dimensioning shaft of a change to 4 marches

[tarty88]

Good morning, I write because I have to make a maximum sizing of a deferring tree of a 4-speed gearbox of a rear traction car. the incoming shaft rotates at 4800 rpm for any gear to transmit 180nm of torque (high-power conditions) and then there is a fixed tau0 ratio that trams and multiplies the pair in the reference shaft, on which the various gears of the various marches are placed. My question is: is the pair in the reference tree constant because it is multiplied always by tau0, or should I obtain it by multiplying tau0 for the tau of the gear inserted? I have already found by balance of internal forces the diameters of the various gears of each march.. .
Thanks for the attention!

 

[PierArg]

Hello and welcome,
If you place a box is better. in all cases varies according to the triggered wheel.

I suggest you present yourself in the special section (if you have not already done it)

 

[meccanicamg]

egreggio student, please read the forum rules before posting :mixed:

at your house you come in and say: I need this! or you ring the bell, you say good morning, you show up and wonder what you need?
... do a little yourself:biggrin:

 

[tarty88]

I'm sorry, the fact is that I didn't see a thread called presentations, now I'm going, sorry!

 

[tarty88]

I have attached a scheme, with 0 = fixed reference and the iii are the 3 marches, the iv is in direct grip. So if I didn't understand badly, the pair in the reference shaft is 180nm of the motor shaft multiplied by the fixed reference tau and the ratio used, right?

 

[PierArg]

Hi, I'll correct what I said before.

the deferral shaft sees 180 nm per tau0...the graft of the other wheels is transmitted to the exit shaft. It's the exit shaft that sees a different torque by the wheels in summer.

I ignore what I said at the first post.

 

[PierArg]

However returning to the dimensioning I would focus on the 4 cases with the 4 gears inserted once at a time. you find the various reactions that the wheels transmit to the shaft, the reactions of the bearings and then see the stress state to bending and twist.

 

[tarty88]

However returning to the dimensioning I would focus on the 4 cases with the 4 gears inserted once at a time. you find the various reactions that the wheels transmit to the shaft, the reactions of the bearings and then see the stress state to bending and twist.

yes because however the torque is force applied to the teeth of the toothed wheel by radius of the wheel and if the maximum power conditions do not change, the torque in the reference shaft is always that... I'll be fine and see what I get for now, thank you very much!

 

[PierArg]

yes because however the torque is force applied to the teeth of the toothed wheel by radius of the wheel and if the maximum power conditions do not change, the torque in the reference shaft is always that... I'll be fine and see what I get for now, thank you very much!

theoretically you have to consider the alpha angle (usually 20°...always if they are straight teeth) but if you do not do it it is better because you cauteli (I refer to the radial component).
attention to the type of toothed wheels you have (right or helical teeth? )
the power you must always consider it constant...in fact it is equaling the power in the incoming with that in exit (obviously taking into account the performance) that you have the various transmitted pairs and the various turns of the three trees (entry, referral, exit).

 

[meccanicamg]

I propose an excel sheet as I did when I analyzed the change of point... so determine the value of the reactions in all conditions of regime and you will see by yourself in which gear and if at the maximum power state or torque you will have maximum stresses.

and you can also set fatigue verification, see how and where it will be the worst point on your tree and if it will be able to resist unlimited cycles.

automate calculations and you will have the theoretical world of all change

 

[PierArg]

I propose an excel sheet as I did when I analyzed the change of point... so determine the value of the reactions in all conditions of regime and you will see by yourself in which gear and if at the maximum power state or torque you will have maximum stresses.

and you can also set fatigue verification, see how and where it will be the worst point on your tree and if it will be able to resist unlimited cycles.

automate calculations and you will have the theoretical world of all change

super-quoton.

has mechanical reasonmg, you will lose some time but you will understand much more. In this way you will have a complete vision.

 

[MBT]

I understand the educational purpose. . .
but it will be at least 40 years that car changes do not have direct grip.. .

 

[viscardo baldo]

I propose an excel sheet as I did when I analyzed the change of point

Thanks for the advice.
the work you're referring to has already been posted here on the forum?

Could you please give me the link so I can study it?
Thank you.

 

[tarty88]

I propose an excel sheet as I did when I analyzed the change of point... so determine the value of the reactions in all conditions of regime and you will see by yourself in which gear and if at the maximum power state or torque you will have maximum stresses.

and you can also set fatigue verification, see how and where it will be the worst point on your tree and if it will be able to resist unlimited cycles.

automate calculations and you will have the theoretical world of all change

Good idea, I think I'll do this afternoon, thank you!

 

[meccanicamg]

Thanks for the advice.
the work you're referring to has already been posted here on the forum?

Could you please give me the link so I can study it?
Thank you.

I would say that I have never posted it and I think I will never post it, otherwise all those who have to study the usual change that they give to the university put in the values of the wheels and of the motor characteristics and have finished the work cost at least one week and some maternity :biggrin:

I teach walking, then everyone uses his legs:finger:

 

[viscardo baldo]

Right! :finger:

So can you tie me up a point change pattern?
and can you tell me what input data is and what output is? ?
So I start walking on my legs too:wink:

 

[MBT]

depends on the point type, the motorization
Of course, it does not have a direct iv ;-)
for reports.. are generally found on the fiat site or on other "technical" sites dedicated to the automotive world

 

[meccanicamg]

Right! :finger:

So can you tie me up a point change pattern?
and can you tell me what input data is and what output is? ?
So I start walking on my legs too:wink:

all that is on the first page is the data. on the second page there are the results of the curves obtained by analyzing the various aspects.

the design of the schematized tree and the original fiat tree.
attention to fatigue testing in the throat of the ii march.

in all this there is to get the curves, get the calculations of the forces on the shaft/engineering, check the static and fatigue resistance of the tree by analyzing the internal actions.

good study, here is to work a whole month:biggrin:

 

[viscardo baldo]

Thank you, I'll let you know in a month as it went. :finger:
by curiosity: the curve of the torque, of the power and velocity have you obtained or provides the fiat?
I think these curves are always kept secret.

I'll let you know and... thank you

 

[meccanicamg]

Thank you, I'll let you know in a month as it went. :finger:
by curiosity: the curve of the torque, of the power and velocity have you obtained or provides the fiat?
I think these curves are always kept secret.

I'll let you know and... thank you

I created the curves with the data they gave me. You have to put us in the world to have the torque and power curves. you have returns, transmission relationships to change and differential.

of course the curves are at the counter, without aerodynamic frictions etc. then in practice there are a tide of things to consider to have the actual working curve in every road/wind/aerodynamic condition etc.

I forgot, the conical wheels have yield 0.96