A number of railroad companies had been reporting difficulties with diesel electric locomotives under buffing or pusher operation. This action was evidenced by lateral instability between the several units, especially those under the largest buffing forces and resulted in lateral displacements and lateral forces of such magnitude that the rails were turned over and derailments caused in some cases. To obtain as complete an understanding of the jackknifing action as possible it was decided to make measurements on both the locomotive and the track. A test location was picked on a right curve of 8 deg. 6'. The grade was 1.72 percent at the curve but within a mile became 2.20 and 2.40 percent so that part of the train on the steeper grade when the recordings were made. The rail was 131 lb. RE Section laid in 1946 and rather badly curve worn. The test locomotives were GP-7 Electro Motive general purpose road switchers. The following conclusions were drawn: Jackknifing is the result of lateral instability of the several units and its severity is dependent on the magnitude of the buffing force and the eccentricity of the force. It is evident the eccentricity of the force will depend on the amount of overhang and the clearance available for lateral movement. Reduction of the bolster clearance to a small amount improves the conditions sufficiently that operation is not excessively difficult. Lateral forces are reduced about 50 percent. Operation of the general purpose units with full bolster clearance and standard couplers under buffing forces is not practicable with four units and probably undesirable with three units. Forces of almost 25,000 lb were measured at 10 mph and 140,000 to 175,000 lb tractive force and higher forces can be developed at lower speeds or under impact conditions. These laterals applied continuously will be very detrimental to rail and wheels, cause journals to run hot, and may cause derailment. The use of the alinement control coupler attachments reduced the forces to a normal amount for the curvature of the test location. The lateral forces under full regenerative braking with alinement control couplers for an undetermined reason were a little higher in the few tests made than in the pusher operation which had twice the tractive force. However, they are still quite moderate. The jacknife position, once assumed, remains until the train is stretched out.

  • Corporate Authors:

    Association of American Railroads

    50 F Street, NW
    Washington, DC  United States  20001-1564
  • Authors:
    • MAGEE, G M
    • Keller, W M
    • Ferguson, R
  • Publication Date: 1955-1

Media Info

  • Features: References;
  • Pagination: 21 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00033743
  • Record Type: Publication
  • Report/Paper Numbers: Rept. 10838
  • Files: TRIS
  • Created Date: Jul 8 1994 12:00AM