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

21–30 of 150 posts

Re: Smartbolts

#21

Post by blamazon »

ominous_prime wrote: post #13
blamazon wrote: post #8

Earlier quoted context omitted.

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 moni…

A problem with installation is that torque is only a proxy for tension. Torque alone is not incredibly accurate, so there are a lot of cases that could benefit from an easier way to accurately indicate tension than by externally measuring the stretch of the bolt (which often is not an option)

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.

Re: Smartbolts

#22

Post by dominicdoty »

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)

Re: Smartbolts

#23

Post by blamazon »

mc32 wrote: post #20
blamazon wrote: post #19

Earlier quoted context omitted.

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 forge…

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): _ _ _______| | _| |__/ | | ______ | |_ ____/ |_| |_|

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…

Re: Smartbolts

#24

Post by auxym »

PaulHoule wrote: post #12
blamazon wrote: post #8

Earlier quoted context omitted.

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 moni…

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.

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.

Re: Smartbolts

#25

Post by ycIsGarbage »

sfifs wrote: post #10

Seems like something that would be very useful for furniture or mechanisms that are self assembled like Ikea, chairs etc by regular people. Easy visual inspection when things are loose.

Way too expensive for that kind of application.

Re: Smartbolts

#26

Post by auxym »

mojomark wrote: post #17
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…

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 autonomou…

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.

Re: Smartbolts

#27

Post by blamazon »

mojomark wrote: post #17
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…

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 autonomou…

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.

Re: Smartbolts

#29

Post by auxym »

blamazon wrote: post #23
mc32 wrote: post #20

Earlier quoted context omitted.

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): _ _ _______| | _| |__/ | | ______ | |_ ____/ |_| |_|

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…

Unless I'm misunderstanding the diagram, it does not look like fatigue at all but rather yielding from shear loading.

The definition of fatigue is a small crack (in fact microscopic in the beginning) that grows through the application of cyclical loading (typically about 10k cycles is the lower bound for high cycle fatigue, which does not involve macro yielding).

Thus a fatigue failure would look like a fully ruptured part , usually with two distinct zones of the fracture face: one smooth zone from crack growth ( sometimes with characteristic "beach marks") and the final sudden rupture which is usually rough.

https://en.m.wikipedia.org/wiki/Fatigue_(material)

Re: Smartbolts

#30

Post by blamazon »

maxmcd wrote: post #9
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…

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

Fireball Tool is a great YouTube channel! I recommend it for any hackers interested in fabrication. The content is very approachable.
Post reply on HN