Second, the planet gear bearings need to play an active role in torque transfer. Planetary systems split the torque insight from the sun gear amongst the planet 
gears, which in turn transfer torque to a world carrier linked to the gearbox output. The bearings that support the planets on the carrier have to bear the full brunt of this torque transfer.
Or, in acute cases, they may select angular get in touch with or tapered roller bearings, both of which are created to withstand axial loads.
In planetary gearboxes, however, it’s much more difficult to design around these axial forces for two related reasons. First, there is typically hardly any room in a planetary gearbox to incorporate the type of bulky bearings that can tolerate high axial forces.
The existence of axial forces makes things very different for the bearings that support helical gears. But it’s important to make a distinction between fixed-axis and planetary gearboxes. In fixed-axis gearboxes, the additional axial forces total little more than an inconvenience. Gearbox designers will often upsize the bearings to accommodate the additional forces.
Since they won’t need to withstand any axial forces, spur gear bearings enjoy just a supporting role in the functioning of the gearbox. The bearings simply need to support the rotating equipment shafts, Helical Gearbox however they do not play an active part in torque transfer.
Helical Gears Place Higher Demand on Bearings