The easier it is to check something, the better the chance you’ll know if it’s not right, that’s the idea behind these torque indicating bolts. I ran across these while cruising through an interesting site called the Inventables, the “innovator’s hardware store.” With a tag like that, how can you not check it out?
The idea behind these bolts is a dot in the center of the head that turns dark when properly torqued or red when it gets loose. There’s a clear window in the center of the head covering a pouch with a dark blue liquid. At the proper torque that’s all you see. If loose, a red tipped plunger in the center turns the window red.
If you know at a glance something is loose, there’s a pretty high probability you’ll snug it up, at least you will if you’re the tech type who is concerned about those sorts of things.
This is actually a conversion to standard grade 8 bolts and the indicator can be cycled for the life of the bolt. Sizes range from 7/16 to 1 3/8. Strength of the bolt is not affected except in smaller, shorter bolts.
The bolts are pricey so you won’t be using them everywhere but in some critical applications they could be ideal. Nice idea.
Inventables launched in 2002 as a supplier to such major companies as Black & Decker, Nike, P&G, Microsoft and Mattel. In October 2010, CEO and co-founder Zach Kaplan scrapped the original business plan and launched the online-only R&D supply marketplace.
There are a lot of other very unusual items at the site, the kinds of things, if you’re technically inclined, that would just be nice to have at your workbench to play around with. Definitely worth checking out.
Papasan says
What an excellent idea. I have forwarded this on to many of my friends. Thanks!
P.S. Good to see you are up and running again, hope all is well!
JustThunkin says
I’m guessing you don;t know what a torque wrench is, or how to read a service manual that states the specified torque readings found in any and every Service Manual.
Foo says
Why bother with any of that if the bolt itself knows the torque rating?
Seems absolutely perfect to me!
Decline says
It isn’t about knowing of or owning a torque wrench.
It is about being able to walk out and look at a bolt and know if it is coming loose. Under your model I would have to go get my torque wrench and walk along checking each bolt, with these one could just look over the item to check for anything that might have come loose. I don’t see it as a replacement for a torque wrench but rather as a maintenance warning.
Papasan says
My guess is you paid big bucks to go to UTI [fail] and think you know everything, that combo makes for a terrible mechanic.
Call back when you become an Engineer…
Jim Gribble says
Torque DOES NOT EQUAL Tension! Please read our article about this: http://www.smartbolts.com/the-smartbolts%c2%ae-advantage/tension-not-torque/
Hawk says
What an excellent idea. I can see extensive use in the aircraft industry. Yes, they get torqued and lock-wired but over time, fatique can play havoc with those settings. Ask a pilot who has had an engine fall off or worse, flip up top of the wing blowing forward. (eg Turkish DC-10 at ORD a few years back.)
A “visual” may have prevented it ….
Paul Crowe - "The Kneeslider" says
I don’t think you can use a standard grade 8 on aircraft, I believe you have to use AN hardware. AN hardware is pretty interesting stuff. Very strong, high quality, and proper selection gives you exactly the right length with the right number of threads showing when torqued correctly, those A&P guys are very picky about such things. I used AN hardware long ago working on an old Jaguar when I needed some suspension bolts and couldn’t find good replacements. Worked perfectly, though not properly British.
Bob says
Bolt torque targets are intended to develop a certain amount of bolt preload into a joint. The idea is to develop enough bolt tension so: the joint doesn’t separate when a tension load is applied; so that load transfer between the joined parts is primarily through friction between the parts (instead of carrying that load in the bolt, bending it or shearing it); so the bolt develops enough friction load as not to loosen and back out.
Classic engineering texts calculate bolt preload as F = T/(µ*D); T = torque, D = bolt diameter, µ = coefficient of friction. Typically it’s assumed dry bolt µ = 0.2 and lubed bolt µ = 0.1. So T = 5*T/D (dry) or T = 10*T/D (lubed).
Reality doesn’t follow classical theory all that well. On a commercial airplane program, they started to snap bolts on installation, following the same bolt torque guidelines. Upon investigation, it was found that there was a change to the permitted finishes in the washers. The finishes on bolts, washers, and nuts can dramatically change the coefficient of friction. So, from manufacturer to manufacturer who use different bolt/washer/nut finishes that each meet the same spec requirements, there can be huge variations in measured bolt preload (and µ). Even for a single vendor, the batch to batch variation in µ can be large. There’s a lot of scatter in the test results.
So, how do you reliably determine bolt preload? One alternate method to the dye indicator describe above is an instrumented bolt. A piezo-electric transponder is built in to one end of the bolt. The other end is carefully machined to be perfectly parallel to the face with the transducer. The transducer can be used to send an acoustic pulse down the bolt (at the speed of sound) and then listen for the reflection of the sound wave off of the other end of the bolt. Measure the time it takes to hear the reflection tells you how long the stretched bolt is and what the corresponding preload is.
I work in aerospace where we would love to know precisely how highly preloaded our bolts are. Where did this instrumented bolt technology develop? I’m told it came out of the automotive industry: commercial diesel engine head bolts. The high compression ratios and cylinder pressures really test head bolts. Preloaded too high, bolts snap on installation or have short fatigue lives. Too loose and heads lift off blocks allowing the combustion gases to blow-by. Size the bolt adequately so it doesn’t stretch or fail, then install it with the proper preload so that it has a long service life, you can reduce the maintenance cost and down time for your customers.
HoughMade says
I think it’s a pretty neat invention. A reliable visual check would enhance maintenance and speed it up by not having to put a torque wrench on every bolt to make sure it’s still in spec.
I own a torque wrench and shop manuals for everything I do maintenance on. What I don’t have is a condescending attitude.
Bob Nedoma says
Simple! No application involves one bolt. If I have eight bolts to monitor, I will torque and wire-lock them for pennies and spend the two hundred thus saved on something else. Buy a round of drinks maybe. Nothing condescending here.
Casey Cook says
Interesting, I believe I read about dye-filled aircraft fasteners that would leak brightly colored dye when and if there was a crack or failure. I wonder if anyone has devised a “smart” fastener that has a passive RFID tag that reads an internal strain-guage or sensor that can wirelessly indicate torque and/or failure modes?
Dano says
Wondeful idea for a quick check of safety items. Axle bolts, engine mount bolts and others that don’t get all the attention they deserve. They would speed up tech inspection also, even though all critical bolts are safety wired they could be cracked, stripped thread or broken and still appear to be just fine but the indicator would show red.
B50 Jim says
Yes, I own a torque wrench (the old beam-and-scale style) and know how to use it, but this is a flat good idea. What’s wrong with determining at a glance if a fastener needs snugging up? If only one or two need attention, it would save a lot of time and reduce the risk of over-torquing bolts that already are correct.
Paul, those AN bolts you used on your Jaguar might not have been properly British, but they also wouldn’t break and strand you 150 miles from Nowhere. Nor would they leak. Bolts can’t leak, you say? Those of us who have driven and ridden English machinery for several decades will swear that a plain, solid bolt can somehow leak oil. There’s no other explanation for those drips and seepage that appear in places where such things are impossible.
B*A*M*F says
What a clever idea. I didn’t glean from the site what torque ranges it was able to indicate. “Tight enough” is different for a number of different applications.
Also, what a fantastic site. It’s like a bizarro world version of McMaster-Carr, which I’ve used for years.
OMMAG says
Things like this are intended to benefit manufacturing/assembly operations…. the benefit is that these bolts would eliminate the need for ensuring proper tools are used and that the tools are calibrated…. both are big problems. It also makes the QC inspection a lot easier.
Next step … make the fastener activate an RFID chip when turned to spec.
Tom327Cat says
Torque is just a way of indirectly measuring what you really want to know, which is strain on the fastener. Torque is very fallible due to the friction involved in turning the fastener to achieve that strain. I have seen fasteners “achieve” proper torque before they actually were completely screwed in. If this device works as I think it does (on fastener strain), it would be the bolt I wanted in any critical application.