Second, the planet gear bearings have to play an active part in torque transfer. Planetary systems split the torque input from sunlight gear amongst the earth gears, which transfer torque to a planet carrier linked to the gearbox 
result. The bearings that support the planets on the carrier need to bear the Helical Gearbox entire brunt of that torque transfer.
Or, in extreme cases, they may select angular get in touch with or tapered roller bearings, both which are designed to withstand axial loads.
In planetary gearboxes, however, it’s much more difficult to design around these axial forces for just two related reasons. 1st, there is typically very little space in a planetary gearbox to incorporate the kind of bulky bearings that may tolerate high axial forces.
The presence 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 additional axial forces total little more than a hassle. 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 play just a supporting part in the functioning of the gearbox. The bearings should just support the rotating gear shafts, however they do not play an active role in torque transfer.
Helical Gears Place Higher Demand on Bearings