Helical Inline Gear Motors Helical gears aren’t specifically much like worm or bevel gearbox systems. They are in fact an helical spiral bevel gear motor alternative to spur gears where the tooth are parallel to the axis of the gear itself. For example, within an inline application, you can have either spur OR helical gears. An inline helical gearbox engine will most likely be quieter and will bring higher loads than motors using a spur gearbox. They could be more expensive in initial cost, and manufacturers have to take into account axial thrust. Nevertheless, the actual fact that the helix position may differ from 15 to 30 degrees allows for flexibility when it comes to design. They are found in in-line applications and also parallel shaft applications.

The benefit of helical gears is that it produces a rolling action, is quieter, and has less vibration in comparison to spur gears. It also produces much less friction and permits more teeth to be engaged at the same time as the teeth roll across each other.
There are myriad types of gearing. Some manufactures use spur gears instead of helical gearing, for example. However, there is not as much surface contact, as mentioned above and because of this there is more noise and less torque transfer possible.

Another system where noise is usually common are planetary gear systems, where the one gear is completely within the other. In addition they require grease lubrication and they must be constructed with expensive materials to be able to maintain a long-existence and bearing integrity. An easier variant, internal gearing, suffers 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 really intersecting. The sliding action can create large amounts of high temperature and the alignment requires great care.