Second, the earth gear bearings need to play an active role in torque transfer. Planetary systems split the torque input from the sun gear amongst the planet gears, which in turn transfer torque to a world carrier connected to the gearbox result. The bearings that support the planets on the carrier need to bear the entire brunt of this torque transfer.
Or, in extreme cases, they may select angular get in touch with or tapered roller bearings, both which are created to withstand axial loads.
In planetary gearboxes, however, it’s much more difficult to create around these axial forces for just two related reasons. Initial, there is typically very little room in a planetary gearbox to include the kind of bulky bearings that may tolerate high axial forces.
The presence of axial forces makes things very 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 amount to 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 role in the functioning of the gearbox. The bearings should just support the rotating gear shafts, however they do not really play an active role in torque transfer.
Helical Gears Place Better Demand on Bearings
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