Attaching Items to Walls ??? - Event Date: 29 Mar 2020 - 29 Jun 2020

Just for fun, before posting this, I weighed our 10" Lodge cast iron skillet.  It weighed 5 lbs.  I'd never hang something like that on a trailer wall, even with a fastener going into the aluminum frame.  Aluminum is famous for giving way to constant pressure, I think they call it cold flow, and eventually the fastener would likely pull out.  For things of that weight and up, I'd want it through bolted with washers or multiple fasteners all attached to a structural element.  

I've used this product on a number of applications and it's VERY strong.  Don't expect it to ever come off and plan accordingly.  I haven't used it yet in my Pod.  I got mine from Amazon.

https://www.amazon.com/3M-Heavy-Mounting-Multiple-Sizes/dp/B01EOEW25S

lostagain, cold flow (aka creep)  is a phenomenon that occurs with some materials when they are subject to mechanical stress at elevated temperatures. That is what the problem has been with Al household wiring from the 70's. Poorly designed and installed electrical terminations get hot from the current flow and then the Al creeps, getting looser and looser until the terminations wind up catching fire.

That shouldn't be a problem with mechanical fasteners at normal temps. Another property of Al can be a problem with those. Steel has a fatigue limit, meaning that stresses imposed below that level don't cause fracture (crack) propagation. Aluminum has no fatigue limit, so even low stress levels can cause crack propagation, just more slowly. That's why Al aircraft parts often have life limits, but they're usually in the range of tens of thousands of hours. 

In reality, neither of these is likely to be a concern with hanging stuff on the aluminum structure of your rPod. The parts aren't under a lot of stress to being with and the over the road stresses don't go on for a long time. 

If I wanted to hang something heavy to the outer walls I would attach it to the Al tubes, and I'd use multiple self tapping fasteners as suggested. There are specs for fastener shear and pullout strength depending on material type and thickness, or you could do a couple of pullout tests on your fastener of choice in the same material and use that information to decide how many to use. Typical good practice would be to use a 2 or 3x safety factor on top of the 2 to 2.5x bump load increase, so around 6-8x as much fastener strength as the weight of the thing you're hanging. 

As for 3M tapes, these like the Command ones  use adhesives that are in the family of pressure sensitive adhesives (PSA's). They can work well if you are careful to control application conditions, but they can also fail really badly if not applied right, if temperatures are out of range, or if surfaces you are attaching are not compatible or properly prepared. Take a look at the wikipedia article on them for example.

Personally I don't trust the adhesive tapes for anything important, especially in one off or field applications where you're not sure you're getting things perfect.  I once had a whole 250 kilowatt solar array that someone had the bright idea to attach with VHB tape come apart in a windstorm. Broken glass everywhere. Give me nice properly engineered mechanical fasteners anytime, they are much more tolerant of imperfect application conditions than the PSA tapes are. Our use both, can't hurt. 

The other thing you can do is attach your stuff to a closet wall where you have access to the other side so you can add backing material and reinforcement that will end up concealed. Then you can attach whatever you want.

Ford is now using adhesive and rivets on their new aluminum bodied trucks from 3M.  I hope the chemists and engineers got it right.