Second, the earth gear bearings need to play an active part in torque transfer. Planetary systems split the torque input from the sun gear amongst the earth gears, which transfer torque to a planet carrier connected to the gearbox result. The bearings that support the planets on the carrier have to bear the entire 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 made to withstand axial loads.
In planetary gearboxes, however, it’s a lot more difficult to design around these axial Helical Gearbox forces for just two related reasons. Initial, 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 completely different for the bearings that support helical gears. But it is critical to make a distinction between fixed-axis and planetary gearboxes. In fixed-axis gearboxes, the excess axial forces amount to little more than a hassle. 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 part in the functioning of the gearbox. The bearings should just support the rotating equipment shafts, but they do not really play an active function 
in torque transfer.
Helical Gears Place Better Demand on Bearings