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The Dangers of Train Yards, Through the Eyes of Railroad Employees

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Re: The Dangers of Train Yards, Through the Eyes of Railroad Employees

#61

Post by LoSboccacc »

TylerE wrote: post #31
adrianN wrote: post #25

Earlier quoted context omitted.

You'd have to upgrade all the rolling stock as well. That's not always possible, for technical or financial reasons.

The locomotives, not all the rolling stock. I'm not saying it wouldn't be hard/expensive, but it seems better to spend money on things that will be useful for decades rather than stopgaps that just kick the can a little further up the road.

And not all locomotives, only the new one that reach speed where the signal is not visible in the given timeframe.

Re: The Dangers of Train Yards, Through the Eyes of Railroad Employees

#62

Post by LoSboccacc »

ythn wrote: post #60
kposehn wrote: post #20

Earlier quoted context omitted.

A 30,000 ton ore train in Brazil will take about that long to stop, due to the nature of that weight strung out over 2.5 miles of distance. That said, I think an emergency stop (air loss) would stop it faster.

> A 30,000 ton ore train in Brazil will take about that long to stop, due to the nature of that weight strung out over 2.5 miles of distance. I once learned in a physics class that weight has nothing to do with the stopping distance, but rather the steel on steel friction coefficient.

Weight and ground pressure cancel each other out in the friction equation. The issue is where all that heat goes. Heated brakes will fade, glaze, fail, break, burn or a combination of the above, so there are limits on how much braking force you can apply to wheels

Re: The Dangers of Train Yards, Through the Eyes of Railroad Employees

#63

Post by DC-3 »

donarb wrote: post #26
sandworm101 wrote: post #13

Earlier quoted context omitted.

>> 5mph would take nearly 1000' to bring to an "emergency" stop. That seems far fetched. 1000' is a long way at 5mph. The number of engines doesn't matter. Each car has its own brakes in an emergency. Cut pressure in the line and every car will brake itself. Perhaps they meant situations involving hills, not uncommon for ore trains heading from mines.

You don't want to lock up the wheels in an emergency. Locked wheels will skid on the rails, creating flat spots on the wheel. Later, if not repaired, the rotating wheel can hammer the rail at the flat spot, causing the rail to break.

It's an emergency. Who cares about flatspotted wheels? Parts can be replaced.

Re: The Dangers of Train Yards, Through the Eyes of Railroad Employees

#64

Post by Animats »

21 wrote: post #54
sandworm101 wrote: post #53

Earlier quoted context omitted.

Electricity wouldn't scale. Solenoids on each brake system would take current. Adding new cars would increase the load on whatever is providing that current. To ensure that cars could be swapped in and out, the cables on all cars would have to be large enough to provide current for even the longest train. Air brakes, once pressurized, don't take much to maintain. Relatively small pipes work on even very long trains.…

I meant electricity just for the triggering, not for the action. A small electric signal could for example open a valve in the air tube. Thus all cars would break at the same time.

Passenger trains have used electropneumatic brakes for decades. A few freight trains use them. Trains with distributed power (locomotives spaced along the train) have sectionally controlled braking. Sometimes, there are "repeater air cars" with air compressors and a radio link to the locomotive. Those are used mostly on flat terrain, where more braking power is needed but not more engine power.

Re: The Dangers of Train Yards, Through the Eyes of Railroad Employees

#65

Post by marvin »

ythn wrote: post #60
kposehn wrote: post #20

Earlier quoted context omitted.

A 30,000 ton ore train in Brazil will take about that long to stop, due to the nature of that weight strung out over 2.5 miles of distance. That said, I think an emergency stop (air loss) would stop it faster.

> A 30,000 ton ore train in Brazil will take about that long to stop, due to the nature of that weight strung out over 2.5 miles of distance. I once learned in a physics class that weight has nothing to do with the stopping distance, but rather the steel on steel friction coefficient.

There are lots of assumptions in that entry-level physics exercise, for instance that all the energy can be dissipated without destroying anything (that the brakes are able to utilize the full friction available) and also that the entire weight of the vehicle rests on top of the wheels performing the braking.

Re: The Dangers of Train Yards, Through the Eyes of Railroad Employees

#66

Post by ant6n »

lbriner wrote: post #6

Because of signal sighting rules in the UK, we experienced a lot of trouble upgrading lines to higher speed. All of a sudden, that signal that you could see for 10 seconds could now only be seen for 8 due to a bridge or whatever. Muchos dollars relocating signals and in some places not being able to increase the line speed at all. Boring but very real reasons why we "can't just update things"

How about using some sort of advance signal?

Re: The Dangers of Train Yards, Through the Eyes of Railroad Employees

#67

Post by cup-of-tea »

code_duck wrote: post #23
bigjimmyk3 wrote: post #16

Earlier quoted context omitted.

A train's emergency braking system is somewhat sacrificial (using it can damage engines, cars, etc.) so you're probably correct. I'd say that in either case, most people who are not "train people" will dramatically underestimate the required stopping distance. The mass of a fully loaded train is surprisingly large.

Car drivers tend to underestimate the amount of space it takes for a semi to stop. Heck, every time I load up my car or attach a trailer, it takes time to become accustomed to the decreased braking performance. Drivers likely could not give an accurate estimation for how many feet it takes to do anything on the road, such as come to a stop in an SUV going 50. Given the extreme mass of a cargo train, I wouldn't be sur…

Car drivers underestimate the amount of space it takes a car to stop.

Re: The Dangers of Train Yards, Through the Eyes of Railroad Employees

#68

Post by grkvlt »

code_duck wrote: post #23
bigjimmyk3 wrote: post #16

Earlier quoted context omitted.

A train's emergency braking system is somewhat sacrificial (using it can damage engines, cars, etc.) so you're probably correct. I'd say that in either case, most people who are not "train people" will dramatically underestimate the required stopping distance. The mass of a fully loaded train is surprisingly large.

Car drivers tend to underestimate the amount of space it takes for a semi to stop. Heck, every time I load up my car or attach a trailer, it takes time to become accustomed to the decreased braking performance. Drivers likely could not give an accurate estimation for how many feet it takes to do anything on the road, such as come to a stop in an SUV going 50. Given the extreme mass of a cargo train, I wouldn't be sur…

> how many feet it takes to do anything on the road, such as come to a stop in an SUV going 50

Isn't knowledge of stopping distances for vehicles at various speeds and different road surface conditions a requirement for obtaining a driving license? (At least, in the UK I believe it is, and I think the Highway Code tables probably over-estimate these distances for safety purposes)

Re: The Dangers of Train Yards, Through the Eyes of Railroad Employees

#69

Post by ant6n »

UnderProtest wrote: post #40
lawnchair_larry wrote: post #5

Earlier quoted context omitted.

This is an old urban legend. Feel free to Google it, and you will see everyone who has worked near trains knows a guy who knows a guy who this exact thing happened to. Edit: https://www.snopes.com/fact-check/the-last-kiss/

It's also absolutely real and has been fairly common. https://en.wikipedia.org/wiki/Crush_syndrome It's hard to understand why Snopes has this marked as a myth. The specific anecdote structure with the wife showing up is clearly a meme but that doesn't make it a mythical type of event. We're much better at dealing with this situation in developed countries now. It's still a serious hazard. Around the turn of the 20th…

This seems to involve patients being 'crushed' for an extended period of time. Like more than 15 minutes, where tissue dies and basically creates a poison, that enters the blood stream when the patients get released.

That doesn't seem to describe a situation like the ggp was talking about.

Re: The Dangers of Train Yards, Through the Eyes of Railroad Employees

#70

Post by grkvlt »

21 wrote: post #37
adrianN wrote: post #28

Earlier quoted context omitted.

It takes a while until the brakes in the last car start braking because the pressure doesn't drop everywhere simultaneously.

Why not also use an electric cable? Sounds like a problem, since the first car will have to "resist" the rest of the train.

Because the pneumatic system is fail-secure, since a break in the line causes the pressure to drop and brakes to engage. I suppose you could have a system which required constant power to hold the brakes open, and loss of power would cause them to engage, which would have the same result?
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