Bed stiffeners...yay or nay??

It wasn't a clear question to me, so I took a guess

I haven't had any issue with bed access. I barely notice they are there. The added tie down points they bring are also greatly appreciated.

 

Sorry about that.

Thanks! That my guess as my situation is the same.

@b3itz

 

Well shit. I put about a grand in body damage on my truck this weekend from a 4ft deep mud hole lol. I'm gonna need a bigger budget.

I'll prioritize this

 

That sucks!

Good luck with the fixes.

 

Thanks! It's all part of the game when you're planning to get into the woods IMO. Sucks though! I'd rather spend that grand on something more fun lol.

Anywho - i just ordered the victory stiffeners. Cheers and thanks as always!

 

You're welcome!

 

I should have done the stiffeners sooner......





I don't think it's all that bad. I wonder if installing the stiffeners will somewhat bring it back in?

Edit: Oh, and the dent wasn't me, it was my gf rolling back in the driveway into the house

 

Mine was like that before stiffeners and it was resolved when I put them on so you might see the same.

 

any issues with an air mattress?

 

Alright, here we are. I received my stiffeners from victory 4x4. The driver's side went on without a hitch, but the passengers side just won't line up. I cannot get the stiffener far enough towards the side of the truck. No matter what I do, I cannot get the torx55 or torx35 to bite.
I don't think it's my truck bed that's misaligned due to the direction of the misalignment. If the bed was bent from my tent etc, the bed would be too far out. Instead, it's like the bed was almost pushed in? Any ideas? Hopefully that made sense.
Is it a possibility that they were manufactured just a hair off??

 

Installed some rago fab stiffeners a few weeks ago, install was very simple and everything lined up first try.

 

Appears to be. Probably will have to enlarge the holes a bit.

Or maybe attach the bottom first, and then the side.

 

I may enlarge the holes, but I hate to do that to a $100 piece of steel lol. I feel bummed that the product wasn't dead on.
I tried attaching the bottom first but the bracket won't go to the side of the bed enough.

 

Don't fret about drilling or dremeling them if you are up for it, just use some touch-up paint on the bare metal afterward. We'll still offer the full warranty. Or, if you'd rather, shoot us a message and we would be happy to help you work through it. I doubt the holes are off since it's all done on a laser cutter, but something may be up with variances on the truck. info@victory4x4.com

The other option is to put a prybar, socket extension, screwdriver, etc in this hole and leverage it all over enough to get your bolt started.

 

Thanks - i got in touch over email and got it lined up.

The passenger bracket was clearly not the same size or dimensions as the drivers side, and even after doing a bunch of drilling, i couldn't make it work. I couldn't get the t55 or t35 bolts started...









I appreciate the customer service! I look forward to the new set when they arrive. Fingers crossed it works out this time.

 

Interesting, sorry about the hassles! Let us know if you still have issues with the new set.

 

Alright, I will attempt to shed some light on this topic as I see it brought up numerous times a year and I feel qualified to offer a sophisticated opinion on the matter.

I am a practicing Structural Engineer with a degree in Mechanical Engineering (meaning I understand dynamic motion, kinematics, kinetics, etc.) and another degree in Mathematics.

Alright, so let's start with the difference between static load and dynamic load.

Static load is stationary. This is the weight of all of your camping stuff if you placed it all on a scale and summed the weights. For explanatory purposes, let's say this is 500 lbs in total, 300 is stuff in the bed of the truck, secured to the bottom of the truck bed in various ways, and 200 lbs is your RTT and rack. Rack connection style (i.e. fully welded, or modular/bolted together) is not important, as we are analyzing the truck bed and not the rack. Either connection style (of all manufactured racks I have seen, someones DIY rack may not be designed properly) will perform the same.

Dynamic load is a static load under movement. Think of yourself standing on a scale, without moving, and seeing a displayed weight of 150 lbs. Now, to get off of the scale you decide to crouch down and jump off of the scale. At the moment of maximum force (when your body begins to accelerate from it's lowest position, assuming accel is constant throughout the jump) the scale reads 320 lbs (arbitrary number as it is a function of how hard you jump up). This 320 lbs is the dynamic load generated from a 150 lb person through movement.

Ok, so now that we understand the fact that static loading can be modified to dynamic loading via motion/movement let's move on to the next topic.

The translation of forces. As an astute follower of Physics 101 you may say, "I know the weight of an object acts towards the center of the earth, which for all intents and purposes is perfectly vertical towards the ground" which is 100% accurate. But what is important to understand is what happens to purely vertical forces once they are resisted at a location that is not co-linear with their center line or neutral axis or center of mass. You see, when you're driving down a bumpy road with your RTT loaded onto your truck and you're causing your rear suspension to compress and elongate as you travel, your RTT is moving up and down. But due to the fact that it's center of mass is a distance truckbedwidth/2 from the sides of the truck bed and (truckbedheight + rackheight (to tents COM)) from the bed of the truck a portion of that vertical force is translated into lateral (side to side) force. This force is what ultimately damages your bedsides.

This is why rack support hardware that allows for the installation of a tonneau cover, i.e. the KB Voodoo rack in the video linked above, are inherently flawed. Flat plates are terrible in resisting bending forces caused by the lateral motion in this system. This is also why a flat plate system can easily support 1,000 lb while you and your family and your dog are sleeping in the tent at night, but the manufacturer imposes a weight limit for the flat plate system that is far below that (200 or 300 lb IIRC). The flat plates could never handle the dynamic forces caused by a static load of 1,000 lb, which we have demonstrated above as being much larger than 1,000 lb.

This takes us to our final topic for this post. Shape properties.

We have now left the RTT and tops of the bedsides alone and we are looking at the bottom inside corners of the bed near the tailgate, as this is the location where all of the lateral forces created by the dynamic motion of the static load are resolved/handled/dealt with.

There are a lot of things to think about here but a couple important ones are as follows:

Stress concentration factors (k factor): This is a factor that is a function of the shape and size of a discontinuity in a shape i.e. a 90 degree bend with a very small radius in the case of our truck beds. This situation has one of the highest k factors, second only to a perfectly square 90 degree angle with a radius of 0.

Distances: The bottom inside corners of the bed near the tailgate resist what are called 'moment forces'. These are forces that have units of force*length (or distance) (i.e. ft*lb or k*ft). These are not pressures btw, which features units of force per area. Now, moment forces are real things, but they need to be resolved into shear/tension/compression forces. And to do this we need to modify the units from force*length to simply force, as force is the units of shear/tension/compression (i.e. your body weight on a scale - 150 lb). To do this we need to divide force*length by length (of the same units (i.e. feet by feet or inches by inches). Based on simple math, if you divide a moment of say, 100 ft*lbs, by anything less than 1 ft, you end up with a shear/tension/compression (s/t/c from now on) force that is higher than 100 lbs. Dividing 100 ft*lbs by .5 ft results in a force of 200 lb. But, if you divide the moment force by anything larger than 1 ft, you end up with a force less than 100 lb, with the larger the distance, the lower the force (all the way to infinitely long with a force of 0 lb.)

Section Modulus: The easiest way to explain this is to think of a piece of flat steel or aluminum from your local hardware store. If you grab a 4 ft piece from the bin there and you hold it so the flat side is pointed towards the ceiling, you can easily bend it in your hands by rotating your hands from your palms being flat with the ground to your palms being parallel to each other. However, if you rotate the piece 90 degrees so that the skinny side points towards the ceiling and the flat side is towards your chest, all of a sudden the piece cannot be budged even a fraction of an inch. What happened? This is the function of the section modulus, which is a variable that determines a shapes ability to resists bending forces (Fb = M/S). For this example of a piece of steel/aluminum with a rectangular cross section, the section modulus (S) is calculated by the simple equation (b*h^3)/12 with b being the width and h being the height. A quick look at that equation shows you that the height of the section (in relation to the axis about which it is being bent) is much, much more important than it's width as the h term is cubed in this equation and it is located in the numerator of the equation.

So, what does all this crap mean?

What it means is, you need to reduce the stress concentration factor by increasing the radius of the discontinuity, you need to maximize distances away from the point of inflection and you need to be intelligent in the way you design the bracket by using the inherent strength of properly designed/chosen shapes.

This is why, as posted above, a bracket with a small angled piece of steel near the corner is better than the bed itself, as it modifies the k factor, and increases the distance between point of inflection and the resolution of the forces (the small piece of angled steel). Also, the flat plate approximately 1/16" above the lowest bolt does little to nothing to reinforce the bed corner and can be omitted from future designs as it is a waste of material and weight. However, while this bracket is better than nothing, it pales in comparison to a more mainstream stiffener, as these stiffeners takes advantage of the section modulus of a more intelligent shape (i.e. the plate that runs to the top and side of the plates parallel to the bed floor and wall).

So, with all that said, what is my verdict?

Get bed stiffeners if you have a RTT that you mount on a rack that places the COM of the tent/rack combo anywhere above the floor of the truck bed. You see, we ignored the 300 lbs of stuff strapped to the floor of the bed, as all of its lateral forces are resisted co-planar to the floor of the truck, and thus do not impart any moment forces on the corners of the bed (which is what we were concerned about in this discussion). Only a weight a distance above the floor can do that, with the higher the location of the same weight resulting in higher forces.

Now, with that said, I have not performed an analysis of this system to determine the moment forces being resisted at the bed corners, and therefore cannot determine the appropriate size of a bed stiffener to mitigate any potential damage. Until someone pays me to do that I can't say that the smaller angled homemade bracket above does anything less than what is required relative to the more mainstream stiffeners. But I can tell you, based off of first principles in engineering, that the more mainstream mounts are a much better choice for this situation at this time.

This is not the end all be all analysis of this situation, but it is certainly a well thought out one presented by an individual with the necessary credentials to understand the phenomena we are witnessing.

Alright, that took an hour. Let me know if you have any questions.

 

It also places a lot of stress on the hardware of those brackets. I don't know if makers of those mounts make customers aware that it changes the load capacity of the rack, but it absolutely does. Nothing at all wrong with that if people are aware of the limitations, however.

I think your points on stiffeners are very valid. In this industry, we tend to overengineer a lot at the expense of weight, but try and limit taking up space. A̶s̶ ̶f̶a̶r̶ ̶a̶s̶ ̶s̶t̶i̶f̶f̶e̶n̶e̶r̶s̶ ̶a̶n̶d̶ ̶a̶ ̶b̶e̶d̶ ̶r̶a̶c̶k̶ ̶g̶o̶,̶ ̶t̶h̶e̶ ̶b̶e̶s̶t̶ ̶t̶h̶i̶n̶g̶ ̶a̶n̶y̶o̶n̶e̶ ̶c̶o̶u̶l̶d̶ ̶d̶o̶ ̶i̶s̶ ̶p̶u̶t̶ ̶a̶ ̶b̶a̶r̶ ̶o̶r̶ ̶c̶a̶b̶l̶e̶ ̶h̶e̶r̶e̶ ̶a̶t̶ ̶t̶h̶e̶ ̶r̶e̶d̶ ̶l̶i̶n̶e̶,̶ ̶b̶u̶t̶ ̶t̶h̶a̶t̶ ̶w̶o̶u̶l̶d̶ ̶k̶i̶n̶d̶ ̶o̶f̶ ̶b̶e̶ ̶i̶n̶ ̶t̶h̶e̶ ̶w̶a̶y̶.̶ ̶W̶o̶u̶l̶d̶ ̶s̶o̶l̶v̶e̶ ̶t̶h̶e̶ ̶b̶e̶d̶ ̶i̶s̶s̶u̶e̶ ̶t̶h̶o̶u̶g̶h̶

Edit: I was wrong, read more below to find out why.

 

Nice explanation. One addition is that there is mass in the bed sides / fenders themselves that can be enough of a dynamic load offroad to potentially cause issues. I believe that I felt a difference after installing my stiffeners when going over some bumps.


My rationale is that this undercut for stress relief is wholly insufficient to handle a bending load applied at the top of the bed rails:


The way that I look at it is that the stiffeners relieve the moment load from the corner and create more or less pure tension / compression between the stanchion and stiffener and remove bending stress from that undercut.

 

A bar there would resist spread, but it doesn't stop the moment from being applied to the bed rails. Basically, there would still be the same sway on the bed sides.

To do that, you would have to cross brace either the corner of the rack to the opposite bed floor. Cross bracing the bed rail to bed floor would be similar and a bit less effective. This is essentially what the bed front wall does as a shear panel. Of course, neither of those are generally useful ideas, so we have stiffeners.