Planetary gear constraints.
I have downloaded from here a typical planetary gear train. What am i trying to do is simulate the motion of a planetary gear with siemens NX.
Up till now what i have achieved is to have the ring rotate around the sun and the planets, the planets are staying in the same position.
What i want to do, and i have failed miserably after reading a lot, is keep the ring fixed keep the sun fixed and have the planets move around. I dont want to do it through contact i want to do it with constraints.
Essentially what i want is to have the planets rotate around their own axis and around the centre of the sun, but i don't know how. If i apply a joint in a planet lets say it fixes the centre of rotation around one point and the gear cant rotate around the ring it stays in the same position.
If you have any idea how can i tackle this problem i would appreciate it a lot as i spend a lot of hours over the past couple of days.
Thanks
5 Answers
Can you provide the link to the assembly you downloaded? Being able to see the models will help a lot.
what i am doing at the moment is :
1) adding a revolute joint to the sun gear around its own axis (and i give a motion to the sun)
2) adding a fixed joint between carrier and sun gear
3)adding a fixed constraint between pin that goes in each of the planet gears and the carrier
so with these 3 i am achieving the rotation of the sun gear and because of the constraints also of the carrier and the 3 pins
Next
4) i add a revolute joint to the ring gear (ideally i want it fixed in place, but if i fix it i cant use it in the gear coupling)
5) a revolute constraint in each of the 3 planets and i pick as a centre the centre of pin which rotates with the carrier
6) i add another revolute constraint to the planets around its own axis (which is the same as the axis of the pin)
7) i add gear couplings between the sun gear and the planets, and the planets and the ring gear.
but this does not work. what i get is first of all the ring gear to rotate which i dont want and secondly NX is not recognising the gear couples and it just rotates around without solving the contact between gears
this is where i am at the moment :(
so what you are saying essentially is that i only have to give a motion to either ring carrier or sun and then the other 2 are going to be one fixed and the remaining the output. In my case although i am constraining sun to carrier i still get a motion i dont know how. I am gonna have a look at you models. trying to play with those. Thanks, i ll get back to you to let you know
i managed to do something, i think everything is constrained good, my only problem now is contact cause i cannot apply gear couples between the gears i am applying a generic contact so the simulation works up till one point and then struggles to converge. but anyway at least i see a bit of proper movement thanks
