Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Smartbolts

smartbolts.com

Post reply on HN
Print view View original

41–50 of 150 posts

Re: Smartbolts

#41

Post by lbhdc »

blamazon wrote: post #5
mc32 wrote: post #4

Earlier quoted context omitted.

I'm not an ME or anything, but it would seem washers attest to pressure (tension) at some point in time (when the nut was tightened -unless the washer is "springy", which I doubt as it seems it simply yields at some point), whereas smartbolts attest to the tension when you look at them --so during maintenance and not only during installation, so from that PoV, they are more useful (informative).

That’s true, but you can have a qualified inspector mark bolts with goo with a paint line that straddles to the fastening surface. Then you can just inspect the paint line for movement, which gets you most of the same functionality at significantly lower cost. Of course, that requires a trustworthy inspector, which is one application where smartbolts become useful, if you don’t have a trustworthy inspector available…

The paint line is the most common method I have seen. I was an inspector and for fasteners in a critical load path we would use an ultrasound machine to measure the length of the bolt (these were installed in flange like connections). We would measure them when first installed and compare measurements after that piece of equipment was used.

For really critical components we would disassemble them after every use and would perform multiple tests on each piece including fasteners.

Re: Smartbolts

#42

Post by rsync »

dominicdoty wrote: post #22

I've always liked ultrasonic bolt length measurement as the ultra high reliability way of measuring preload. It can also be used for confirming the correct preload is still present, with the downside of having to track the original length of every fastener (which isn't really a big deal in high reliability applications)

I consult with a seismic expert at UC Berkeley about once yearly and he's pretty cavalier about pre-loading ...

Which is to say, he wants me to "pre-load the shit out of it".

Which is to say, our "indicator" is that we start to bend the HDB with the threaded rod. For instance, if we have two of these, horizontally, on either end of threaded rod:

https://www.strongtie.com/boltedholdowns_holdowns/hdb_holdow...

... he tells me to tighten that threaded rod between them until we just start to see the hold downs bend (toward each other).

So, not very scientific at all, but easy to tell that you're pre-loaded ...

Re: Smartbolts

#43

Post by avianlyric »

samstave wrote: post #35
blamazon wrote: post #3

I’m a mechanical engineer - smartbolts are cool but rarely used in my experience. Much more commonly used are DTI washers: https://en.m.wikipedia.org/wiki/Direct_tension_indicator Due to the washer style can be used with a wide range of fasteners. The most common type, in my experience, due to the ease of use, has a little bit of colored goo inside the arched cells. The goo squirts out when the specified torque is re…

Just curious = how do these SmartBolts handle under full tension load AND fire conditions... You have effectively drilled out the core of a bolt and replaced it with "goo" and you are using this as an indicator of the health of that fastening node? So what if you burn out the goo? What if you get side/compression damage on the device -- what does the thing do when you over-tight/strip? isnt a "goo core" less structur…

> isnt a "goo core" less structurally strong than a solid bolt?

Yes, the oil used in the centre offers zero structural support.

> Is a bolt tightened to a setting using a SmartBolt vs a regular bolt with tension wrench going to manage the same loads or not?

Depends on what the original bolt is made out of, and what the SmartBolt is made out of. Two different bolts are always going to have different properties, it up to the designer to match the size and strength of the bolt to their application. You would need to validate you design with SmartBolts to ensure they have the properties demanded by your application, you wouldn’t just swap normal bolts for SmartBolts without making sure SmartBolts were at least as strong as the original bolts.

Re: Smartbolts

#44

Post by avianlyric »

JohnJamesRambo wrote: post #2

I don’t ride rollercoasters but if I did I would want them to use these.

SmartBolts won’t help if nobody looks at them. Unfortunately most rollercoaster accidents are caused by humans simply failing inspect structures, ignoring the results of inspections or disabling safety systems. Rather than inspections being too difficult to perform.

Re: Smartbolts

#45

Post by xyzzyz »

arminiusreturns wrote: post #18
noughtme wrote: post #7

Some crazy canuck cut one in half to show how they (don't) work: https://www.youtube.com/watch?v=ClPwlpa86bY

Really informative comment on that video: "Nice video. Couple of points: 1: As per the title of your video, its worth emphasizing that these are tension indicating bolts, not torque indicating bolts. 2: With any bolted connection its the tension that is important. Whilst torque and tension should be correlated, that relationship varies considerably from bolt to bolt, lubricant to lubricant, hot to cold, state of corr…

One thing missing here, but talked about (albeit not very clearly) in the video is that it’s not even a tension indicator, but rather, extension indicator. As long as we are in elastic regime, tension and extension are the same thing (Hooke’s law). However, once you go beyond it, tension goes down even as extension goes up. This is what the canuck meant when he talks about people tightening the loose bolt by giving it extra tweak, around minute 3:40 in the video. Once you leave the elastic regime, the bolt holding strength is permanently reduced, and by periodic tightening, sooner or later you’ll see it yield altogether.

Re: Smartbolts

#46

Post by JKCalhoun »

blamazon wrote: post #3

I’m a mechanical engineer - smartbolts are cool but rarely used in my experience. Much more commonly used are DTI washers: https://en.m.wikipedia.org/wiki/Direct_tension_indicator Due to the washer style can be used with a wide range of fasteners. The most common type, in my experience, due to the ease of use, has a little bit of colored goo inside the arched cells. The goo squirts out when the specified torque is re…

The idea has been around since at least 1971.

https://archive.org/details/PopularMechanics1971/Popular%20M...

Re: Smartbolts

#47

Post by GistNoesis »

I am surprised there aren't already some chip for it, or is there ?

Something based on RF-energy harvesting, you beam it with radio waves, it uses the energy to take a pressure measurement and send you back the result, along with the id of the bolt. And you inspect all your factory bolts in a matter of seconds, and everything is nicely logged, even those hard to inspect bolts.

To measure the pressure either some piezo-resistance, or some capacive-sensing between two washer separated by a squeezie dielectric (Could a FR4 pcb-washer hold the pressure ?), or an integrated MEMS-pressure sensor.

If your technician needs to tighten the bolt, he has to get close so he can transmit more RF energy so you can even have a led, that could turn on when the pressure is right.

Re: Smartbolts

#48

Post by disposableuname »

karaterobot wrote: post #34

It's annoying that, as you scroll down the page, the bolt animates to show it turning, but it scrolls out of view before it gets to the point where the main feature of the product would be shown .

Not just me, then. I played around with scroll, with zoom, doing everything I could to try to see the actual main feature.

Re: Smartbolts

#49

Post by taneq »

blamazon wrote: post #3

I’m a mechanical engineer - smartbolts are cool but rarely used in my experience. Much more commonly used are DTI washers: https://en.m.wikipedia.org/wiki/Direct_tension_indicator Due to the washer style can be used with a wide range of fasteners. The most common type, in my experience, due to the ease of use, has a little bit of colored goo inside the arched cells. The goo squirts out when the specified torque is re…

The thing about torques is that they’re often written into safety standards, and safety standards often have to explicitly detail how critical values are measured. So until fancy bolts are recognised in the current standards as best practice for confirming correct torquing (are they? I dunno), it’s gonna be really hard to get them into production.

Re: Smartbolts

#50

Post by pimlottc »

blamazon wrote: post #3

I’m a mechanical engineer - smartbolts are cool but rarely used in my experience. Much more commonly used are DTI washers: https://en.m.wikipedia.org/wiki/Direct_tension_indicator Due to the washer style can be used with a wide range of fasteners. The most common type, in my experience, due to the ease of use, has a little bit of colored goo inside the arched cells. The goo squirts out when the specified torque is re…

> I’m a mechanical engineer - smartbolts are cool but rarely used in my experience. Much more commonly used are DTI washers: https://en.m.wikipedia.org/wiki/Direct_tension_indicator

Here's an (old) video showing how DTIs work:

https://www.youtube.com/watch?v=s677UKFiRdA&t=60s

Post reply on HN