thomas malenich
sound beach, new york 11789
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Quote:Thomas,
Finally, we agree 100% on something. This is exactly why I proposed the definitions in Tongue Weight and Hitch Load - What are they and how are they different? and referred you to them in my very first response to you.
Quote:Part of quote from above:
"Yes, the WD system distributes tongue weight over both the front and rear axle (that is the purpose of it). "
I say this is misleading if that is not what happens. ---
I think this is an excellent example of how lack of definition leads to misinterpretation.
First of all, my dictionary's definition of "mislead" implies an intention to deceive. Given that definition, I do not think the statment is misleading, but I do think it is subject to misinterpretation.
I certainly was not implying anyone was trying to deceive - bad choice of words. I should have used misinterpretation as that is what I meant.
A reader easily could interpret this as meaning that a WD hitch decreases tongue weight. The same reader could believe that decreasing tongue weight can contribute to sway and, therefore, choose not to use a WD hitch.
Secondly, if I knew nothing about how a WD hitch operates, the statement would lead me to believe that weight is removed from the tongue and added BOTH to the front axle AND to the rear axle. We know this is not the case.
Thirdly, there is no mention of the fact that the WD hitch causes the load on the TT's axles to increase. This is fundamental to understanding how the WD hitch works.
So, please consider the following two statements:
1) The WD system distributes tongue weight over both the front and rear axle (that is the purpose of it), and
2) The WD system removes load from the TV's rear axle and distributes it to the TV's front axle and to the TT's axles.
Which of these do you think is the better definition (meaning less subject to misinterpretation) of the purpose of a WD hitch?
Ron, I choose #2 !!
Ron
Thomas and Laura Malenich
1988 Suburban 1500, 4WD
Scotty 16 1/2' , smaller and loving it
2 kids and 3 dogs
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thomas malenich
sound beach, new york 11789
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I am very happy that all of you kept your discussion very civil and under control. That is sometimes hard to do in these forums. Thank you! Lets keep it open for the time being and see where we go. Let the Games (oops- wrong quote) err- "Discussion" continue! If, and when, you come to an agreement, I will petition Admin to make it sticky.
Barney
______________________________________________________________________
Barney, Thanks for not locking this thread. It was a wonderful discussion. I know that I repeated myself alot, but I was only trying to come up with different ways of testing Ron's points and/or the language. I was always calm and understanding but relentless in making Ron prove his theory. I think if I was in the same room with Ron he would have hit me over the head with his Statics 101 book. I really did not understand exactly how the WD system works but I sure do now.
After reading "distribute tongue weight" for over a year it gets burned in your mind, and you can see how easy it is to misinterpret things.
Thanks again, Tom
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tluxon
Kirkland, WA
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Hi Ron,
I just ran across this Very interesting discussion. You've done a real nice job of trying to explain how weight distribution systems for travel trailers work. I hope people appreciate how much work is involved in trying to describe the workings of these systems so they can be followed and understood by most. Thanks for the diagram and the diligent attempts to explain and clarify things. I'm guessing you put more detail into it than many people would follow without making it impossible by breaking it down to the finest point. I really got a great chuckle out of the very simple illustration that Kenneth provided, using you as the load bearer.
Since he hasn't pursued it further, I'm assuming Thomas has realized that about the only way he can observe a different loading between the tongue and the hitch ball is with a load cell - not a standard scale that relies on gravity.
As with most real life problems put on paper, a lot of simplification must be done and it looks like you did it very well. However, I've got to admit I was looking at some of the details from a little different angle. I'm positive that I haven't spent as much time thinking about it as you have, so maybe you can correct me where I'm mistaken.
I'm wondering what consideration should be given to the [i]levers[/i] created by the virtual attachment of the WD bars to the frame of the TV. I liken it to handles of a wheelbarrow where there is a front wheel to keep you from being able to tip it up. If you pull up with enough force, the big wheel of the wheelbarrow (rear wheels of your TV) will eventually leave the ground. As Kenneth so vividly described, you could use this new lever without any chains to transfer weight to the front tires of the TV. So, if you break down a TV/TT combination looking along the horizontal, you basically have two rigid planes hinged at the hitch ball. This is why I'm confused by your statement,
[quote][i]Ron Gratz wrote:
[blue]"Now, having added a load of 300 lbs at the TT axles, we must balance the TV/TT teeter totter. Using the TV’s rear axle as the fulcrum, to balance the 300 lbs at the TT’s axles we must add some load at the TV’s front axle.
The lever arm from the rear axle to front axle is 130”. The lever arm from the rear axle to the TT axles is 65+200 = 265”.
The required balancing load at the front axle is 300x265/130 = 611.54 lbs."[/blue][/i][/quote]
I guess I just don't see how the rear axle of the TV can serve as a "fulcrum" for ADDING weight to the front axle. Since the pivot point of these two rigid planes is the hitch ball, how can the fulcrum be anywhere other than at the hitch ball? The way I see it, the weight added to the front axle should be derived by the moment equation, (300 lb)(200 in) = (____ lb)(195 in), or 308 pounds. Perhaps you could explain the error of my thinking here and explain how the rear axle of the TV is used as a fulcrum.
There's another thing that this thread has made me think about that I had never given consideration to before. That is the issue that arises when a dual axle trailer is not level, moving the virtual axle further forward or further back depending on whether the trailer is sitting front low or back low. I haven't done the math, but as contrary as it would first appear, I believe you could actually [i]increase[/i] tongue weight by [i]raising[/i] the tongue so the rear axle is supporting the bulk of the axle load. Of course, whether it can actually happen or not is dependent on how the axles are attached to the suspension and frame of the trailer.
[edited to clarify quote from Ron]
Note: Due to invalid formatting, all formatting has been ignored.
* This post was
edited 08/31/04 05:33pm by tluxon *
Tim -
wife Beverly & 2 boys who love camping
2002 K2500 Suburban 8.1L 4.10 Prodigy
2005 Sunnybrook 30FKS HP Dual Cam
Replaced 2000 Sunnybrook 26FK on 8/6/04
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BarneyS
S.E. Lower Michigan
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Joined: 10/16/2000
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I also choose #2!
Tim, welcome to the discussion. ![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/smile.gif "smile") Stick around, these guys are sharp and will give you a run for your money!!!
Barney
2004 Sunnybrook Titan 30FKS TT
Hensley "Arrow" 1400# hitch (Sold)
Not towing now.
Former tow vehicles were 2016 Ram 2500 CTD, 2002 Ford F250, 7.3 PSD, 1997 Ram 2500 5.9 gas engine
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ffrnemtp
Brooksville, FL
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OK, I was wrong. "Weight carrying" is 600--"weight distributing" is 1500. I don't mean to be a problem child, but I'm lost. I tried front loading and moving up in weight a little, and now my tires are exploding. I'll get the trailer weighed as soon as I can, but I'm a fire department officer, and we have a hurricane approaching. I won't be able to do it this week, and I'll likely be on duty for at least the weekend. Unless the manufacturer is off on empty and gross weight by nearly 1,000 pounds, I'm not overweight, and there's nothing heavy remaining in the rear of the trailer. I recognize I do need to use the WD system. I remain, however, at a loss on how to correct these issues. I appreciate all the help I've been offered.
Doug & Lorri
2004 F-250 XLT 6.0L PSD SC SB FX4 DiabloSport Predator
2004 30' Thor Chateau TT with Reese HP Dual Cam
2004 Seadoos GTX 4-TEC Supercharged & GTI LE RFI
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#20 Home Depot
Mississippi/China
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I say #2 and lets all have a beer![[emoticon]](http://www.coastresorts.com/sharedcontent/cfb/images/biggrin.gif "biggrin")
#20 Home Depot
04 GMC 2500HD SWB EC D/A SLT 4x4,Michelin LTX AT2
Timbrens, Bilsteins , color backup cam, Doran tire pressure monitor Reese Tow Beast, Torklift tiedowns w/ fastguns
Lance 8SCS Polar Cub AC Honda EU2000">
2007 Chaparral 256 SSx
2005 Jeep Wrangler
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Ron Gratz
full time RVer
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Joined: 12/27/2003
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Tim,
Thanks for your kind words and good questions. I will try to provide some good answers.
Quote:I guess I just don't see how the rear axle of the TV can serve as a "fulcrum" for ADDING weight to the front axle. Since the pivot point of these two rigid planes is the hitch ball, how can the fulcrum be anywhere other than at the hitch ball?
With a WD hitch, the hitch ball no longer is a pivot point because it is "bridged" by the WD bars and chains. The bars become a part of the structure and allow torques (moments) to be transmitted through the hitch assembly. The WD hitch acts as a rotational spring.
Quote:The way I see it, the weight added to the front axle should be derived by the moment equation, (300 lb)(200 in) = (____ lb)(195 in), or 308 pounds. Perhaps you could explain the error of my thinking here and explain how the rear axle of the TV is used as a fulcrum.
Static equilibrium requires that the sum of all external forces acting on a body is zero and that the sum of all external torques (moments) is zero. The summation of torques can be done using ANY point as a fulcrum or "pivot". We could use the ball coupler and the answers would be the same. The calculations would be more difficult.
We also could isolate the TV from the TT and calculate the TV axle loads. In this case the external forces are the two axle loads, the 2000# acting UP on the rear ends of the spring bars, and the 1700# acting DOWN on the ball. If we use either the front axle or the rear axle as the fulcrum, we can calculate the axle reactions directly. If we use the ball as the fulcrum, we would have to solve simultaneous equations.
Using the front axle as the fulcrum allows us to solve for the rear axle load (RAL) using the moment equation RAL x 130" = {2000# x (130"+65"+30" - (1700# x ( 130"+65")} giving RAL = (2000x225 -1700x195)/130 = 911.54#. This is the wheelbarrow analogy and the result is a "lifting" of the rear of the TV. IOW, a decrease in the rear axle load.
Using the rear axle as the fulcrum allows us to solve for the front axle load (FAL) using the moment equation FAL x 130" = {2000# x (65"+30") - {1700# x 65"}) giving FAL = (2000x95 - 1700x65)/130 = 611.54#. The 2000# with its longer lever arm overcomes the 1700# and tries to push the front of the TV down. IOW, the front axle load increases by 611.54#.
Quote:There's another thing that this thread has made me think about that I had never given consideration to before. That is the issue that arises when a dual axle trailer is not level, moving the virtual axle further forward or further back depending on whether the trailer is sitting front low or back low. I haven't done the math, but as contrary as it would first appear, I believe you could actually increase tongue weight by raising the tongue so the rear axle is supporting the bulk of the axle load. Of course, whether it can actually happen or not is dependent on how the axles are attached to the suspension and frame of the trailer.
Tandem axle trailers can have either "independent" suspension or "equalized" suspension. For either type, if you put the nose down, you move the TT's center of gravity forward slightly giving a slight increase in "tongue weight".
For the "independent" suspension, if you put the nose down, you increase the load on the front axle and decrease the load on the rear axle. This results in a decrease of "tongue weight". Depending on the spring constants, the decrease due to axle loads probably will be greater than the increase due to shifting the COG forward giving a net decrease in "tongue weight".
For the "equalized" suspension, putting the nose up or down does not cause any significant change in axle loads -- thats part of the purpose of the equalizer link. Therefore, there will be a slight increase in "tongue weight".
To quantify "slight", consider a TT which is 200" from ball to the axle fulcrum point. If the nose is dropped 2", the slope is 2/200 = 1%. If the TT's COG is 30" above the fulcrum point, the COG will shift forward about 30" x 1% = 0.3". If the TT has an equalized suspension, the change in spring angle might also shift the axles rearward by 0.1 to 0.2"
If the "tongue weight" percentage is 12% with the TT level, the COG initially will be 24" ahead of the fulcrum. With the nose down 2", the COG might be 24.5" ahead of the fulcrum. This changes the "tongue weight" percentage from 12% to 12.25%. It's hard to imagine how this small a change can affect "sway". If having the nose down does in fact improve TT stability, I think we should be looking for another explanation.
Thanks again for the good questions.
Ron
On edit: Tim, I forgot that I had discussed the "nose up/down" topic some time ago in this post and the one following it.
* This post was
edited 08/31/04 08:41pm by Ron Gratz *
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Ron Gratz
full time RVer
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Joined: 12/27/2003
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To all the participants in this thread,
Thanks for all your questions and comments. Special thanks to Tom for "keeping me honest". I think I now know considerably more about the WD hitch than I did when I first posted due to having to respond to Tom's pointed questions. No, Tom, I would not have hit you with my Statics 101 book but might have jabbed you with my slide rule.
Also thanks to Barney for tolerating the seemingly endless debate and for making his own valuable contributions.
Tomorrow we head to Canada for a week of fishing, so you won't be hearing from me for a while. Don't distribute any tongue weight while I'm away.
Ron
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tluxon
Kirkland, WA
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Ron,
Thanks for your detailed reply. I knew that if I thought about it for more than a few minutes it would eventually come clear to me. Pointing out that the WD system works as a rotational spring is what did the trick.
Have a great week of fishing!
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#20 Home Depot
Mississippi/China
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Thank you Ron. I thoroughly enjoyed this lecture and learning experience! Thanks also to Thomas for pushing it on and Barney for his great oversight.
Quote:Tomorrow we head to Canada for a week of fishing, so you won't be hearing from me for a while.
Enjoy yourself catching those fish and don't get caught yourself trying to solve all the mathmatical equations involved with setting that hook!
Quote:Don't distribute any tongue weight while I'm away.
LOL, how could we??? We all know NOW that is impossible!
* This post was
edited 09/01/04 03:36am by #20 Home Depot *
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