Any structural engineers here (a different problem)?

My neighbor is moving into a property with two CNC machines. Each one of these machine weights about 3 tons. One problem is that the property has a basement so he’s worried that the loading may be a bit much and the vibration could affect the quality of the machined work. So he’s saying to buy aluminum tubing with 1" thick walls and use it to buttress the floor under the machine (basically he will stick tubing right under the machine) to hopefully dampen the vibration…

I told him that the right way to do this is steel I beams, likely at least a foot in cross section, that is placed under the floor where the machine sits, then a hydraulic jack is used to preload the beam and then steel plates are placed under it to put some strain on it so the beam would actually bear some of the weight of the machine. Then the whole work is kinda welded together so it doesn’t move.

He got upset at me because I contradicted him, and he seems to think he is smarter than me. I told him nobody uses aluminum for structural purpose, and there is a reason for that otherwise everyone would have done so (because aluminum does not rust). I said repeatedly that steel I beams, preloaded then steel plates placed under it as spacer so the beam would take up the weight. He plans to DIY the whole thing, and basically get large aluminum tube with 1" wall thickness (it will be quite heavy I might add), then he would machine this aluminum tube with his CNC machine until it fits exactly under the floor to take up the load… He’s upset at me because I disagreed with him, not because I might actually know something about structural loading. This isn’t really a DIY job and I told him to consult a structural engineer, at that he basically got pissed and sulky and told me to STFU.

He actually had a mason widen a rear door on the property he is about to move to, and upstairs neighbor complained against him because they were concerned that the work would weaken the structure and cause the building to collapse during an earthquake… so he basically had the same mason restore the wall (and it is likely not going to be any good for load bearing because it wasn’t part of the original structure.

Does the neighbor have a point or is he just an idiot who is probably going to get himself and others killed for this? The property was previously used as a toolmaker, so they had CNC machines too but smaller ones for (re)grinding end mills and stuff.

Quick Tip. Speak your thought once if presented with an opportunity. Rarely give unsolicited advice. If it’s not affecting you, then let other people fail.

Yeah No.

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This is quite hard to do with Asperger’s… I would require very concerted willpower.

You have to do it. 0 is good. Once is enough. Two is too much.

Not your problem.

Only speak when it’s your problem. That’s how you avoid the fights. I’m teaching you the social rule. Trust me.

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Also, if said neighbour has a successful business, it might be wise to ask for advice rather than presume to give it.

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I’ve made the mistake of using aluminum for load-bearing components in machine designs. To achieve the same stiffness as steel it’s much more expensive as well as bigger. It will eventually develop fatigue cracks under cyclical loading whereas steel won’t if you stay below its fatigue limit. If you weld it you’ll lower its resistance to fatigue cracking even further so your neighbor’s aluminum structural support – which will cost more than steel for a given level of stiffness – will most likely fail at a weld site under cyclical loading.

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In a building I am remodeling, they extended the loft all the way across the floor. Everything is steel I-beam with corrugated steel on top and leveled out with concrete. I know it’s not nearly as heavy as those machines and no way would I trust aluminum pillars.

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And neither would local building codes if you live in a place where building codes are actually enforced.

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I’m just concerned about the walls now. I have no idea the integrity required for them in this situation, but I think an architect will be able to check the plans before anything is done.

Aluminum doesn’t bend as well or as easily as steel. You won’t dampen shit with Aluminum as deformation is the major dampening mode.

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Damping. I know, I’m being a b****.

Trust me brother, i get your stuggle to not let it go. But marco was right in saying you should say your peice and let him fail. Anythig after that isnt aspergers, its ocd. As hard as it is to let…marco is right here. Let him fail. Only get involved when it seriously concerns other peoples safety. It is his right to fail, lose money and kill himself. Let darwinism run its course, its not really a net loss. As cold as it seems.

  1. 1" walled al tubing is generally going to be strong as fuck…what diameter, what alloy, and how many is he thinking? I suspect it’ll be easily strong enough.

  2. why aluminum isn’t used in construction instead of steel - it’s about cost and ease / familiarity with materials. It’s not like you’re generally worried about strength/weight in a building

  3. Masonry work not being original - irrelevant. It’s about the relative quality of the work and how well it’s tied in to the og structure.

Well, fuck that, if he actually knows there’s a structural issue - earthquakes aren’t exactly tare in Taiwan. That’s a little more important than not getting into an argument. Problem is, from what he’s said, he doesn’t seem to know jack shit about the topic ( if he does,.apologies, and the complaint is then he doesn’t know how to bring the relevant info forward).

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Well I know aluminum has crap fatigue strength… which is why aircraft has to be inspected every so often so they don’t end up like Dehavlind Comet. And when they reach that they can fail catastrophically. Also I know from experience it does not take much to deform aluminum… hit it a few times with a hammer, even 6061 T6 and you know what I mean. Try doing the same with steel, the result is quite different. Or rather stand on an empty aluminum can vs. steel can of the same thickness. The difference is quite remarkable.

There have been building collapse in China because someone knocked out a load bearing wall for whatever reason… so for me it isn’t just about wanting to speak up and all that, it’s about not getting a bunch of others killed because he wanted to save a few bucks. There’s a huge difference between scooter parts vs. load bearing structural member for buildings…

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So given he’s already clearly told you to butt out and mind your own business, what is the purpose of this thread?

Did he end up solving the issue?

‘crap’ is relative. The comet was designed basically when we didn’t know jack about fatigue; now we do. We’ve subsequently produced many thousands of aluminum airframes with little issues, despite wings that flex 10-20 feet - an al column with 1" thick walls, dealing with the hum of a machine probably ain’t gonna do jack in terms of fatigue.

Try doing that on 1" walled tubing and get back to me. What was the diameter of the proposed tubing, and what alloy?

Stand on a al can and steel can of the same weight.

Even I know you never tell a Taiwanese gearhead he’s wrong. Tell him he might end up wasting money if he has to redo everything so he may want to get a second opinion before proceeding and you’ll likely get his attention.

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