What happens to the tongue weight with a WDH?

Discussion in 'Tow Vehicles, Hitch & Towing' started by Dammitjim, Feb 7, 2013.

  1. Dammitjim

    Dammitjim New Member

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    Ok, I don't know why I got curious about this and maybe there is someone who can explain the physics maybe even with a shear and moment diagram of what happens to the tongue weight on the hitch of the TV. I ask this because I am confused as to why if the tongue weight of the trailer is say 150lbs, if one uses a WDH, the force on the hitch of the TV is diminished to 100lbs?!?! [:!]
    Does that mean that if you have a TV with a max tongue weight of 500lbs, you could have a trailer with a tongue weight of 600lbs, but since you are using a WDH, you haven't reached the max tongue weight rating of the TV?
     
  2. Raycfe

    Raycfe Waterford Ct.

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    Yes ...
     
  3. Unstable_Tripod

    Unstable_Tripod Well, there's your problem!

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    A weight distribution hitch redistributes the weight on the hitch. Some is moved forward onto the TV's front axle and some is moved backward onto the trailer's axle(s).
     
  4. Dammitjim

    Dammitjim New Member

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    Without a WDH, I always worried that I was putting too much stuff on the tongue of the trailer, but always wanting to have 10-15% of the total trailer weight to avoid much side to side movement. How much should one shoot for to put on the front vs the back of the trailer when using a WDH, then? That's why I'm asking about a shear and moment diagram. I'm sure there is an ideal weight distribution for the trailer when using a WDH.
     
  5. Snow

    Snow Well-Known Member

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  6. arthuruscg

    arthuruscg Active Member

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    Think of the hitch point changing from a point load (on the ball) to an upside down leaf spring. One end connected to the trailer's axle and the other connected to the middle of the TV. The more the center point (ball) is pressed down, the more the attachment points are pressed down.
     
  7. rabird

    rabird Howdy!

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    Weight Distribution (WD) Hitch --- How it Works

    diagram and math.
    The spring bar moment causes the front and trailer tires to carry more load, like a bridge.

    The geometry of the vehicle and trailer, etc., determine how much load goes to the front and how much to the trailer. One method is to return the front (distance from ground to wheel well) to its original position. I noted in a new vehicle manual I recently read called for returning the front 1/2 way and and all the way based on different TW loads. The ever changing vehicle manufacture WDH adjustments.

    IE, if the TW unloads the front axle 200 lbs, setting the WDH to return the 200 lbs. WDH also helps the rear axle being overloaded.
    By 'definition' the TW doesn't change, the load on the ball goes up!
     
  8. BigBaron

    BigBaron Dreaming of Tommy's chili cheeseburgers...

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    That's some nostalgia!
     
  9. marcham

    marcham New Member

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    Most WDH will not work with a 150 lbs tongue weight

    The WDH applies torque to the hitch. Think of lifting a wheel barrow at the bin vs at the handles. You're still lifting the same weight at the handles but you have more leverage, so it's easier to do.

    No. You can't overload your hitch. Not all vehicles and hitches are approved for use with a WDH. However, if you have a tongue weight nearing the max for your vehicle and you find it adversely affects handling, the WDH can ensure that the front end of the vehicle is at the same height with and without the trailer attached, thus assuring positive steering and braking.
     
  10. marcham

    marcham New Member

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    The WDH doesn't care about the weight distribution on the trailer, it only cares about the weight on the hitch (although it requires a min tongue weight, usually around 300 lbs). That being said, your towing and braking performance will be affected if the trailer is overloaded on the axle or overloaded on the hitch.

    The WDH owner's manual usually specified a procedure to set the right hitch level and spring bar tension which keeps the trailer level and returns the front of the vehicle to an unloaded height.
     
  11. Dammitjim

    Dammitjim New Member

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    So, are you saying there is no ideal weight distribution of stuff inside the trailer in terms of the WDH?
     
  12. twstdpear

    twstdpear Party like it's 2012!

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    You should still distribute the cargo weight inside the trailer and have the proper tongue weight (10-15% of trailer weight) as if you aren't using a WDH.

    The tongue weight is important because your ball, ball mount and receiver need to be rated for the tongue weight of the trailer and the tongue weight is still fully present when using a WDH. The key with a WDH is where that weight is transmitted by the load bars: it shifts the center of that load from the rear axles more toward the center of the vehicle and also backwards to the trailer axle. The actual tongue weight doesn't change in the process, however.

    The wheelbarrow analogy mentioned earlier isn't perfect, but it helps visualize what's going on. Picture the wheel barrow as the rear half of the tow vehicle and you are the trailer. When you lift up on the bars, you shift the weight forward to the imaginary front wheels by pivoting the load forward around the rear axle, but also take some weight on yourself (the trailer) and it's transmitted to the ground via your feet (trailer axles). However, the weight on your hands (tongue weight) stays constant, you've only distributed that tongue weight across the imaginary front axle, wheelbarrow's wheel and your feet (TV and trailer axles).

    One could potentially argue that it does affect your TV's payload since your TV isn't actually carrying the full tongue weight any longer (due the WDH shifting the TV to the trailer's axle) but from my reading a lot of people argue against that.
     
  13. FarmerDave

    FarmerDave Active Member

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    Cool old article, thanks for sharing. Back from the days a CAR could tow something, try finding a car towing a TT now!
     

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