Second, the planet gear bearings need to play an active part in torque transfer. Planetary systems split the torque insight from the sun gear amongst the planet gears, which transfer torque to a planet carrier linked to the gearbox output. The bearings that support the planets on the carrier have 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 of 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 hardly any room 
in a planetary gearbox to include the type of bulky bearings that can tolerate high axial forces.
The presence of axial forces makes things very 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 an inconvenience. Gearbox designers will often upsize the bearings to accommodate the additional forces.
Since they don’t need to withstand any axial forces, spur gear bearings enjoy just a Helical Gearbox supporting role in the functioning of the gearbox. The bearings simply need to support the rotating equipment shafts, but they do not play an active function in torque transfer.
Helical Gears Place Higher Demand on Bearings