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This was George Westinghouse's big invention from the 1860s: https://en.wikipedia.org/wiki/Railway_air_brake https://en.wikipedia.org/wiki/Railway_air_brake It

by tlb 7y ago

This was George Westinghouse's big invention from the 1860s: https://en.wikipedia.org/wiki/Railway_air_brake https://en.wikipedia.org/wiki/Railway_air_brake It'd be great if you could use a spring to apply the brakes and an air cylinder to hold the brakes open. But the force needed to apply brakes is too much for springs, so it uses an air cylinder to apply the force. There's a complicated system where under normal conditions, pressure in the hose running the length of the train is fed into a reservoir in each car. When the pressure in the line drops (either a disconnect or the engineer hitting the brakes), a valve connects the brake cylinders to the reservoir and the air pressure applies the brakes. So yes, if you leave some isolated rail cars sitting there with the air brakes applied, the pressure will slowly leak away over hours or days and the car will start rolling.

deleted 7y ago
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jacobolus 7y ago
Apparently before air brakes dudes would run around on top of the moving train (even in rain/snow) manually cranking the brake on each car whenever the train needed to stop. https://en.wikipedia.org/wiki/Brakeman https://en.wikipedia.org/wiki/Brakeman
NikkiA 7y ago
One of the advantages of the british vacuum brake system was that it passively failed into a 'brakes on' state because of atmospheric air pressure. However, this was about the ONLY major advantage it had, and decades of pro-westinghouse propaganda against it blew the significance of all of the disadvantages* up to be greater than the advantage of fail-safe, and we switched to the westinghouse system. * One of the biggest claimed disadvantages is the fact that vacuum brakes are less effective as you increase altitude, this is a HUGE disadvantage to operating vacuum brakes in the US where a large amount of rail traffic is at altitude, but in the UK where our highest peaks are 3000' and we don't generally run railways to the peaks of those hills, it's almost a non-issue.

by tlb 7y ago

deleted 7y ago

[deleted]

jacobolus 7y ago

Apparently before air brakes dudes would run around on top of the moving train (even in rain/snow) manually cranking the brake on each car whenever the train needed to stop. https://en.wikipedia.org/wiki/Brakeman https://en.wikipedia.org/wiki/Brakeman

NikkiA 7y ago

One of the advantages of the british vacuum brake system was that it passively failed into a 'brakes on' state because of atmospheric air pressure. However, this was about the ONLY major advantage it had, and decades of pro-westinghouse propaganda against it blew the significance of all of the disadvantages* up to be greater than the advantage of fail-safe, and we switched to the westinghouse system. * One of the biggest claimed disadvantages is the fact that vacuum brakes are less effective as you increase altitude, this is a HUGE disadvantage to operating vacuum brakes in the US where a large amount of rail traffic is at altitude, but in the UK where our highest peaks are 3000' and we don't generally run railways to the peaks of those hills, it's almost a non-issue.