Weight Distribution Hitches

Ok Skip, certainly didn't mean to offend if I did. Let's change it to welcome to the group of active participants on the forum. We'd love for you to share the benefits of your experience here.

And a good discussion/debate about wdhs is great too, thats
how we all learn.

For better or worse, the cost of steel and other materials is ever increasing, as is the cost of fuel and the proportion of lighter vehicles on the roads. All that combines to reduce the design margins we used to see in vehicle frames. And in structures of all kinds for that matter. Look how little wood goes into home construction today compared to 40-50 years ago. I miss that solidity too, but it's gone forever I'm sure. One reason bought a 27 year old class B this time, it's built like a brick you know what.

Re front frame bending vs rear, it's been a few years since I did my calcs, so I don't recall the exact numbers. I do recall that bending failure at the rear axle occurred at around 2 Gs or a bit lower, which is a pretty low number. You can easily get that if you hit a pothole or curb hard. So the design is marginal at that spot, which is born out as there have been several frame failures there reported. And a wdh can increase that by a couple hundred pounds, so around the 5 to 10 percent range.

I recall the front frame loads are less, and to my knowledge no one has reported a frame failure there. Yet. The wdh increases the load there too.

Flexing (aka deflection), is a separate calculation from yeild in bending. Deflection isn't permanent, bending beyond the yield point is. Can't now recall if I looked at that before or not. At the time I was more interest in understanding all the bent trailers.

So yes it is possible that displacement could be high enough to flex the wall attachments but not high enough to bend the frame permanently. And no doubt too much defection will damage the trailer box. I'll try to revisit this when I get the chance.

Skip, can you clarify how the Anderson wdh allows more or different adjustment of trailer frame loads than other wdhs? AFAIK all of them are adjustable for tension, which is what changes the TV front rear balance, and the frame and trailer axle loading.



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You think I don’t like my pod, wrong I love it!

I wonder why wall to side separation in in the front only? The WDH forces? Rusty screws should also rust on the back and sidewalls! 

Just going to "weigh" in here a little. he he.

First, Skip and JPDub, welcome to the forum.

Skip, you are absolutely right on two of your points. Rpod frames are undesigned. And, WDHs do increase frame loading.

But, that doesn't mean that the wdh is the reason the trailer frame might fail in any specific case. There are many factors involved. The forces and moments imposed by the wdh depend on its design and how much its tensioned. Those forces and moments act in combination with the ones imposed by the way the trailer and tow vehicle are loaded, the shape of the pothole or curb you hit (you're not going to bend your trailer frame while your parked after all), the rig speed, the axle torsion arm attachment position, the presence or absence of a trailer lift kit. There might be some other factors I'm forgetting at the moment. IOW it's complicated.

So let's look at this from the manufacturer's perspective. FR and Lippert (who produce and warranty the frames and suspensions for FR) are well aware that WDHs are in widespread use by their customers. They know they would kill their sales if they disallowed them. So they aren't going to do that.

They also know better than anyone how lightly constructed their trailers are. They deal will the warranty claims and repairs every day.

So they're not going to formally approve use either. Because if they did, they they'd have to establish limitations. And that opens that whole complicated can of worms. Even if they could distill all that into a set of restrictions, which I doubt, they would have to try to write that section of their warranty in a way that a consumer could understand. And then they would be forever dealing with questions and evaluations of customers specific use cases. They'd probably have to hire a bunch of engineers, customer service reps, and attorneys just to deal with that one issue. So they're not going to do that either.

So their approach, and I think most other manufacturers', is to neither approve or disapprove, and deal with each customer's warranty claim as it comes up. If that claim can be attributed to something that is excluded in their written warranty terms, they won't fix it. If it can't, then they will.

This approach isn't unique to the trailer industry btw. No product warranty exclusions I've ever seen, and I've written many myself, can address every possible issue that might occur. Customers are very creative and are always finding new ways to break the stuff you sell them.

So where does that leave us as owners? Right where StephenH said.

Be an educated user. Evaluate the risks (bent trailer frame) and rewards (safer and more stable towing) of using a wdh on your particular rig loaded as you prefer to travel, on the road surfaces you like to travel on.

Use this and other forums to learn. Please
actually weigh your loaded rig so you have real data and you're not guessing.

Then decide for yourself if the benefits outweigh the risks.

FWIW, most of us here with tow vehicles lighter than an F150 have decided using a wdh is worth it. Most folks with a TV in the F250 category or higher have not, and in that half ton truck range in the middle some do and some don't.

I can tell you what I decided to do after analysing the forces and moments of my particular pretty extreme use case as best I could by hand calcs lacking access to a conputer finite element model of the trailer. In my case (heavily loaded 179 with 5000 lb rated TV, lots of boondocking on rough forest service roads), I decided a wdh was absolutely necessary. It increased trailer loads at two locations: roughly where the tongue assembly is welded to the frame rails, and at the axle and the axle to frame attachment point.

The tongue area loads weren't that bad, but the axle area loads were, even without a wdh. The wdh increased them by about 5 to 10 percent IIRC. So I tried to keep the weight behind the axle as low as possible by moving all my heavy supplies forward in the trailer. No bicycles or other stuff except the spare hanging off the back. Kept holding tanks located behind the axle empty as much as possible. I also reinforced the axle itself, as others on this forum have done.

If I'd kept the rpod I would have probably reinforced the frame at the axle attach point too, but I decided to sell it for other reasons before could get to that.

I said I use an Anderson, one of the best, see above.