Quote:
Originally posted by ChrisH
Which explains why locomotive wheels are still cast iron. Actually it might have been in a railroad book that I found that little gem. Unfortunately I don't remember the reference.
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Actually the coefficient of friction of Cast Iron on Steel is 0.4. This is compared to the coeficient of friction of Steel on Steel which is 0.8. By comparison, some rubbers (neoprene, gum) can achieve a COF of 3.0 or more on most surfaces.
The real reason cast iron is used is that it won't deform (compared to steel). Steel can deform as much as 35% before it fractures, whereas cast iron will only deform less than 1%. This is a good thing when you want the wheel to stay round under all that weight. Also, cast iron as better vibration dampening than steel. Keeps everything from rattling as it goes over the many joints of the railroad tracks.