STUDY OF WEIGHING FREIGHT CARS - TWO DRAFT COUPLED IN MOTION ON THE WESTERN MARYLAND RAILROAD

This study was conducted for the purpose of obtaining data on coupled in motion weighing on the "Railweight" track scale on the Western Maryland Railroad at Baltimore, Maryland in November, 1964. The study was conducted in accordance with a design prepared by the Operations Research Section, Computer Sciences Department, IIT Research Institute in order to take full advantage of modern statistical procedures. The test train consisted of 19 cars and one buffer car. Four of the cars weighed approximately 50,000 lb; four, 100,000 lb; four 150,000 lb; four 200,000 lb; and three, 250,000 lb. Sixteen runs were made with coupled in motion weighing with a different sequence of cars for each run, pulling the cars over the scale. Four weighings of the 19 cars were made on a nearby single draft static scale and four on the Railweight scale with two draft static weighings. The significant findings were: (1) No effect was indicated of the position of the car in the train or the weight of the preceding car. (2) A bias of approximately 20 lb per 25,000 lb of succeeding car weight was indicated. (3) The statistical analysis indicated that approximately 95 percent of the weighings on the Railweight scale coupled in motion would have a deviation of less that 320 lb from the true car weight; for the single draft static scale, less than 160 lb. A graphical analysis confirmed these values in that 94 percent of the weighings on the Railweight scale coupled in motion were less or exceeded the 320 lb deviation by only about 10 lb. From the graphical analysis the single maximum deviation for the Railweight scale coupled in motion weighing was 580 lb and for the single draft static scale, 150 lb. (4) No relation was found between the amount of deviation and the car weight on either scale; i.e., the amount of deviation in pounds was as much on the 50,000 lb cars as on the 250,000 lb cars. (5) The average weighing time per car was reduced from 2 min, 13.5 sec on the single draft static scale to 9.4 sec on the Railweight coupled in motion scale. Additional savings in time in coupled in motion weighing would depend upon local circumstances and might include the time required to take cars to and from the scale for static weighing, bleeding the air before weighing and recoupling the air hose after weighing, per diem, etc. (6) In the first ten test runs before the weights were affected by rain, the total Railweight coupled in motion weight for the 19 test cars in a test run varied from a maximum of 2,750,720 lb to a minimum of 2,748,080 lb, a difference of 2,640 lb. Increase in recorded weight related to the weight of the succeeding car. The significant conclusions from the study are given in the statistical analysis, pages A-5 and A-6, and need not be repeated here.

  • Supplemental Notes:
    • Conducted under sponsorship of AREA Committee 14 - Yards and Terminals.
  • Corporate Authors:

    Association of American Railroads Research Center

    3140 South Federal Street
    Chicago, IL  United States  60616
  • Publication Date: 1965-9

Media Info

  • Features: Appendices; Figures; Tables;
  • Pagination: 21 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00095872
  • Record Type: Publication
  • Source Agency: Association of American Railroads
  • Report/Paper Numbers: ER-63
  • Files: TRIS
  • Created Date: Jul 24 1975 12:00AM