11 ms·

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/Direc

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 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 reached. That being said, there are a lot of approaches to this same problem. Another common technique is breakaway bolts that are driven with a piece that snaps away when a certain torque is reached: https://youtu.be/lrCoi3gaLfU https://youtu.be/lrCoi3gaLfU

mc32 5y ago
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).
- blamazon 5y ago
  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 at install time. But many projects that have importantly torqued fasteners (bridges, buildings, rollercoasters) have certified inspectors anyway… which is why smartbolts are a niche product I think. Speaking to the trust problem - if you trust the operator of the torquing install device, you don’t need fancy torque indication at all, just mark the paint line at install. That is the most cost effective.
  - mc32 5y ago
    Yes, that seems like a cheaper option; however, I think when you have constant stresses over time, bolts can stretch or simply parts can wear over time and a paint score or even a frozen nut won't reveal lessened tension. Though maybe in this case the issue would have become a concern way before the bolts start to indicate a problem?
    - blamazon 5y ago
      Interestingly that has kind of moved upstream to a design phase consideration in modern times due to the incredible depth of understanding we have about materials. Structures can be designed such that their expected loading will not stress fasteners beyond their ‘yield strength’, which is well characterized. Fatigue complicates the analysis, but we understand that too nowadays, although that is an understanding forged by many unfortunate consequences, such as: https://en.m.wikipedia.org/wiki/Aloha_Airlines_Flight_243 https://en.m.wikipedia.org/wiki/Aloha_Airlines_Flight_243
      - mc32 5y ago
        Maybe the following has been designed out; however, I've on occasion seen the following wear pattern which compromises the initial strength of a fastener (usually due to friction over time): _ _ _______| | _| |__/ | | ______ | |_ ____/ |_| |_|
        blamazon 5y ago
        First, I love the plain text diagram! (Edit: not fatigue) This failure should be predictable during the design phase and that fastener is either wrongly specified or should have a recommended number of cycles after which it should be inspected and replaced if found to be out of specification. Of course, many items in our built world do not receive the same level of design scrutiny as I would wish, nor the maintenance regime…
        5y ago
lttlrck 5y ago
Smartbolts seem to be useful in applications where there is an expectation the bolts will loosen over time/the maintenance lifetime, reducing/easing inspection time. Similar to the tell-tales used on truck lug nuts: https://www.dealsonwheels.co.nz/trucks/features/1302/new-tyres-check-the-wheel-nuts https://www.dealsonwheels.co.nz/trucks/features/1302/new-tyr...
- blamazon 5y ago
  Installing to a known torque and painting a line on the fastener is a lot less expensive, which becomes important when your project has potentially tens of thousands of key fasteners, like a bridge. But for something like an MRI machine where there’s fewer fasteners and higher stakes - would make a lot of sense to use Smartbolt I think. Tangential: related to trucks, there is a somewhat similar product to easily monitor tire pressure visually, which is popular: https://www.linkmfg.com/products/specialty-products/cats-eye https://www.linkmfg.com/products/specialty-products/cats-eye
  - PaulHoule 5y ago
    Yeah, a quality torque wrench isn't cheap (particularly the kind you find in fixed installations like auto repair shops and factories) but there's got to be some crossover when you are buying enough bolts that you're better spending money on tools that are more idiot proof.
    - deleted 5y ago
      [deleted]
    - auxym 5y ago
      Adding on to that, tensioning bolts using torque is convenient and inexpensive but not very accurate at all. Some data reproduced in Shigley's Mechanical Engineering Design showed a +/- 30% variation in tension for properly torqued bolts, if my memory is correct. Emphasis on properly torqued: in the field threads or bolt heads might be dirty, or torque wrenches might be out of calibration, adding even more uncertainty.
maxmcd 5y ago
Nice video of the colored goo in action: https://youtu.be/5BMQE5XnKww?t=372 https://youtu.be/5BMQE5XnKww?t=372 Breakaway bolts are discussed/demonstrated a few seconds earlier.
- blamazon 5y ago
  Fireball Tool is a great YouTube channel! I recommend it for any hackers interested in fabrication. The content is very approachable.
- kortex 5y ago
  Release the schmoo! That is pretty neat. The Wikipedia page on DTI does a pretty poor job of describing how they work, so thank you for the visual.
- jcims 5y ago
  Thanks for the link, looks like a great channel!
mojomark 5y ago
Out of curiosity, on a somewhat related topic, have you tried nord-lock washers [1] in any of your applications? We looked at them for a small work boat we designed and built, but they were a bit pricey and it was just a prototype, so we ended up just using a dab of lock tight to avoid vibration. Was always curious to find someone who had practical experience with these things. I may use them on an upcoming autonomous boat project where there's nobody around to do rounds and tighten loose bolts that have shaken loose unexpectedly. 1. https://www.nord-lock.com/nord-lock/products/washers/ https://www.nord-lock.com/nord-lock/products/washers/
- auxym 5y ago
  When I worked on railway vehicles (bogies for passengers vehicles, more accurately), Nord locks (or equivalent clones) were standard on all structural joints. Especially on a prototype I'd recommend them. Prototypes are really expensive, a complete supply of Nord locks for your project is probably less than a single one-off CNC part. Note that Nord locks are specced to be single use. Not that I've never reused some on prototypes, but, well, I'd never do it on a life-critical joint that is meant to be taken apart often.
  - mojomark 5y ago
    > Nord locks (or equivalent clones) were standard on all structural joints. > Especially on a prototype I'd recommend them. > I'd never do it on a life-critical joint that is meant to be taken apart often. Very good/helpful feedback. This thread is giving me much more confidence to make the extra upfront investment. Thanks!
- blamazon 5y ago
  I have used Nord-lock washers, they are demonstrated to be one of, if not the most effective thread locking washer devices under heavy vibration, but as you say they are quite pricey. I would certainly recommend them if you have the time/cost budget, especially for something like an autonomous boat where vibration is expected and routine inspection is challenging or impossible. When I’ve used them, it’s been for critical fasteners where ease of assembly was important, and could not be effectively decoupled from vibration, and where our recommended inspection/maintenance cycle was not guaranteed. You might also consider something like a pinned castle nut, or safety wire, etc. These are not as simple to specify or install but more cost effective. Also, I’ve seen safety wire used as a conductive link to detect failure in a remote application.
samstave 5y ago
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 structurally strong than a solid bolt? 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?
- avianlyric 5y ago
  > 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.
JKCalhoun 5y ago
The idea has been around since at least 1971. https://archive.org/details/PopularMechanics1971/Popular%20Mechanics-11-1971/page/n107/mode/2up https://archive.org/details/PopularMechanics1971/Popular%20M...
taneq 5y ago
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.
pimlottc 5y ago
> 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 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 https://www.youtube.com/watch?v=s677UKFiRdA&t=60s
asah 5y ago
(not an engineer) I watched the video - smartbolts seem a lot more time & labor efficient and can be tested visually?
alkonaut 5y ago
The bolts I worry most about coming off are this in my car wheels. I’m not sure I could use washers there and they are recessed in the rim so the gap isn’t inspectable. That seems to be the biggest benefit of these, that the only part of a bolt that is always inspectable/servicable is the top and that’s where the indication is?
- smiley1437 5y ago
  If it worries you, buy a good torque wrench, look up the torque rating for your vehicles lug nuts and check it yourself. That’s what I did after some garage monkey messed up my wheels.
dansult 5y ago
I haven't heard anyone talk about DTI's in years. We used to call them "squirters". Takes me back to when I worked in the shop as a kid. Made my day

mc32 5y ago

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).

blamazon 5y ago
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 at install time. But many projects that have importantly torqued fasteners (bridges, buildings, rollercoasters) have certified inspectors anyway… which is why smartbolts are a niche product I think. Speaking to the trust problem - if you trust the operator of the torquing install device, you don’t need fancy torque indication at all, just mark the paint line at install. That is the most cost effective.
- mc32 5y ago
  Yes, that seems like a cheaper option; however, I think when you have constant stresses over time, bolts can stretch or simply parts can wear over time and a paint score or even a frozen nut won't reveal lessened tension. Though maybe in this case the issue would have become a concern way before the bolts start to indicate a problem?
  - blamazon 5y ago
    Interestingly that has kind of moved upstream to a design phase consideration in modern times due to the incredible depth of understanding we have about materials. Structures can be designed such that their expected loading will not stress fasteners beyond their ‘yield strength’, which is well characterized. Fatigue complicates the analysis, but we understand that too nowadays, although that is an understanding forged by many unfortunate consequences, such as: https://en.m.wikipedia.org/wiki/Aloha_Airlines_Flight_243 https://en.m.wikipedia.org/wiki/Aloha_Airlines_Flight_243
    - mc32 5y ago
      Maybe the following has been designed out; however, I've on occasion seen the following wear pattern which compromises the initial strength of a fastener (usually due to friction over time): _ _ _______| | _| |__/ | | ______ | |_ ____/ |_| |_|
      - blamazon 5y ago
        First, I love the plain text diagram! (Edit: not fatigue) This failure should be predictable during the design phase and that fastener is either wrongly specified or should have a recommended number of cycles after which it should be inspected and replaced if found to be out of specification. Of course, many items in our built world do not receive the same level of design scrutiny as I would wish, nor the maintenance regime…
        5y ago

lttlrck 5y ago

Smartbolts seem to be useful in applications where there is an expectation the bolts will loosen over time/the maintenance lifetime, reducing/easing inspection time. Similar to the tell-tales used on truck lug nuts: https://www.dealsonwheels.co.nz/trucks/features/1302/new-tyres-check-the-wheel-nuts https://www.dealsonwheels.co.nz/trucks/features/1302/new-tyr...

blamazon 5y ago
Installing to a known torque and painting a line on the fastener is a lot less expensive, which becomes important when your project has potentially tens of thousands of key fasteners, like a bridge. But for something like an MRI machine where there’s fewer fasteners and higher stakes - would make a lot of sense to use Smartbolt I think. Tangential: related to trucks, there is a somewhat similar product to easily monitor tire pressure visually, which is popular: https://www.linkmfg.com/products/specialty-products/cats-eye https://www.linkmfg.com/products/specialty-products/cats-eye
- PaulHoule 5y ago
  Yeah, a quality torque wrench isn't cheap (particularly the kind you find in fixed installations like auto repair shops and factories) but there's got to be some crossover when you are buying enough bolts that you're better spending money on tools that are more idiot proof.
  - deleted 5y ago
    [deleted]
  - auxym 5y ago
    Adding on to that, tensioning bolts using torque is convenient and inexpensive but not very accurate at all. Some data reproduced in Shigley's Mechanical Engineering Design showed a +/- 30% variation in tension for properly torqued bolts, if my memory is correct. Emphasis on properly torqued: in the field threads or bolt heads might be dirty, or torque wrenches might be out of calibration, adding even more uncertainty.

maxmcd 5y ago

Nice video of the colored goo in action: https://youtu.be/5BMQE5XnKww?t=372 https://youtu.be/5BMQE5XnKww?t=372 Breakaway bolts are discussed/demonstrated a few seconds earlier.

blamazon 5y ago
Fireball Tool is a great YouTube channel! I recommend it for any hackers interested in fabrication. The content is very approachable.
kortex 5y ago
Release the schmoo! That is pretty neat. The Wikipedia page on DTI does a pretty poor job of describing how they work, so thank you for the visual.
jcims 5y ago
Thanks for the link, looks like a great channel!

mojomark 5y ago

Out of curiosity, on a somewhat related topic, have you tried nord-lock washers [1] in any of your applications? We looked at them for a small work boat we designed and built, but they were a bit pricey and it was just a prototype, so we ended up just using a dab of lock tight to avoid vibration. Was always curious to find someone who had practical experience with these things. I may use them on an upcoming autonomous boat project where there's nobody around to do rounds and tighten loose bolts that have shaken loose unexpectedly. 1. https://www.nord-lock.com/nord-lock/products/washers/ https://www.nord-lock.com/nord-lock/products/washers/

auxym 5y ago
When I worked on railway vehicles (bogies for passengers vehicles, more accurately), Nord locks (or equivalent clones) were standard on all structural joints. Especially on a prototype I'd recommend them. Prototypes are really expensive, a complete supply of Nord locks for your project is probably less than a single one-off CNC part. Note that Nord locks are specced to be single use. Not that I've never reused some on prototypes, but, well, I'd never do it on a life-critical joint that is meant to be taken apart often.
- mojomark 5y ago
  > Nord locks (or equivalent clones) were standard on all structural joints. > Especially on a prototype I'd recommend them. > I'd never do it on a life-critical joint that is meant to be taken apart often. Very good/helpful feedback. This thread is giving me much more confidence to make the extra upfront investment. Thanks!
blamazon 5y ago
I have used Nord-lock washers, they are demonstrated to be one of, if not the most effective thread locking washer devices under heavy vibration, but as you say they are quite pricey. I would certainly recommend them if you have the time/cost budget, especially for something like an autonomous boat where vibration is expected and routine inspection is challenging or impossible. When I’ve used them, it’s been for critical fasteners where ease of assembly was important, and could not be effectively decoupled from vibration, and where our recommended inspection/maintenance cycle was not guaranteed. You might also consider something like a pinned castle nut, or safety wire, etc. These are not as simple to specify or install but more cost effective. Also, I’ve seen safety wire used as a conductive link to detect failure in a remote application.

samstave 5y ago

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 structurally strong than a solid bolt? 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?

avianlyric 5y ago
> 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.

JKCalhoun 5y ago

The idea has been around since at least 1971. https://archive.org/details/PopularMechanics1971/Popular%20Mechanics-11-1971/page/n107/mode/2up https://archive.org/details/PopularMechanics1971/Popular%20M...

taneq 5y ago

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.

pimlottc 5y ago

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

asah 5y ago

(not an engineer) I watched the video - smartbolts seem a lot more time & labor efficient and can be tested visually?

alkonaut 5y ago

The bolts I worry most about coming off are this in my car wheels. I’m not sure I could use washers there and they are recessed in the rim so the gap isn’t inspectable. That seems to be the biggest benefit of these, that the only part of a bolt that is always inspectable/servicable is the top and that’s where the indication is?

smiley1437 5y ago
If it worries you, buy a good torque wrench, look up the torque rating for your vehicles lug nuts and check it yourself. That’s what I did after some garage monkey messed up my wheels.

dansult 5y ago

I haven't heard anyone talk about DTI's in years. We used to call them "squirters". Takes me back to when I worked in the shop as a kid. Made my day