This shows the carrier vehicle moving around a turn to the right. The grooved upper wheels (blue) that are on the carriage (light green) have moved the carriage to the left relative to the main frame (brown) to rotate the front and rear bogies in clockwise and counter-clockwise directions through fifteen degree angles. The displacement of the point of connection of the carriage to each bogie from the turn axis of the bogie is preferably about one-fourth the distance to the turn axis of the other bogie, i.e. the displacement is about one-fourth the wheel base when the turn axes intersect the wheel axes. With a wheel base of 108 inches, the displacement is about 27 inches and with bogie turn angles of fifteen degrees, the turn radius is only about 17 feet. In these conditions, as well as with any smaller bogie turn angles and correspondingly larger turn radii, the axis of each wheel will be in a vertical plane that is at approximately a right angle to the portion of a track engaged by the wheel.

Highly accurate wheel tracking is thereby obtained. The vehicle is normally kept on the desired path through the friction between the wheels and the tracks that is developed through vertical forces applied by the wheels to the tracks. Any transverse forces that need to be applied between the upper wheels and the upper tracks to keep the vehicle on the desired path are normally quite low. However, the flanges of the upper wheels on the bogies serve to prevent any transverse movement from the desired path that might otherwise result from side-wind or centrifugal forces that are excessive in relation to transverse frictional forces that are developed through vertical forces applied between the wheels and the tracks.

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