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01 Series
XZWD
Four-point contact ball Slewing Bearing
This configuration is arguably the most common style of slewing ring for cranes as well as other applications rotating slowly and transmitting significant forces. A single row of balls rotate within deep grooves located in both the inner and outer races. This groove or raceway in each race is precision ground or machined to the shape of a Gothic arch. A Gothic arch, basically two radii within each race, allows the ball to contact each race in two spots. Two contact points on the inner and two contact points on the outer race equates to a four-point contact slewing ring.
The angle between the aforementioned contact points and the horizontal centreline of the ball is referred to as the contact angle. Slewing ring designers select a contact angle based on the application. An application such as a gun mount, for example, with significant radial loads due to the recoil from firing, will commonly have a low contact angle, usually in the 35° to 45° range. A crane, with significant thrust and overturning moment loads, generally will have higher contact angles, of between 50° and 60°.
Four-point contact ball slewing rings are among the most lenient of configurations when mounted to inadequate mounting structures. Out-of-flatness and lack of rigidity, within reasonable amounts, generally are more readily accepted by four-point contact styles. Since the slewing ring is designed with ‘point’ contact, the points or contact angle move to accommodate an inadequacy. While not an ideal situation from a slewing ring manufacturer’s standpoint, such forgiveness can be an advantage to the crane manufacturer with respect to cost and the mounting structure.
Four-point contact ball Slewing Bearing
This configuration is arguably the most common style of slewing ring for cranes as well as other applications rotating slowly and transmitting significant forces. A single row of balls rotate within deep grooves located in both the inner and outer races. This groove or raceway in each race is precision ground or machined to the shape of a Gothic arch. A Gothic arch, basically two radii within each race, allows the ball to contact each race in two spots. Two contact points on the inner and two contact points on the outer race equates to a four-point contact slewing ring.
The angle between the aforementioned contact points and the horizontal centreline of the ball is referred to as the contact angle. Slewing ring designers select a contact angle based on the application. An application such as a gun mount, for example, with significant radial loads due to the recoil from firing, will commonly have a low contact angle, usually in the 35° to 45° range. A crane, with significant thrust and overturning moment loads, generally will have higher contact angles, of between 50° and 60°.
Four-point contact ball slewing rings are among the most lenient of configurations when mounted to inadequate mounting structures. Out-of-flatness and lack of rigidity, within reasonable amounts, generally are more readily accepted by four-point contact styles. Since the slewing ring is designed with ‘point’ contact, the points or contact angle move to accommodate an inadequacy. While not an ideal situation from a slewing ring manufacturer’s standpoint, such forgiveness can be an advantage to the crane manufacturer with respect to cost and the mounting structure.
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