how to use elastic rosettes

[marcof]

navigating almost "sanza meta... " [cit.] and fishing, among others, under the heading "tribology" I came across this thesis:

eccles, William (2010) tribological aspects of the self-loosening of threaded fasteners.http://clok.uclan.ac.uk/6649/I have last index and also treats topics discussed in this thread. mark it because perhaps someone may be interested, regardless of the grower survey:smile:.

 

[gioask]

Yeah, okay.
but this is relative.
How to say: what does a bicycle drive? ovvia answer: the cyclist pedaling. correct, but the true indispensable thing is the friction between wheel and asphalt! I can take off the cyclist and put on a motor, I can take off the pedals and put levers, but without friction between wheel and asphalt the bike does not move!

the vine works like a "molla" or less.
I take the two pieces, put them close and put a "molla" (vite) that keeps them united.
Well, the screw spring preloads the piece, generating the friction I need to avoid the two pieces flowing between them.this is the true indispensable element: friction generated by the tightening force!the vine itself is subject to these forces, since its head gets the same force that they exchange the pieces.
similar speech for the bolt, of course.
if this force is sufficiently high, the friction that is generated between the head (of the screw) and piece is sufficient to avoid unscrewing.
This works on paper, now let's see how it works on the iron!
actually there are a couple of things to take into account
first, the surfaces of the pieces affected by the speech. Everything perfectly quiet? all worked as you should? roughness? perpendicularity? no one can guarantee them with high precision, unless they pull up the quality of the processing with costs that become disproportionate.
second, the locking of the screw. the precarious of the vine is the "foreseen" to have the necessary friction? and how do I misjudge this precarious? stick strain gauges on the screw??? ? ?
Third, working conditions. the iron does its job and dilates, deforms, "moves".... I made a perfect coupling at 15°, but the month of August (not this year) I arrived at 45° and the deformations became felt.... if then we talk about machines with operating temperatures of a few hundred degrees.... "mandi vigj" (cit.)

But... There is a need to satisfy these shortcomings. Maybe in an economic way. and if necessary also psychological.
then here are the rosettes, of various type and various form
those planes perform two functions. they adapt to the irregularities of the piece ( pillow case) so that the head of the screw supports correctmethn. Moreover, if they are wide, they can distribute strength on a larger area, reducing pressure on any soft material.
then there are the "sprayed" rosettes, the famous growers. They work in two ways. behave like a kind of additional "mode" to compensate for any expansions of the various components, in addition "dead" the pieces trying to prevent the rough screw and avoid. has the defect to "rovinate" the pieces and create a small trick. for that you will not find them inside the gearboxes, for example
mug rosettes, like schnorr, obviate to the problems of growers. the "molla" effect is more accentuated and friction between the components is emphasized by the zigrinatures.
various schools suggest to use rosettes exclusively as springs, so there are rosettes that are at all effects of mug springs, so smooth.
then... special executions for special cases. then rosettes with foldable fin to lock the nut, for example
or, in extreme cases, dice with crown for coppies, contradades, perforated screws and tied with iron fil. . .
each adopts his techniques according to his assumptions, his experience, his needs. . .

I like, well explained and agree with all the speech
But I have some extra questions (maybe after 8 years ... the argument is completely closed, but I have searched for info about the growers now..I need some more specific tip)
1- is there a better positioning choice? on the side of the head of the hexagonal screw or on the side of the nut?
2- if I put two, for each side of the locked object, double the security, does nothing change or even cancel it?
3- putting the grower without the flat washer has a better or worse effect? (excluding the question of greater support area)

Thank you.

 

[Vitreo]

I try to answer you: if I say nonsense maybe more experienced users will correct me.
1) the insertion of the grower introduces in the system bolt+plate an additional elastic element. for the purposes of operation, which puts it under the head or under the nut, nothing changes. usually puts under the nut when under the head the flat washer is put. in the case of dead screw, it is obvious that it is put under the head of the screw.
2) I have never seen applications of two growers on the same bolt and I do not think it makes sense. the reaction force of a grower I think is enough. other systems are used in critical applications, such as other washers, high-strength brakings, and so on. Basically, it depends on the application.
3) In my opinion it is not correct to put the grower over the flat washer. the latter is not supportive to the plate, so in case of strong vibrations it could rotate by carrying behind the grower.

 

[gioask]

I try to answer you: if I say nonsense maybe more experienced users will correct me.
1) the insertion of the grower introduces in the system bolt+plate an additional elastic element. for the purposes of operation, which puts it under the head or under the nut, nothing changes. usually puts under the nut when under the head the flat washer is put. in the case of dead screw, it is obvious that it is put under the head of the screw.
2) I have never seen applications of two growers on the same bolt and I do not think it makes sense. the reaction force of a grower I think is enough. other systems are used in critical applications, such as other washers, high-strength brakings, and so on. Basically, it depends on the application.
3) In my opinion it is not correct to put the grower over the flat washer. the latter is not supportive to the plate, so in case of strong vibrations it could rotate by carrying behind the grower.

Thank you. @vitreofor point 1 also here in the office we are quite convinced that the situation does not change between head screw or nut but we are opting for the position on the nut for a matter of smaller mass involved in any vibrations (although... if we consider that it can vibrate the whole "system" screw-washers.give then the mass does not change)

point 2: the fact is that the application where I need an anti-savory safety is in very special conditions (temperature and particular attention to the "clean") so I can not use glues or brakings. an excellent alternative could be the washers to fold... but I would need so many and in case of disassembly I should reshape all and replace, too complicated

point 3: here several old designs have been made with flat washer and coupled growers although some of us have always argued that it can be deleterio7annullante for operation. the motivation that someone gives is the greater surface of the flat washer and the fact that the underlying hole many times is a little too wide to be able to operate all the surface of the grower that instead is very narrow


However, thank you again, I am still looking for any studies/test that can give a firm point to the question
if I find something I will share

Hi.

 

[bip]

the only anti-sustaining washers that work are the north lock, if the bolt is tightened correctly; grover, dentellate, schnorr, very little.

for your application(no braking or self-locking, probable need to disassemble), also evaluates the good old cup, always does its duty

 

[gioask]

the only anti-sustaining washers that work are the north lock, if the bolt is tightened correctly; grover, dentellate, schnorr, very little.

for your application(no braking or self-locking, probable need to disassemble), also evaluates the good old cup, always does its duty

ciao News and thanks for suggestions
What you suggest in the first line is the direction I wanted to take but... as also in the second point we have a risk of dispersion of undesired material in the equipment
the northern-lock washers and all the similar ones of other brands are "pre-assembled" not to miss the pair of washers and not to reverse them in the assembly
to do this are held together by glue (poco... but there is)
we risk having glue particles that "turn" in the equipment when we do the vacuum and that they go to place in undesirable points or in the filter by blocking it (partially or later)
same thing for the cup: to place it well I should drill into work but I'm not allowed not to make chips in clean environment. . .
I think we will stay on the growers because the only alternative with certain fixing is that of the washers to be folded but it is not good even that method not to have to bend tens of washers and cut them (and replace them) in case of disassembly

Thanks again

 

[NicolòCalìNL]

ciao News and thanks for suggestions
What you suggest in the first line is the direction I wanted to take but... as also in the second point we have a risk of dispersion of undesired material in the equipment
the northern-lock washers and all the similar ones of other brands are "pre-assembled" not to miss the pair of washers and not to reverse them in the assembly
to do this are held together by glue (poco... but there is)
we risk having glue particles that "turn" in the equipment when we do the vacuum and that they go to place in undesirable points or in the filter by blocking it (partially or later)
same thing for the cup: to place it well I should drill into work but I'm not allowed not to make chips in clean environment. . .
I think we will stay on the growers because the only alternative with certain fixing is that of the washers to be folded but it is not good even that method not to have to bend tens of washers and cut them (and replace them) in case of disassembly

Thanks again

Good morning.
I am new on the forum and I wanted to congratulate you for the content discussed, complete and correct.

I was trying to add a couple of potentially useful points about the northern-lock washers

the anti-life obtained by means of the northern-lock washer is due to its principle of operation, based on geometry instead of friction.

the tilted planes between the two washers have a wider angle than the angle of our thread and this makes the screw more "comfortable" in staying in place instead of unscrewing.

the external teeth instead, creating an engraving assure a mechanical grip. (attention in choosing the right washer in case of high surface hardness or, on the contrary, increased external diameter in case of soft surfaces)

below must not be placed any flat washer or element able to rotate.

attention on passing holes, apply a pair of washers per side, under-head and bolt
Your emails, on the basis of materials and quantities I can request the production site to be supplied without glue. if it can still serve you we can deepen