Second, the earth gear bearings need to play an active role in torque transfer. Planetary systems split the torque insight from the sun gear amongst the earth gears, which in turn transfer torque to a planet carrier linked to the gearbox result. The bearings that support the planets on the carrier need to bear the full brunt of this torque transfer.
Or, in acute cases, they may select angular contact or tapered roller bearings, both which are made to withstand axial loads.
In planetary gearboxes, however, it’s a lot more difficult to create around these axial forces for just two related reasons. 1st, there is typically very little room in a planetary gearbox to incorporate the type of bulky bearings that can tolerate high axial forces.
The presence of axial forces makes things very different for the bearings that support helical gears. But it is Helical Gearbox critical to make a distinction between fixed-axis and planetary gearboxes. In fixed-axis gearboxes, the excess axial forces total little more than a hassle. Gearbox designers will often upsize the bearings to support the additional forces.
Since they won’t need to withstand any axial forces, spur gear bearings perform just a supporting part in the functioning of the gearbox. The bearings should just support the rotating 
gear shafts, however they do not play an active function in torque transfer.
Helical Gears Place Greater Demand on Bearings