Technical Reports

Radial Axle Passenger Truck Evaluation: Life Test Results and Vehicle Performance Problems

  • 01
  • Jun
  • 1982
AUTHOR: K. J. Simmonds
SUBJECT: Evaluation
KEYWORDS: Stability, Rail Forces, Wheel Tread Wear, Curve Performance, Effective Conicity
ABSTRACT: A pair of prototype radial-axle passenger trucks was tested at the Transportation Test Center, Pueblo, Co. With steering cross-links to provide yaw-angle compliance and axle stability, these trucks can execute axle radial alignment when negotiating curves; primary suspension is made up of separate vertical and horizontal springing. Curving performance, stability, ride quality, braking performance, and component life were evaluated during extended service tests. This report covers vehicle safety, resolution of technical problems, wayside rail force data, and the extended service life testing. A separate report on the performance test phase has been prepared by Ensco, Inc. for the sponsoring agency (shown above); the Ensco report also cross-references this report. Safety factors considered were: overturning stability, wheel derailment, and equipment failure. A secondary suspension static instability was cured by doubling airspring roll stiffness. A running bias to the right, causing flanging, was solved by improving axle alignment, correcting axle lateral offset, and shimming the chevron primary springs. Vertical and lateral rail force data, compared to Pioneer III truck data, showed that the radial trucks generated less lateral force. Life Test I was stopped when truck cross-link components failed; failures were analyzed. Life Test II began with the original wheel profiles and no speed restrictions. Wheelset hunting occurred at lower speeds as treads wore further. 'Effective Conicity' studies verified that critical speed decreased as effective conicity increased from wheel tread wear. Suspension stiffnesses, increased by spring modifications, were evaluated in curving and stability tests during Life Tests III and IV.
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