Tongue weight limits and wdh

[waynefi]

What happens with the tongue weight limit when you are using a weight distributing hitch?

My Tacoma says the the tongue weight limit is 650 lbs. Does that mean that if my trailer has a tongue weight over 650 I need a wdh, or that I shouldn’t pull that trailer even with a wdh?

The function of a wdh is to take weight off the tongue, right? How would you even measure the tongue weight with the wdh in place?

My current trailer has a nominal tongue weight of 380, but that is before water, a second battery, etc.

[Grit_dog]

valhalla360 wrote:


I understand perfectly what you are saying.

So when the WDH is connected and fully engaged...Does the frame and suspension of your truck see:

- The receiver load (and associated moment arm).

or

- The theoretical trailer hitch load that would be present with the WDH portion of the hitch disengaged.

Not sure you do understand. The weight of the trailer hitch is somewhat irrelevant. The 2 frames (vehicle and trailer) see bending stresses placed on them by the spring bars, however much is placed on them. The net effect is the rear suspension on the vehicle sees less weight on it than a conventional setup.

[valhalla360]

ktmrfs wrote:
It reduces the reciever LOAD. It doesn't alter the trailer tongue weight.

READ and TRY to understand the mechanics involved! It's a pretty simple statics problem.

I understand perfectly what you are saying.

So when the WDH is connected and fully engaged...Does the frame and suspension of your truck see:

- The receiver load (and associated moment arm).

or

- The theoretical trailer hitch load that would be present with the WDH portion of the hitch disengaged.

[Grit_dog]

valhalla360 wrote:


Funny...the very first post in the diagram is a statement "TV Receiver Load WDH Removes 300lb"

:R

[ktmrfs]

valhalla360 wrote:

ktmrfs wrote:

Huntindog wrote:
If you really want to "know" how it works. click on this link.
Or you can find it in the towing forum.
It has been a sticky there for years.


Ron Gratz explains WD

yes, great reference and a good summary of a force analysis one would learn in a statics 101 ME class.

Funny...the very first post in the diagram is a statement "TV Receiver Load WDH Removes 300lb"

It reduces the reciever LOAD. It doesn't alter the trailer tongue weight.

READ and TRY to understand the mechanics involved! It's a pretty simple statics problem.

[valhalla360]

ktmrfs wrote:

Huntindog wrote:
If you really want to "know" how it works. click on this link.
Or you can find it in the towing forum.
It has been a sticky there for years.


Ron Gratz explains WD

yes, great reference and a good summary of a force analysis one would learn in a statics 101 ME class.

Funny...the very first post in the diagram is a statement "TV Receiver Load WDH Removes 300lb"

[ktmrfs]

Huntindog wrote:
If you really want to "know" how it works. click on this link.
Or you can find it in the towing forum.
It has been a sticky there for years.


Ron Gratz explains WD

yes, great reference and a good summary of a force analysis one would learn in a statics 101 ME class.

[Grit_dog]

Also, thanks all for helping me realize I haven't completely forgotten all my highschool and college physics and statics and dynamics learnins....

[Grit_dog]

Huntindog wrote:
Try to imagine a tiny scale that would fit between the top of the ball and the coupler. What it would measure is the actual TW.... And that scale would read the same no matter what is done with WD.

You can put yourself in the "I don't understand" category, as well as the
"I don't read so well" category, since you quoted Ron Gratz, whoever that is, and his thread on here.
I looked at it for about 45seconds and he understands and halfway down the first page, he says this...
"No, the load on the BALL actually INCREASES by the assumed 1700#. The load on the receiver DECREASES by 300# as explained above."

Take a number, back of the line, try again when it's your turn...

Edit, in your tiny scale example, it would not be a measurement of tongue weight, it would be a measurement of the force that the coupler is applying to the hitch ball. A component of which is the remaining effective tongue weight after distribution and another component of which is the force applied to the connection (irrespective of tongue weight, actually).

[Huntindog]

If you really want to "know" how it works. click on this link.
Or you can find it in the towing forum.
It has been a sticky there for years.


Ron Gratz explains WD

[Grit_dog]

ktmrfs wrote:


the force the reciever places on the axles change, the force on the axles changes all due to the force from the WD hitch the actual WEIGHT of the trailer tongue does NOT change.

You're correct, anything besides this is wrong... but it is fun to watch people who think they know what they're talking about!

[valhalla360]

ktmrfs wrote:

valhalla360 wrote:

ktmrfs wrote:
saying tongue weight goes down with WDH is like saying I just lost 20 lbs because when I was on the scale and pushed down on the counter the scale dropped by 20 lbs. No your weight stayed the same, you just applied an opposing force in another place and the counter to that force lifted force off the scale. It didn't change your weight at all.

That's all WD bars do. They apply an opposing upward force reducing the load on the rear axle and since the sum of the forces must equal 0 the counter to that force is downward force on the TV and trailer axles

Good analogy but incorrect analysis.
- Your total trailer or body weight stays the same. This goes into the Tow Rating & GCVWR.
- The weight the scale needs to support does go down if you push on the counter. This goes into the Truck Payload & Max Hitch Weight.

the force the reciever places on the axles change, the force on the axles changes all due to the force from the WD hitch the actual WEIGHT of the trailer tongue does NOT change.

The weight that the hitch supports does change since more of the trailer weight is on the trailer axles. Plain and simple.

You are speaking of a theoretical value that has nothing to do with towing with a WDH because when the WDH is connected, the NDTW is not the weight that the truck hitch or suspension sees.

[ktmrfs]

valhalla360 wrote:

ktmrfs wrote:
saying tongue weight goes down with WDH is like saying I just lost 20 lbs because when I was on the scale and pushed down on the counter the scale dropped by 20 lbs. No your weight stayed the same, you just applied an opposing force in another place and the counter to that force lifted force off the scale. It didn't change your weight at all.

That's all WD bars do. They apply an opposing upward force reducing the load on the rear axle and since the sum of the forces must equal 0 the counter to that force is downward force on the TV and trailer axles

Good analogy but incorrect analysis.
- Your total trailer or body weight stays the same. This goes into the Tow Rating & GCVWR.
- The weight the scale needs to support does go down if you push on the counter. This goes into the Truck Payload & Max Hitch Weight.

the force the reciever places on the axles change, the force on the axles changes all due to the force from the WD hitch the actual WEIGHT of the trailer tongue does NOT change.

[valhalla360]

ktmrfs wrote:
saying tongue weight goes down with WDH is like saying I just lost 20 lbs because when I was on the scale and pushed down on the counter the scale dropped by 20 lbs. No your weight stayed the same, you just applied an opposing force in another place and the counter to that force lifted force off the scale. It didn't change your weight at all.

That's all WD bars do. They apply an opposing upward force reducing the load on the rear axle and since the sum of the forces must equal 0 the counter to that force is downward force on the TV and trailer axles

Good analogy but incorrect analysis.
- Your total trailer or body weight stays the same. This goes into the Tow Rating & GCVWR.
- The weight the scale needs to support does go down if you push on the counter. This goes into the Truck Payload & Max Hitch Weight.

[valhalla360]

Sport45 wrote:
This thread reminds me of a commercial I watched a long time ago showing a small car without rear wheels towing a trailer. The picture below is not from the commercial (it’s from eyershitch.com) but shows a couple of vintage cars configured similarly. It’s caption indicates the tongue weight. The magic of a WDH!

Yeah, I've seen those. Keep in mind, they were explaining the whole idea of a WDH, so referencing the hitch weight prior to implementing the WDH was a key aspect for people to understand what it does.

If we want to be pedantic you could list two tongue weights:
- Non-Distributed Tongue Weight (NDTW): The weight on the receiver without a WDH bars connected.
- Distributed Tongue Weight (DTW): The weight on the receiver with the WDH connected.

Note: I said "receiver" not "ball" because as shown previously, a WDH can substantial increase the weight on the "ball" but that can be misleading as the bars negate a large part of what the receiver sees.

So assuming you are towing with a WDH connected, you would want to use the DTW as that's what your truck suspension sees.