What keeps a train on the track?
Why Hacker News recommends it
HN links it as a great, surprising explanation whenever rail wheels, gauge or curves come up.
What it is
A short clip of Richard Feynman explaining how a train stays on its tracks, through the conical shape of wheels and how it handles curves without differentials.
Recommended by 1 HN commenters across 1 different months, 2019 to 2022.
What Hacker News said
Recommends frosted-flakes · 2020-06 · on “New slats make the Golden Gate Bridge sound like a David Lynch movie”
> unlike the cylindrical profile which again just steers with the flange basically rubbing against the edge of the railhead. That's crazy. That means that the wheels are actually slipping when going around a corner, because the wheels are all the same diameter. Unlike conical wheels, which are essentially self-steering. Here's a great explanation by Richard Feynman: [this video] How could the BART trains possibly have cylindrical wheels? Conical wheels have been used on trains for ages, so that's seems weird. But doing some research, it seems that, yes, they were cylindrical: > Queensland Railways, for its first hundred years, used cylindrical wheels and vertical rails. With non-inclined rails an
Cites JackFr · 2019-06 · on “The Space Shuttle and the Horse's Rear End (2000)”
Snopes rates it as partly true, and the author is a pedantic killjoy. It is broadly true that for 2000 years European vehicles matched their roads and adapting existing vehicles to new technology led to using axles that were the same size. Do other gauges exist? Of course. Are the true elements of this worth repeating? Sure. As an unrelated aside here’s Richard Feynman explaining why train axles don’t need differentials. [this video]
Cites texaslonghorn5 · 2022-07 · on “Why BART uses a nonstandard broad gauge”
[this video] (video of Feynman explaining how trains stay on the track) Is this it? I found it in my YouTube history. Or this one, which superimposes free body diagram (of forces) on the wheels to show how it is self stabilizing? [LINK]