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I assumed the brakes were applied unless air pressure was available. Same as truck / trailer brakes. In the article it references air pressure is required for t

I assumed the brakes were applied unless air pressure was available. Same as truck / trailer brakes. In the article it references air pressure is required for the brakes to be applied - is there a reason it can't be the other way around?

886 7y ago
hand brakes were applied, but only to the first 5 lead cars only. the engineer also used air brake, but it lost its pneumatic pressure after the engine got shut off. "Though exhausted after the journey, Mr. Harding took the laborious step of setting the mechanical hand brakes — a train’s version of an automobile parking brake — on the five lead locomotives, an equipment car and an empty boxcar. That was the first big mistake. Investigators calculated that Mr. Harding should have also secured the hand brakes on 18 to 26 of the tank cars before retiring to his hotel."
henvic 7y ago
New trains are like that. https://en.wikipedia.org/wiki/Railway_air_brake https://en.wikipedia.org/wiki/Railway_air_brake
- nerdponx 7y ago
  If the technology has been in widespread use since 1869, why would locomotives presumably made some time in the latter half of the 20th century not incorporate it?
  - betterunix2 7y ago
    https://en.wikipedia.org/wiki/Railway_air_brake#Limitations https://en.wikipedia.org/wiki/Railway_air_brake#Limitations
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
  [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.
phs2501 7y ago
Air pressure is required for the brakes to be applied, insofar as if you bleed all the air off the cars their brakes will release. However, air is stored in reservoirs on the cars, and once charged when the air pressure in the brake pipe that goes down the train is reduced below the reservoir pressure the brakes apply (by using air stored in the local reservoirs). As such, the brake pipe is simultaneously an air charging system and a signaling system. It's also fail-safe for normal operation since a train that breaks in two will come to a stop. Passively-applied brakes would break a ton of standard railroad operations which depend on cars rolling free, such as in "hump" classification yards which use in-track retarders to control speed, and in other situations such as "kicking" cars into tied-down cuts.

886 7y ago

hand brakes were applied, but only to the first 5 lead cars only. the engineer also used air brake, but it lost its pneumatic pressure after the engine got shut off. "Though exhausted after the journey, Mr. Harding took the laborious step of setting the mechanical hand brakes — a train’s version of an automobile parking brake — on the five lead locomotives, an equipment car and an empty boxcar. That was the first big mistake. Investigators calculated that Mr. Harding should have also secured the hand brakes on 18 to 26 of the tank cars before retiring to his hotel."

henvic 7y ago

New trains are like that. https://en.wikipedia.org/wiki/Railway_air_brake https://en.wikipedia.org/wiki/Railway_air_brake

nerdponx 7y ago
If the technology has been in widespread use since 1869, why would locomotives presumably made some time in the latter half of the 20th century not incorporate it?
- betterunix2 7y ago
  https://en.wikipedia.org/wiki/Railway_air_brake#Limitations https://en.wikipedia.org/wiki/Railway_air_brake#Limitations

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
[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.

phs2501 7y ago

Air pressure is required for the brakes to be applied, insofar as if you bleed all the air off the cars their brakes will release. However, air is stored in reservoirs on the cars, and once charged when the air pressure in the brake pipe that goes down the train is reduced below the reservoir pressure the brakes apply (by using air stored in the local reservoirs). As such, the brake pipe is simultaneously an air charging system and a signaling system. It's also fail-safe for normal operation since a train that breaks in two will come to a stop. Passively-applied brakes would break a ton of standard railroad operations which depend on cars rolling free, such as in "hump" classification yards which use in-track retarders to control speed, and in other situations such as "kicking" cars into tied-down cuts.