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Smartbolts

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Re: Smartbolts

#141

Post by SAI_Peregrinus »

aqfamnzc wrote: post #123
gkop wrote: post #101

Earlier quoted context omitted.

In case anyone else needs to look this up, torque-plus-angle means seating the threaded fastener to a base torque, and achieving the target tension from there by further turning the fastener a specified angle. So super duper simple and something that many of us have done instinctively or from instructions, now we know there is a term for this general technique. Cf https://dannysengineportal.com/torque-specification-t…

So "tighten till you hear a crack, then back a quarter turn" has merit after all?

Yes, though instead of the bolt or part cracking it's the click of the torque wrench, and you're going a quarter turn extra not back.

So really the exact opposite.

Re: Smartbolts

#142

Post by euroderf »

globular-toast wrote: post #71
WalterBright wrote: post #69

At Boeing, I learned that bolts should be lubricated before torquing them in order to ensure an accurate torque. I initially thought wouldn't the lubrication allow the bolt to unwind itself? Surprisingly, no. Since then, on my car, I always put a bit of grease on a bolt beforehand. It keeps the water out, preventing the bolt from rusting itself together. It makes for an accurate torque. I've never had one unscrew its…

I grease all the threads on my bicycle ever since I had a bottom bracket seize into a frame and lost the frame. I have heard that you shouldn't grease lug nuts on a car, though. I'm not sure why, so take it with a a large pinch of salt. It might be simply because most people don't regularly check the torque on the nuts and in that case it's more desirable to have them seize than fail.

If you live up north, every autumn take off every lug nut on every car wheel, and one at a time oil it and put it back on. You'll thank yourself when you're caught with a flat in freezing cold and howling winter winds.

Re: Smartbolts

#144

Post by robbrown451 »

brudgers wrote: post #133
robbrown451 wrote: post #127

Earlier quoted context omitted.

That safety factor and testing and inspection has costs associated with it. Basically, it is a "solved problem" by designing things stronger than they have to be, and spending more on testing and inspection than necessary. I'm sure the cases where these things are economical are fairly few, at least today, but if everyone took your attitude no progress would happen at all.

Safety factors; testing; and inspection are engineering. The Smartbolt doesn't eliminate engineering. More importantly, safety factors; testing; and inspection are progress. We have robust assemblies built first time based on rational analysis and formal processes. We have sky scrapers, suspension bridges, and space telescopes.

Obviously it doesn't eliminate all engineering. What it could do, though, is reduce costs. The idea is you could potentially achieve the same level of safety with less material or less testing.

Those things are progress in a sense, sure, but...

It's as if someone finds a way to make an alloy less prone to metal fatigue, and you just say "but you can use thicker metal, and test more." Sure, but.... well I don't see the point explaining this further to you, but I assume people reading this that don't see everything in black and white already understand.

Re: Smartbolts

#145

Post by brudgers »

robbrown451 wrote: post #144
brudgers wrote: post #133

Earlier quoted context omitted.

Safety factors; testing; and inspection are engineering. The Smartbolt doesn't eliminate engineering. More importantly, safety factors; testing; and inspection are progress. We have robust assemblies built first time based on rational analysis and formal processes. We have sky scrapers, suspension bridges, and space telescopes.

Obviously it doesn't eliminate all engineering. What it could do, though, is reduce costs. The idea is you could potentially achieve the same level of safety with less material or less testing. Those things are progress in a sense, sure, but... It's as if someone finds a way to make an alloy less prone to metal fatigue, and you just say "but you can use thicker metal, and test more." Sure, but.... well I don't see th…

Have you ever taken direct personal legal liability for structural fasteners as a licensed professional?

I have.

Re: Smartbolts

#146

Post by CRConrad »

deltaonefour wrote: post #118

This is a bad name. The word "smart" implies the bolt can connect to my phone via bluetooth and I can download an app that will tell me the status of the bolt.

It does imply that... Nowadays, unfortunately. This is bad, because "connect to my phone via bluetooth and I can download an app" is often not a very smart way at all to do something.

Yet another example of how marketing abuse of language fucks up everything.

Re: Smartbolts

#147

Post by Doxin »

alhirzel wrote: post #84

This reminds me of frangibolts: https://www.ebad.com/tini-frangibolt/ Conop: an electric heater temporarily modifies the crystal structure and axially overloads the bolt, breaking it. We used these on a satellite that I worked on with deployable panels.

What's the actuation time on these? I can imagine that it'll take a hot second due to it being based on a heater.

Re: Smartbolts

#148

Post by robbrown451 »

brudgers wrote: post #145
robbrown451 wrote: post #144

Earlier quoted context omitted.

Obviously it doesn't eliminate all engineering. What it could do, though, is reduce costs. The idea is you could potentially achieve the same level of safety with less material or less testing. Those things are progress in a sense, sure, but... It's as if someone finds a way to make an alloy less prone to metal fatigue, and you just say "but you can use thicker metal, and test more." Sure, but.... well I don't see th…

Have you ever taken direct personal legal liability for structural fasteners as a licensed professional? I have.

Does that give you the ability to have nuanced, big-picture, long-term view thinking?

You might as well argue that someone who works in a bank must understand macro-economics, or that someone in the military must have an excellent grasp of foreign policy.

You are steeped in the status quo. Your thinking on this is expected.

Re: Smartbolts

#149

Post by albrewer »

gkop wrote: post #106
blamazon wrote: post #21

Earlier quoted context omitted.

True, but this caveat is generally pre-empted in design phase through safety factor principles - multiply certain design parameters by a coefficient greater than 1 to account for the inaccuracy in things like torque-tension correlation.

I’m not getting your point here, won’t there always be inherent trade offs? If you scale the specified torque, you risk over-tensioning. If you scale the dimensions of the fastener, that has lots of consequences. Is there some safety factor here you can add “for free” that I’m not seeing? Otherwise, why is it that you “generally” pre-empt this caveat with safety factor versus coming up with a more reliable way to ach…

There's a fantastic set of two textbooks covering bolted joint design by John H. Bickford. One for gasketed assemblies and another for non-gasketed assemblies, if you want to really _really_ dive deep into it.

At the end of the day you get the final clamping force by multiplying a bunch of modification factors together that have been empirically measured and the bolting procedure has been verified. When you step outside any of the parameters you've verified in the past, you have to substantiate the math with experimental proof. The size of the fastener, fastener style (e.g., stud vs. bolt), fastener length, thread pitch, torquing method, presence of a washer, presence and type of lubricant, fastener material, base part material, and bolt arrangement ALL play into the final bolt assembly procedure. A lot of these are well-known and published.

Nobody is out there on assemblies like this just slinging unsubstantiated numbers around, at least if they're doing their due diligence.

Re: Smartbolts

#150

Post by albrewer »

smiley1437 wrote: post #94
WalterBright wrote: post #69

At Boeing, I learned that bolts should be lubricated before torquing them in order to ensure an accurate torque. I initially thought wouldn't the lubrication allow the bolt to unwind itself? Surprisingly, no. Since then, on my car, I always put a bit of grease on a bolt beforehand. It keeps the water out, preventing the bolt from rusting itself together. It makes for an accurate torque. I've never had one unscrew its…

I've always read that lubricating the threads can cause over-tensioning of the bolt if you torque it to the (typically) unlubricated torque spec: https://www.engineeringtoolbox.com/torque-lubrication-effect... If you are measuring the bolt tension directly then it doesn't matter but torque is only a proxy for tension.

> lubricating the threads can cause over-tensioning of the bolt if you torque it to the (typically) unlubricated torque spec

This is correct. My main exposure to it was from the ASME's boiler and pressure vessel post construction code - ASME BPVC PCC-1 - which is entirely about bolted joint assembly and torquing procedures.

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