Weight Distribution across a flatbed trailer?

You might want to read this thread.

Load weight distribution

 

I just noticed or maybe just didn't pay attention earlier, more fbs hauling two coils by having one in the center of the trailer axle and the other one over the fifth wheel. What's the physics behind that? I can get it over the axles (probably not due to manufacturers not recommending that) but not over the fifth wheel.

 

Splitting the coils will cost you a 10th or 2 of fuel mileage aerodynamically but is much easier on the trailer than a concentrated load and will ride much better.
It will cost some time tarping as you need to use 2 smaller (hopefully)tarps and do 4 ends instead of 2.
The front part of the load does not need to be exactly over the fifth wheel just near it, then the rear can be forward of the trailer suspension center.
I used to haul palletized bagged product 2500miles from southern AL to Edmonton AB and loaded 8 forward and 10 rear and loaded starting at the ends of the trailer. Balanced great and rode much nicer than gut loaded. It took maybe 10 min more to tarp.
This is like singling out pallets in the middle of a load in a van to spread the weight.

 

This is exactly why I wrote as I didn't think it was easier on the trailer. Not to argue but to understand why. Also, palletized loads aren't good example here since they have their weight distributed evenly. Contrary to the two pretty hard points here. Having them equally and enough spaced from the center (say, two diameters of the coils) sounds like what manufacturers would recommend. But that's my guess.
P.s I'm just not a fan of putting much load on the fifth wheel or close to it when there are ways to avoid it. No physics behind it, I may be wrong

 

First off, palatized loads aren't always distributed evenly. Ideally they get stretched put so the weight can be balanced, but often they don't and you deal with it.

Secondly, if I had a choice between being drive heavy and trailer heavy, I want the weight on the drives - better ride, better fuel economy. When the trailer is much heavier than the drives you get a "crack the whip" effect, which can lead to cargo shifts and loss of control.

 

The weight at the red arrows is the same or close in both cases but with a spread load the flex(and therefore metal fatigue) is reduced.

 

Agreed. I call it the tail waggin the dog.

 

I call it "oh, my friggin back"

 

Speaking of the tail, we still have a coil that is more in the back compared to positioning like I painted in yellow.

In this case any tail wagging I suspect to be less intensive. To make it easier, we can assume (and actually do that) that center of the load in both scenarios is in the same place on the trailer. AND the axles loads are equally distributed and the same, too. However, the larger spacing will obviously make the tail less stable. Tried to paint that, too.

The point of more cross members involved is clear. However, I don't see it to be significantly more stressed compared to the spread like I painted. Especially given that the two main members are designed to hold and distribute the weight starting from the center. Again, I'm not talking about both coils placed close in the middle. It's about finding an appropriate distance between them but in between the truck's and trailer's axles.

 

I tried new technologies and they're insane. This is ChatGPT. Taking my hat off.


Upd. Continuation. That's nuts.