SDHQ Slider Measurement Needed

To clear up any confusion, we never designed our sliders to simply save weight or just for looks. 100% from the beginning our goal was to produce the best slider on the market. After carefully engineering our design and material choices, the weight saving was an added bonus. Hey more payload for all those other accessories!
Our sliders are supported front to back because of their design. That being said we feel it is unnecessary to have plates running the entire length of the frame to get that strength. First we mount to the front body mount for several reasons, one being it is a very strong part of the frame, and second it is as close to the front tire as you can get. This has many benefits to strength as the slider is fully supported at the very front tube union. We then designed the front mount to be boxed in a way to maximize and reinforce the strength of the body mount and slider. The backbone of the slider is (2) 4130 .120” wall tubes (2" for the Tundra and 1.75" for the 4Runner and Tacoma) running the entire length, while 4130 is significantly more expensive it is equally stronger and well worth the premium in our opinion. Then from there we use 4130 tubing to connect the center of the slider in two locations. These attachment points might not “look beefy”, but it is in the way that they attach that makes them strong. Not only do we utilize existing holes in the frame to bolt through into our CNC machined reinforcements, but we also wrap around the bottom of the frame and attach to the inner lip where the frame is double plated and welded, essentially creating a triangulated mounting point. This is another point where looks can be deceiving, as a long plate with a couple bolts going through the bottom of the frame might look stronger, all the force applied to the slider is relying on the shear strength of those few bolts, essentially making that large plate look beefier than it really is. With our design we are wrapping around the frame and utilizing the strength of the material while complimenting the strength of the frame, all without drilling or welding. Last but certainly not least, we have the rear of the slider were our mount is not only at the very rear of the slider, but we take it a step farther by extending our mount farther to the rear and upward. This creates a very nice triangulated mounting point that is designed for optimal strength while complimenting the strength of the frame design. In essence when we say fully supported we mean we have no “dead tubes” and our sliders are supported evenly front to back.

 

Tooo many science... more tubes

 

Too much science... more group buys.

@SDHQ OFFROAD

 

Doooo eeeeiiiitttt!!!! lol

 

Hey Joey, I know I just dropped it off yesterday but are my DCLB sliders done yet? lol j/k. I miss my truck already!

Meanwhile, I'm driving this gem...

 

Word!

 

How much water can I store in the SDHQ slider outside tube?

 

all of it

 

Damn, posting my emails and name on a public forum. Now I want a discount.

 

I scoff at that request

PS, dont fess up to that being your name. Could of been an alias.

 

http://www.fourwheeler.com/how-to/0901or-metal-weights-and-strenghts/

I’ll drop this here for education purposes. Seems 4130 is slightly stronger, slightly.

 

I have debated on whether to respond or not. I'm not interested in stepping on toes; this is a thread about another vendor's product after all. I will limit my analysis and comments to only discussing slider design in general and doing so I hope to help everyone learn a little about engineering.

So let's get to it. The biggest thing I want to discuss is the engineering principles behind designing rock sliders. They are designed to prevent your truck's body (pinch seam/rocker panel, door, etc) from contacting rocks. They sit just 1" below the pinch seam and need to hold the entire weight of the truck (maybe more if you drop hard on the rock) without hitting the pinch seam. Because of this we are focused on limiting deflection of the slider whether that is the mount plate or the tubing it self. There is a lot of deflection in the mount plates with bolt on sliders and many ways to mitigate it, but we will ignore that for now and talk about the other major contributor: deflection in the tubing. The tubing needs to be able to support the force with minimum bending or the slider will contact the truck. The short support legs from the frame mount plates to the lengthwise tube are the main contributors to the the total deflection of the tube assembly. This is a classic cantilever beam bending problem. The elastic deflection of a cantilever beam under load is given by:



where

= Force acting on the tip of the beam
= Length of the beam (span)
= Area Moment of Inertia of the beam's cross section
= Modulus of Elasticity

If you notice, the deflection is based on the Force, Length of the beam, Area Moment of Inertia and Modulus of Elasticity.

I know everyone isn't an engineer so let me discuss the later two variables. The Area Moment of Inertia is a basically the tubing's resistance to bending. It is completed based on the size, shape and wall thickness of the tubing. Essentially, the bigger and thicker the tubing the higher the Area Moment of Inertia and the less deflection you get under the same load.

The last variable is Modulus of Elasticity. The elastic modulus of an object is defined as the slope of its stress-strain curve in the elastic deformation region: A stiffer material will have a higher elastic modulus. Here is a list of the elastic modulus for various metals:



As you can see, the modulus is nearly the same for all steels. Even with high Chromium content the modulus only increases by ~3%. Not particularly significant.

So what does all of this mean? It means that to make sliders, you need to manage deflection. There are many ways to do it, mostly with clever mounting solutions and appropriate tubing size selection. If you choose steel, it really doesn't matter the grade steel (with respect to the current discussion. DOM is useful to prevent denting of the tubing). All steel performs essentially the same in bending.

So why is Cr-Mo used at all for anything if it doesn't make a difference? It does make a difference in designs/products where the material is used as tension and compression elements (like roll cages and truss structures). In those cases, yield strength will be a key factor and Cr-Mo has a higher yield strength than mild steel. Also, if you are designing something that you don't care about how much it deflects but are only interested in the max weight it could hold, then Cr-Mo might make sense.
Sorry for the long winded post. I hope this doesn't start a shit storm. This is solely an engineering and design discussion. This post isn't intended to debate the quality of any vendor's product. I'm not familiar enough with other vendors' products to comment on the quality/performance. What I do know is there were some misunderstandings about engineering being casually thrown around and I wanted to help the greater TW community understand the basics a little better. I hope this has been helpful and feel free to contact me if you want to discuss any specifics.

-Joe
@Mobtown Offroad

 

Nerd