This is especially true of bearing gears, which have large diameters and large center distances that demand greater manufacturing tolerances. Gear teeth are hardened through to their full root radius to resist high surface pressuresĪll gears need backlash room. A full root radius with root hardening (see Figure 4) is also recommended the tooth pattern and depth of hardness are critical here. An example of this would be an excavator or logger that undergoes high acceleration rates and rapid deceleration during a swing cycle. When high tooth surface pressures are constant, induction-hardened gear teeth with a minimum surface hardness of 55 Rc should be considered. These stress approximations are for maximum or stall torque conditions.when shock is included in the loading, stresses may be higher. With core hardness of 23 to 30 Rc, allowable bending stress is 34,000 psi. Full depth tooth forms provide a greater contact ratio for smoother operation, but they also have lower bending strength. The form requires less material in the ring forging than full depth tooth forms, and less gear cutting time. Y = Tooth form factor (from tables-see Figure 3)Ī stub tooth form is often used in large gears, primarily for economy.

L = SFY P (where L = Tangential tooth load) The tooth size and form is then selected using the following Lewis equation: Machine designers generally select slewing ring bearings based on load capacities (see Figure 2). To accommodate different application requirementsĪ pressure angle of 20° is most common because 20° cutters are standard, but 14.5°, 25°, or special pressure angles may also be used. Gear teeth can be cut into a number of slewing ring bearing surfaces, Whatever its style, the success of a slewing ring gear depends on four factors: gear static strength, resistance to pitting, gear fatigue, and gear/pinion interfaces (or mesh). These gear details can take on many styles and features: Fellows stubs, full-depth involutes, straight or helical, hardened or unhardened, ground or unground. In addition to saving space, a designer can use a slewing ring bearing to simplify a drive system by incorporating gear teeth on the inner or outer race. This makes it practical to use one bearing instead of two, reducing the height required for an application and often improving performance. Kaydon white papers Shifting gears: simplify your design with slewing ring bearingsĪ slewing ring bearing has rolling elements designed to create a reactive moment within the bearing's dimensions envelope, to oppose applied (overturning) moment load.

Slewing radius