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
levers 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,
Ron Gratz wrote:
"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."
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
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.
[edited to clarify quote from Ron]
