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Old 08-25-2012, 10:10 AM   #15
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Yes, the weight borne by the receiver on the tow vehicle is unchanged.

In my tyro towing days, I improperly closed the latch on my ball. I engaged the WD bars and they popped the trailer hitch completely off the ball. Nobody was hurt and I quickly lowered the tongue jack to stabilize this mess. I concluded that the spring bar engagement sockets on my truck's hitch bar accounted for much of the tongue weight transfer in my case.
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Old 08-25-2012, 10:11 AM   #16
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Tongue weight?

I would like to make one comment about what happens to tongue weight when WD is in use. The discussion of does it change is actually a discussion of semantics. Before the trailer is coupled to the TV, the "what is being called tongue weight" is actually the resultant downward force of a complex shaped mass resting on one or two fulcrums (the axles) As soon as you couple the trailer to the tow vehicle, the tow vehicle and trailer become one system and you cannot calculate the vertical force at the trailer hitch without taking the geometry of the total system into account. From this point on, the hitch of the trailer is tightly coupled to the hitch on the TV and they are the same point. From this point on there is no such thing as trailer tongue weight. It does not exist as a single force. So as far as I'm concerned the argument is about something that no longer exists. Both statements," tongue weight changes" and "tongue weight doesn't change" are true when looking at some part of the system only. However, when looking at the coupled system, the term tongue weight no longer has any definition. So you are basically arguing about how to look at something that has no defined meaning. When the TV and trailer are stationary, the only thing we know for sure about that point in the system is that the sum of all forces at that point is zero. If it were not zero, that point would be moving.

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Old 08-25-2012, 10:36 AM   #17
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Perhaps a better term would be apparent tongue weight.
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Old 08-25-2012, 10:44 AM   #18
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Originally Posted by Timofeevich View Post
The WD system changes the distribution of the load, but doesn't move any mass anywhere, and therefore it can't (nor can any technology known to science) make the weight happen anywhere other than where the mass is. The tongue weight stays where it always was, on the hitch ball. It's just a matter of which tires support the whole mess.'
Is above statement 100% true and correct ?
Most of your comments are correct. While the tongue weight exerted by the trailer does not change the force on the ball does. In order for a WD hitch to transfer weight it has to create forces and if you accept the theorem that a state of equilibrium exists after hitched than the force used to distribute weight to the trailer and the TV has to be reacted to somewhere. That point is the ball /coupling. Equal and opposite reaction.
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Old 08-25-2012, 10:52 AM   #19
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Perhaps a better term would be apparent tongue weight.

The real problem is not what it's called. The problem is how it's defined, and is everyone in the discussion defining it the same? We are so used to saying the word weight interchangeably with both mass and force that the only place it seems to have common meaning is when it comes to "how hard is it going to be to pick it up". If we nail it to the floor with weightless nails does it weigh more? Of course not or maybe depending on what weight means. however put that object in a complex system, and the question of does it weigh more or less is lot harder to answer. What does "weigh" mean in that system where the object no longer exists as a single entity?

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Old 08-25-2012, 03:18 PM   #20
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The weight on the ball can actually decrease to zero.
How is this possible ? I can't understand... If you don't move your stuff inside the trailer backward and don't move the axles of RV forward, then the weight on the ball can't decrease to zero ! Do you mean the down force applied to rear axle of TV can decrease to zero if spring bar set too tight ?
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Old 08-25-2012, 03:30 PM   #21
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The weight on the ball can actually decrease to zero.
No Andy this is not possible. Yes it would be possible to remove all of the weight directed to the ground at the tongue were the jack on a scale, ie the Oldsmobile Toronado demonstration, but that is not the same as the weight on the ball. In fact any WD hitch will increase the actual Load exerted by the coupling towards the ball. A WD hitch does not remove anything it just redistributes it
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Old 08-25-2012, 03:58 PM   #22
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See what I mean about how this can turn into a never ending discussion?
The scale is the most accurate way to get the answers you are looking for.
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Old 08-25-2012, 04:24 PM   #23
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No Andy this is not possible. Yes it would be possible to remove all of the weight directed to the ground at the tongue were the jack on a scale, ie the Oldsmobile Toronado demonstration, but that is not the same as the weight on the ball. In fact any WD hitch will increase the actual Load exerted by the coupling towards the ball. A WD hitch does not remove anything it just redistributes it
It indeed is possible.

When a scale at rest says "0" then so to speak it's not weighing anything.

Then when a few hundred pounds are placed on it, it reads that.

In the test setup we had, the scales were checked to make sure they "worked".

Then we started the testing.

Yes indeed, the scale indicated weigh. The load equalizing hitch bars were then readjusted, to the point they should be and "WOW".

Next to zero weight, that I would think most people would call zero, if that weight was almost zero.

It's interesting of the many negative opinions against actual research work.

The bottom line real life answer, is if someone does not think something is correct, then they certainly are free to spend the time and bucks to research anything they may so wish.

That will usually put an "opinion" to rest.

Many years ago, some people said torsion axles last forever.

They are absolutely correct.

BUT, the rubber rods in them, do age out and therefore make the axle useless.

However, the axle proper is still OK, unless it has a ton of rust on the inside of the square tube, as most of them do.

Cut one apart and see the rust, as I have, hundreds of times.

That's exactly why the rebuilding of torsion axles was discontinued, many years ago.

Andy
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Old 08-25-2012, 05:52 PM   #24
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Originally Posted by Inland RV Center, In View Post
It indeed is possible.

When a scale at rest says "0" then so to speak it's not weighing anything.

Then when a few hundred pounds are placed on it, it reads that.

In the test setup we had, the scales were checked to make sure they "worked".

Then we started the testing.

Yes indeed, the scale indicated weigh. The load equalizing hitch bars were then readjusted, to the point they should be and "WOW".

Next to zero weight, that I would think most people would call zero, if that weight was almost zero.

It's interesting of the many negative opinions against actual research work.

The bottom line real life answer, is if someone does not think something is correct, then they certainly are free to spend the time and bucks to research anything they may so wish.

That will usually put an "opinion" to rest.

............................

Andy
Where do you place a scale to measure tongue weight when the hitch is properly connected? That would be pretty difficult unless you have some ultra thin electronic strain guage. Unless the measurement is between the trailers ball socket and the TV hitch ball, it is not measuring tongue weight, it is measuring tongue weight +/- a bunch of other factors.


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Old 08-25-2012, 08:26 PM   #25
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Weigh the truck by itself, then hitch the trailer to it. Drive only the truck onto the scale and weigh it. With the trailer off of the scale. The difference is the tongue weight. Without the WD system bars under tension. Then adjust the bars and see if the overall truck weight changes. That should give you the answers you are looking for.
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Old 08-25-2012, 09:12 PM   #26
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Weigh the truck by itself, then hitch the trailer to it. Drive only the truck onto the scale and weigh it. With the trailer off of the scale. The difference is the tongue weight. Without the WD system bars under tension. Then adjust the bars and see if the overall truck weight changes. That should give you the answers you are looking for.
That is too simple, there must be something wrong with it.

So.., with that method, if you are using a Hensley or a ProPride, does that weight belong to the truck or the trailer's tongue? if you say it is part of the tongue weight, it will put the truck's hitch a lot closer to its max.

I have always felt that that ProPride was part of the tongue weight and to counteract that, I load heavier items in the trunk of trailer that I would otherwise.

Ken
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Old 08-25-2012, 11:33 PM   #27
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To the OP: Yes, the correct use of a WDH "moves the weight to the various axles"by measurement. The correct use involves weight scale readings. Rough it in according to hitch directions using fender height measurements, and then off to the public weight scale you go. We are looking for a "distribution" of the tongue weight. These are all static measurements to ensure best performance in handling & braking under dynamic [adverse] conditions. That TW may not be 800-lbs in some roadgoing instances, but over 5,000-lbs. Spreading the weight around keeps steering feel and response closest to what the solo vehicle experiences without the trailer in tow.

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Old 08-26-2012, 05:02 PM   #28
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This is an interesting thread and I think some actual scales data might help to explain how a WDH transfers load to/from all three axles. The data are from a post on another forum RV.Net Open Roads Forum: Towing: Sharing Scale Numbers.

The F-250’s wheelbase is 156.2” and the ball overhang is estimated to be 64” (based on 52.4” rear overhang). The TT is a Jay Feather 29Y. The assumed ball to axles’ midpoint distance is 235”.

The scales data are -- TV only: front axle = 4300, rear axle = 3720
TV&TT attached with no WD: front axle = 3980, rear axle = 4820, trailer axles = 5380, GCW = 14180
TV&TT attached with WD: front axle = 4340, rear axle = 4280, trailer axles = 5560, GCW = 14180

The first two data sets show that TW caused 320# to be removed from the front axle and 1100# to be added to the rear. The indicated tongue weight is 1100-320 = 780#.

In theory, for this TV, the 780# TW would remove 780*64/156.2 = 319.6# from the front axle, and 780*(156.2+64)/156.2 = 1099.6# would be added to the rear.

The 2nd & 3rd data sets show that application of WD caused 540# to be removed from the rear axle with 360# being added to the front and 180# being added to the trailer axles.

In theory, for this TV/TT combination, transferring 180# to the trailer axles would correspond to 180*(64+235)/156.2 = 345# being added to the front axle. And a corresponding load of 180*(156.2+64+235)/156.2 = 525# would be removed from the rear axle.

The net result shown by the scales data is 360-320 = 40# (5.1% of TW) added to the front axle, 1100-540 = 560# (71.8%) added to the rear axle and 5560-5380 = 180# (23.1%) added to the trailer axles.

As for a 1/3, 1/3, 1/3 distribution – it is possible, but quite unlikely. First, you would have to transfer a load equal to 1/3 of the TW to the trailer axles. This requires an unusually high loading of the WD bars. A range of 15-25% is more typical. Second, the distance from the ball coupler to the midpoint between the trailer’s axles would have to be exactly equal to the TV’s wheelbase plus two times the ball overhang. Obviously, this cannot apply to all TV/TT combinations.

Hope this helps,

Ron
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