I'm a former mechanical engineer specializing in fastening (now I'm a Javascript developer).
It's certainly interesting that they're managing to keep the tightness up without resorting to any truly strange designs.
However as some have noted, cost will keep it from being adopted. Let's face it, fastening is the last thing considered in a project and the last thing bought. Even for large projects it's at most a few percent of budget and people are desperate to limit it's cost as much as possible.
Also, truly there's no need for a product like this unless the stress on the bolt, nut and what's being fastened have to be manage just perfectly. Otherwise the simplest solution to relaxation is just tightening more. Then it relaxes to an appropriate stress.
Almost all bolts in the world are under-tightened. Greater analysis of the joint you're tightening rather than a fancier nut will pay off many more dividends.
Let me clarify. I applaud the effort, fastening needs research and development badly, but this is no miracle nut, rather it's a specialized application.
As a cyclist who does my own maintenance as a hobby, I am pretty willing to pay retail-type prices on exotic hardware that requires less effort on my part and is more reliable on the road.
Not the biggest market, sure, but it's a market where you could very plausibly sell a single fastener for ten-plus dollars with the right marketing.
Also a cyclist, biggest issue I have is getting things to the correct torque as carbon fibre can be a bit of a bugger, I can't recall anything coming lose on my bike in a long time though.
I doubt I'd buy a 10 dollar but either but if you marketed it as aero I know some who would ;)
i suppose if they market it right, such a boutique style use-case is viable. But i doubt it'd be all _that_ profitable...i m going to guess it's going to be a family style business at best.
> However as some have noted, cost will keep it from being adopted. Let's face it, fastening is the last thing considered in a project and the last thing bought. Even for large projects it's at most a few percent of budget and people are desperate to limit it's cost as much as possible.
This is incredibly true IME. When I was working at Xerox, they were in the process of switching to vastly inferior fasteners just to save a couple bucks per $500K machine.
I agree it's a little specialized and likely quite pricy, but as a sometime roboticist this kind of innovation makes me hopeful. Fasteners and connectors are unsolved problems, and robotics is plagued with such issues. Even an expensive solution for a few critical points would be valuable. Loc-tite works OK most of the time, but the ideal is a nut that actually stays tight all by itself.
Likely high temperatures and/or chemical resistance, maybe very high tightening torques or force, but possibly others, too. Mostly more specialized fastening, I would guess.
But think about the bolts and nuts that hold the exhaust system to a car engine. Temperatures are going to be very high and nylon wouldn't withstand those temperatures. Things like that.
According to a NASA fastener design manual[1](page 9) split-ring style lock washers are useless for locking purposes. They say that star washers do proved some additional friction/locking action, but at the cost of damage to the surface(the friction comes from digging into the surface).
Engine blocks aren't all that crazy. Most of the time (at least these days) they're made out of aluminum. That means that the stress on the bolt is limited more by the aluminum threads that the bolt mates with rather than by the bolt itself.
Further engine blocks are pretty cheap, all things considered. Turbines have tighter engineering constraints and wider price constraints so I would look there before looking at reciprocating ICEs.
Blown head gaskets have a lot less to do with bolt torque and a lot more to do with a lot of stuff all going on at roughly the same place. If they didn't separate combustion from coolant and both of those from oil, they would fail a lot less.
Yes the bolts must be torqued properly but that has more to do with ensuring that even pressure is applied across a huge gasket face than anything to do with the bolts self-loosening. If the heads on an engine were steel and much thicker you could do the same job with a couple of bolts instead of a dozen.
If an auto manufacturer was enterprising they could probably move some of the oil passages away from the coolant and combustion (which by their nature need to be close to one another) and they could make cavities for o-rings and seal the oil from the coolant a lot more effectively. But the failure rate for head gaskets is fairly low already and that would be adding a fair amount of cost and fiddly-ness to a not-that-big problem. When I say "fairly low" what I mean is that it might comprise 10% of engine failures but engine failures are already pretty rare, so 10% of 1% isn't all that big of a deal. Those are made-up numbers, btw, so don't crucify me if they're wrong.
"Yes the bolts must be torqued properly but that has more to do with ensuring that even pressure is applied across a huge gasket face than anything to do with the bolts self-loosening."
Ensuring that even pressure continues to be applied cross a huge gasket face is somewhat helped if the nuts do not become loose.
Agreed, but performing head gasket maintenance is a rare occurrence and loosening of the head gasket bolts is even rarer. Most of the time that head gasket failures happen is due to process problems on the part of the gasket manufacturer. The auto manufacturers have figured out how to ensure that they're torqued properly at the factory.
Most of the plain old torque specs in that brochure are at least 60 ft-lbs and there are some upwards of 100ft-lbs. That is no joke. If the bolt is a grade 5, 5/8" nominal diameter tightened to 57 ft-lbs that's over 4 tons of clamp force. At 82 ft-lbs it's just shy of 6 tons. At 113 ft-lbs it's over 7 tons. That's PER BOLT.
Applying 60 or 80 or 100 ft-lbs of torque to a bolt will cause huge amounts of clamp force which highly motivates the bolt not to wiggle loose. A lot of the problems where bolts (or nuts) self-loosen in high vibration environments is due to a torque spec for a sub-maximal amount of clamp force. If you're making machine tools and you need to tension ball-screw bearings (an application mentioned in the video) you can't torque the shit out of things because of the bearing pre-load needing to be a substantial but not insane level. A few hundred pounds of preload (a reasonable range for CNC spindles or ball-screws) can be achieved with only a few foot-pounds of torque; it's exactly what the machine needs but not enough for the bolt to keep itself from working loose.
Engine heads and head gaskets are complicated because you have to apply a lot of clamp force very evenly over a large area. The bolts are more than good enough for this, I've got several friends who are mechanics and none of them has heard of a head bolt that's loosened itself. The problem is that manufacturers often use "inferior" (less expensive) grades of head gaskets because the failure rate is already quite good.
EDIT: I don't disagree that needing to maintain even pressure is necessary (it is), nor do I disagree that nuts which can't wiggle loose doesn't help mitigate the problem. What I'm trying to say is that the failures which do happen are caused by the weakest link, and that in many cases the weakest link these days isn't the bolts or the heads or the block or whatever, but the gasket itself.
This could mean a lot for suspension components like spindle nuts where torque is so critical. Not only would that potentially mean no more cotter pins and staking the nut to the spindle, the preload on a wheel bearing would be more precise potentially leading to an increased MTTF just by using a different fastener.
You're correct in that for applications of limited complexity it's not likely cost effective. However we don't know what the premium is over traditional fasteners. It's also probable that in an assembly with many fasteners it may be cost advantageous to just use a product that solves the problem, rather than spend time and money on man-hours and possible production delays.
I vaguely remember seeing a TV show on amusement parks and thought that mechanics had to check and tighten every every bolt on a roller coaster rather frequently. I wonder if this type of nut would result in any labor savings for them?
I don't know a lot about mechanical engineering, but at least in many aviation applications, the issue of nuts coming loose is resolved with a split pin that is bent into a locking shape after the nut has been tightened.
Of course, this adds some extra overhead when disassembling the part, but the nut won't come loose unless there's a different problem (e.g. corrosion).
could the force that is trying to loosen the nut bend the split pin? would the self-tightening bolt perform better in this situation under the same condition?
So you are also saying as a former mechanical engineer there are no applications were tighter nuts are needed?
Well personally I know a few scenarios were the nut has keep steady when its hard to do. But for that case I prefer two nuts stacked on top of each other.
They're called jam nuts and they're a nightmare in production. These days I think they're only used where the application isn't critical, the labor is skilled and underpaid, and you're fresh out of lock washers and nylocks.
If you're bored, try to find anything other than journalist sites reporting on this. I spent at least five minutes searching and couldn't find anything other than that. Weird. I was hoping to find the mfgr or a data sheet. My guess, looking at the one pix available, is the threaded portion acts as a spring. If you know how a ballscrew works this is kind of a sleeved sprung version of one. Interesting. Probably a little delicate under high loads. Most likely I'll continue to use nylocks and/or traditional lockwashers when I build things, but its and interesting idea.
I wonder how all the patents and trademarks collide vs the "semi-well known" Hytorc nut, which is basically the same idea but with an integral washer at the base. Hytorc's are strange little differentially threaded nuts, so instead of the tension coming from a spring half moon shape, the tension comes from the secondary fine threading. They're kind of expensive, outta my price league, so I'm guessing this new nut is going to be out of my league.
You can see the fine level of finish on the completed display units, which would indicate "expensive" to me as well. Also note that they're going after machining/manufacturing as the target market rather than, say, automotive, where cost is king.
As soon as I saw this, I thought of Aerospace applications. Especially things like engine mounts, landing gear assemblies, etc. The expensive but few safety critical fasteners.
I saw it the other way, relying on spring pressure isn't wise from a safety perspective and when it fails parts are going to fall into other parts etc and torques are pretty high on stuff like that which makes me wonder about torque limits on this gadget. Also there's no specs on stuff like sideloads or impact loading or anti-corrosion plating. I'm kinda mystified how this thing could work if cad plated without scraping off the cad plate, so ...
Where I do see it making an impact, is "every gram counts" and if you took every washer and lockwasher off an instrument panel and replaced the nuts with these, you might save a small but measurable mass, which translates directly into a small but measurable increase in payload or range or lower fuel consumption or performance. Even on a small plane this might be a pound or two, but imagine a giant jetliner and it adds up to a respectable mass, probably financially a good idea... if its ever aerospace rated.
Note that there's kind of big gap between being listed for sale on a foreign web page with no documentation at all and no specs or datasheets or certs, and being COTS at a place like "aircraft spruce and specialties". For laughs I went there and the price to beat for certified aerospace grade locknuts is like 48 cents a piece, so I donno if this new gadget can compete in the aerospace market at the typical 100x price markup... I mean sure saving weight and fuel is cool, but not if each aircraft certified nut costs $500.
A bolt with nut is supposed to work like a kind of high-tension spring pulling the pieces being fastened together. For large safety critical projects there is a technology to directly measure the tension of the bolt so that you know you have tightened the nut enough: http://www.checkline.com/product/TI-MINIMAX
This is better than a torque spec (where you don't know the friction exactly, so the bolt tension is an estimate).
It may be better than adhesive when repeated removal is necessary. Thread locking fluid is a pain in smaller applications when the material flakes off as you untighten, which you have to clean up afterwards. In a clean-room or other delicate environment, having loose particulates is a big problem.
In a vibration-sensitive application, it may be needed in addition to a torque spec. The radar hardware I used to support had either Loctite or locking helicoils on nearly every mechanical attachment point. Our hardware would not have passed our vibe tests without it.
Would this solve the lose holds problem on climbing gyms?
Where the holds because of the constant pulling and tension unscrew themselves form the wall and start to rotate, until some unlucky bastard goes for it...
If you want to become a climbing gym-supplying tycoon and fix this problem, invent a new connector for holds based on a carabiner's autolock. You could pop the hold into a pre-set receptacle and it could spring closed, and a special tool could go into the bolthole to release the spring lock and pop the hold off the wall. No more re-tightening + faster route setting, and based on existing technology. Would probably cost the same as this special bolt, but provides enough extra features that a gym might rationalize the price.
Nope! There's no way any climbing gym would rebuild its walls to be full of expensive proprietary nuts. If they cared, they could use loctite or lock washers.
It seems there's very little money in fixing spun holds.
The only solution to the problem which I would trust would be continuous maintenance and a design that doesn't rely on thread strength to maintain a joint.
Yes, all holds need testing but it's reduces the maintenance cost if the holds don't need tightening all the time, surely? Also if the expectation value for loosening is lower per unit time it means there is less likelihood (other values being constant) that the hold has loosened since testing, with the same testing regime that makes it safer so far as I can see.
Those things look ridiculously well-made. Moreover, the thread is not simply cut in the nut, but rather a threaded insert is joined with the nut casing. That looks like it is more expensive to make, and could be an Achilles' heel if it is botched in production. Suppose a manufacturer cuts costs by using a cheaper metal for the casing, thinking only the threads have to be good quality; but then the nut is easy to strip. What if the two parts expand at different rates under heating.
By the way, you can use two nuts to prevent loosening:
this could be cheaper than a much more expensive single nut. This article section explains how vibration causes loosening. The second nut ensures that the first nut stays in firm contact with the bolt threads even during moments when the pre-load is momentarily lost due to vibration, and so cannot rotate loose.
Saw this on diginfonews a while back, it's a neat concept.
There's one thing that might be problematic with this design. The nut has a threaded c-shape insert. Due to the threading, when it is in the "wedged" position, it doesn't just have to close the gap between the tips of the "C" (let's suppose that this deformation is in the horizontal plane), it also has to deform vertically due to the threading.
This vertical plus horizontal deformation must be either harsh on the material, require a relatively small amount of "wedge" (reducing the usefulness), or have a complex initial shape in anticipation of this type of deformation.
I love the idea of a two part nut that cams itself tight. If weight and corrosion isn't a problem, this could see some good applications. Maybe locating on spinning shafts in high heat, or in blind holes?
Stage 8 and safety wire seem simpler and they should offer more predictable torque for critical applications. Hoping to see some comparisons to existing solutions and failure analysis.
Could be huge! Just the increased safety margins could be worth the cost - no lawsuits when a grinding head dismounts during operation due to loosening nut or whatever.
The RepRap 3D printer I assembled used lots of these (Jam Nuts), and I can confirm that it was very annoying to keep making geometric adjustments. The instructions were - assemble loose to keep general structure, then tighten to exact fit, and then tighten to keep that fit. I ended up buying 4 wrenches to make my job easier.
It's certainly interesting that they're managing to keep the tightness up without resorting to any truly strange designs.
However as some have noted, cost will keep it from being adopted. Let's face it, fastening is the last thing considered in a project and the last thing bought. Even for large projects it's at most a few percent of budget and people are desperate to limit it's cost as much as possible.
Also, truly there's no need for a product like this unless the stress on the bolt, nut and what's being fastened have to be manage just perfectly. Otherwise the simplest solution to relaxation is just tightening more. Then it relaxes to an appropriate stress.
Almost all bolts in the world are under-tightened. Greater analysis of the joint you're tightening rather than a fancier nut will pay off many more dividends.
Let me clarify. I applaud the effort, fastening needs research and development badly, but this is no miracle nut, rather it's a specialized application.