Railcar Stability: How Do They Stay Upright on a Narrow Track?

[ScienceGuyOrg]

Hello, new to this forum. My work is in computers but I have hobbies that are related to physics; model airplanes, water rockets, solar model cars, and kites. I have a science related website << link deleted by berkeman >> (non-profit), but my question which relates to an article I am working on, is how do rail cars that sit on a track 5 feet wide and are much taller, not tip over going around a bend?

I know the wheel trucks are very heavy but it still apears there can be a lot of weight up high like in an autorack or stacked containers.

Thanks for any replies,

Bill Kuhl

 

[minger]

It's basically gravity. If you draw a free body diagram, there is the center of mass, with gravity acting -vertically, and any side loads acting horizontally. Each, then produces a moment about each wheel.

So long as the moment created by the weight is greater than the inertial load, you're good. A quick google shows a somewhat humerous solution at cow-tipping.
http://emweb.unl.edu/Mechanics-Pages/Matt-Semke/The Statics of Cow Tipping.htm

 

[ScienceGuyOrg]

I like your example! clever

 

[turbo]

I like your example! clever

And, BTW, rail cars DO tip over. The curves in all tracks cannot all be approached with the same speeds. There are some small, relatively sharp curves in switching yards that have to be negotiated at a crawl, though it would be very expensive to have to travel those speeds on long lines or spurs.

Rails that were laid many years ago might not have been bedded and tied in such a way as to support the heavier engines and freight cars that we use today. As a result, the tracks and beds have to be repositioned and re-compacted. In the old days, reconditioning the lines was done by hand, with crews of tampers and gandy-dancers. Google on "Tamp 'em up Solid" by Ry Cooder.

 

[SystemTheory]

Also, as in speedways and highways, when properly designed for a rated speed the tracks are banked. There was a passenger train in England designed to tilt the cars into turns so it could run on older tracks, according to a history channel show.