Loctite advice please

General cycling advice ( NOT technical ! )
landsurfer
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Re: Loctite advice please

Postby landsurfer » 15 Oct 2016, 7:30pm

Brucey wrote:one of the things claimed by the manufacturers of such products is that (when applied in liquid form) the uncured threadlock provides a consistent kind of lubrication to the threads, so that the torque setting vs bolt tension isn't so variable as it might be otherwise.

However, on the minus side, many torque settings are specified dry, and the use of any lubricant can result in excess tension in the fastener.

cheers


Exactly the point, both torque values and rotational setting are rendered inaccurate by lubrication.
Loctite is a lubricant.
Correctly torqued fasteners / fittings will not work loose. If you have to glue a fitting in place you need to review your procedures.
It's just like that, it's just the way it is.
The road goes on forever.

gerrymcm
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Re: Loctite advice please

Postby gerrymcm » 15 Oct 2016, 7:36pm

Wow! I find this stuff fascinating, there's so many "switched on" folk use this forum.

Thanks guys for the info and I'll stick to copper grease.

landsurfer
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Re: Loctite advice please

Postby landsurfer » 15 Oct 2016, 8:57pm

The Metkameyr bros used "engineering adhesive" to hold together the FMV series of F2C engines used to win the world Team Race champs in the 80's.
The main shaft housing was an interference fit in the crankcase, glued in place ....
Engineering adhesive has its place but only if designed that way.
The rear fuselage of the Nimrod / Comet was designed to be built without rivets.
It was glued, Redux Bonding.
Any component using Loctite must have been designed for it.
It's just like that, it's just the way it is.
The road goes on forever.

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DaveP
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Re: Loctite advice please

Postby DaveP » 15 Oct 2016, 9:22pm

Do you not feel that there might be a question of scale here?
I can well imagine that torque alone can do a splendid job when dealing with relatively massive structures that can easily withstand the results of using a flogging spanner and a 12lb sledge to assemble and reassemble them.
In cycling, however, we tend to be more focused on much more delicate parts - thin walled tubes, small diameter bolts with the female part of the thread often in the form of a tapped hole rather than a cheaply renewable nut - assemblies where you just cant use massive torques. Thread lubrication, of some form, becomes important as a protection for threads during initial assembly and as a precaution against future maintenance requirements.

For most of my cycling "career" I've been quite happy tightening things until it feels as if I'm approaching a limit. The things that cause me most concern are stem-handlebar clamp bolts - don't want them snapping! and more recently, noting the use of Loctite on brake disc mounting bolts. If I find Loctite on a bolt I attempt to apply some to its replacement. I'm not sure if I'm being sensible or just following a trend, but I don't really see a downside to it. Tiny bolts need all the help they can get, don't they?
Trying to retain enough fitness to grow old disgracefully...

Brucey
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Re: Loctite advice please

Postby Brucey » 15 Oct 2016, 9:39pm

landsurfer wrote:
Brucey wrote:one of the things claimed by the manufacturers of such products is that (when applied in liquid form) the uncured threadlock provides a consistent kind of lubrication to the threads, so that the torque setting vs bolt tension isn't so variable as it might be otherwise.

However, on the minus side, many torque settings are specified dry, and the use of any lubricant can result in excess tension in the fastener.

cheers


Exactly the point, both torque values and rotational setting are rendered inaccurate by lubrication.
Loctite is a lubricant.
yes it is a lubricant, and in some cases torque vs fastener tension values are claimed to be more consistent with it than without it. You can design and specify torque settings for lubricated bolts and in some cases this gives better results than if the same machine is specified for dry assembly (even with the appropriate torque settings).

Correctly torqued fasteners / fittings will not work loose.


that is only ever true given the caveats that I mentioned previously, and sometimes not even then; there are all kinds of machines that occasionally see vibration conditions that are very likely to loosen even correctly torqued bolts.

If you have to glue a fitting in place you need to review your procedures.


or it might have been designed to work best that way; very many modern machines are designed to use bonding agents on threaded as well as unthreaded assemblies, for cost, weight, performance, safety reasons.

It perhaps ought to be instinctively obvious that loosening of fasteners is a very commonplace (and thus most probably not invariably avoidable) occurrence; one only needs to look into a fastener catalogue to see all manner of devices that are intended to prevent fasteners from backing out/loosening/falling off. If there were no reason for them to exist I doubt there would be as many as there are, and if they could be avoided entirely then for cost reasons they would be, in all kinds of mass-produced machines.

cheers
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NATURAL ANKLING
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Re: Loctite advice please

Postby NATURAL ANKLING » 15 Oct 2016, 9:55pm

Hi,
landsurfer wrote:No loctite. Apply the correct / manufacturer approved torque load. "Glue" is for fixing broken things.


Cant quite agree with that.

Normally some sort of locking devise or agent is used on steering and brake components even on bicycles.
If You Don't Try You Don't Do.....Don't Do You Don't Get...I'm Still Trying....Well Very..
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NATURAL ANKLING
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Re: Loctite advice please

Postby NATURAL ANKLING » 15 Oct 2016, 10:06pm

Hi,
landsurfer wrote:we design and repair train dynamics. Loctite is banned. torque loading is the only way



Heavy engineering :?:
If You Don't Try You Don't Do.....Don't Do You Don't Get...I'm Still Trying....Well Very..
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NATURAL ANKLING
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Re: Loctite advice please

Postby NATURAL ANKLING » 15 Oct 2016, 10:13pm

Hi,
landsurfer wrote:
Brucey wrote:one of the things claimed by the manufacturers of such products is that (when applied in liquid form) the uncured threadlock provides a consistent kind of lubrication to the threads, so that the torque setting vs bolt tension isn't so variable as it might be otherwise.

However, on the minus side, many torque settings are specified dry, and the use of any lubricant can result in excess tension in the fastener.

cheers


Exactly the point, both torque values and rotational setting are rendered inaccurate by lubrication.
Loctite is a lubricant.
Correctly torqued fasteners / fittings will not work loose. If you have to glue a fitting in place you need to review your procedures.


Up to know what Brucey say is correct I.M.O.

Think about car cylinder head bolts / nuts they specifically specify lubricant........................not all.

Most fasteners require friction to prevent them rattling lose etc, dry condition cannot always be guaranteed repeatable due to contamination and corrosion, specifying a lube In Certain instances allows a more accurate torque thus fastener component tension.

P.S. Adhesive or fastener security preventative?
If You Don't Try You Don't Do.....Don't Do You Don't Get...I'm Still Trying....Well Very..
You'll Find Me At The Top Of A Hill...............Somewhere...After Dark..

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Mick F
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Re: Loctite advice please

Postby Mick F » 16 Oct 2016, 6:26am

What about adjustment screws?
Zero torque, just a set position.
Front and rear derailleurs stop screws?

Next time you're fettling, take one out and see if it has blue Loctite on it.
Mick F. Cornwall

tim-b
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Re: Loctite advice please

Postby tim-b » 16 Oct 2016, 7:36am

Hi

Threadlock is a complex subject. There are several variables including fastener material, etc, and it isn't as simple as "blue" (compare Loctite blue 243 to 248 to 249, including breakaway/breakloose figures)

There's a catalogue here to help you to choose. Purple 222MS is suitable for low-strength metals and typically for smaller thread sizes (under 1/4"), but you need to decide what's suitable for your application

Amazon has a good selection for a one-stop shop

EDIT: What do I use? As little as possible on one component that I've had problems with, the rest is threadlock-free
EDIT EDIT: And a handlebar stem that came with blue-coated bolts, but I've never seen it/used it on a stem before

Regards
tim-b
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goatwarden
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Re: Loctite advice please

Postby goatwarden » 16 Oct 2016, 8:24am

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


This is a nice idea but idealistic. Engineers rarely have the luxury of designing stuff "properly" (you work in a safety critical field where idealism is more highly valued). In most engineering there must be compromises to aesthetics, economy or customer taste (often totally opposite to good aesthetics or engineering good practice e.g. modern cheap "fixes")

I am fairly sure it would be possible to hold securely a bike brake disc with eight M20 bolts, a 50mm thick steel flange and no adhesive. It wouldn't be very nice to ride though. So if the disc is to be held with tiny bolts and little thread engagement in order to give a practical package, I think adhesive is necessary.

The OP was asking about making his existing bike stay safe and reliable. I think use of an adhesive is probably a more practical solution than "reviewing his procedures" and utterly redesigning and remanufacturing his bike.

Brucey
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Re: Loctite advice please

Postby Brucey » 16 Oct 2016, 8:26am

the blue (or sometimes pink) threadlock paste that is pre-applied to bolts, BB assemblies etc is clever stuff; it has micro-spheres within it, each containing a tiny amount of the locking agent. This means that the parts can have an extended shelf life, yet once fully assembled under load, the micro-spheres are broken and this releases the locking agent.

The bolts that go into stems etc can be coated during manufacture (at low cost) and even if it only stops the bolts from dropping out of the assembled part during shipping, it might be 'worth it'.... very many parts come with bolts that are treated this way these days.

cheers
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Mick F
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Re: Loctite advice please

Postby Mick F » 16 Oct 2016, 8:53am

tim-b wrote: ............ handlebar stem that came with blue-coated bolts, but I've never seen it/used it on a stem before.
My Moulton's original stem came with blue Loctite on all the threads.
The replacement stem from Spa, had none.
Mick F. Cornwall

Flinders
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Re: Loctite advice please

Postby Flinders » 24 Oct 2016, 6:26pm

Brucey wrote:in terms of 'is it necessary?' the answer is 'not always'. But for manufacturers and riders alike there is a risk vs consequence calculation to be done. In this, the 'might do some good, won't do any harm' for modest outlay of time and effort seems persuasive.

It is as well to note that even in the days of nutted brakes, they were nearly always supplied with some kind of shakeproofing to the fasteners, be it special washers, crush nuts, or nylocks. Thus there is a precedent there, and (say) the use of blue Loctite on brake centrebolts is an equivalent measure that works easily with modern allen key fixings.

As to 'why do some fasteners come loose?' this ought not to happen if a connection is well designed, well manufactured, and well installed. However these things are by no means guaranteed; in particular there are a number of parts on a bicycle where there is likely to be an issue, e.g.

- the bolt cannot be torqued fully because the (lightweight) parts are not strong enough to sustain a full bolt load in that direction. Very many lightweight aluminium parts and carbon parts are like this.

- the nature of the service loads is such that a small (and rather likely from time to time) variation in tolerances means that at any given torque, loosening is likely in service unless threadlock is used. BB assemblies are a good case in point.

- the joint is liable to settle in service (for various reasons) and the length of the bolt is (unavoidably) insufficient to maintain tension should such settling occur.

The latter point applies to all kinds of things where the parts don't quite mate accurately or (say) there are liable to be burrs on the parts or the fasteners. If the parts are connected by a long bolt of some kind, the amount by which the bolts stretches when tight might easily exceed any reasonable amount of settling that may occur, and the connection will remain tight (car head gasket bolts often work this way). However the same parts, if connected by short bolts, cannot work the same way; any settling in the joint will more easily exceed the stretch in the bolts, and the connection will become loose.

A good example of this might be a comparison between an M5 threaded QR skewer and (say) an M5 threaded rack mounting bolt. The former is considerably stretched when the QR is tightened (by about 0.25-0.4mm), so that instances of decent internal cam QRs 'working loose mid ride' are (in the absence of thick powder coating on the dropouts or similar) almost unheard of. By contrast the mating faces in a rack mounting are very rarely perfectly flat and burr-free, and the bolt is very short, so cannot stretch much at all (eg a rack bolt might stretch elastically by 0.01 or 0.02mm, so will become completely loose if the joint settles by more than that). Thus most folk know very well to check their rack bolts after a short period of use, else run the risk that they may loosen and fall out or perhaps wear/break through being rattled about too much.

Note that threadlocking ought to prevent loss of a loose fastener in such cases but it certainly won't stop the joint itself from working loose in every case, and indeed it cannot be expected to. Devices such as spring washers etc can maintain a weak tension in a joint that settles but IME this is rarely enough to hold a bolted connection on a bicycle securely.

Needless to say bicycle parts are not usually overengineered in such a way as longer bolts and fancier spring washer systems (such as stacks of Belleville washers) can effectively mitigate against settling and loosening; more usually the bolts are made as short and lightweight as possible, and this nearly always increases their chances of working loose.

In my opinion very many joints on bicycles are commonly overtightened (i.e. so that the parts start to yield) and this provides some increased chance that the joint won't settle and loosen in service (whilst incurring a very real danger that the fastener might break if it is re-used). So for example when you fully tighten a rack mounting bolt, you might lose the (thick, soft) paint on the dropout. Losing the paint thus may be inevitable; if you tightened the bolt less to start with, the joint could repeatedly work loose until the paint was removed anyway.

So when choosing whether or not to use threadlocking, it is as well to ask yourself what it is you are hoping to achieve; not all bolted joints work the same way or derive the same benefits from threadlocking.

cheers


That's an excellent post- could this be put in the section for 'keepers'?

Flinders
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Re: Loctite advice please

Postby Flinders » 24 Oct 2016, 6:30pm

landsurfer wrote:we design and repair train dynamics. Loctite is banned. torque loading is the only way


For what you do, no doubt you're right, that's your job. But as Brucey explains, there can be good reasons for using it in some other applications, for instance, where the components aren't as heavy duty as (I would imagine) yours might be. Horses for courses.