Helical Inline Gear Motors Helical gears aren’t specifically much like worm or bevel gearbox systems. They are actually an alternative 
to spur gears where the tooth are parallel to the axis of the apparatus itself. For example, in an inline application, you can have either spur OR helical gears. An inline helical gearbox electric motor will usually be quieter and can carry higher loads than motors using a spur gearbox. They may be more expensive in initial price, and manufacturers have to account for axial thrust. Nevertheless, the actual fact that the helix position can vary from 15 to 30 degrees permits flexibility in conditions of design. They are found in in-line applications in addition to parallel shaft applications.
The advantage of helical gears is that it produces a rolling action, is quieter, and has less vibration in comparison to spur gears. In addition, it produces less friction and allows for more the teeth to be engaged simultaneously as one’s teeth roll across each other.
There are myriad types of gearing. Some manufactures use spur gears rather than helical gearing, for instance. However, there isn’t as much surface contact, as noted above and as a result there is more sound and less torque transfer possible.
Another program where noise is usually common are planetary gear systems, where the one gear is completely within the other. In addition they require grease lubrication plus they must be built with expensive helical spiral bevel gear motor materials to be able to maintain a long-lifestyle and bearing integrity. A simpler variant, internal gearing, is suffering from the same issues and can only be utilized with parallel shaft.
Finally, hypoid gearing may be best understood as similar to bevel gearing, but with the gear axes not intersecting. The sliding actions can create huge amounts of heat and the alignment needs great care.