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https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

Diamond Ramping to Reduce Noise and Vibration

This paper describes how diamond crossings allow two rail lines to cross each other. However, the high magnitude and frequency of impact loads on the gaps in these crossings often result in shortened component lives, increased deterioration of the ballast layer and the subgrade, as well as substantial noise and vibration transmitted to both passengers and those who live close to the right of way. Capital Railway, a light rail transit system in Ottawa, Ontario, has two crossings with freight railroads. Transit system personnel noticed numerous shallow dents on the field side of some of the wheels. A careful inspection revealed that the cause of the dents was the impact of the wheels as they traveled over the gaps in the diamond crossings. Also noticed during the inspection were dents on the running bands as well. As an interim measure, Capital Railway introduced speed restrictions over the diamonds, which interfered with operations. The National Research Council of Canada’s Centre for Surface Transportation Technology (CSTT) was retained to develop a method that would decrease the vertical dynamic loading on the wheels while traversing the diamonds at track speed. CSTT designed a non-linear ramp which could be ground into the crossing frogs’ running surface just ahead of the crossing gap. This would allow the wheels on a light rail transit vehicle to unload as they traverse the gap reducing the dynamic load on both the wheels. The ramps were designed using a CSTT developed vertical vehicle/track dynamic model capable of modeling impacts. The model was used to analyze the dynamic behavior of vehicle and track and led to an optimum ramp design for the desired vehicle operating speeds. CSTT made before and after measurements of the wheels’ vertical accelerations. Tests on the un-ramped diamonds were done at speeds varying from 5 to 35 mph to monitor the effect on the vertical accelerations of the axles and to establish baseline against which to compare the accelerations after the ramps were installed. The acceleration tests were then repeated after the ramps were installed and fine-tuned. The speeds measured ranged from 15 to 30 mph. The results of the before and after measurements of vertical accelerations showed reductions of as much as 50% due to the installation of the ramps. In addition, the ramping has successfully allowed Capital Railway to increase speed across the diamonds. Although reducing wheel damage was the primary purpose for this project, it is clear that the reduced vertical accelerations also reduce noise and vibration from the impacts that would be generated then the wheels traverse the gaps on an un-ramped crossing diamond.

Language

  • English

Media Info

  • Media Type: Print
  • Features: Figures; References;
  • Pagination: 4p
  • Monograph Title: Rail Transit Conference Proceedings, 2005

Subject/Index Terms

Filing Info

  • Accession Number: 01002147
  • Record Type: Publication
  • ISBN: 1931594155
  • Files: TRIS
  • Created Date: Jul 19 2005 9:31AM