Railway rolling stock – Trucks – Radial
Patent
1995-08-02
1998-03-24
Morano, S. Joseph
Railway rolling stock
Trucks
Radial
105169, B61F 538
Patent
active
057300640
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to railway bogies as widely used on railways, tramways, and the like to support a carriage or locomotive.
BACKGROUND
The principle conventionally used to guide a carriage on a railway track, introduced by Stephenson in about 1830 is to employ two wheelsets each comprising an axle having a wheel rigidly attached at each end the wheels having conical running surfaces, tapered away from the middle of the axle. This arrangement is usually termed the conicity principle.
The angle of the taper is about one in twenty, and it is common practice to incline the surface of the rail heads at a similar angle to ensure adequate load distribution over the area of contact between wheel and rail. Because the wheels are solidly mounted on the axle (and not free to rotate independently as in automotive practice), any displacement of the axle from the center line of the track causes the outboard wheel to roll on a larger diameter and the inboard wheel on a smaller diameter causing the axle to steer back to the center of the track. In a curved section of track each wheelset takes up a position displaced outwardly from the center of the track an amount appropriate to the degree of curvature, and provision must be made for the axles to steer so that their axes converge. This steer angle for a given radius increases with the spacing between the axles and becomes impractical for long carriages, which lead to the adoption of bogies having closely spaced axles at each end of carriages. The taper of the wheels must be great enough to allow the bogie to traverse the given track radius without undue sideways displacement but not great enough to precipitate cyclic yawing oscillations of the bogie which tend to increase in severity with speed. Such oscillations are inherent in the conicity principle wheelset.
In recent decades, attempts to increase greatly the speed of trains has led to the adoption of special profiles and very close tolerances in the profiles of the running surfaces of the wheels which tend to deteriorate rapidly at high speeds. Grinding techniques have been developed to regularly restore the wheel profiles and also those of the rail heads in some cases. Low cone angles reduce the tendencies of such bogies to oscillate but preclude trains equipped with such bogies negotiating curved tracks less than hundreds of meters in radius. However, when new railways are built, particularly in suburban environments, they often require tracks that include tight bends and also steep gradients.
Summarising, the shortcomings arising from the use of conventional bogies using the conicity guidance principle are as follows: comfort for passengers which problems increase with speed. noise, and the risk of derailment. slippage zone occurring within the contact area which is inevitable using conical wheel treads. resistance of a train is substantially greater than if, for example, cylindrical wheels-are used. makes new railway installations more expensive due the cost of land resumptions or tunnelling.
Many attempts have been made to overcome the problems of conicity-based wheelsets. However, these attempts have met with limited success, and designers are turning to bogies having four independent wheels for a solution. For example, UK Patent 1,496,190 by Arthur Seifert entitled "A Truck for a Railway Vehicle" discloses a pair of indepently rotating wheels for a railway bogie, the wheels secured to rotating axles which are downwardly inclined between 5.degree. and 45.degree.. The arrangement is intended to operate on conventional tracks having substantially flat rail heads and it follows that the wheel running faces comprise steep cones with their apexes in board of the wheel. This arrangement claims to provide less flange wear and friction and improved distribution of wheel loads to the bearings of the axles. However, such an arrangement would inevitably increase the frictional drag and wear of the main lead carrying lead contact area between the wheels and rails. No steering of the wheels is
REFERENCES:
patent: 4058065 (1977-11-01), Seifert
patent: 4324187 (1982-04-01), Sambo
patent: 4362109 (1982-12-01), Panagin
patent: 4459919 (1984-07-01), Lemaire et al.
patent: 5081934 (1992-01-01), DeRo et al.
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