, isn't this all that matters? What it reads on the scales?

Ute and van with WDH.jpg

-- Edited by Are We Lost on Saturday 27th of January 2024 04:20:15 PM

Peter_n_Margaret · Senior Member

Not correct.
Front of the tug is heavier than shown. 1250 according to the other numbers.
Cheers,
Peter

Are We Lost · Guru

Peter_n_Margaret wrote:
Not correct.
Front of the tug is heavier than shown. 1250 according to the other numbers.
Cheers,
Peter

Correct Peter. I noticed that when I double checked after posting. I briefly edited the post to remove the image and said I was correcting it. I fixed it, removed that image and that note while you were posting your comment. The new image has a different name.

You were too quick.

-- Edited by Are We Lost on Saturday 27th of January 2024 04:27:26 PM

yobarr · Guru

Are We Lost wrote:
Yes, please let's stop this never ending saga where words and meanings get misinterpreted, and next thing the thread gets closed. Apart from the inner workings of the forces involved, is anyone disagreeing with the resulting weights as per these hypothetical diagrams? Weights are just approximate as a guide.
Without bringing discussions on mass vs weight, newtons or kilograms, forces, moments or whatever, isn't this all that matters? What it reads on the scales?

Excellent post Stephen, particularly the illustrations that clearly show the simple process that I have many times outlined.

Your diagrams should help even the slowest of people to understand how a WDH works.

When I first joined the forum and posted these simple facts I was shot down in flames by some members, but I've stuck to my guns and have again been proved right. Thankyou.

Your comments about weight versus mass, newtons or kilograms, moments or whatever are most pertinent as such terms only are introduced by members who are attempting to appear knowledgeable, when all that we really want to know is how a WDH effects its distribution of weight.

As you succinctly state, all that matters is "What it reads on the scales". Period.

However, my concurrence with your assertions is exactly that, and is not to be confused as being at odds with my opinion that, whether mandated or not, a WDH is used ONLY by those who are trying to make a car do things for which it never was designed.

Some of the smaller cars now rated to tow 3500kg would be an accident looking for a place to happen if a 3500kg PIG trailer was towed. One model has a dangerously low 1650kg rear axle capacity. And 2800kg GVM. (From memory) You'd have to be joking.

Again, thanks for outlining the procedure and the results. Cheers

-- Edited by yobarr on Saturday 27th of January 2024 10:08:15 PM

KJB · Guru

yobarr wrote:
Are We Lost wrote:
Yes, please let's stop this never ending saga where words and meanings get misinterpreted, and next thing the thread gets closed. Apart from the inner workings of the forces involved, is anyone disagreeing with the resulting weights as per these hypothetical diagrams? Weights are just approximate as a guide.
Without bringing discussions on mass vs weight, newtons or kilograms, forces, moments or whatever, isn't this all that matters? What it reads on the scales?

Excellent post Stephen, particularly the illustrations that clearly show the simple process that I have many times outlined.
Your diagrams should help even the slowest of people to understand how a WDH works.
When I first joined the forum and posted these simple facts I was shot down in flames by some members, but I've stuck to my guns and have again been proved right. Thankyou.
Your comments about weight versus mass, newtons or kilograms, moments or whatever are most pertinent as such terms only are introduced by members who are attempting to appear knowledgeable, when all that we really want to know is how a WDH effects its weight distribution.
As you succinctly state, all that matters is "What it reads on the scales". Period.
However, my concurrence with your assertions is exactly that, and is not to be confused as being at odds with my opinion that, whether mandated or not, a WDH is used ONLY by those who are trying to make a car do things for which it never was designed.
Some of the smaller cars now rated to tow 3500kg would be an accident looking for a place to happen if a 3500kg PIG trailer was towed. One model has a dangerously low 1650kg rear axle capacity. And 2800kg GVM. (From memory) You'd have to be joking.
Again, thanks for outlining the procedure and the results. Cheers

Well done....much needled

Just about enough clear info to cause this Forum to close down.

.. o need for any more arguing!!

yobarr · Guru

Greg 1 wrote:
As usual when this subject comes up, invariably it keeps going around in circles. At least just agree that if used correctly, a WDH does exactly what it says on the tin.

Hi Greg, there is no disputing that, used correctly, a WDH does exactly what it says on the tin.

However, the vast majority of WDH users that I encounter on my travels have NO idea how a WDH works, what it does, or how to set it up, and have one only because some other equally-uninformed individual told them they should have one.

Neither does it change the fact that a WDH, mandated or not, is only ever used by those who are trying to make a car do things for which it never was designed. Get a better car or a smaller van. Cheers

yobarr · Guru

KJB wrote:

Well done....much needled

Just about clear enough info to cause this Forum to close down.

.. no need for any more arguing!!

Great observation Kerry, but undoubtedly there still will be a couple of members who refuse to learn.

For these members there is little hope. C'est la vie. Cheers