standards of reference wheels dentate

[meccanicamg]

hello to all, this morning I looked at the wheels of helical teeth, I think I understood most things, I would like to ask you, as yesterday, if I understood these things correctly. another curiosity concerns the forces acting on the teeth in the grip: on the khk manual I have seen that there are no special formulas for the determination of such forces (axial, radial, tangential), for gears with displacement of the profile, from that I deduce that you should use the formulas for normal gears, even if they contain the primitive diameter and the angle of reference pressure and not the operating ones.... is this my doubt....

the forces on straight or helical teeth are calculated with the three classic formulas:in reference to gear images:as usual the forces are calculated on the application point belonging to the primitive diameter (which is the circumference where the rooms are as wide as the teeth) even if it is not the real one of ingraining. Moreover the pressure angle on the primitive diameter is 20° while on the primitive diameter of operation does not have the same value. it is assumed that behavior is almost identical and therefore the classic primitive is used.

 

[Mattymecc]

thanks for clarification, however it is a simplification or wrong? tomorrow I will disturb you with endless gear and screw!!!! ....

 

[meccanicamg]

thanks for clarification, however it is a simplification or wrong? tomorrow I will disturb you with endless gear and screw!!!! ....

of fact is a simplification. wheels with profile shift gear on a diameter other than the incorrect one and if that circle shifted gear....there they touch and there they exchange forces.

 

[Mattymecc]

Thank you again!!!

 

[Mattymecc]

today I looked at the endless screws + helical wheel and on the manual khk I did not understand certain basic things (transverse, normal and axial module that I did not understand why on screw and wheel the formulas are reversed) that do not allow me to go ahead with the study of this type.... Can you help me? thanks in advance

 

[PIETRO2002]

I try to answer you:

wheel axes and screws are perpendicular, so, as from the first table you have attached the parameters you reverse.

The module, like the toothed wheels you've already seen, must be the same for both the screw and the wheel.

You have to imagine the screw as a toothed wheel, if at a principle with z= 1 , if at 2 principles with z= 2 and so on..

If you have any other doubts we are here!

 

[meccanicamg]

I try to answer you:

wheel axes and screws are perpendicular, so, as from the first table you have attached the parameters you reverse.

The module, like the toothed wheels you've already seen, must be the same for both the screw and the wheel.

You have to imagine the screw as a toothed wheel, if at a principle with z= 1 , if at 2 principles with z= 2 and so on..

If you have any other doubts we are here!

exactly, they work almost like two skewer wheels though they are a screw and a wheel. everything is transposed by 90°. If you have technic legoes with endless screws you can view the spins and the fact that a screw that rotates moves forward and then its axial force pushes to rotate in circle the wheel providing a tangential action.

 

[Mattymecc]

I thank you for your answers, now that I understand these two things I look good at the other formulas and I will know if I understand.... then I want to try to make three excel sheets, one for every type of cylindrical gear. . .

 

[Calender]

I don't know what the pressure angle has to do with moving the profile, which I haven't seen well in what it is, would you explain to me what it is?

hi, suppose we want to approach the basic circumferences of the two gears in order to be able to reduce the pressure angle (and consequently reduce the radial component of the force transmitted between the gears in favor of the tangential one, to pairs parity),
"geometrically" if it adopts a modular proportion of risks that one of the points where the head circumferences intersect the act of force (in the case in the image point a) is outside the segment that unites the two points with which the same line touches the two basic circumferences (h1h2). ..this means, without too many mathematical physicists,that, in rotation, for a certain stretch one of the two teeth "penetra" in the other...to avoid this is reduced the addendum of one of the two wheels (wheel 2 in the image) to bring it back at least in h1 (if not within the segment h1h2) ...however you make so risks that the contact arc is too small and risk of enough... provided the segment that unites ab is not external to h1h2...

other metropolitan legend and that the gears with an evolving profile cannot work at an interasse higher than the theoretical one...the transmission ratio changes but there are no big problems for the rest...

tomorrow I also verify the speech of the vine-ruota and see if I can give you an answer.. Meanwhile good evening

 

[Mattymecc]

I thank you for the clarification, about metropolitan legends is it true that it is better to have pinions with odd teeth or better still in first numbers and wheels with teeth in even number?

 

[meccanicamg]

I thank you for the clarification, about metropolitan legends is it true that it is better to have pinions with odd teeth or better still in first numbers and wheels with teeth in even number?

I personally consider it a half legend.
Actually the pair of teeth that is formed by teeth with first numbers has the effect of gearing at each turn with a different tooth. this is theoretically fantastic because it lasts to wear very well all gear. In fact, with the programs that are there and with the knowledge of the times of now, the important thing is to verify that the duration of the teeth is greater or equal to the desired one.
was much more sensitive and truthful once the gears were rode with oil and abrasive powder. today corrections if used correctly make mirror teeth without step or form errors.

 

[Mattymecc]

thank you, in fact I was told by an engineer quite old mold.... other question: hi looked at straight teeth wheels, helicals and worms without end, but I saw that there are many other types, besides the conical ones which I would like to look at?

 

[PIETRO2002]

bhe there are conical couples.. straight teeth, spiral type gleason, spiral zerol always gleason, hypoids, etc...
To begin with, I would say that starting with the right tooth conical couples, the others are more complex and are calculated by appropriate programs.

 

[Mattymecc]

Okay thank you these days I will have a look, definitely to those conics. . .

 

[Calender]

thank you, in fact I was told by an engineer quite old mold

I also do not do so much, but there is a fundamental reason...everything originates from the fact that theoretically it is better to have teeth of the gear wheels not divisible among themselves: in this way, a possible defect on a tooth of a wheel does not always affect the same teeth of the coupling but affects them all; Moreover it considers that the cadence with which a certain pair of teeth is inversely proportional to the minimum common multiple of the two wheels in coupling, so, if it is possible to obtain for z a first number, the rate of ingration is minimized. this is at the origin of the "law" .. but that of legend has very little... because it has a sense as reasoning... which then made more sense in the past is another speech

 

[meccanicamg]

thank you, in fact I was told by an engineer quite old mold.... other question: I looked at straight teeth wheels, helicals and worms without end, but I saw that there are so many other types, besides the conical ones which I would like to look at?

If you are not going to put yourself in a company that only manufactures gears, I would say that to leave, there is enough if you consider:
- cylindrical wheels straight teeth (helicoidal with \( \( \0 \)) and helical, as well as inner wheels
- straight tooth conical wheels (\( \beta=0 \))
- endless screw and helical wheel

then as applications, I would say it should be analyzed:
- parallel axis gearboxes in line
- parallel coaxial axes (same interax for several stages)
- epicycloidal gearboxes (to straight teeth \( \beta=0 \))
- pingone and cremagleira teeth straight and helical

then when you have mastered the thing, you can push yourself on things a little more evolved, but keep in mind that if a tomorrow I really do, you would go to use specialized computing programs like kisssoft.

I can tell you that in the steel/metalmechanical field, where big machines for medium/heavy processing are built, many parallel axle reducers and some endless screws are used. It's true that you normally buy already made, but it's also true that in some cases you design the reducer (empty for timing, you want because the machine is really special, you want for particular dimensions, you want for containment costs....), so you still need a certain ability to calculation and analysis.

Another important thing is the bearing speech and therefore loads that develop on the trees. the skf manuals that I mentioned several times there are in pdf free on the site and are very useful to address and then to develop the speech of the loads.

look for example This is what discussion and you will find different ideas.
check the various discussions on the gearboxes. every year we have students who need support and so we try to give them everything you need.

 

[Mattymecc]

thanks to both for your answers, now I will also look at the skf manuals and the cuscinettery, and I will break you a bit with the gears!!! about what I want to do tomorrow I don't know, but the world of power transmissions (not exclusively gears) I like a lot, but also other fields, like the generation of energy (hydraulic and steam turbines).

 

[meccanicamg]

thanks to both for your answers, now I will also look at the skf manuals and the cuscinettery, and I will break you a bit with the gears!!! about what I want to do tomorrow I don't know, but the world of power transmissions (not exclusively gears) I like a lot, but also other fields, like the generation of energy (hydraulic and steam turbines).

good start as a technician. Are you going to enroll in university and improve knowledge? would be a successful path, given the interest in technical topics.

 

[Mattymecc]

I tell you the truth: I think I'm enrolled, at least in the three-year period, but if with the diploma of technical institute we could still enroll in the rank of the experts, I don't know if I would even do the three-year, because to hear some who attended the university it seems that not even 50% of the things are needed in the profession and many others, instead useful, you have to learn them independently. .

 

[meccanicamg]

I tell you the truth: I think I'm enrolled, at least in the three-year period, but if with the diploma of technical institute we could still enroll in the rank of the experts, I don't know if I would even do the three-year, because to hear some who attended the university it seems that not even 50% of the things are needed in the profession and many others, instead useful, you have to learn them independently. .

There is one thing to specify: Schools and universities teach the method of reasoning and give some useful notion to address some technical issues. Unfortunately they lack practical feedback and this means that you will arrive then in the company, even from graduate that you have difficulty because missing the practical side and therefore you are too "academies". But if you go to companies that want to invest and train people you may have less problems.
the fact of doing the triennial surely can give you some extra mathematical tool, some extra knowledge in the productive field and some technical aspect of construction of machines. Unfortunately some exams of the 4th year would be useful for any engineer who wants to fit into the practical design world of our Italian medium fabric.
Surely if you are so, and you continue to be curious you will be able to fill several technical aspects that while they can serve and that no school can/wan give you.

I am also always looking for explanations, new things, insights etc. and unfortunately the company does not pay me the training and therefore it is my duty to arrange at night and when I can in order to improve the technical skills that are always increasing (empty for the increasingly demanding customers, you want to build more complex machinery etc.) or get some space in my work where I can deepen the topics, maybe because the customer compels me to face special themes.

for the times that run, however, a graduate, although junior remains a step more on the peritum, at equal capacity and equal skill to the profession (obvious two different categories).... then a tomorrow who knows...think us.