Cargo carrier and tongue weight reduction??????

I would apologize to the OP for hijacking the post but I think that ship sailed a couple of days ago. Besides, it is cold and wet where I am and the trailer is in the shop getting a replacement axle. All that is hard on a new retiree that would prefer to be enjoying the fall colors and a good campfire.

RON - Thanks for the WD hitch analysis, but there are a couple of questions in that analysis that go to my previous point. Referring to the first equation reproduced below (I can't figure out how to copy and paste here):

1. You summed the moments around the axis of the coupler ball, but in order to create a load at the WDH ell brackets (F1 in your equation) the WDH hitch has to be engaged and the tongue jack retracted. When you do that the truck and trailer become one rigid member and you then have to consider the loads at the TV wheels in this sum of the moments and the equation has two more elements.

• We had a flat on the front of our TV in Oklahoma this summer and a 4 ton jack would not lift the front corner of the TV. If finally dawned on me I was trying to lift the entire truck about the trailer axle axis. I disengaged the WDH bars and then was able to jack up the front corner of the TV with normal effort

2. Where were you going to get the constant F1, the load applied to the A frame by the WDH ell brackets? This was exactly the point of my comment - we don't know that number.

When the bars are engaged and you retract your tongue jack and everything settles, a good bit of the classic tongue weight on the ball is transferred back to these L brackets PLUS a moment force is created at the hitch (about 750-800 foot lbs for my case) which is what forces weight back to the TV front wheels.

The force transferred to the ell brackets as things settle from unloaded to loaded state depends on the spring rate of the WDH bars and the spring rate of your truck suspension, neither of which is linear, and neither of which is really known by us.

Ron, please don't take offense at the comments. This is an absolutely fascinating analysis. I'm 42 years out of college but it is still just Statics 101, and I recognize I may be making it more complicated than it is as we try to visualize the free body diagram and forces around the WDH. In my case I decided the theoretical analysis was 80% of the work for an answer that is only 20% more correct. That's why I weighed mine in various states and determined the moment created by the WDH with field data, and now just apply that as a constant in my spreadsheet that calculates tire/axle loads as I load the trailer and truck. It isn't exact for every situation, but it is close enough.

Again, If I'm missing something or making this overly complicated, I welcome your insight. No flames were intended.



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Estimating load transfer via a WDH doesn't get any simpler than the following.


Let:
F1 = combined downward force exerted on A-frame at WDH lift brackets
F2 = downward load added to TT axles
d1 = distance from ball to WDH lift brackets
d2 = distance from ball to axles' midpoint.
Then:
F2 = F1*d1/d2

scbwr wrote:
I appreciate the responses. I've pretty much decided to buy a tongue weight scale sometime over the winter and then I can get an accurate reading with whatever I put on the rack. I'll get a baseline reading by measuring the tongue weight with just added weight of the hitch being welded to the trailer frame. Then I can see how it changes with the empty rack added, and then with cargo added to the carrier. If I have any problems, I'll take the trailer back to the CAT scales and get an updated weight of the trailer alone, so I'd really know exactly what the tongue weight is as a percentage of total weigth.

Using a TW scale or using a CAT scale will provide an estimate of TW changes.
However, don't be fooled into thinking that you can measure TW changes with an accuracy of 1# or even 10#.

To get an estimate of change in TW, you'll need to subtract two readings -- each of which might have an error of +/- 25# if using a Sherline or +/- 20# if using CAT scales.
You'll be lucky if the difference is within 20# of actual and shouldn't be surprised in it's off by 40# or more.

Given the information you've provided and assuming your TT has an axle spread of 5', I believe it's reasonable to expect a TW reduction equal to about 55% of the weight of cargo carrier and its cargo.

Ron

I appreciate the responses. I've pretty much decided to buy a tongue weight scale sometime over the winter and then I can get an accurate reading with whatever I put on the rack. I'll get a baseline reading by measuring the tongue weight with just added weight of the hitch being welded to the trailer frame. Then I can see how it changes with the empty rack added, and then with cargo added to the carrier. If I have any problems, I'll take the trailer back to the CAT scales and get an updated weight of the trailer alone, so I'd really know exactly what the tongue weight is as a percentage of total weigth.

Ron Gratz wrote:

Gdetrailer wrote:
If you look closely you will notice that the axles are 2/3 the way back from the front (IE tongue)..

If you place 100 lbs on the rear bumper your will remove 1/3 of that weight from the tongue or roughly about 33 lbs..

In the example I used, the distance from ball to added load was 28.5' and distance from ball to axles' midpoint was 17.8'.
That puts the axles' midpoint at 17.8/28.5 = 62% of overall length.
If the TT had a single axle at 17.8',
100# added at the rear would cause about 100*0.38/0.62 = 61# to be removed at the ball.

In your example where "the axles are 2/3 the way back from the front" (and if the trailer is single axle),
100# added at the rear would cause about 100*0.333/0.666 = 50# to be removed at the ball.
In order to remove a load of 33#, the axles would have to be 3/4 of the way back -- not 2/3.

Ron

Well Ron, I have very bad news for you..

I have PERSONALLY weighed the tongue weigh difference using my 26ft dual axle TT and the result IS what I have mentioned above.

for 100 lbs my tongue LOST 33 lbs..

I also tested 200 lbs and the result was pretty darn close to 66 lbs..

Typically your axles ARE at 1/3 from the back and two thirds from the front in order to get proper 10%-15% tongue weight balance.

The dual axle tends to foul up calculations since the center is between the two axles and your axles do shift front to back a bit..

In other words measurements are a bit dynamic even when sitting still..

Additionally COG can affect the tongue weight which is an often overlooked item.. COG will shift some weight to the tongue if tongue is lower than level and if above level it is shifted towards the back..

TundraTower wrote:
I made a couple of attempts this summer to calculate the forces generated by the WD hitch. It is a very messy calculation, I could not find all the constants I needed (like spring rate of the bars and my truck suspension with Timbrens added), and ultimately it was more trouble than my situation warranted.

For my own situation and based on many many weigh tickets (I know the guys at the truck stop by name now), I have determined that my own Equalizer hitch redistributes the static tongue weight as follows: 22% to the trailer wheels, 82% to the rear wheels, and -4% to the front truck wheels.

If you find a reasonably simple formula for the WD hitch, let me know.

Estimating load transfer via a WDH doesn't get any simpler than the following.

Let:
F1 = combined downward force exerted on A-frame at WDH lift brackets
F2 = downward load added to TT axles
d1 = distance from ball to WDH lift brackets
d2 = distance from ball to axles' midpoint.
Then:
F2 = F1*d1/d2

Let:
d3 = TV wheelbase
d4 = distance from TV's rear axle to TT axles' midpoint
Then:
F3 = load added to TV's front axle = F2*d4/d3
F4 = load removed from TV's rear axle = F2*(d3+d4)/d3

For example:
If your tongue weight causes 500# to be removed from the TV's front axle and 1500# added to the rear axle,
and if you wish to restore 500# to the front axle,
and if TV's wheelbase is 130" and rear axle to TT axles is 260",
Then:
the WDH would be adjusted to transfer 250# to the TT axles
causing 250*260/130 = 500# to be added back to the front axle, and
causing 250*(130+260)/130 = 750# to be taken from the rear axle.

The net load changes would be
250# added to TT axles, 500-500 = 0# change on the front axle, and 1500-750 = 750# added to the rear axle.

The theoretical net distribution would be
0 change on front axle, 75% added to rear axle, 25% added to TT axles
Versus your measured values of
4% removed from front, 82% added to rear, 22% added to TT axles.

Ron

Gdetrailer wrote:
If you look closely you will notice that the axles are 2/3 the way back from the front (IE tongue)..

If you place 100 lbs on the rear bumper your will remove 1/3 of that weight from the tongue or roughly about 33 lbs..

In the example I used, the distance from ball to added load was 28.5' and distance from ball to axles' midpoint was 17.8'.
That puts the axles' midpoint at 17.8/28.5 = 62% of overall length.
If the TT had a single axle at 17.8',
100# added at the rear would cause about 100*0.38/0.62 = 61# to be removed at the ball.

In your example where "the axles are 2/3 the way back from the front" (and if the trailer is single axle),
100# added at the rear would cause about 100*0.333/0.666 = 50# to be removed at the ball.
In order to remove a load of 33#, the axles would have to be 3/4 of the way back -- not 2/3.

Ron

If you look closely you will notice that the axles are 2/3 the way back from the front (IE tongue)..

Makes it pretty simple to figure out..

If you place 100 lbs on the rear bumper your will remove 1/3 of that weight from the tongue or roughly about 33 lbs..

200 lbs on the rear bumper will remove roughly about 66 lbs.

I made a couple of attempts this summer to calculate the forces generated by the WD hitch. It is a very messy calculation, I could not find all the constants I needed (like spring rate of the bars and my truck suspension with Timbrens added), and ultimately it was more trouble than my situation warranted.

We engineers have to be careful about perspective. Measure with a micrometer, mark it with a piece of chalk, and cut it off with an axe. Once in a while it just makes more sense to tack-weld it together and see if it works.

For my own situation and based on many many weigh tickets (I know the guys at the truck stop by name now), I have determined that my own Equalizer hitch redistributes the static tongue weight as follows: 22% to the trailer wheels, 82% to the rear wheels, and -4% to the front truck wheels.

If you find a reasonably simple formula for the WD hitch, let me know.

TundraTower wrote:
IF you have a single trailer axle I think you will see some change at the tongue - but at 22 feet and 6500 lbs this MUST(?) be a double axle. If you have a double trailer axle, the calculation gets messy and the impact at the tongue is probably less because the pivot point at the wheels is almost 5 feet long and provides resistance to the teeter-toter effect of the weight change.

No extra charge: you will be adding load on your trailer wheels equal to 230-T

Change to WD hitch probably depends on number of axles, whether the WD hitch is adjusted correctly before the new load is added, and whether the current adjustment is light or aggressive. We pull a 7600 lb trailer with a '13 Tundra and I have to set my Equalizer hitch very aggressive to push the front of the truck down due to the length(double cab). If yours pulls OK now, I would be shocked if you had to adjust it for 230 lbs on the back.

mosseater wrote:
My trailer has a huge cargo bay in the rear bedroom area and I put a whole bunch of weight back there. Firewood, 3 bikes, drinks, probably well over 500 lbs. It takes my tongue weight from almost 1200 lb to about 1050. There seems to be a law of diminishing returns, though, because at some point, more weight doesn't equal proportional reductions of tongue weight. Not sure if spring compression comes into play or what. It will help, just a question of how much.

The previous quotes correctly speculate that distance between axles and spring compression can affect the relationship between load added at the rear and resulting load removed at the front.
The graph below quantifies the effects of axle "spread".
TT dimensions were chosen to approximate the OP's 2014 Winnie 2201DS -- ball to front of body = 4', ball to axles' midpoint = 17.8', and ball to rear of body = 27'.

For these dimensions, the results converge to the single-axle formula provided by TundraTower which gives a load of 230*10.7/17.8 = 138# removed from ball due to 230# added at the rear.
If the axles are spaced at 5', the load removed from the ball is reduced to 126#.
As axle spacing increases, more load is added to the TT's rear axle, less load is added to the front axle, and less load is removed from the ball.

The results on the graph assume WD is not in use. Effect of WD is yet to be quantified.
The results also assume the load/deflection relationship is equal at the ball, the front axle, and the rear axle. Results of these "spring coefficient" effects will be posted as soon as I decide how to present them.

Ron

DutchmenSport wrote:

wanderingbob wrote:
The two axles will take a lot of the weight , Try putting your mother-in-law on the bumper and see if her weight makes a lot of difference !

Oh, that's bad, really bad! (But, if you want to use MY mother-in-law, you are welcome to use her for the experiment!) :B

And if you need more weight you can use my mother-in too and if it works out you can keep her.