There are also effects on the coned-tread-wheel and railhead interaction, and on the way the axles try to ‘steer’ the truck frame.
This is in part inherent in Mr. Goding’s description of how the trailing axle of a powered C truck is the only one that experiences ‘radial’ centering. You can easily model some of the force couples that the leading and center tread, fillet, and flange face experience when this is true on a pin-guided truck with three motors independently pulling (at what can inherently be three slightly different resultant speeds for a given common admitted voltage, but will not be different for an early EMD single-inverter-per-truck AC drive).
The role of the geometry involved is also important, both for the pivoted and semi-attached ‘centerless’ styles of truck rotation accommodation. As a comparison, look at the American Arch ‘articulated’ truck frame as seen on the early Woodard Super-Power engines. Here the rear wheelset (especially when fitted with a booster) was supposed to take up a radial position relative to the track – but the front articulation pivot location and the need for proper weight distribution make the subsequent location of the leading wheelset geometrically improper for proper Bissel steering of a two-axle truck that is providing active guiding for the chassis. The ‘solution’ circa 1927 was to float that axle with minimal lateral ‘friction’ restoring force between it and the truck frame, but still with full springborne weight transfer to the equalization – this was done with a pair of hardened steel rollers acting on hardened bearing surfaces. Now, since this was an idler axle, there was no particular need to steer it radially, but it would ‘theoretically’ be possible to use Cartazzi-style curvature of the guide plates in the pedestals so the axle would ‘float’ in radial alignment with the effective forward pivot point of the articulated tr