Originally Posted by
riff_raff
AGMA 6123-B06 table 8 provides planet gear mesh design load factor recommendations based on numbers of planets, gear accuracy grade, application, mounting arrangement/flexibility, pitch line velocity, etc. The EC225 output stage would seem to fall under "application level 3" which recommends using a mesh load design factor of 1.30 for the "heaviest loaded planet". These are load factors used for design/analysis of the gear system, are based on accumulated industry experience, and tend to be conservative. However, obtaining even load sharing when you have a large number of planets (ie >4) and a very lightweight, flexible supporting structure, can be extremely difficult in practice.
Here is a good article on the
issue of planet gear load sharing analysis if you're interested in reading more about it.
Interesting article, thank you. The 225 planet carrier certainly looks like it has low enough stiffness to share the load well over 8 planets.
Just compare it against the industrial planet carrier on the cover photo of the article (pdf download version).
One significant drawback of making the pins and carrier 'flexible' is that it puts a greater share of planet load on the upper bearing race. That effect on the raceways could easily outweigh any benefit to the gears of having carrier/pin flexibility especially as the bearing load distribution becomes more unequal as torque increases.
Doubtless this will all have been factored into the original fatigue design(?). It should be evident in higher occurrence of spalling in the upper races than lower ones.