A Qualitative Analysis of the Dynamics of Self-Steering Locomotive Trucks

Abstract

The primary purpose of this study is to provide a qualitative analysis of the dynamics of the self-steering trucks that are commonly used for freight locomotives ± namely, EMD's Radial Truck and GE's Steerable Truck ± on improving curving performance and increasing adhesion in curves. Although there exists a number of anecdotal statements on the ability of steerable trucks to reduce curving forces and increase adhesion in curves, to the best of our knowledge, there exists no study that provides a qualitative or quantitative analysis of these features of steerable trucks. Two aspects of locomotive trucks are essential for their ability to deliver small curving forces and high adhesion in curves. First, the ability to allow the axles to yaw suf®ciently relative to the truck frames, such that they can hold a small angle of attack with the rail. Second, providing suf®ciently large longitudinal stiffness between the end axles and the axles and truck frame, to accommodate high adhesions. An equivalent stiffness analysis is used to show that the two steerable trucks that are considered for this study are far superior to conventional, three-axle, straight trucks in providing both a smaller angle of attack and a higher longitudinal stiffness for better curving and adhesion characteristics. The qualitative analysis of this study agrees with the experience the railroads have had with their self-steering trucks. The ®ndings of this study indicate that self-steering trucks can result in lower lateral forces, accommodate tighter curves, and deliver higher adhesion in curves; without lowering the critical hunting speed of the locomotive. The results further show that the steering mechanism stiffness can have a large effect on the lateral, longitudinal, and yaw stiffness between the end axles; therefore, signi®cantly lowering curving forces, and increasing adhesion and critical hunting speed of the truck.

A dynamics study of asymmetric forced-steering bogies

“…When a locomotive negotiates a curve, the self-steering radial bogie 5,6 totally relies on the wheel–rail creep force, whereas the forced-steering radial bogie 7 also takes advantages of the relative displacement of the angle of attack between the carbody and bogies. On consideration of the vibration of steel rail at the wheel–rail contact points, the longitudinal creepage ξ x − i , the lateral creepage ξ y − i , and spin creepage ξ Spin − i are defined as 8,9 where i = 1, 2, represents the left and right contact point, respectively.…”

Study on the Characteristics of Traction Forces Difference Asymmetric Steering Bogies

“…Due to the technological difficulty, the first DR-1 locomotive radial bogie [2] was not successfully developed until 1978. Totally dependent on wheel/rail creep force, self-steering bogies [3] have inferior steering performance to forced-steering bogies [4]. To solve the contradiction between traction and steering, actuated wheelset yaw bogies [5] come into being, wherein forced-steering bogies with driven motors, controlled radial bogies, electromechanical active steering, and stability control devices are among the successful applications at present.…”