The teeth of a helical gear are set at an angle (relative to axis of the gear) and take the form of a helix. This enables the teeth to mesh steadily, starting as point get in touch with and developing into collection get in touch with as engagement progresses. One of the most noticeable advantages of helical gears over spur gears is less noise, especially at medium- to high-speeds. Also, with helical gears, multiple teeth are at all times in mesh, which means less load on every individual tooth. This results in a smoother changeover of forces in one tooth to another, to ensure that vibrations, shock loads, and wear are reduced.
But the inclined angle of the teeth also causes sliding get in touch with between your teeth, which creates axial forces and heat, decreasing efficiency. These axial forces enjoy a significant part in bearing selection for helical gears. As the planetary gearbox bearings have to withstand both radial and axial forces, helical gears need thrust or roller bearings, which are usually larger (and more expensive) compared to the simple bearings used with spur gears. The axial forces vary in proportion to the magnitude of the tangent of the helix angle. Although larger helix angles provide higher rate and smoother motion, the helix position is typically limited to 45 degrees because of the production of axial forces.