Appeal No. 2003-0387 Page 4
Application No. 09/772,275
where:
FwW.E. is the required warp friction force - worn - empty;
:2w is the slope warp coefficient - max;
:1w is the column warp coefficient - max;
a is the bearing centers;
b is the wheelbase;
ww is the wedge [width];
Vc.[,/]W.E is the maximum compression damping force per suspension - empty;
:1d is the column damping coefficient;
:2d is the slope damping coefficient.
The teachings of Hawthorne
Hawthorne's invention relates to improvements in three-piece freight car truck
assemblies. In the Description of the Prior Art section, Hawthorne teaches that
In a three-piece truck assembly, the side frames and bolster normally are
square, i.e., the wheelsets and bolster (parallel to one another) are disposed
normal to the side frames. Occasionally, however, at certain car speeds, the
truck may become dynamically unstable, a phenomenon known as truck hunting,
manifested by the truck going out of square or warping. The prior art teaches
several ways of preventing truck hunting, e.g., the use of resilient side bearings,
increasing warp stiffness, steering the wheelsets, the use of conconical wheel
profiles, reducing lateral resistance, etc., and the literature has reported certain
levels of warp stiffness achieved by three-piece truck assemblies. But numerous
tests run to confirm the reported data show that warp stiffness of the levels
reported by the literature cannot be achieved with known designs of three-piece
freight car truck assemblies, and it appears that the reason for the lack of warp
stiffness is instability of the wedges within the pockets.
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