tolerance on biella

[Stan9411]

Good evening to all
I am here to ask you another question and once again the topic is on tolerances. at the university explained to us that the element interposed between tree and hub (cuscinetto, bronzina ) goes in interference with the component that feels dynamic load and in play with the component that feels static load (classic example: bearing for the shaft of a gearbox --> pins of fixed bearings in space --> play on the frame and interference on the shaft ).
instead it sends me in confusion to apply this concept to a bronzine for biella-manovella. I have considered that in the act of motion are generated inertias that have equal or multiple frequency of the rotation speed of the crank, so at first impact I would have said play between bronzine and crank and interference between bronzine and biella head. then I thought that those inertial forces are usually balanced and there I told myself that rather than making other mental movies maybe it was better to ask who knows more about me!!! What do you think? Thank you all.

 

[meccanicamg]

I've never heard of this stupid definition anywhere. It's so unclear that you didn't even explain it.
tolerances on a biella? Well I would say that they will be the ones that need perpendicularity axes with biella axis and the usual things.
you will plant a beautiful bronzina stuck in the foot of biella... I don't understand what you really need to know.

 

[Stan9411]

is not a definition but a criterion that is commonly adopted in the design courses of the Milan Polytechnic. I do not question his competence because I often read his speeches on this forum, but before defining "idiom definition" a concept explained in a university with 163 years of experience at least could think about it a moment. I understand that your work experience allows you to say "I plant bronzine in the head of biella and I did", but I just wanted to talk about the question from a more academic point of view. If I was unclear then I was another speech.

 

[Stan9411]

This is the concept of my post, I don't understand why it's stupid

 

[paulpaul]

I think our friend was referring to the radial locking of bearings: there is actually a general rule, reported on all manuals, which provides for the locking of the mobile ring with respect to the load, so as to prevent this root in its own seat (or on the shaft, depending on which the ring in question is) and usurins.
this general rule collides (at least in my experience, but I also believe in yours), with the fact that sometimes it is not so easy to understand which is the mobile or fixed ring compared to the load, and especially with assembly/disassembly/maintenance requirements.
the result is therefore necessarily a compromise, but the general rule remains "valid".
Hello, everyone.

 

[paulpaul]

@ stan9411

instead I struggle to understand the speech applied to the bronzine of a biella: normally these are always mounted "in interference" with the biella: the foot bushing is normally forced into the biella with the press as it said mechanicalmg, the head one (normally in two pieces for assembly/disassembly needs) is forced into its seat by the tightening of the hat screws of the biella itself (or also forced to the press in the case of a bushing in a single piece, but in this case you have to have the shaft to be dismantled or with a crank.
This is a standard assembly for "commun" alternative machines.
Maybe I didn't understand the question well.
Bye!

 

[Stan9411]

@ stan9411

instead I struggle to understand the speech applied to the bronzine of a biella: normally these are always mounted "in interference" with the biella: the foot bushing is normally forced into the biella with the press as it said mechanicalmg, the head one (normally in two pieces for assembly/disassembly needs) is forced into its seat by the tightening of the hat screws of the biella itself (or also forced to the press in the case of a bushing in a single piece, but in this case you have to have the shaft to be dismantled or with a crank.
This is a standard assembly for "commun" alternative machines.
Maybe I didn't understand the question well.
Bye!

I feel great as an answer. I just saw my inexperience thinking that even for the bronzines of a biella, a reasoning similar to that of the bearings was made. thank you very much paulpaul

 

[paulpaul]

I feel great as an answer. I just saw my inexperience thinking that even for the bronzines of a biella, a reasoning similar to that of the bearings was made. thank you very much paulpaul

no because the problem is different, in a bearing a ring can be rotated in its seat for "building" of the bearing. the bronzine sees it as an extension of the hole, to which it must therefore be supportive, within which rotates the tree (or the spindle), extension that has the function to mediate the contact tree/hole and to cover the hole with an anti- friction material suitable to be, albeit in small part, consumed when the oil meato is not often enough to guarantee the sustenance (starting, typically). Incidentally, even in bronzines anti-rotation systems are often adopted, also having the axial reference function to the assembly. I refer to bronzine of alternative machines, for which I have more experience. in other applications it is not said that the same solutions are adopted.

However, there are cases where the biella are also equipped with bearings and not bronzine, on the foot and sometimes even on the head! and it is just one of those cases where the need for locking rings contrast with those of assembly! :

 

[Stan9411]

However, there are cases where the biella are also equipped with bearings and not bronzine, on the foot and sometimes even on the head! and it is just one of those cases where the need to lock rings contrast with mounting problems! :[/QUOTE]That's exactly what was confusing to me. I simply thought that the same speech could extend approximately to bronzines. If I had directly named the bearings I would probably have been clearer right away. Thank you very much

 

[meccanicamg]

demonstration that the general rule does not apply.
radial bronzines, whether they undergo rotary, oscillating or axial translating bite, are always mounted stuck in the hub. the pin will be the object that will have guoco of coupling.
but this defines the common sense of mechanics.

for the bearing there is a special consideration because it consists of two counter-rotating elements separated from the desired bodies. the rule is not general but special.

 

[meccanicamg]

simply, for bearings there are a tide of prescriptions http://www.doppiaemme.it/it/informazioni-tecniche/montaggio-dei-cuscinetti.html which exult from the application of tolerances for a biella, especially not defined as use and characteristics of components.
all that is too academic and not dropped in reality creates confusion as soon as you look at things in reality.

 

[paulpaul]

demonstration that the general rule does not apply.
radial bronzines, whether they undergo rotary, oscillating or axial translating bite, are always mounted stuck in the hub. the pin will be the object that will have guoco of coupling.
but this defines the common sense of mechanics.

for the bearing there is a special consideration because it consists of two counter-rotating elements separated from the desired bodies. the rule is not general but special.

In fact, our friend wanted to refer to the bearings and not to the bronzines (as from the first post seemed), for which the "rule" just does not apply because meaningless (even I had understood)!
Also speaking of bearings, I do not consider it a "academic rule": This is a prescription of assembly, but it must be reconciled with many other needs dependent on the application, often in contrast with each other: the designer competes the final choice according to his evaluations and experiences.
bye;

 

[meccanicamg]

That's right. for bronzine makes no sense.
as a rule you can not always follow.
It is like the old rule as the beak that says to use number of teeth of the first gears to have an optimal mutual wear.
from the experience I tell you that dimensioned also to the bone, multiple gears between them and even have never broken for wear and even for bending of the tooth, clamorously pleading the speech of the first teeth.....only one of the many examples of very academic issues not just cast gold.

 

[MBT]

Take, in the library or library, the book "high power motors specific" of the ing. giacomo a. pinion, giorgio nada publisher
there is a nice chapter that speaks precisely of lubrication and bearings (both smooth and desired), with short notices and rules.
because, especially in the bearing that couples biella and piston, there are "particular" things, being there an oscillating motion, load inversions etc.

 

[Luca1234yf]

Good evening to all
I am here to ask you another question and once again the topic is on tolerances. at the university explained to us that the element interposed between tree and hub (cuscinetto, bronzina ) goes in interference with the component that feels dynamic load and in play with the component that feels static load (classic example: bearing for the shaft of a gearbox --> pins of fixed bearings in space --> play on the frame and interference on the shaft ).
instead it sends me in confusion to apply this concept to a bronzine for biella-manovella. I have considered that in the act of motion are generated inertias that have equal or multiple frequency of the rotation speed of the crank, so at first impact I would have said play between bronzine and crank and interference between bronzine and biella head. then I thought that those inertial forces are usually balanced and there I told myself that rather than making other mental movies maybe it was better to ask who knows more about me!!! What do you think? Thank you all.

hi, stan, I think I understood your question well and since I was looking for the logic of ratings about equal, I don't find answers. In my opinion, the biella semicuscinets sell products that in the two housings each have the protrusion of about a tenth or a little more, and these two components closing themselves generate an interference in the external seat not easily measurable. there must be a mathematical model to evaluate and design this. This week they are struggling with a change of tolerance on this, and seeing your question is in there. But the internal game, i.e. between semi-cuscinet and tree, is about a centimeter per centimeter. However, competition supplies generally exceed this of two cents, e.g. tree diameter 50mm game 0.05mm supply then measured 0.07mm. and for this reason I sometimes carry out corrections. I am not naive, I am an electronic industrial expert who has been doing the mechanic for forty years and I have also worked as c.off in lance, ford, and also in audi volk as a worker.
I don't know if you have found answers and if you see my message.
thanks and greetings, luca

 

[TETRASTORE]

if you can be useful, in course of automotive technology, p. 359, the author claims that: "the value of the game cannot be determined by calculation because many and various are the elements to be considered" and makes a list. then indicates an approximate formula.

 

[Luca1234yf]

if you can be useful, in course of automotive technology, p. 359, the author claims that: "the value of the game cannot be determined by calculation because many and various are the elements to be considered" and makes a list. then indicates an approximate formula.

hi tetrastore and thanks, I just saw the link you kindly sent me; According to the facts I have in the specific case the 55mm biella necks, and according to the formula would exit a game of 0.0385mm approximately 0.04. as the engine is old and brings oil not like modern 0w20 / 0w30 , but 10w40 obviously with much larger molecules precisely, the game is around from mother's house to 0.05/max 0.06mm and the competition to new provides already pieces that if you mix them go at least 0.02mm not to mention also 0.03mm in more lasco for the rod pins and on the bench feed even of +0.04 /0 at this point changing brand of semi-cuscinets I have partly solved, and on a countertop I slightly hand corrected the hats of 1/2 cents and I would have solved well for the bench, for the biellas in the next days I see again the situation.
the real point of the matter in my opinion that it was the discussion of stan, which first specified the difference between game on the hills / or tree and hub; Then by difference to this first point he asked the interference between semi-seal and biella head (as the semi-cuscinets are blocked both by the possible tabs in the grooves if present + an interference) , and by the head of biella is the largest part that is not that connected to the piston rod but the part that breaks into two pieces connected to the colli of biella (motor shaft).
In other words, when you mount the biella or bench semi-shoulders, one realizes carefully that on both sides, by fitting them well slightly, they are placed in its two ends, compared to the bases of the biella hats and the head of the biella opened on the opposite side. If you serene them and open them also empty or on the cranks of the tree, reassembling you will find at the ends still a slight protrusion (i.e. back of a very little), this protrusion is the source that determines the interference obviously not easily measurable as the head of biella you can close it by locking, the two semi-carpets, but empty open will never be measured precisely because they work optimally only if you tightened in the counter. This is in my opinion what stan wanted to say and is not easily translated, therefore excuse the boringness of the long debate, perhaps as soon as the new pieces arrive, if I can send a photo to transmit better to the practical side.
thank you many and good Sunday,
Luca.

 

[paulpaul]

@luca1234yf I take care of medium/large alternative compressors, which have a manovellism very similar to that of a motor and which is dimensioned with similar criteria, although the speeds are much lower (not greater than 1500/1800 rpm) and the loads are much higher, at least comparing them with those of motor mci (we speak, in the models I deal with, even of about 100-120 kn at the neck of biella, and shortly we will arrive a machine.
the head bearings, all trimetallic, are either found by trade (usually trucks, trucks or tractors) for cheaper machines or built ad hoc by specialized companies, which also build them for large engines, mainly for static and naval applications.

the very first dimensioning is at play and specific pressure: the first is held at about 0.001xd (d nominal diameter), the second around 15-20 mpa, understood simply as p=f/bd, where f is the load we talked about before, b the length of the bearing. from this data you have a first sizing with which to throw down the study (but that by experience is already so to 80% correct). it can be that in motors, which must last less, you will get to specific pressures greater to contain the dimensions of the biella.

Later, we proceed (at least we do so) to a more accurate assessment of the state of the oil meate: we do it through the diagrams of raimondi and boyd, available everywhere in technical literature, obviously digitized for example on excel (it is also possible to use specialized software dedicated, but they are less immediate use). with these graphs, also inserting the speed of work and viscosity of oil (it must be hypothesized a temperature in the bearing, which in our case is around 70-110 °c depending on the model of machine) some interesting things occur: minimum meato height and its radial position (to compare with the roughness of bearings to exclude metal-metal contact), required oil flow, lost power, etc.

regarding the sizing of the seat (head of biella), we stick to the info of the product if commercial (federal mogul or others) or to specific studies/experience of the supplier, after communication of the torque of the biella screws and often supply of a sample, so having - once tightened the biella with the correct couple - the hole of the exact tolerance. I think they have also been made theoretical studies on this assembly, but typically following the indications of the supplier (which has more experience than us) the result is guaranteed.
Maybe you don't have these directions?

 

[Luca1234yf]

@luca1234yfI take care of medium/large alternative compressors, which have a manovellism very similar to that of a motor and which is dimensioned with similar criteria, although the speeds are much lower (not greater than 1500/1800 rpm) and the loads are much higher, at least comparing them with those of motor mci (we speak, in the models I deal with, even of about 100-120 kn at the neck of biella, and shortly we will arrive a machine.
the head bearings, all trimetallic, are either found by trade (usually trucks, trucks or tractors) for cheaper machines or built ad hoc by specialized companies, which also build them for large engines, mainly for static and naval applications.

the very first dimensioning is at play and specific pressure: the first is held at about 0.001xd (d nominal diameter), the second around 15-20 mpa, understood simply as p=f/bd, where f is the load we talked about before, b the length of the bearing. from this data you have a first sizing with which to throw down the study (but that by experience is already so to 80% correct). it can be that in motors, which must last less, you will get to specific pressures greater to contain the dimensions of the biella.

Later, we proceed (at least we do so) to a more accurate assessment of the state of the oil meate: we do it through the diagrams of raimondi and boyd, available everywhere in technical literature, obviously digitized for example on excel (it is also possible to use specialized software dedicated, but they are less immediate use). with these graphs, also inserting the speed of work and viscosity of oil (it must be hypothesized a temperature in the bearing, which in our case is around 70-110 °c depending on the model of machine) some interesting things occur: minimum meato height and its radial position (to compare with the roughness of bearings to exclude metal-metal contact), required oil flow, lost power, etc.

regarding the sizing of the seat (head of biella), we stick to the info of the product if commercial (federal mogul or others) or to specific studies/experience of the supplier, after communication of the torque of the biella screws and often supply of a sample, so having - once tightened the biella with the correct couple - the hole of the exact tolerance. I think they have also been made theoretical studies on this assembly, but typically following the indications of the supplier (which has more experience than us) the result is guaranteed.
Maybe you don't have these directions?

thanks paul, I am at work and I read quickly, some data should find them in a rhiag catalog on glyco bronzine, and perhaps if in the weekend I can, check if I have something or find it as federal mogul, in fact years ago also they were known suppliers, now in the last decade less. for temperature consider that even if it is a 35-year engine turbo diesel, and without thermometer, the oil can generally reach up to 120/125 degrees uphill or towing. has already an oil/water exchanger integrated in the monobloc, so I believe that the temperatures on the hills of the tree arrive above . As for the load that would become the interference in the head of biella, I see if on the arrival of new bronzines I can translate (in a similar and practical way ) the formunla that you kindly put in the message and make it an assessment on it; for now I can anticipate this in temporary response.
thank you very much for the information, I hardly would have found it with ease since I am a mechanic... I will give you;
Good day and greetings Luca.

 

[Mattymecc]

hi paul, it seems to me to remember that you work in the field of oil & gas, so I imagine it is alternative compressors for natural gas... a curiosity: in addition to the bronzine of the biella-manovella system you also do a study of inertias and verification of resistance?