sizing system pinion-cremagliera

[pierp.flour]

Hello everyone, they are struggling with an exercise that concerns the static and fatigue dimensioning of a lazy-cremagliera system for the drive of a sliding electric gate.
Sorry if I start a new discussion, but I found nothing exhaustive in this subsection of the forum.
as data I have:
-band width;
-power of the engine;
-reduction ratio from the engine to the pinion of the system to be dimensioned;
- maximum painting, electrically limited for safety reasons;
-gate run;
-Mass of the gate;
- number of wheels on which the gate rests and diameter;
-coefficient of wheel-binary friction.
As for static sizing, I assumed that the maximum thrust on the gate was equal to the tangential force to be used for the static sizing of the wheel. having noticed the band width I obtained from the static calculation in contact hertziano the number of teeth required, going to check it then with the formula of lewis.
no problem.
when I go to make the calculation of the tangential force from the friction couple (known by the text as the only strong couple), calculated on the wheels of the gate in contact with the track, I noticed that it assumes a value greater than that I used for static sizing.
from this emerges the question, it is necessary to use the relationship of reduction of the motor, the power of the motor and the maximum speed of translation of the gate, or simply, can not be considered legitimate and I wrong to enroll in mechanical engineering?
thanks in advance to those who will answer

 

[meccanicamg]

first you have to have the engine curve (pair/turns and power/turns) to decide. However the engine could be a 4 pole and with the kw indicated it will give to 1500rpm the nominal torque.
this power will push the pinion teeth on the rack and a 2% will dissipe it by friction. the wheels that carry the weight of the gate will eat the friction force of the bearings... of the type weight gate x invoice.
If you don't take a big engine, you have to use a gearbox to have more torque.

 

[Stan9411]

Hi, what does the maximum thrust mean? to me it seems a problem of reverse dynamics... you have the strengths -> power balance -> get the torque motion -> check that your engine can dispense it and to what regime... from there make the measurements and verifications... I don't understand why for a verification you use the maximum thrust (which I don't understand what it is) and for another laughter to the forces agents on your transmission starting from the resistant forces. correct me if I'm wrong... I would also like to learn the modus operandi for these procedures

 

[pierp.flour]

[MENTION=70985]Stan9411[/MENTION] the maximum push, is called so on the track of the exercise, I assume that, saying that it is limited for security reasons, both the force that pushes the gate.
for static calculation, I think we have to sum the famous push to friction force and multiply everything for the maximum speed of translation of the gate, verifying that it is less than the power of the engine. Is that what you mean?

 

[Stan9411]

presumably therefore it is the maximum tangential force that exchange sprockets and racks.
I repeat, I would solve the reverse dynamics of the system (classic mtu from applied mechanics) to regime of course, from them I will get the couple motion; presumably the torque at the point will be 2 or 2.5 times higher than the torque at regime. Once I calculate this pair, I divide it to the sprocket radius and get the tangential force. now if this force is less than the maximum push all ok and my checks I do it with this force; if they are beyond the maximum push threshold I hypothesize that there is an electronic control to adjust the engine and I verify everything using the maximum push.
so it would solve a student probably a little bigger than you
Surely here there are people who will be able to clarify our ideas to both of us.