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 > Can I use a WDH on a DP

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DrewE

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Posted: 01/15/19 08:25am Link  |  Quote  |  Print  |  Notify Moderator

discovery4us wrote:

Never used a WDH on the MH and have never seen one used on a MH with air bags. It would seem to me that any adjustment made to the WDH would be negated by the air system.

I typically don't hook up my cargo trailer with the MH running because it is too loud but the few times I have as soon as the tongue weight of the trailer is felt the air system pumps back up to level. Wouldn't this be the same effect of the WDH? As the air levels out the MH and trailer it is spreading some of the tongue weight to the front of the MH and some to the trailer axles. Being the center pivot point as you raise or lower the air suspension it should push some of the weight in either direction.

I have no experience with a WDH as I have always added air bags or upgraded springs to level trucks and trailers so I am probable missing something but I would think that you either need the air suspension or the WDH but not both.


Adjusting the leveling doesn't significantly change the axle loading, it just makes things level. The only weight shifting would be due to the center of gravity of the motorhome being above the axis around which it rotates slightly when being leveled, and so move a teeny tiny bit towards one end or the other. It's utterly negligible, perhaps even to the point of being nearly impossible to measure with ordinary vehicle scales. You would get far greater weight transfer by having a passenger move from the rear to the front of the motorhome.

A weight distributing hitch simply applies a torque to the hitch point, which has the effect of increasing the force (weight) on the trailer axle and the front axle of the vehicle, and reducing the force on the tow vehicle rear axle. Due to the lever arm lengths involved in a motorhome vs. a pickup or SUV, the amount of weight transfer in the motorhome would be comparatively smaller (I think--I haven't actually sketched out and solved a free-body diagram).





wildmanbaker

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Posted: 01/15/19 08:36am Link  |  Quote  |  Print  |  Notify Moderator

D J, yes and no. BJs example is good for a pickup and trailer, but you are going to add some weight to the rear, front and trailer axels. With a MH, the spring bars would probably have to be a lot bigger than the heaviest ones available now. and who and how you would flip them up would be interesting.


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Smitty77

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Posted: 01/23/19 11:53am Link  |  Quote  |  Print  |  Notify Moderator

hotjag1 wrote:

Lancslad wrote:

Have you tried moving the trailer contents around to reduce the tongue weight?


The only two heavy items in the trailer are a side x side utv and a small suv(Suzuki grand Vitara).

With the Suzuki facing forward I have a tongue weight of close to 1500lbs. Iif I back it in so that the engine is behind the trailer axles, it puts the tongue weight at 1200 lbs. Too much weight unless I find out that my hitch is rated for more than the 1000lbs that I think it is.


I'd keep doing what your doing, and ensure the hitch is up to snuff to handle the tongue weight. That being said, I know a gent that had a similar problem with is two axle enclosed trailer. He was not over the weight of the trailer itself, and was about 3K under his DP's hitch 10K capacity. But, his tongue weight was high. He tried, as you did, to balance the load better with more over the twin axles. helped some, but not enough to get him comfortable. He had his DP looked at from a well known trailer hitch shop in the area, and they suggested he cold improve his tongue weight by some rather dramatic cutting and welding to beef up where his hitch attaches to the frame. (Probably the H pattern mentioned earlier(?) - but never got into the specifics with him on what was involved.) But the shop said they could for a fraction of the cost add some weight to the back of his includes trailer rails, to pendulum wise get the tongue weight back within capacity. He elected to go that route, as he was using the trailer to run back and forth to the desert from the San Diego area.

So if you don't mind the extra weight being towed, which for your usage is always vs weekend warrior usage.... Possibly consider adding more weight to the trailer rear end. (They welded a new bar between the rear frame, with some heavy pieces of solid metal added the new cross member to get the weight they wanted. All galvanized and properly painted - clean job.)

Best of luck to you. And glad to see you being proactive on this. Safety is not an accident[emoticon]!
Smitty

majordad

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Posted: 08/04/19 11:59pm Link  |  Quote  |  Print  |  Notify Moderator

My DP says not to use we’d bars with air ride

oldave

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Posted: 08/05/19 06:57pm Link  |  Quote  |  Print  |  Notify Moderator

The simple cheap answer is to get 2 or 3 bags of sand .
Put them in the in the rear of the trailer .

I don't think a WDH will confuse our air ride height at all
After the WDH has distriduted some weight mostly to the trailer
the air ride will adjust as necessaary .

My ride height system takes over after I start the engine .
How will it matter if the coach is already level ?

Now if you decide to dump the air or level the coach when you
park that may put a lot of stress on things .

hotjag1

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Posted: 08/05/19 10:27pm Link  |  Quote  |  Print  |  Notify Moderator

oldave wrote:

The simple cheap answer is to get 2 or 3 bags of sand .
Put them in the in the rear of the trailer .

I don't think a WDH will confuse our air ride height at all
After the WDH has distriduted some weight mostly to the trailer
the air ride will adjust as necessaary .

My ride height system takes over after I start the engine .
How will it matter if the coach is already level ?

Now if you decide to dump the air or level the coach when you
park that may put a lot of stress on things .


I was surprised to see this topic appear again, but since you suggested sand bags, I did try a similar approach. I had a Class 3 receiver hitch welded onto the frame rails of the trailer. I then loaded a 270lb scooter onto a rack mounted in the new hitch, which made for a combined weight of about 300lbs. According to my tongue scale, adding 300lbs to the rear of the trailer only reduced tongue weight about 80lbs. It looks like I would need a lot of sandbags...


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majordad

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Posted: 12/17/19 07:29am Link  |  Quote  |  Print  |  Notify Moderator

My DP hitch states to not use WDH with airride. I got a trailer toad to go with the 8000 lb toyhauler and it was the best decision I ever made for towing. No sway or swerve from passing trucks except for the worst roads.

I definitely can recommend the trailer toad, it does add another 3 feet to your O/A length, but definitely worth it.

Good thing The limit here in Nevada is 70 because I am at 68.5..
Tows like a dream

* This post was edited 12/18/19 09:07pm by majordad *

hohenwald48

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Posted: 12/17/19 09:08am Link  |  Quote  |  Print  |  Notify Moderator

old guy wrote:

a wdh will increase you tongue weight capability. most hitches will have a tag on them telling you what the limit is with and without the wdh.


I don't think this is a true statement. WD hitches do not change the tongue weight. They just redistribute that tongue weight among the available axles. If your tongue weight is 1400 pounds with a regular hitch it will still be 1400 pounds with a WD hitch. It will just be carried by different axles but there will still be 1400 pounds on the ball.

The only solution to the OP's problem is to move some weight further back in the trailer or move the trailer axle further forward.

I could be wrong but I don't think so.


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bjbear

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Posted: 12/17/19 09:31am Link  |  Quote  |  Print  |  Notify Moderator

hohenwald48 wrote:

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

I don't think this is a true statement. WD hitches do not change the tongue weight. They just redistribute that tongue weight among the available axles. If your tongue weight is 1400 pounds with a regular hitch it will still be 1400 pounds with a WD hitch. It will just be carried by different axles but there will still be 1400 pounds on the ball.

The only solution to the OP's problem is to move some weight further back in the trailer or move the trailer axle further forward.

I could be wrong but I don't think so.


If weight is moved to the axles, it must come off the hitch. In other words, the total weight of the vehicle and trailer do not change so if you move some of the weight to an axle, it must be reduced from the hitch.

One of the things that a WDH does is reduce the torque on the receiver. That is why receivers are rated for higher loads when you use a WDH.

The following is a simple illustration.
[image]
http://www.visualsc.com/WD_hitch_illustration.png

A difference when you have air bags, is that the rear end of the MH is maintained at the same height. That, however does not mean that the weight did not transfer. It just means that as the weight is added to the drive axle, air is added to the rear air bags to compensate.


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hohenwald48

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Posted: 12/17/19 12:02pm Link  |  Quote  |  Print  |  Notify Moderator

bjbear wrote:

hohenwald48 wrote:

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

I don't think this is a true statement. WD hitches do not change the tongue weight. They just redistribute that tongue weight among the available axles. If your tongue weight is 1400 pounds with a regular hitch it will still be 1400 pounds with a WD hitch. It will just be carried by different axles but there will still be 1400 pounds on the ball.

The only solution to the OP's problem is to move some weight further back in the trailer or move the trailer axle further forward.

I could be wrong but I don't think so.


If weight is moved to the axles, it must come off the hitch. In other words, the total weight of the vehicle and trailer do not change so if you move some of the weight to an axle, it must be reduced from the hitch.


I'm not going to spend a lot of time debating the point because it's about the same as getting into a discussion about RV shore power wiring. You can certainly do all the google research you want. Here's one "experts" explanation.

https://www.etrailer.com/question-180152.html

Weight is not "moved to the axle" from the ball. As soon as you connect the trailer the tongue weight is on the rear axle. Moving some of it to the front axle doesn't lighten the tongue, it just lightens the rear axle.

All a WD hitch does is move tongue weight from one axle to another. What used to be carried by the rear axle can be moved to the front axle or trailer axle. But it stays on the hitch ball. The tongue doesn't magically get lighter.

Simple physics dictates that all weight on the tongue of a trailer is carried by either the towing vehicle axles or by the trailer axles. Moving some of that weight from a front axle to a rear axle does not change the amount of that weight. It's still all on the tongue. It's a very common misconception that WD hitches lighten the tongue weight. But it's still wrong.

.

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