Smartbolts
smartbolts.com
smartbolts.com
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
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.
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
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|_|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…
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.
For really critical components we would disassemble them after every use and would perform multiple tests on each piece including fasteners.
What I find somewhat surprising is that they make the "ok" indication black. The cry for attention state in red seems nicely intuitive at first glance, but given the market they serve they should be far more concerned with false negatives than with false positives and I imagine that it would be very easy for dirt or bad lighting to make a red indicator remain unnoticed in an inspection. Perhaps the color choice is an inherent property of the chemistry involved?
Similar to the tell-tales used on truck lug nuts: https://www.dealsonwheels.co.nz/trucks/features/1302/new-tyr...
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
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.
Ever wonder why the tire shop has tightened your wheel lug nuts so tight that you can't get them off with the hand wrench when you need to change a tire? They spin them on with a pneumatic impact wrench, and then "check" the torque with a torque wrench. Of course it clicks, because the nuts are already way too tight.
(I could of course have bought new bolts, but I always forgot about it after spending 2 hours changing the tires …)
If you think dealership/tire shop/corner shop garage techs touch a torque wrench for lug nuts, you're dreaming. They blast each nut on with the gun and walk away.
Techs never are incentivized to get everything done as fast as possible because they're paid by book rate, and there's zero disincentive for not doing it properly.
Torque sticks were an attempt to address the problem but most techs can't even be bothered with those.
Proper torque for lug nuts is multi-step anyway. Star pattern partial tightening, with the wheel placed correctly on the hub if it doesn't have a concentric ring - then full tightening, then re-checking after the vehicle has been driven for a few minutes, because of fretting between the wheel, rotor, and hub surfaces...even if you've carefully prepped the surfaces, which again, no automotive tech does.
A torque wrench is better than a Smartbolt once it's put on the fastener, but the Smartbolt can be measured just by looking at it.
An HN company does a similar thing with RFID tags for grease zerks:
Again, it's not so much about measuring that the precisely right amount of grease was dispensed, but that every one of the 37 grease points was at least near the tip of the gun once every 30 days for the life of the equipment; the operator didn't forget about that one zerk that's hard to see and grease only 36 zerks for 5 years...
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 achieve the right tension?
To put it another way, the right tension includes a safety factor. And engineering practice specifies testing and inspection and proven materials.
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.
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.
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.
I have.
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.
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.
So really the exact opposite.
https://www.srtorque.com/error-proofing-tools/digital-torque...
There's also too many variables in the real world if the application is critical enough. Clamp load changes with how many times the fasteners have been assembled due to the threads getting polished, how clean and dry the fasteners are, etc.
what if the bolt doesn't actually turn any, but the material itself stretches and loses tension?
Edit: way too expensive.
Breakaway bolts are discussed/demonstrated a few seconds earlier.
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.
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.
> 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!
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.
Which is odd, given their simplicity and ease of manufacture, etc.
Can you get them stainless or just HDG ?
> 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.
Taken to heart - sincerely appreciate the insight!
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?
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.
https://archive.org/details/PopularMechanics1971/Popular%20M...
Here's an (old) video showing how DTIs work:
That’s what I did after some garage monkey messed up my wheels.
Made my day
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 itself, and I can always get the lug nuts off!
Of course, you still need to use lock washers. For critical bolts, use a cotter pin or a safety wire.
But this, of course, is anecdotal data. Do what you judge is best for your situation.
Is 80 foot pounds of torque not 80 foot pounds of torque no matter the level of lubrication?
To tension on lubed and unlubed bolts will be different at 80 ft-lbs due to friction loses.
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.
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.
e.g. https://mechanics.stackexchange.com/questions/29690/what-are...
The inspectors would then use a telescope to check every mark. Completely blew my mind that they relied on this method, rather than something that measured the force directly.
If you didn't torque the bolt tight enough then it will come loose sooner, and the lines won't line up. I'm sure there are situations where the torque of the bolt is critical for handling peak load on the system, but for a lot of situations where a torque wrench keeps you from damaging by over-tightening, and makes sure you got it tight enough that it stays tight.
I should say there's one other failure mode a torque wrench can test that that the paint doesn't by itself, and that's a failing bolt. If you've ever seen a broken bolt, and the entire surface isn't uniformly shiny, then you've seen a bolt that cracked a long time ago and then failed recently. That crack is going to show up as less torque. So if the bolt hasn't spun but the torque has dropped, you might have a problem, rather than having a freak incident where the nut spun exactly 360° since you checked it last.
I could see an argument for using paint and smartbolts for fasteners with epic failure modes, like people dying or generators exploding.
For what it's worth, we tightened all the bolts down according to the procedure, despite pressure from boss-man to do otherwise for a few of them.
On bikes, car repair and a few other items, mine and others, I've seen sheared off bolts. In at least two of those I was involved with the tightening prior to failure, and the lightbulb moment where we figured out why the sequence of events made sense.
"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 corrosion etc... 3: So a bolt torqued to say 100NM may well have a tension variance of over 100%. The result is that bolts are often over or under tensioned, which can compromise the entire bolted connection. 4: Bolts like this (I've personally used Rotabolts, which are similar in concept but in my opinion better as they rely on a mechanical indication rather than a subjective color hue.) are very useful for certain applications, for example, sub-sea connections where divers have limited time and feeling, and sea conditions affect the bolt lubrication. 5: Other uses are for ensuring correct bolted connections on sensitive flanges, again offshore and sub-sea sees a lot of this. 6: Bolts like this are, in summary, brilliant for when you need a good quality bolted connection with correctly tensioned bolts. For most applications however they are unnecessary. Keep up the good work! :-)" - drawingboard82
Side note: youtube mobile when I tried to copy the comment wants me to sign in, to just copy a comment! wtf youtube! I just opened it in newspipe instead and copied from there
here is the desired effect they were looking for (added margin-top to <body>) https://i.imgur.com/tehEWx9.gif
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.
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)
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 ...
vs.
I worked at an amusement park during summers in highschool and coaster track maintenance was serious business. The entire tracks were walked and inspected end to end twice a day (at open and at close). There was a meticulous paper trail of any and all maintenance, measurements, conditions, etc. Their insurers demanded a high standard because ultimately it would have cost the park millions and millions of dollars in liabilities if there were accidents.
I've never inspected them to see if they have indicators painted on, etc. - one would assume they should ...
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.
In some real deal applications like connecting rods on engines you can stick your head into. Techs will measure when a bolt has reached a correct torque spec when the bolt has stretched to certain dimension measured with a micrometer.
Torque is also very misleading depending on material. Steel bolts stretch in what feels very linear. Stainless steel bolts, when those are tightened up it's like hitting a wall going from loose to tight.
Click sticks (torque wrenches) also have something to say. Where you hold your hand on the wrench will affect the torque value. Usually there is a line on the handle showing you exactly where your hand should be placed and pulling from.
If it's for some specific scientific applications, more power to them. But let's not pretend they just saw something so obvious everyone else has been missing.
Edit to add: I actually feel like these should be reverse designed. A small tit that sticks up would probably be much more evident than a hole in most applications.
Once that red spot gets dirty, you're not going to be able to tell if it's brick red because it's loose, or brick red because it has dirt on it. It's probably going to take you longer to clean the bolt than to get the torque wrench on it.
I was thinking of brown specifically but black has the same effect. When it's partially covered the color will be the average of the two. Probably black if it's near pavement, brown if exposed to nature.
This isn’t “Smart” as I have understood we define it now.
Yet another example of how marketing abuse of language fucks up everything.
> Unmatched Benefits
> Unprecedented Value
They think they are Apple, lol.