Railroad Thread

[3WE]

Adding crap to the discussion.

I was joking, as air pressure actually applies the brakes, but zero PSI in the line triggers braking valves to send pressure in tanks on the cars to the brakes. (Others have said this).

I agree with J that there’s roughly 90 PSI available.

If brakes are applied and released repeatedly, the on-car reservoir can be depleted.

There’s one brake shoe per wheel.

I witnessed one emergency stop when a hose failed. It wasn’t terrible in terms of performance, but conversely, it’s slower than a greyhound bus stopping gently. It wasn’t the “mile” that is so often mentioned. On the other hand, I think long and “steep” mountain grades can result in runaways if not managed.

[Gabriel]

2) The significant weight of the train (about 286,000 lbs or 130,00 kg per car) represents a lot of momentum.

It is also a lot of normal force, so the braking acceleration should not be affected... unless the weak link is not the friction between the wheels and the rails but between wheels and the brake pads, which would make no sense (to me, an aeronautical engineer).

[3WE]

I think the wheels generally turn during emergency braking, making the brake-pad-wheel the weaker link, BUT wheel lock/rail slippage is not_unheard of.

One other trivia (again, ass-hat outsider blathering). Because of the time it takes to “empty” the air line, the on-car brake valves can detect a sudden PARTIAL reduction in pressure and trigger emergency/full braking for a faster response.

[J]

I have only a limited familiarity on the issue but will note that yes, the brake system is designed not to slide the wheels. if they were to slide, they would develop costly flat spots. Sometimes you will hear a train rolling by with some wheels thumping loudly. Typically, those flat spots are caused by someone dragging a car around a yard with the mechanical hand brake still applied.

Some cars have "load / empty devices" that will allow a higher brake shoe force from the pneumatic brakes when the car is loaded.

Most locomotives also have dynamic brakes that turn the traction motors into generators to slow the train. The resulting electricity is turned to heat in large grids cooled by fans. Many electric locomotives can redirect this excess power back into the overhead wires.

Here is a video showing such grids glowing red hot.

https://www.youtube.com/watch?v=Gy4DCQoFYDI

[Gabriel]

In any case, having a gazillion ton vehicle with a gazillion wheels and a gazillion brakes and have it slow down at 0.5 MPH per second at best is either stupid, or bad engineering, or there is something wrong with the condition of the brakes and people don't care.

It is so ridiculous that it defeats my imagination to understand how could this be the case.

And J, locking the wheels may be costly for everyday braking, but for emergency braking when an oil train is about to crash against a grain train and catch fire and spill an obscene lot of oil causing a huge environmental impact, believe me it is pennies.

[elaw]

To be fair, a lot of people have experimented with alternate means of stopping trains, like putting buses or tractor-trailers in front of them, and it never seems to work very well.

[3WE]

In any case, having a gazillion ton vehicle with a gazillion wheels and a gazillion brakes and have it slow down at 0.5 MPH per second at best is either stupid, or bad engineering, or there is something wrong with the condition of the brakes and people don't care.

It is so ridiculous that it defeats my imagination to understand how could this be the case.

And J, locking the wheels may be costly for everyday braking, but for emergency braking when an oil train is about to crash against a grain train and catch fire and spill an obscene lot of oil causing a huge environmental impact, believe me it is pennies.

Evan (yeah you are being somewhat bold).

First of all, there’s a very powerful “it’s always been this way” and some years ago rail was often a primary transportation (roads & trucks were not_what we have today.).

Secondly, braking has never been better. Brakemen used to run down gang planks turning brake wheels one car at a time.

It is a fact that train braking is not_that strong.

You and this forum aren’t going to change that.

Additional spewing: emergency braking is kind of bad and can derail trains. If the air dumps at the front, you have lots of braking up front scrunching the train together.

I think engineers (train drivers) are limited to a 30 PSI reduction (to 60 PSI) resulting in a delta of 30 PSI for brake actuation.

And…you can get MSTS if you want to try it out: my understanding is that there’s a fair bit of mechanistic models in MSTS.

[Gabriel]

Evan (yeah you are being somewhat bold).

The grain train lost 28 mph in 38 seconds of emergency bake application.
The crude oil train lost 1 MPH in 8 seconds of emergency brake application.
THIS is bold.

Brakemen used to run down gang planks turning brake wheels one car at a time.

The Westinghouse Air Brake Technologies Corporation was founded on September 28, 1869 by George Westinghouse in Pittsburgh, Pennsylvania. Earlier in the year he had invented the railway air brake in New York state.

The first form of the air brake consisted of an air pump, a main reservoir (pressure vessel), and an engineer's valve on the locomotive, and of a train pipe and brake cylinder on each car. One problem with this first form of the air brake was that braking was applied to the first cars in a train much sooner than to the rear cars, resulting in shocks and damages when the rear cars bunted against the cars ahead of them.

In 1872, George Westinghouse invented the automatic air brake by inventing the triple valve and by equipping each car with its own air cylinder. Air pressure is maintained in the auxiliary reservoirs and in the train pipe at all times when the brakes are not applied. An equilibrium of air pressure is maintained in the train pipe and in the auxiliary air cylinders.

In the 1930s, the company developed a wheel slide protection system called Decelostat that worked with its air brake.
Decelostat is a wheel slide protection system developed by Westinghouse Air Brake Company that is used in railroad cars to prevent over-braking that causes wheel-slide, a condition of reduction in friction between train wheels and rails. This low wheel/rail adhesion condition reduces braking performance and causes damage to wheels (wheel spalling and wheel flat) and the rails.
That is, ABS / Antiskid.

It is a fact that train braking is not_that strong.

The grain train lost 28 mph in 38 seconds of emergency bake application.
The crude oil train lost 1 MPH in 8 seconds of emergency brake application.
THIS is NOT "not_that_strong". This is THAT WEAK. A coefficient of 0.1 would more than double the better of those and the friction between the rail and wheels would at last double 0.1.
In the case of the crude-oil train that is essentially no braking whatsoever.

It's not like we need to develop new materials with more traction. The coefficient of friction is already there.
Anything less than 4 mph/s is horribly bad braking, and rules and regulations should require trains have better than horribly bad braking.

(Bold is as bold does, and I can be a bold bald guy)

[Gabriel]

[/post delete function]

[Gabriel]

To be fair, a lot of people have experimented with alternate means of stopping trains, like putting buses or tractor-trailers in front of them, and it never seems to work very well.

Yeah, it's called conservation of momentum.

[3WE]

As Flyboy once told Evan, if you want to affect something, go into the industry. Proclamations on internet fora (especially train advice on an obscure aeroplanie forum) don’t do much.

[3WE]

From YouTubez and rail perving, it’s been my observation that dynamic brakes aren’t half bad at slowing a train. Conversely it’s one unit working to stop 30 to 40 cars or more so it can’t be THAT effective…you got 6 axles of braking vs 160 axles of momentum. 16:1, roughly.

[Gabriel]

From YouTubez and rail perving, it’s been my observation that dynamic brakes aren’t half bad at slowing a train. Conversely it’s one unit working to stop 30 to 40 cars or more so it can’t be THAT effective…you got 6 axles of braking vs 160 axles of momentum. 16:1, roughly.

What on Earth are you talking about? I have no clue what is that dynamic brakes thing you mention. But trains have brakes in all the wheels of all the locomotives and of all the cars. If you have 160 axles you have 320 brakes (and 640 brake shoes).

[3WE]

Busted. You are not_a train perv.

J mentioned dynamic brakes above- check out his YouTube link.

Locomotives can “reverse” the traction motors and generate electricity which is burned in giant heater grids (with cooling fans) (In electric passenger rail this electricity is often dumped back into the electric grid kind of like electric cars that do electric braking.)

It’s not that special for quick stops, but reduces friction brakes wear and heat. It also needs care because cars get bunched up.

It’s called dynamic braking because it only works when you are moving (and because the motors become dynamos).

Maybe not rocket surgery, but still kind of cool.

[3WE]

There was a classic runaway train Swiss cheese automation fueled derailment in CA.

First, the dispatcher didn’t know what he was doing, fudged on car weights and maybe even sent the train without enough locomotives.

The train had front and rear locomotives- not_electronically linked, but crews and radios.

They noted the train was running away.

The crew of the rear locos, went emergency on their own.

This caused an automatic shutdown of all dynamic brakes. Normally that’s wise to prevent too many crazy braking forces, but in this case, Without the additional dynamic braking, the train ran away and crashed.

I think the engineers could have over ridden something to get the dynamic brakes back, but cue Evan on more training and oversight as well as “what’s it doing now?”

Search Runaway train San Bernardino on YouTube

Oh yeah, I missed a an additional piece or two of Swiss cheese…(watch the documentary).

Ironing, this happened on the San Gabriel mountains.

[Gabriel]

There was a classic runaway train Swiss cheese automation fueled derailment in CA.

First, the dispatcher didn’t know what he was doing, fudged on car weights and maybe even sent the train without enough locomotives.

The train had front and rear locomotives- not_electronically linked, but crews and radios.

They noted the train was running away.

The crew of the rear locos, went emergency on their own.

This caused an automatic shutdown of all dynamic brakes. Normally that’s wise to prevent too many crazy braking forces, but in this case, Without the additional dynamic braking, the train ran away and crashed.

I think the engineers could have over ridden something to get the dynamic brakes back, but cue Evan on more training and oversight as well as “what’s it doing now?”

Search Runaway train San Bernardino on YouTube

Oh yeah, I missed a an additional piece or two of Swiss cheese…(watch the documentary).

Ironing, this happened on the San Gabriel mountains.

Ok I didn’t know it was called dynamic braking.

Anyway, dynamic braking or not, non-locomotive cars are surely still fitted with brakes, right? RIGHT?

[elaw]

Something I thought of re braking... take a look at this (what I think is typical for the USA) attachment of a railroad rail to a tie:


The rail is restrained vertically by lying on the tie (downward) and the spike (upward, in case gravity suddenly stops working). And it seems pretty well restrained laterally. But longitudinally, not so much. I wonder if under the right circumstances, train brakes being more effective could make the rail move fore-and-aft?

[3WE]

Anyway, dynamic braking or not, non-locomotive cars are surely still fitted with brakes, right? RIGHT?

The general discussion is braking & effectiveness.

Trains have four “systems”

-Air-powered friction brakes on cars.

-INDEPENDENT air-powered friction brakes on the locomotives

-Dynamic brakes

-Mechanical-actuation of the friction brakes by a wheel on each car (used for parking)

The whole train brakes in emergency is fairly effective by my adjectives- you boldly disagree. I do concur that if a school buss full of nuns and orphans pulls onto the tracks, it’s not-a go around, but a go through. If you can write a strongly worded letter and change anything before we did died, kudos. RRs are pretty damn extreme about tradition, and the working hours thing is downright insane…it would be good to fix that, too.

The independent brakes are apparently important, but we will never know the feeling of pulling a handful of brake levers with 40,000 tons in tow. (Supposedly it’s important to gently compress the train to help it get started, later.). It would seem to be a quick red-hot, melt, fall off if this was used to stop a full train going at a high speed or down a long grade.

Dynamic brakes: In 3BS’s opinion, they’re pretty effective, acknowledging that they are like spoilers. You can burn off a lot of energy and MANAGE speed, but certainly not_good to effect the final, full stop. They were cited as possibly preventing the Saint Gabriel crash.

Get out of the sterile bubble and ride your bike to some train tracks, watch some YouTubez…and don’t call me Shirley.

[3WE]

I wonder if under the right circumstances, train brakes being more effective could make the rail move fore-and-aft?

It’s firmly connected to miles of rail each direction so it can’t slide too much.

[Gabriel]

Something I thought of re braking... take a look at this (what I think is typical for the USA) attachment of a railroad rail to a tie:


The rail is restrained vertically by lying on the tie (downward) and the spike (upward, in case gravity suddenly stops working). And it seems pretty well restrained laterally. But longitudinally, not so much. I wonder if under the right circumstances, train brakes being more effective could make the rail move fore-and-aft?

The normal force between the train and the rails also act between the rails and the ties, and between the ties and the floor.
All of them have coefficients of friction too (possibly better than between the steel rail and steel wheels).
And then, if the friction alone was not sufficient (which very likely is), then you have compression of the rail ahead of the train and tension of the rail behind of the train. That should suffice.

[Gabriel]

Anyway, dynamic braking or not, non-locomotive cars are surely still fitted with brakes, right? RIGHT?

The general discussion is braking & effectiveness.

That may be YOUR general discussion. Not mine.

The whole train brakes in emergency is fairly effective by my adjectives-

What are your adjectives, again? The ones that reconciliate that with:

The grain train lost 28 mph in 38 seconds of emergency bake application.
The crude oil train lost 1 MPH in 8 seconds of emergency brake application.

[J]

Railroad brakes do not immediately retard the train - just like a ship's propeller thrown into reverse does not immediately stop a ship. We're dealing with significant weight and momentum. Perhaps someone can explain what would happen if the track was mounted on a conveyor belt.

A person mentioned the potash train derailment in San Bernardino, CA back in 1989 that might be instructive.
https://www.ntsb.gov/investigations/Acc ... AR9002.pdf

NTSB will point to dynamic brake failure on the lead locomotives and the manned helpers and the something like 3000 additional tons of lading, but a major cause was the engineer making a series of brake reductions (remember, reduce the pressure in the train pipe and the reservoirs on the cars provide compressed air to apply the brake shoes to the individual wheels.)

The train was several thousand tons heavier than the crew's paperwork. Each time the train would slow a little but soon start to accelerate again as it descended the hill. The link to the report does not allow one to search for key words so I can't easily search for the prevailing speed limit at that time. I recall it was something like 20 or 25 mph. The train was not holding its speed (heavier load and defective dynamic brakes on some of the locomotives) and I recall that after making a 25 lb. reduction the train once again accelerated and so the engineer placed it in emergency. At that time the speed was too great for the brakes to regain control over the speed and the train accelerated to close to 100 mph before derailing on a curve. The brakes were working but the wheels on the cars got so hot they turned blue, and the NTSB commented on how the steel surface of the wheels liquified almost like a lubricant.

Today, if a train is not holding its speed with an 18 lb. reduction, the crew is instructed to immediately go to emergency and stop.

Fun fact, about 2 weeks after the derailment, a gasoline pipeline buried along the right of way ruptured and sprayed gasoline into the air until it found an ignition source. The pipeline operator noticed a pressure drop and turned off the pumps but there was no check valve in the pipe, so the gasoline continued to flow down the hill and out of the pipe until it was depleted.

[Gabriel]

It's a pity that the NTSB did not analyze why these trains' braking was so poor.

[3WE]

What are your adjectives, again?

The regulators don’t give a flying nor rolling-on-rails phugoid what my adjectives are, what you think of my adjectives, what your adjectives are nor what you think about the general performance of train brakes.

Sure, in a perfect world, trains would brake much better, and I’d have no problem with that.

In the derailment + collision, I am betting that the brakes on both trains performed within approved ranges, thus no need for the “further analysis” you’d like to see.

I know you don’t like it, but bitching about my adjectives won’t fix it. Have you drafted your letter to the regulators yet? Will you refer them to this excellent thread for further recommendations?

As long as we’re providing liberal outsider advice, I always wondered if having the flanges an inch taller might reduce derailments…they really aren’t all that big…

[Gabriel]

In the derailment + collision, I am betting that the brakes on both trains performed within approved ranges, thus no need for the “further analysis” you’d like to see.

If not_you doesn't do the analysis, how does not_you know that they performed within approved ranges?
The analysis can be as short as "After the application of emergency braking, the grain train lost 28MPH in 38 seconds, a rate of almost 0.74 MPH/s which complies with the minimum established in FRR part 25.03 b iii of 0.000001 MPH/s"

I am starting to suspect that approved ranges don't exist.

If they do and this was within approved ranges, then the approved ranges are a disgrace.

Or, I may be wrong, approved ranges do exist, this almost_no_braking braking was within the approved ranges, and there is a valid and reasonable reason why that is ok. I'd love to learn about that.

The regulators don’t give a flying nor rolling-on-rails phugoid what my adjectives are, what you think of my adjectives, what your adjectives are nor what you think about the general performance of train brakes.

I know you don’t like it, but bitching about my adjectives won’t fix it. Have you drafted your letter to the regulators yet? Will you refer them to this excellent thread for further recommendations?

I apologize. I thought that this discussion forum was a forum to discuss.