Design Features
Simple Design
Rotation element does not have critical tolerances compared to pots with sealing ring or curved, mating, sliding surface bearings. No greasing or PTFE lining needed to accommodate rotation.
Simple Installation
Alternate anchorage details are provided for all structure types. Jacking ports are standard and flexible guides are available. The designer selects the features desired.
Simple Inspection
Rotation element visible from all sides.
Simple Modification
The shear restriction mechanism is easily modified to allow lateral movement for a series of fixed and uni-directional bearings. Seismic and base isolation designs also available.
Performance Features
Confined Virgin PTFE Horizontal Sliding Surface
PTFE provides low coefficient of friction against the bright annealed finished stainless steel (less than 0.127 µm (5 µin) root mean square finish). Less than 0.03 coefficient at 10.4 MPa (1508 psi). Test reports available for friction values at dynamic seismic cycling.
High Rotational Capacity
Designed to rotate up to 4º. The shift in center of gravity is low within structural design guidelines of less than 3% of the column diameter at 1% rotation. Full rotation at low loads is accommodated within the bearings.
Unique Shear Restriction
The unique shear restriction mechanism uses DYMAT® alloy to allow rotation with uniform distribution of forces between bearings in the structure.
Compact Design
The shear restriction mechanism eliminates shear on the disc due to horizontal forces, while allowing high vertical loading on the unique disc material. The result is a compact bearing.
Easy Design for High Horizontal Force
A larger shear restriction mechanism is introduced when the horizontal force is above 25% of the total vertical load.
Internal Uplift Restraint. Special bolts with DYMAT® alloy rotation elements provide uplift restraint while allowing rotation at the same time.
Unique Disc Shape
Eliminates stress point “V” used in older designs.
Material Specifications
Steel Components
All steel plate, G40.21M, 300W or A572 (grades 36, 42 or 44) minimum specification. Custom steel available on request.DYMAT® disc meets requirements of AASHTO specifications.
Stainless Steel Components
Sheet shall conform to ASTM A-240, Type 304. Stainless steel in contact with PTFE sheet shall be less than 5µin (0.127µm) root mean square finish. Thickness of stainless steel shall be 0.063 in (1.6mm) minimum.
Exposed Steel Surfaces
Steel surfaces exposed to the environment are painted with structural primer to design authority specifications. Surfaces can also be galvanized or Metalized if required.
PTFE
Polytetraflouroethylene (PTFE) Sheet and Strip PTFE is pure virgin (unfilled) polymer. Properties conform to the following:
Requirement: Tensile Strength MPs (psi)
Test Method: ASTM D-638
Value: 19.3 (2800) min.
Requirement: Elongation
Test Method: ASTM D-638
Value: 200% min.
Requirement: Specific Gravity
Test Method: ASTM D-792
Value: 2.13 ± 0.03
Reinforced PTFE can be used in higher load applications. Different thicknesses are available. PTFE with grease retention cavities is available.
PTFE to Steel Bonding
Special etched, one side virgin PTFE is bonded with DYMAT® adhesive to grit blasted steel using special bonding procedures. Virgin PTFE guides are bonded and mechanically fixed in place.
Manufacturing Tolerances
± 0.125 in (3mm)
Overall plan sizes
± 0.125 in (3mm)
Overall height (except for very large bearings)
Standard machined surfaces to finish ASA 125
0.625 in (1.6mm)
Standard total gap on guide bars
± 0.0312 in (0.8mm)
Standard tolerance on guide bars
These are normal tolerances for DYMAT® bearings unless designer specifies other requirements.
Specially compounded PTFE is available for minimal wear when a higher coefficient of friction is tolerable.
Test reports available to 500,000 cycles.
