Loctite advice please

[landsurfer]

Comments aside, if anyone can find a professional stress engineer that will recommend the use of thread lock or any variant, working in a safety critical environment, let me know.
My bike is not a train or an aircraft but the stuff that works is the stuff that works.
Torque and rotational measurement keeps things tight, not glue.

[Mr Evil]

Comments aside, if anyone can find a professional stress engineer that will recommend the use of thread lock or any variant, working in a safety critical environment, let me know.
My bike is not a train or an aircraft but the stuff that works is the stuff that works.
Torque and rotational measurement keeps things tight, not glue.

NASA uses the stuff on the Internaional Space Station.

Although I'm generally of the opinion that correct torque is all that's needed, there are always exceptions; I have some Loctite on the screws between my mudguards and their stays, because there is just no way to do them up tight enough without damaging something.

[landsurfer]

I think it is fair to say that what works for individuals is what works.
It's a bit like on bike tool kits, we all have different stuff in ours, but it works for us.
I will avoid glue, others swear by it, nobody's wrong.
My correctly torqued bottom bracket came loose last week ......... the joys of engineering lol

[NATURAL ANKLING]

Hi,

Comments aside, if anyone can find a professional stress engineer that will recommend the use of thread lock or any variant, working in a safety critical environment, let me know.
My bike is not a train or an aircraft but the stuff that works is the stuff that works.
Torque and rotational measurement keeps things tight, not glue.

Well car manuals etc, do say apply threadlock, on critical safety parts, brakes etc, etc.

Racing and aero stuff I know uses wired nuts & bolts etc,

[NATURAL ANKLING]

Hi,

I think it is fair to say that what works for individuals is what works.
It's a bit like on bike tool kits, we all have different stuff in ours, but it works for us.
I will avoid glue, others swear by it, nobody's wrong.
My correctly torqued bottom bracket came loose last week ......... the joys of engineering lol

And although I have had the similar on plastic (including broken too) and using the wrong locking sleeve, they probably need to be tighter than the torque wrench says, as long as its greased too.

One of those things where its prudent to apply grease but then it will more likely come loose, so check often?

[Brucey]

this brochure

http://www.loctite.com.au/aue/content_data/133403_LT_4985_Threadlocking_Users_Guide.pdf

is interesting because

a) it makes it quite clear that adhesive threadlocking is in many cases an alternative to other means of fastener retention (e.g. prevailing torque nuts of various kinds) and

b) p11 has a list of companies that use these products. That in every single instance these companies might put their reputation at risk by using these products without due diligence is not a reasonable assumption.

I can think of several reasons why you might prefer a Philidas nut to some other prevailing torque retaining system, or a threadlocking system, but when all is said and done in very many applications you would be daft not to use something and very often there is little to choose between the alternative approaches.

A good example is the method of fastener retention on car/truck steering linkage components with taper joints; these can (depending on when they were manufactured, and who manufactured them) use any of the following;

- split pins
- nylocks
- crush nuts
- threadlock

to retain the nuts that secure the taper joints (which if lost, might allow the steering parts to move independently of the steering wheel, which is widely regarded as 'a bad thing'... ). In point of fact I have seen all four methods used on different OEM parts that were intended to go on the same model of vehicle.

To implacably oppose a single method of fastener retention in a particular application might well be a policy that is founded in common sense; there are slight differences that may be important in some cases. However to similarly oppose the use of any given system in all applications makes a lot less sense.

cheers

[Vorpal]

No loctite. Apply the correct / manufacturer approved torque load. "Glue" is for fixing broken things.

Except... all kinds of things go on where you can't see it happening. In particular, vibration, such as from riding on the road (or transporting bikes) can cause stress relief in bent tubes, welded joints, machined parts, etc. and this in turn can reduce the force in a bolted joint, when then allows the screw/bolt/nut to loosen.

In many cases, Loctite *is* unnecessary. But I would think of it as insurance, rather than glue.

[NUKe]

Loctite also stops the reaction between dissimilar metals. So can also be used to stop steel screws corroding into an alloy frame for instance.

[Vorpal]

Comments aside, if anyone can find a professional stress engineer that will recommend the use of thread lock or any variant, working in a safety critical environment, let me know.

The stuff is used extensively in every industry to which I have had exposure, including:
aerospace
oil & gas
automotive
machinery (several different companies & types of machines)
consumer goods

I will say that I actively discourage it being used as a corrective action when threaded parts come loose. But I have no objection to its use in a preventive manner.

[landsurfer]

I have also seen component and control system failure as a result of contamination by phenolic resins or other types of thread lock liquids hardening and flaking off into the hydraulic systems.
Possibly its use on components within hydraulic disc brake systems on road and off road bikes should be considered.
Thread lock use within aircraft power flying control systems was always banned during my 23 years in the aircraft industry.

[landsurfer]

Brucey. I do not oppose the use of thread lock. I work in a safety critical industry that will not allow it's use as a primary or secondary retention method.
For a reason .... it's unreliable, causes contamination and is not considered as providing adequate locking.
Many aerospace companies use it, but for what?
One respected aerospace company I work with uses thread lock.
To secure it's coffee machines from coming loose in the galley ....
Important I know ......Genuinely ....

[goatwarden]

Brucey. I do not oppose the use of thread lock.

I am puzzled then why you have undermined this thread from the start then; simple male urge to indulge in genital fencing perhaps?

[NATURAL ANKLING]

Hi,
I remember walking into the car parts shop (main agent) one day and I was taken back by the inclusion of a sump drain washer taped to top of oil filter box.
The parts guy said we had had a drain bolt drop off...............well from experience in such things for many years I can conclude that a mechanic never did it up, you would know that if you try to undo them they can be very tight even though you did not yank them up so on last oil change.
I had my fair share of forgetting to tighten and check fasteners when I worked on motorcycles professionally, but fortunately no harm was done.
On bicycles today its common to find brake boss to frame bolts with thread lock (adhesive thread lock is another thing altogether, it can render the thread so fixed that the bolt will shear first, without damage by heat at ? 150-200C, I have been informed here) and calliper & disc bolts.

I don't think that there are any other common applications on a standard bicycle?
Luggage rack m5 bolts I do not use such as when you do them up they seem to tighten nicely, problems here are probably more due to the movement of the rack under load which should not really happen, if it does then I suggest investigation.
If I did not use it I don't think I would lose any sleep at all, but If I sell on then it would be mandatory.

40 years ago I was riding my Tiger Cub (Triumph 200cc motorcycle) and realised the rear wheel was loose, cant remember exact configuration but rear axel had large nuts either side, I couldn't have tightened it for sure.
Triumph T90 exhaust head pipe clamps used to loosen every ride due to typical parallel four stroke primary vibration, and Honda 250 four stroke 180 degree parallel twins would shake off the single bolt and nut on the rear footrest / exhaust silencer mount bolt, later two bolts on the silencer cured that problem.
Most of this is poor design 30 - 40 years ago and longer it was just part of everyday motorcycling.

All this would be severely frowned on today.
Just after I bought my camper van and probably thrashed it more than the original owner ever did I got a clicking from rear of gearbox when driving, the single bolt to the rubber mount had loosened but had a nylock / crush nut so it did not drop off.
I noticed that when you did it up it did not stretch much, probably a high tensile bolt? (nut and bolt 4" long clamping two strips of steel and spacer bush in rubber mount)....................it came undone again several years later Decided to give it a bigger yank and has been ok for 10 or so years, this might be a candidate for thread lock?

I have never had a car wheel nut come lose and am particular in making sure the nuts have no grease (hence twenty seven years old and nuts and studs run finger free and never been replaced).
Any way found a few nuts not so tight one day on one front wheel I am the only one that does them up (taking wheels to tyre fitter in back of car), thought no more about it................then after limping home after a holiday in camper, nodding gear lever and chronic vibration shaking camper side to side at certain revs / speed, guess what all four wheel nuts were just nipped, I normally have to use most of my weight to remove them with a 18-20" bar.

The vibration was a failed and seized CV driveshaft joint, Ok so maybe the 3 ton truck if used commercially would maybe require a bit more torque on nuts to be extra safe, the nut seats are tapered into the wheel, both steel.

I am not sure that thread lock within any hydraulic system would ever be specified by the makers
I only ever apply grease to threads where seizure due to corrosion might make it impossible to remove, in that case periodic fastener checking is mandatory.

When I was riding, servicing, many off road motorcycles, both wheel spindles and rear swinging arm through bolts were kept liberally greased or in just months the fine mud and water seeping into every space would render these parts impossible to remove with a 14Ib sledge hammer, frame supported on solid concrete laid on its side

[ThePinkOne]

Our latest project, traction control system for 220 Voyager, using sand as a medium to provide enhanced adhesion in both traction and braking modes is hardly "heavy engineering".
Light precision eng is more like it ..... Guess what ?
Not a drop of thread lock in sight.
Nuts and bolts, plain washers and twin bent beam locknuts, ( Philidas ).
7 - 10G loads .... a doddle ....

I work in train overhaul. I could relate interesting things about Philidas nuts. Or about things like embrittlement of the fasteners holding important stuff in place.

There are certain grades of loctite used for some train overhaul applications eg the spec for installing the toothed wheel on a 158 WSP calls for torque load plus locktite. Go look up the NIR (3134 from memory) if you want to know what happens when you forget the loctite.

Ok maybe theoretically suboptimal design but in rail often lived with, cost balance being what it is, and bearing in mind that with loctite it works. (If you want to see really suboptimal design in rail, look at the fastening system for 313 brake discs, is a human factors nightmare as regards installation).

In bike repair mode in my own time I think red/blue loctite. In work, in train overhaul mode, I expect to see the grade of loctite as required by the spec being used correctly, and the actual bottle to be stored correctly and within use by date.

TPO

[Brucey]

Brucey. I do not oppose the use of thread lock. I work in a safety critical industry that will not allow it's use as a primary or secondary retention method.
For a reason .... it's unreliable, causes contamination and is not considered as providing adequate locking.....

That is several reasons and in certain instances any (or all) of them may be quite legitimate. Certainly if a safety-critical system is designed to be sealed/locked in a certain way, it would make no sense to allow (say) field repairs using some other system. A change of sealing/locking system (from/to any type) could require a load of certification work in return for little benefit and some added risk. If you were starting again with a blank piece of paper (for your whole industry...) you might in some cases make a different choice though.

It's unreliable

: the use of threadlock has a lot in common with any other adhesive bonding operation, in that the quality of the work is ultimately very dependent on procedural controls. Inspections of various kinds after the event don't prove very much. A lot of this is a cultural thing, but there are practical objections too; you certainly wouldn't want to specify a safety critical adhesive bonding operation (the object of which could be achieved some other way) to be carried out by fitters who are not familiar with the technology, working in an environment that is loaded with substances that might degrade the joint quality. That would make no sense. However it doesn't make it 'bad technology' per se, just misplaced. Horses for courses...

It causes contamination

; maybe, but then so can loads of other things. Horses for courses....

It is not considered to provide adequate locking

; by comparison with what? There are many different sealant/threadlock strength grades and different compounds that work variously well in different environments; many of these outperform the vast majority of prevailing torque retention systems in supposedly realistic tests. Again it is horses for courses.

No single system is entirely free of issues! If there were one such then it would be used for everything! Even if you are using one system, you can successfully argue that a second supplementary system (eg using threadlock on a philidas nut, or lockwire on a locking nut of some kind) may provide additional security of benefit in some applications. Some fasteners are so critical that no single locking/retention system is considered adequate by itself; I have heard of situations where up to four different retaining systems are in use at the same time on the same fastener!

The converse of threadlocking is perhaps safety wiring of bolts; this is incredibly time-consuming, it is potentially dangerous (in that the holes need to be drilled in situ in many cases, bringing a whole load of other problems) and arguably nothing like as effective as many other methods of fastener retention (should bolts actually start to back out etc). However it has other advantages in that it can be inspected after it has been done (and the method employed is evident from the appearance), the wires can be tagged which makes it traceable, and if the assembly starts to move or has been disturbed in some way this is also usually evident on a simple visual inspection.

If you have a fee choice of system it is as well to be aware of the pros and cons of each, as well as how they match the skill-sets and working conditions of the people who have to use them. It is not at all unusual to find the same parts retained in different ways in different industries.

For the pros and cons of threadlocks/sealants it is perhaps instructive to look at something like this data sheet;

http://tds.henkel.com/tds5/Studio/ShowPDF/542-EN?pid=542&format=MTR&subformat=REAC&language=EN&plant=WERCS

-which is for a cyanoacrylate based hydraulic sealant. Similar chemistry is used in a lot of threadlocking compounds, so the details will vary but the kinds of things that make a difference to joint strength will likely be similar. This particular material is exactly the kind of thing you mustn't use in an aircraft hydraulic system (for perfectly good reasons) but I don't know of anyone who repairs hydraulic systems in a variety of other industries who doesn't use this stuff at times, again for perfectly good reasons. I've seen such hydraulic systems fail in all kinds of ways but not (to date) due to the use of products of this sort. This is arguably surprising because (in addition to the other issues...) when you look at the data sheet (which itself is far from error-free... ) it is clear that there are many conditions that might lead to substantial variations in joint strength. Despite this it does more good than harm in such systems and it can allow swift field repairs, better reliability and increased system up-time vs several other different approaches.

Horses for courses!

cheers