Does Torque Equal Tension? | Tech Tuesday
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- Опубліковано 28 чер 2024
- What are the differences between TORQUE and TENSION? Both are involved in tightening fasteners, but does one equal the other? On this week's Tech Tuesday, Truman discusses the differences between TORQUE and TENSION, and the potential consequences of adhering to one over the other.
The SRAM story:
www.sram.com/contentassets/10...
Some footage provided Applied Bolting Technology:
www.appliedbolting.com
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I guess this is why you should always follow the manufacturer recommendations of whether or not to grease threads on components? The recommended torque won't result in the correct tension if you don't also follow any grease/lubricant or thread lock recommendations.
This is the best technical video you've made. Bravo👍👍
🔥🔥🔥🔥🔥🔥🔥🔥🔥
Thanks for an excellent overview of a very complex subject. Torquing fasteners is a science in itself. With so many variables, the best method is to go with the manufacturer’s recommenced value. Unfortunately they seldom clarify lubricated or un-lubricated, so always lubricate and go with the minimum stated torque value. With fasteners that have pre installed locking features, we have to hope that the manufacturer took that prevailing-torque into account when stating their torque values. If liquid threadlocker is used, it should be considered the lubricant while it is liquid. As you explained snapping off or stripping out some fasteners always adds to a mechanic’s lessons-learned experience.
Good top level overview, don’t ask questions or a no return voyage down the rabbit hole will begin.
It’s important when torquing any fastener, to find guidance on whether the threads should be dry, lubricated in some way, or with some sort of thread locking compound. And understand what the expectation is if no guidance is given on lubricated or not, because final torque versus the tension achieved will be different for each case.
Dry fastener or oiled? Stretch bolt or conventional? Old torque spec or revised spec? Similar or dissimilar bolts and nuts? Locking washer, pin, wire, or flat washer?
All these things are considered by people turning wrenches in the aerospace industry. Less so in the automotive industry. Periodically in the bike industry. But it all matters… but the meanifactuerer needs to specify, which is a real weakness in the bike industry.
Angle is often used when bolt tension is critical. Torque is, IMO, more a matter of repeatability when fabricating and servicing. I like that squishy silicone washer indicator thing. I've never seen that.
I’d much rather listen to the guys who know Park tool) than so many other sources out there.
I come from the motorcycle mechanic world.
In a service manual, every nuts has a torque value and a specific lubricant listed in a single manual.
Isn't it more than time that bike manufacturers provide such a chart with every bike they sold ?
And please, don't tell me to go to the manufacturers' web site of each and every components on the bike and find the information.
When people don't buy parts but a bike, it's the company that sell this bike's responsibility to provide that information.
Exploded views with torque and lubricant specs of each and every bolts on each specific bike should be available in a single document.
This industry is still behaving like if they were artisan shops.
It's time for manufacturers to clean up their act and act as serious professionals to optimize cyclists safety.
Stop giving stats about watt savings and give me the technical informations that I need and make it readily available.
Bicycles do feel like expensive Swizz watches now
You can blame this on two big things… materials and the relentless quest for lightness.
Back when bikes were all mild steel, it was harder to damage components by over tightening. You’d really have to try.
Easier to mess up today when CF, aluminum, steel, titanium are used in conjunction with each other… not counting differences in metal alloys, which can significantly change ductility, strength, and susceptibility to galling.
Agree. Manufacturers are wilfully irresponsible, both in terms of consistent use of like-fasteners and the technical literature that accompanies them. If any other branch of the transportation sector operated this way, there would be lawsuits galore.
Been fixing stuff my whole life, bikes, cars, everything…i’ve never used a torque wrench. I’ve built entire engines purely by feel. Just something that comes with time and experience. Mechanical sympathy is the most important thing anyone can learn imo.
We have a tendency to go too far with bicycles. The torque window (ex: 5-10Nm) is your friendly helper. Wet or dry should sway you toward either end and not necessarily to the middle of the window. Less than 5 or more than 10 is a danger area established at the manufacturer. The window is yours to play with depending on if the threads are wet or dry IMO and comes with an educated guess. It’s a bicycle not an aircraft
Really good video. Nice job of explaining the different physical properties and how they interact and can be measured (whether by tools or our experienced senses)
Brilliant video! 😊
Excellent video! Could you please rank the spoke nipples in order of the highest tension, (i.e. between linseed, threadlock, lube, nothing)? Which ones were 300% different? What do you find is the best for spoke /nipple interface? Thanks in advance!
Calvin and Co. if you’d like to see a more modern way of tensioning large bolts, check out Heico Tension Nuts and Tension Bolts.
"Have never had the joy or satisfaction of using an easy-out." LOL
And you didn't even get into the wide tolerance values of different torque wrenches. Good video.
Agreed. Torque doesn't equal tension necessarily. Usually I get it right, but my cassette lockring did work loose. I have modified my freehub body and gotten mixed brand cassette cogs and ratios together. I honed the freehub and lockring and used less Torque than usual applying locktite to compensate. 9 speeds on an 126m dropout frame without cold setting 10 speed cogs used. Well, it looks vintage, if you didn't count the cogs and realize that Nuevo Record 1973 derailleur never could Index! It looks real! When you modify parts you're going to have fun. I backyard engineered it into a success in the end.
Square-Taper crank bolts are a quite special case though. It's both easy to not get a crank on tight enough, or too tight. In that case it's a press-fit, so the tension doesn't matter at all.
Bunnings hardware , in Australia had sold hex head set screws with allen socket two years.ago . The bolts would fail a month or so after correct torque at installation time .. A bit odd .
What were those tension values for the different spokes?
Great torque - you my full
atension 😂
Great video, but where can I find a gadget with you name impressed for my working garage?
👍👍 excellent
i will say that i try to follow the torque specs as much as possible, but after finding out that torque itself is apparently only getting within 20% of an accurate preload measurement (as compared to, say, bolt stretch) i do find myself worrying less about hitting the mark/window than i used to
Just a quick summary: When you increase the torque (how hard you turn the bolt), it increases the tension (how hard the bolt is stretched and therefore how much force it is applying to connect the pieces it is connecting). In a world without friction that would be the end of the story -- but also the bolt would undo as soon as you stopped applying the torque :-). You have to overcome the friction of turning the bolt. This increases the torque that you need when turning it. The amount of torque you need in order to get the tension you want varies *wildly*. A corroded bolt will increase friction. Oil, grease or locktite will increase friction. Rough edges on the threads of the bolt or nut will increase friction. While the torque wrench can tell you how much torque you are putting on the bolt, it can't tell you the amount of tension you are getting. You need to use other clues to determine if the tension you got was enough.
How would oil and grease increase the friction? Shouldn't they lower it, which in turn would allow you to increase the tension (eventually even too high)?
I'm just wondering why your subscribers is not increasing,it is still 830 k
Tec tuesdays ❤😂😊
Dommage de ne pas avoir la traduction en français 😢
Spoke tension meter is not a magic tool either, even more so - it is susceptible to deviations because of the state its main spring is in. That means you have to calibrate it for each specific kind of spoke on a special (oftem jerry-rigged) stand to know the value your tension meter shows for a specific tension of a specific kind iof spoke in a specific conditions you have in your shop. Not to mention that all thiese shenanigans render the tension table included with your tension meter completely useless :(
Yeah, it seems far better to use intuition to assess whether a wheel is "tight enough". One shouldn't blindly tension up a wheel. But I think the spoke tension meter is quite useful to assess whether spoke tension is even, and for reproducible wheel-building results.
Look at the range of the recommended tension provided by a manufacturer.
The margin of error is such that when compared in percentage to the spoke tension, it's negligible i.e. around a few 0.1 % . What makes a great wheel is not a spoke tension value but the way in which this value was determined and the consistency from spoke to spoke. The tension value is highly variable but should be selected based on the cyclist weight and intended use. No spoke tension meter, however precise it is, will tell you what that optimal value is.
@@imrevadasz1086 You can assess for the equal tension, but you cannot guarantee that the tension is up to spec, which is critical for bikes used in extreme sports activities like mountain biking.
@@sylvainmichaud2262 True, but the problem not in the meter's accuracy, but in the fact that it changes its accuracy through the life span of its tension spring.
Proxy. The word is proxy. Torque is a proxy for tension. We really want to measure tension, but it's hard to do, so we settle for measuring torque instead.
You're literally measuring how hard it is to push the fastener up a spiral ramp (the thread) against the tension you're inducing on the fastener/member/component. The *quality* of the thread (smoothness & accuracy of the mating ramps) is a significant part of the equation, but hardly any engineering nor mechanical authorities/texts talk about it.
Prominent
Can i have some help with a question about SRAM GX
Please
unfortunately UA-cam comment sections are not good for a back and forth conversation to get your problem resolved. If you would like better help please reach out to tech@parktool.com
Ok thanks
But should I grease square taper bbs?
No pro mechanic here, so take this with a dump truck of salt. Some BBs come with thread lock (blue stuff) pre-applied. I don't think you should add grease to that, just make sure the threads in your bb shell are clean. If you are reinstalling the same BB that did come with thread lock, clean the threads of it and ideally apply some new thread lock. If not available some (assembly) grease is better than nothing. Same goes for a new BB that does not come with thread lock pre applied. Thread lock is an option, but assembly grease, or if not available regular grease is needed there.
Slightly grease the square taper before mounting the crank. The grease is helpful for the crank to slide on evenly and square (no pun intended). The crank bolt is not under tension at all, it's just used to press-fit mount the crank on the spindle. Do *not* tighten up a loose crank-bolt, maybe just screw it in lightly so it doesn't drop out, or fix the bolt some other way.
@@RenAigu It was a joke. I was talking about greasing the actual tapered spindle. It's an argument that every bike mechanic goes through their entire career. FYI the correct answer is no. Do not grease. In fact it should be bone dry. Not even a finger print.
@@peterjv8748 lol humour is difficult. I did grease my square taper spindle though, no complaints.
@@imrevadasz1086 incorrect.
Most of the big brands have this tool they can stripe you or replace you . other meaning of this is dont touch bike just pay £1000 today this is space technology :/
Torque and tension are measurements of two different forces. Haven't seen the video yet but right off the bat that stood out to me. Just sayin.
Torque and tension are two different forces thats for sure. The goal in measuring the torque of a fastener is to get it within a window of prescribed tension.
It 's funny the guy is talking about nuts and bolts and pretension but the footage shown is a concrete building lol!!!
I’m sorry, but you can’t check torque with a Torque wrench that way. Restart torque throws off the value. Friction is about 90% of the torque being applied. Your point on tension is dead on though. HOWEVER, Your instincts on how tight something feels is dead wrong. The most skilled technicians can’t accurately apply torque many studies have been done on this.