17. Reduction in manufacturing cost of C/C composite pantograph contact strips and clarification of their wear limit

C/C (carbon fiber reinforced carbon) composite pantograph contact strips have self-lubricating property, resistance to heat, high strength and toughness. Meanwhile, since they contain a large percentage of costly carbon fiber, they are more expensive than conventional carbon contact strips. Consequently, railway operators have been demanding solutions to reduce the usage cost, i.e. price per usable thickness of the C/C composite contact strips.

To meet these demands, RTRI has developed a C/C contact strip which is 20% cheaper to produce by halving the content of the carbon fiber and by simplifying the manufacturing process with a “Preformed Yarn” technique to form a C/C substrate. Material test results confirm that the developed lower-cost C/C contact strips satisfy all the necessary criteria, such as flexural strength. The lower-cost C/C contact strip showed almost same level of wear resistance as existing strips in wear tests on an actual pantograph (Fig. 1).

Although the wear limit (minimum allowable thickness for use) for C/C contact strips is also an important factor affecting the usage cost, it has not been clarified so far. Bolt-fastening force and strength of worn contact strips were taken into consideration to determine the wear limit. Axial bolt force measurements with worn C/C contact strips were conducted to verify changes in bolt-fastening force due to wear. Bending tests with worn C/C contact strips on a pantograph head were also performed to determine the minimum allowable thickness from the view point of durability. The results clarified that the wear limit for the C/C contact strips should be more than 6mm at the bolt-fastening position, and 4mm elsewhere on the strip.

The combined reduction in manufacturing costs and wear limit clarification made it possible to cut usage cost of these strip by 50%, matching the cost of conventional carbon contact strips (Fig. 2).