Paging my mathematicians and engineers.

[OFC Ranger]

So unable to help myself I am already looking to build out rack platform 3.0 over this summer. One of the necessary evils of utilizing 1" square bar aluminum over a ten foot span was the requirement to use four rubber feet for support in the roof channels to prevent stress bending and bounce over uneven terrain from the weight of the light bar, side paneling, and any weight installed over that part of the platform. The rack is held solid on the front end on uneven terrain utilizing tension by way of adjusting those feet to the point that they put force upwards against the aluminum frame they go through.

I am looking to eliminate this one weakness by moving to ten foot spans of the same 1 5/8 (12 gauge) unistrut I use for the sub frame that connects the system to the RCI bed rack. This from basic overview should eliminate the need for the foot supports at the sacrifice of weight, which honestly I'm not concerned with. The over the cab portion of the can is only 4 feet in length. Below is a simple chart I grabbed off Google. I just want second confirmation, that short of loading an elephant on the front end this component should be far more than enough. I suspect the front load should never really exceed 100lbs as it will only take weight from; large light bar, side paneling, a handful of cross beams, and a two foot solar panel system in the future.

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[P. A. Schilke]

So unable to help myself I am already looking to build out rack platform 3.0 over this summer. One of the necessary evils of utilizing 1" square bar aluminum over a ten foot span was the requirement to use four rubber feet for support in the roof channels to prevent stress bending and bounce over uneven terrain from the weight of the light bar, side paneling, and any weight installed over that part of the platform. The rack is held solid on the front end on uneven terrain utilizing tension by way of adjusting those feet to the point that they put force upwards against the aluminum frame they go through.

I am looking to eliminate this one weakness by moving to ten foot spans of the same 1 5/8 (12 gauge) unistrut I use for the sub frame that connects the system to the RCI bed rack. This from basic overview should eliminate the need for the foot supports at the sacrifice of weight, which honestly I'm not concerned with. The over the cab portion of the can is only 4 feet in length. Below is a simple chart I grabbed off Google. I just want second confirmation, that short of loading an elephant on the front end this component should be far more than enough. I suspect the front load should never really exceed 100lbs as it will only take weight from; large light bar, side paneling, a handful of cross beams, and a two foot solar panel system in the future.

Hi Jack,

You are going to have a cantilevered arrangement, not beam loading...

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

 

[OFC Ranger]

Hi Jack,

You are going to have a cantilevered arrangement, not beam loading...

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

In plain English do you mean one sided support? LOL

 

[P. A. Schilke]

In plain English do you mean one sided support? LOL

Hi Jack,

Yep!

best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

 

[OFC Ranger]

Hi Jack,

Yep!

best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

So... should I just take those numbers and halve them? Then halve the halve for the 4 foot section over the cab?

I mean in your plain jane opinion would 100lbs spread over two 12 gauge unistrut channels (not counting cross beams in addition) pose any problems under any circumstances? I stayed at a Holiday Inn Express once so I'm thinking I should be good.

You know I may just say screw it and over engineer things like I usually do an eliminate cross beams all together and instead run four ten foot channels to put the floor grating over. Then I have 100lbs'ish spread over four instead of two. Hmm why didn't I think of this before. Total platform width is only 46" so running 4 supoorts the length of the truck would be effectively give me cross beam support off 11.5" which is more than acceptable for human walking weight up top. Well shit, I could have saved a ton of money on aluminum raw materials if I had considered this from the beginning... damnit.

Jeez, this rabbit hole was suppose to be coming to an end...

 

[P. A. Schilke]

So... should I just take those numbers and halve them? Then halve the halve for the 4 foot section over the cab?

I mean in your plain jane opinion would 100lbs spread over two 12 gauge unistrut channels (not counting cross beams in addition) pose any problems under any circumstances? I stayed at a Holiday Inn Express once so I'm thinking I should be good.

You know I may just say screw it and over engineer things like I usually do an eliminate cross beams all together and instead run four ten foot channels to put the floor grating over. Then I have 100lbs'ish spread over four instead of two. Hmm why didn't I think of this before. Total platform width is only 46" so running 4 supoorts the length of the truck would be effectively give me cross beam support off 11.5" which is more than acceptable for human walking weight up top. Well shit, I could have saved a ton of money on aluminum raw materials if I had considered this from the beginning... damnit.

Jeez, this rabbit hole was suppose to be coming to an end...

Hi Jack,

Halving the beam strength is a good starting point....it is a bit more complicated but a good starting point...Yes over engineering your design is a good move. You have a couple things. Monotonic yield. Meaning you put weight on it and it bends right away....Then there is cyclic yield that occurs when the member is subjected to cyclic loading. Imagine a 100 lb weight being cycled up and down over bumps and rough roads on your Travels. Without knowing the cyclic fatigue of the material and the cycle life of the truck....hard to predict success or failure. That is why overbuilding is a safety factor. For example we know the loading into the front suspension but we apply a 1.5 factor of safety to address a robust design. maybe not so much a factor of Safety on the Tailgate Damper, you know?

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

 

[OFC Ranger]

Hi Jack,

Halving the beam strength is a good starting point....it is a bit more complicated but a good starting point...Yes over engineering your design is a good move. You have a couple things. Monotonic yield. Meaning you put weight on it and it bends right away....Then there is cyclic yield that occurs when the member is subjected to cyclic loading. Imagine a 100 lb weight being cycled up and down over bumps and rough roads on your Travels. Without knowing the cyclic fatigue of the material and the cycle life of the truck....hard to predict success or failure. That is why overbuilding is a safety factor. For example we know the loading into the front suspension but we apply a 1.5 factor of safety to address a robust design. maybe not so much a factor of Safety on the Tailgate Damper, you know?

Best,
Phil Schilke
Ranger Vehicle Engineering
Ford Motor Co. Retired

Yea I get it 100%.

I guess its one of those things where I just go for it. I imagine four 12 gauge steel channels should be able to handle it for the life time of the vehicle. I have a habit of once a month doing an inspection of the rack for what I know are the weakest possible points on it.

If I am compelled enough I could run a hidden turnbuckle system with sleeved steel wire on top to pull tension from the front to the fully supported rear as a fail safe. Just not sure it would be warranted with the amount of steel we are talking.

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