Second, the planet gear bearings have to play an active part in torque transfer. Planetary systems split the torque insight from sunlight gear amongst the planet gears, which transfer torque to a planet carrier linked to the gearbox result. The bearings that support the planets on the carrier have to bear the entire brunt of this torque transfer.
Or, in acute cases, they may select angular contact or tapered roller bearings, both of which are made to withstand axial loads.
In planetary gearboxes, however, it’s a lot more difficult to design around these axial Helical Gearbox forces for two related reasons. Initial, there is typically hardly any 
area in a planetary gearbox to include the kind of bulky bearings that may tolerate high axial forces.
The existence of axial forces makes things completely 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 most likely upsize the bearings to support the additional forces.
Since they don’t need to withstand any axial forces, spur gear bearings play just a supporting role in the functioning of the gearbox. The bearings simply need to support the rotating equipment shafts, however they do not play an active role in torque transfer.
Helical Gears Place Higher Demand on Bearings