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 in turn Helical Gearbox transfer torque to a planet 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 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. First, there is typically hardly any area in a planetary gearbox to include the kind 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’s important to make a distinction between fixed-axis and planetary gearboxes. In fixed-axis gearboxes, the additional 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 play just a supporting part 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 Better Demand on Bearings