IIRC helical gears have the disadvantage that they are less efficient than straight-cut, because they waste some of the energy in side-thrust (and require some form of thrust bearing/etc to that side to reduce friction losses, and the housing has to take that load too).
So they take up more space than the straight cut gears, along the direction of the shaft they spin on, making them less suitable for things like planetary-geared hubmotors and other small constrained-space applications.
But they're easier on the actual gearing/meshing, and quieter than straight, and are what's used in most gearbox/transmissions I've ever seen.
So they take up more space than the straight cut gears, along the direction of the shaft they spin on, making them less suitable for things like planetary-geared hubmotors and other small constrained-space applications.
But they're easier on the actual gearing/meshing, and quieter than straight, and are what's used in most gearbox/transmissions I've ever seen.
