I have a question I would like to ask that came about as a result of something a friendof mine said. He tells me that train wheels have no friction against the rail and that is why they can move. I think about that and can only say that can't be right; how can anything move without friction to get it going (maglev and other trains like that not included)? SO, here's the question; are train wheels, like my friend says, frictionless against the rails? Thanks.
John
There is relatively low friction, but friction, nonetheless.
John Timm
To get an idea of the difference in friction, take your rubber-wheeler out on a stretch of level highway, take the speed up to 60mph and then apply hard (but not tire-squealing) brakes. You will stop in a few hundred feet. A freight train in the same configuration will take about 1.5 MILES.
If there was no friction between wheels and rail the term 'tractive effort' wold be meaningless. A hamster in a cage geared to a drive axle would be able to spin it while the locomotive remained at a stubborn standstill.
Chuck