Investigation of Rack and Pinion Alignment of the Cass Street Movable Bridge in Joliet, Illinois

Details

• Creators:
  Hahin, Christopher
• Corporate Creators:
  Illinois. Department of Transportation. Bureau of Materials and Physical Research
• Corporate Contributors:
  United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  20° Pressure Angle Bascule Bridges Bridges Involute Stub Tooth Misalignment Movable Bridges Pressure Rack And Pinion Wear
• Publication/ Report Number:
  FHWA/IL/PRR-129
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States ; Illinois
• Edition:
  Final Report, November, 1997 - May, 1998
• Corporate Publisher:
  Illinois. Department of Transportation. Bureau of Materials and Physical Research
• Abstract:
  The Cass St. Bridge is a rolling lift bascule bridge that spans the Des Plaines River, which divides the City of Joliet. The bridge has an average daily traffic (ADT) of 15,500 vehicles/day, and experiences approximately 2,000 lifts per year for commercial barges and casino boats. The racks and pinions, which are essential elements of the drive mechanism for lifting and closure of the bridge, have experienced severe wear in recent months due to misalignment. Wear is ascribed to minor track non-parallelism, insufficient pinion bearing collar bolting, and high rack and pinion tooth loadings. Rack tooth loadings at bridge opening are twice the AASHTO allowable tooth loadings. This report describes the non-standard stub teeth used in the original 1931 design and the retrofit of 1986, the verification of rack and track alignment by survey and gravity methods, and recommendations for realignment. Recommendations include: (1) exchanging unused rearward rack elements with worn forward elements; (2) leveling rack elements; (3) repositioning pinion bearing collars; (4) determining clearances and alignment reference marks and dimensions for final positioning and future monitoring; (5) future modification to shrink-fit the pinion gear bearing to the existing built-up structural plates instead of reliance on a small bolted collar; and (6) increasing rack face width.
• Format:
  PDF
• Funding:
  HR-25-104-98-1
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:d0b256cb577d50d7c1ff8dd783b6cbbad87408e928787f386c02ab2377257c3c03175f2301c0af65cc077ae004d78cccb284f2543aa15b4d43c7ce0cc4563252
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/87557/dot_87557_DS1.pdf
• File Type:
  [PDF - 1.01 MB ]