Second, the earth gear bearings have to play an active role in torque transfer. Planetary systems split the torque input from the sun gear amongst the planet gears, which transfer torque to a planet carrier connected to the gearbox output. The bearings that support the planets on the carrier need to bear the full brunt of that torque transfer.
Or, in acute cases, they may select angular get in touch with or tapered roller bearings, both of which are designed to withstand axial loads.
In planetary gearboxes, however, it’s a lot more difficult to design around these axial forces for just two related reasons. 1st, there is typically hardly any room in a planetary gearbox to include the type of bulky bearings that may tolerate high axial forces.
The Helical Gearbox existence of axial forces makes things completely different for the bearings 
that support helical gears. But it is important to make a distinction between fixed-axis and planetary gearboxes. In fixed-axis gearboxes, the excess axial forces total little more than an inconvenience. 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 play just a supporting function in the functioning of the gearbox. The bearings simply need to support the rotating equipment shafts, but they do not really play an active part in torque transfer.
Helical Gears Place Greater Demand on Bearings