conical multiplier sizing

[MattCHIETI]

hello to all, in this period for a university project I have to dimension a conical couple (for my choice of straight teeth) of which I know the transmission compartment, the power and the speed of the incoming tree; therefore I must first of all choose the material and then know all its properties (think with and without thermal treatments) and obviously hypothesize some parameters.
Taking advantage of the material provided by the machine construction course, I could calculate the module of these conical wheels.
the problem that now arises is to determine the admissible pressure to be inserted in the formula from which I get the form. because the permissible pressure calculation from a formula (fit in photo) in which I have to insert the value of hb (which should be the brinell hardness), that for my chosen material an 18nicrmo5 is about 300 hb if I looked well. inserting this value the admissible pressure I obtain is very low. comparing with exercises performed, examples from university material, this hb has values that act between 4500 and 6000. that in my opinion as brinell hardness is a bit excessive. Now I wonder if that formula is suitable for travailing the admissible pressure, or is the chosen material not suitable?

Thank you.

 

[abelli12]

the dentate wheels should be verified according to the norm iso 6336 (or equivalent to es in use according to agm norms.
such legislation (which I highly recommend consulting) provides all the necessary factors for calculating for different materials.
in the case of 18nicrmo5: cementing steel a sigma h lim = 1500 n/mmq
Say hi.

 

[meccanicamg]

In fact, it would also be time for teachers to wake up teaching that things are designed with regulations. However, you will find mesh dispenses about iso 6336 and the process is a little different than classical theory, limit values are different, you can push over and above all know really when you break the gears.

your material is more hardened cementing, so its hardness will be in hrc. clearly you can convert. on the standards there are formulas to be used to calculate shlim and sflim according to the material and treatment. do not mix the values with the old one otherwise you do not come out anything true unless you follow all the old regulations.

 

[MattCHIETI]

I thank you for the delucidations and advices, I found that there is a specific legislation for the conical gears, and it is the very recent iso 10300, practically introvabile.

having at disposal as university text shigley, for calculation and truth to wear and bending of the conical gears, I tried to perform the verification of my multiplier. shigley exposes the treatment based on the norm Ansi/agma 2003-b97 , is this a valid method of verification? because unfortunately I do not know how to calculate/size in closed form the module, but I start by hypothesize the couple of conical gears and then I verify them.

as regards the old legislation,
do you know what are the rules for straight teeth conical gears?
and would you also tell me where I can at least display it? which I think is easier to interpret.

you could suggest where to find the most interesting characteristics of materials (for us mechanics), beyond the sites of steel manufacturers.
for example I can not find, among the characteristics, the tension fatigue limit or the wohler curve, to dimensional fatigued trees.

Thank you in advance! :smile:

 

[meccanicamg]

Agma bends marked on the shigley is fine. looks like the old one with some graphic modification. The wohler curve doesn't find it because it's experimental. search on the shigley as you build the wohler curves that there are all equations. the fatigue limit voltage is not a number from catalogs but depends on the traction break load and the coefficient of the type of tension if bending or twisting or traction .... if you are looking for the dispenses in the internet you will find that it is worth about 0.5 for the alternating bending.

If you are looking for the forum you will find the topic already covered and you will find as an example my excel son for the wohler curve that is built with the shigley formulas.

 

[meccanicamg]

so much to facilitate the research I attach the relationship between stress and traction breaking load for the main materials.

 

[abelli12]

the characteristics necessary for the calculation can be found directly from iso 6336-5 i.e. the file 5.