mkirsch
Rochester, NY
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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 mean like a weigh safe hitch ball scale?
I am pretty sure the scale would read HIGHER with the WD bars applied. The WD hitch is pulling down on the tongue and up on the shank.
So does that mean the tongue weight is higher? No. It's just being mechanically transferred to a different point of contact.
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Grit dog
Black Diamond, WA
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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.
Try to imagine that it won't...
Your hypotehtical tiny scale will actually read higher with a wdh engaged, as the moment applied to the connection increases the pressure as it tries to pick up the back of the truck and the front of the trailer.
Truck hitch will see less downforce, but that doesn't mean the pressure on the hitch ball is less when you're squeezing the hitch onto the ball with a wdh.
Although now I know why so many blindly buy these things. They don't have a clue of how it works....not to mention if they actually need it or not.
* This post was
edited 08/31/22 10:50am by Grit dog *
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valhalla360
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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.
Yeah...but it won't.
In addition to the weight of the trailer that is sitting on the ball, the bars (which are attached to the truck) are pulling the trailer A-frame down via the chains/L-brackets. Since this downward force is behind the ball and the ball cannot apply any significant moment arm, an upward force that is split between the ball and trailer axles must be applied to compensate.
- The part that goes onto the trailer axles is the reduction in hitch weight (around 200lb per the CAT scale on my current trailer).
- Since the bars are closer to the ball, most of this force goes onto the ball and is quite substantial. (On my trailer, the L-bracket is aprox 2ft behind the ball and the center of the axles about 18ft. If we run the calculations to keep the trailer in balance, the ball will see around 9 times (1800lb) more downward force to balance the moment arms.
So if we use your imaginary scale that fits between the ball and the coupler...with the 900lb hitch weight, the ball is seeing around 2700lb of downward force on my trailer (yes, WDH have some substantial forces within the system).
To find the hitch weight with WDH:
- If you were to cut the hitch at the square receiver (just ahead of both the ball and bar attachments), the upward force needed to stop the hitch head from dropping is the hitch weight. This is force that the truck suspension sees (in addition to the moment arm which is separate) and is really the point of finding the hitch weight, it is the combination of the weight on the ball minus upward lift from the bars. This actually is reduced depending on how stiff the bars are and how far you bend them when connected (again, around 200lb per the scales on my current trailer).
- Or go to the CAT scales and check the truck weight by itself and see how much it increases when you weigh it with the trailer and WDH connected.
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Sport45
Not far enough from Houston, TX
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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!
![[image]](https://eyershitch.com/images/BookGraphics/toronado-distributing.jpg)
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ktmrfs
Portland, Oregon
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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
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valhalla360
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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.
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valhalla360
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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.
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ktmrfs
Portland, Oregon
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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.
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valhalla360
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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.
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Grit dog
Black Diamond, WA
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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!
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