Spherical bearings

For the S4 condition, the triangular prism is supported on partially embedded spherical bearings that permit translation in any direction in the x-y plane, must be zero. 

Spherical bearings are usually furnished in a doublerow mounting that is inherently self-aligning. Both rows of rollers have a common spherical outer raceway. The rollers are barrel-shaped with one end smaller to provide a small thrust to keep the rollers in contact with the center guide flange. 

In fact Van Wyk ° used something similar to a composite structure for the lubrication of silicon nitride and alumina in plain spherical bearings. He incorporated a 90% molybdenum disulphide/8% molybdenum/2% tantalum compact in holes drilled in the surface of the alumina outer ring, and the details have been described in Chapter 8. The system was very successful, giving a forty times increase in wear life. 

Sliney, H.E. and Jacobson, T.P., Graphite-Fiber-Reinforced Polyimide Liners of Various Compositions in Plain Spherical Bearings, Proc. 2nd ASLE Inti. Conf. on Solid Lubrication, Denver, Colorado, (15-18 Aug. 1978) ASLE SP-6, p. 258. 

The boom is mounted on a spherical bearing idilch allows manual slewing of the assembly by approximately +7. This angle is restricted by the access manholes in the circulator outer casing. The forward end of the root box section is equipped with rollers which rest on a support stool inserted into the clrciilator outlet duct during preparation of the route. 

Shear strength. The bulk shear strength of the hardened adhesive at 20 C should be at least 12 MN m -. A specimen 200 mm X 12 mm x 25 mm deep tested in a shear box, as shown in Fig. A.3, is recommended(4). The complete assembly is loaded in compression through a spherical bearing at a rate of 1 mm/min. The failure load is taken as that load at which shear cracking first... 

Roller Bearings Pot Bearings Disc Bearings Spherical Bearings Seismic Isolation Bearings... 

Woven PTFE material is generally used on the curved surfaces of spherical bearings. As noted earlier, woven PTFE exhibits enhanced creep (cold flow) resistance and durability relative to unwoven PTFE. When spherical bearings are detailed to accommodate translational movement, woven PTFE is generally specified at the flat sUding interface also. 

Both stainless steel sheet and solid stainless steel have been used for the convex sliding surface of spherical bearings. According to one manufacturer, curved sheet is generally acceptable for contact surface radii greater than 14 in. to 18 in. For smaller radii, a solid stainless steel convex plate or stainless steel inlay is typically used. The inlay is welded to solid standard steel. For taller convex plates, a stainless steel inlay would likely be more economical. 

Most spherical bearings are fabricated with the concave surface oriented downward to minimize dirt infiltration between the PTFE material and the stainless steel surface. Calculation of translational and rotational movement demands on the bearing must recognize that the center of rotation of the bearing is generally not coincident with the neutral axis of the girder being supported. 

Figure 5-81 shows a spherical bearing, a configuration that allows for high compressive loads in the axial direction while maintaining soft torsion about the axial axis and torsion perpendicular to that axis. This configuration is a combination of Figures 5-78 and 5-79. 

R.R. Boyer, Ti/Cr203 Grease Lubricated Spherical Bearings, Proceedings of the Tkchnical Program from the 1986 International Conference on... 

Figure 21-22 Spherical bearing (cross-sectional view.) (Courtesy of NTN Bearing Corp.)...

Bearings made with PTEE fiber are used in packaging machinery, pulp and paper processing equipment, and other applications. The PTEE fiber is woven into a fabric with some other fiber that will bond well with adhesives. This fabric is incorporated in a RTP (reinforced thermoplastic) structure to form a spherical bearing that will accommodate misalignment. 

Seismic Analysis of Steel and Composite Bridges Numerical Modeling, Fig. 18 Layout and representation of spherical bearings... 

Spherical bearings consist of a sole plate that transfers loads from the superstructure, a concave spherical segment and a convex spherical segment that provides a mating surface for the concave segment and transfers load to the substructure (Fig. 18). PTFE (Teflon) sliding layers are provided between the three parts to allow horizontal displacements and rotation in all directions. Spherical bearings provide... 

Friction pendulum bearings constitute a variation of the spherical bearings, where the plane sliding top surface is replaced by a curved one (Fig. 21a, b). They exhibit, unlike spherical bearings, a re-centering capability and are not subjected to... 

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