AboutChris Holliday Expertise Questions related to contemporary passenger rail vehicles and their technology, including subway, light rail, commuter and intercity rolling stock. Includes all vehicle systems and features along with integration of the vehicles into the general railroad system.
Experience I have over 22 years of experience in the passenger rail vehicle business as both an engineering manager at a car builder and as a provider of engineering services to commuter railroads and transit agencies in the US. I have worked to apply the latest technologies to passanger rail equipment. I have worked with leaders in our industry to develop and establish Standards and Recommended practices.
Expert: Chris Holliday Date: 4/10/2008 Subject: Railcars going round a curve
Question Hi Chris
What is the relative movement between two adjacent say 65 ft railcsrs when going around a typical curve and the worse curves Is there an eqn which describes this change in intercar gap
How do railways deal with overhanging deck level loads using std type flattop cars
Answer Believe it or not, this issue is typically dealt with as a matter of geometry using a relatively unsophisticated approach to analysis. There are no equations per se which address your question in one simple step.
Basically what is done is that a plan-view CAD drawing of two cars coupled together is developed. The cars are constrained as if on their trucks, with allowances for maximum tolerance of the range of relative movement between the moving parts of this system. These moving parts would include:
wheels with respect to to rails,
wheelsets with respect to truck frames,
truck frame with respect to the car body,
draft gear/coupler shank with respect to car body
couplers with respect to each other
Then the two virtual cars are manipulated on the computer as if through minimum radius curves, cross-overs and vertical curves and if interferences are found, changes are made to correct the issue.
You refer to an intercar gap. By this, I am guessing you mean the minimum distance between of any part of the two coupled cars as they move through transitions into and out of curving track. The worst case of end of car displacements are often found in traversing tight crossovers or switches, rather than simple curves. In this situation, the relative displacements between cars ends is most extreme. It is probably possible to use pure geometric equations to describe the motion of any given point along the ends of the cars. However, the graphical geometric approach described above is more useful.
For loads overhanging the end edges of flat cars, depending on what you know about the minimum clearance between cars as they maneuver through curves as derived using the methods suggested above, you might want to add the extents of these loads to the image of the cars and do this analysis to see of there would be interference.
