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by smartscience 1755 days ago
To demonstrate this more fully, consider the case of having the wheel flanges on the outside, with the conicity of the wheels pointing the other way. Gravity would still tend to centre this arrangement, but I'm told that if you build such a system in practice, then it won't run nearly as smoothly.

(PhD was 'Residual stress in rails', for what that's worth. Judging from the profiles of the rails I saw, direct contact with the wheel flange plays a substantial role in keeping the train in place on curved track. But on roughly straight track, I'm satisfied that the argument about conicity applies).
1 comments
lostlogin 1755 days ago
> direct contact with the wheel flange plays a substantial role in keeping the train in place on curved track.

The London Underground has some lines that are horrifically loud. The squealing must surely be at dangerous sound levels. I’d always assumed it was the flange against the rail, and you appear to be confirming that?

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AnimalMuppet 1755 days ago
That's called "flange squeal". Yes, it can be ear-shatteringly loud.

But it mostly (totally?) happens on very tight curves. It shouldn't happen much or at all on gentler curves.

(Of course, this is circular, because I'm kind of defining "gentler" and "tight" based on whether they cause flange squeal. Still, there's a point - there is something like a threshold of curve tightness where flange squeal becomes much more probable.)

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idroveatrain 1754 days ago
It can happen on straightrail on an incline, too. It's hard to assess precisely what's happening in the locomotive, but under traction I believe the running gear will toe out, and align based on the path of least resistance. I believe this leads to the flange pressing, with immense force, against the rail. You also get a lot of wheel slip in this condition.

I surmised this running 2 motors up a 3%(?) grade with 20k ton gross at 10mph. It's about the only explanation I could come up with is that the running gear was twisting under the gravity and the energy being put down to work against it. It might also just be a stringline sort of effect dragging the motors to one side of the track and pressing the flange. Maybe one of the rail engineers will come holler at me for my poor trainhandling skills.

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