Train Brakes: How do they work?

OGR Webmaster posted:

The little tea kettles at Disney World are a world apart from a modern Super-Power 2-8-4 or 4-8-4.

You didn't make that distinction when you wrote, "It is not an acceptable way to brake a steam locomotive under ANY circumstances."

smd4 posted:
When using the automatic brake with a train, both the car brakes and locomotive brakes are applied at the same time. When releasing the automatic brake, the brakes on the cars back off, but the brakes on the locomotive stay applied. Those brakes are "bailed off" using the independent (locomotive) brake lever.

 

Not exactly Steve.
Basically there are two sides to the control valve on the locomotive. The automatic and the independent. Each work separately in application and release.
When using the automatic brake, the brakes come on the cars and the engine through the automatic portion of the engine's control valve. When releasing the automatic brake the brakes release on the cars and the engine through the automatic portion of the engine's control valve. You can stop a locomotive by using just the automatic brake.
The independent brake portion of the engine's control valve allows only the engine brakes to be applied and released.
By pressing down or sideways (on desktop models) it allows the engine brake that the automatic brake valve applied to be released.
So, if only an automatic application has been made, the engine brakes that came on during that application can be released in two ways. Either release the automatic brake or press down on the independent handle and bail them off.
The only way to release an independent application is by the independent brake lever. (There is another way, but, I'm not going to tell how that works.)

Big Jim posted:

smd4 posted:
When using the automatic brake with a train, both the car brakes and locomotive brakes are applied at the same time. When releasing the automatic brake, the brakes on the cars back off, but the brakes on the locomotive stay applied. Those brakes are "bailed off" using the independent (locomotive) brake lever.

 

By pressing down or sideways (on desktop models)

I was talking about a steam engine. Never heard of one with a desktop model. We have a 6ET.

smd4 posted:

Big Jim posted:

smd4 posted:
When using the automatic brake with a train, both the car brakes and locomotive brakes are applied at the same time. When releasing the automatic brake, the brakes on the cars back off, but the brakes on the locomotive stay applied. Those brakes are "bailed off" using the independent (locomotive) brake lever.

 

By pressing down or sideways (on desktop models)

I was talking about a steam engine. Never heard of one with a desktop model. We have a 6ET.

Well,,,,,steam locomotives work exactly the same way! With the 6 or 8 brake schedules, the Engineer must push the independent brake valve handle away from him, in order to "bail off" any automatic air application. That said, if the independent is NOT "bailed off" the brakes will set-up on the locomotive, steam, electric, or diesel, until the automatic brake valve is placed in release.

Didn't  some use a penny or fuse' cap to keep the independent  permanently   bailed off?

How many used a air hose gasket as an egg cup  holder? 

OK, thanks for the clarification guys.

smd4 posted:

OK, thanks for the clarification guys.

What????

All the condescending remarks, and snide comments and THAT'S IT?

Number 90 posted:

rtr12 posted:

After reading about train brakes (link above) and then thinking about the terrible accident at Lac-Megantic, Quebec, when the brake system ran completely out of air, why do the train brakes fail to off and not to on or full stop? Since they can't proceed down the track until the air pressures are all correct anyway, it seems like they could be spring loaded or something to stop the train on complete air loss?

Well, you have to step back and look at the total picture concerning Lac-Megantic.  If the Engineer had secured the train with enough hand brakes before leaving it unattended, It would not have rolled downgrade when the air brakes leaked off.  That was the root cause.  There were other, contributing causes, but, if the train had been properly secured by hand brakes, the train would have remained standing in spite of the contributing causes.

Yes, some type of spring brake could have been built into the air brake systems of the cars, as is done on highway truck trailers, but this is unnecessary, as each rail car also has a hand brake for assuring that -- regardless of the status of the air brakes -- the car will remain stationary.  This is a low-maintenance, easy to operate appliance that, if properly maintained and used, can be relied on without reservation.  Truck trailers lack this feature, and thus have a spring brake which must be overcome by air pressure when the truck driver intends to begin movement.  A spring backup for rail car air brakes would add significant maintenance expense and would be difficult to test in the field when leaving equipment unattended.

Thanks, that is a good explanation that makes sense to me as to why the brakes don't 'fail to on'. I realize (as ReadingFan mentioned above) there were a lot of mistakes made in the Quebec accident and it should not have happened. I also think it  makes no sense to leave a train like that un-attended and running? I know very little about real trains, but I think a one man crew for a train of any size at all is just plain nuts (IMO). I had some experience with crew reductions in my working life as well, although in a different industry. Safety becomes a concern to all. Many times having two people makes a BIG difference when doing a job like this. I am thankful I am retired. At the same time I sometimes worry what our replacements will have to contend with in the future? 

Gregg posted:

Didn't  some use a penny or fuse' cap to keep the independent  permanently   bailed off?

Yes, they did, but, it was strictly against the rules. Why? Because you are by-passing a safety feature in the first place. Secondly, if the two outside hoses get crossed and you bail the brake off or hold it down, you are sending main reservoir pressure into the hose that operates the brake and you will slide the wheels. Don't laugh, some idiots have flattened a lot of wheels doing that stupid stuff.

Undesired releases can also be caused by leaking slip joints in the trainline causing brake pipe pressure to fluctuate. 

As far as the idea of spring brakes on rail cars goes, I think that it would be a BAD Idea, but probably not as BAD an idea that any crew that was switching cars around would think it was.

When switching cars in a yard, or often while spotting them at a customer, the cars are being moved with the air bled off, and relying on the locomotive's independent brakes and hand brakes, to control the cars.

Hump yards would be USELESS if every railcar had spring brakes, There ARE times when railroaders WANT cars to be able to roll freely.

I am surprised that none of the working rails mentioned this point.

In contrast, in almost 28 years/3,000,000 miles driving experience, I can NOT, think of a SINGLE instance, where I WANTED a trailer to move without being connected to my tractor AND me being in the cab controlling the movement.

Trailer Dollies, for building double and triple trailer combinations, on the other hand do behave similar to railcars, in that if the air is completely bled off, they will roll freely, this is also so that they can be maneuvered without having to cut in air to release the spring brakes.

Also, I don't know what year spring brakes became mandatory on highway trailers, but spring brakes were not always required equipment. The company that I have driven for, for the last 13+years had some older trailers, mainly for storage, that were not spring brake equipped, came REAL close to scratching some equipment the first time, I backed under one, and it just pushed along behind my tractor. With non-spring brake equipped trailers, you have to back up to them, couple up the air lines, charge the system with air, and either pull back on the trailer hand valve(if your tractor had one) or charge the system, then dump the brakes, and the parking brake would set, and hold until the brakes were released, or bled off, and then you would be back to no parking brakes again.

27+ years/2,750,000 miles experience moving America's freight,

Doug

Wyhog posted:

Blocking down the indy to automatically bail off the loco brakes is NOT a good idea. It can make for a REALLY bad day at work.

With a tip of the hat to Wyhog in recognition of his talent for explaining complicated railroad operation issues in language understandable to readers who are interested in trains but have never operated them, I will confess that -- back in the 1970's -- I had a couple of bodark wood wedges (nicely shaped and polished, if I do say so myself) that I used to insert into the independent brake valve in order to keep the actuating pipe charged and thus avoid over-working myself by manually bailing off the engine brakes when stretch braking.  Well, I was young and not as sensible as I became later.  Anyway, I ran a train from San Bernardino to Barstow, and after yarding the train, took the locomotive to Barstow Diesel Service and went off duty.  Upon going on duty 8 hours later for the return trip, I reached into my pocket and discovered that my wedge was missing.  This made me a little apprehensive about possible forthcoming demerits.  When I went off duty at the San Bernardino roundhouse, there was a "thousand miler" in my mailbox, containing my wedge.  No note, no report made, no more use of the wedge from then on.  A Hostler had apparently found it and checked to see who had brought the engine to the house.  The thousand miler went into the baggage car of Number 17 and beat me home!

Wyhog posted:

I personally know of 2 incidences caused by such shenanigans.

 

Here's another:

In the early 1950's, an eastward Southern Pacific freight train departed Bakersfield with 4 EMD F-units on the head end and a Baldwin AS-616 equipped with No.6 air brake equipment as a rear-end helper, coupled ahead of the wood caboose.  This route went over Tehachapi Pass.  Approaching Cliff on a 2% ascending grade, the head-end locomotive slipped and recovered, after which the train brakes experienced an undesired emergency application.  This normally means one thing: the train has parted somewhere.  Hopefully it is just a broken knuckle, but could be worse.  The train stopped in emergency with the caboose and the big Baldwin diesel not terribly far inside the west end of a tunnel.  The rear end crew and the helper crew walked out of the tunnel to stay in fresh air, with the intention of listening for the air brakes to release, after which they intended to walk back into the tunnel, board the train, and continue the trip.  The head end Brakeman changed a broken knuckle near the head end and re-coupled the train, sending air into the brake pipe of the formerly-detached rear portion of the train.  As soon as they heard the first hiss of air pressure building up, the two rear-end crews started back into the tunnel.  However, the helper Engineer had inserted a nut into the independent brake valve for the same reason as the BN Engineer in the incident Wyhog described.  When the train went into emergency the lead locomotive had lost all power because of the PC switch opening, and some slack had run in before the train stopped.  Well, when the brakes released the slack ran out and the heavy Baldwin (with the caboose behind it) broke the knuckle on the last car, and rolled backward, gaining too much speed for the crew to board it as it passed them.  It rolled through Bealville, continuing to pick up speed, even though the caboose was very minimally braking.  Unfortunately, at about the same time that the SP Baldwin began rolling backward, a following Santa Fe freight with a 4-unit F7 was just leaving Tunnel No.2 and passing the west switch of Allard.  The Santa Fe was approaching the east switch of Allard, when the SP rear end came speeding around a blind curve and hit the F7 head-on. The wood caboose was crushed into kindling, and the Baldwin did serious damage to the front of the leading F7A.  The Santa Fe Engineer was killed, the Fireman was too seriously injured to ever work again, and I am unsure of the Brakeman's fate.

This tragic wreck happened because the SP helper engine's brakes were prevented from applying by blocking the independent brake valve with a nut and the Engineer did not manually apply them after stopping.

Gentlemen,

    Rich has a fairly decent understand of how the Train Brakes really work, however there is a lot more to it and the true engineering for US&S Magnetic Train Breaking is under patent to the Unions Switch & Signal & combined with WABCO Engineering is very closely guarded modern engineering.  I do know it works with both Air brakes and Magnetic Relays, now controlled by both the engineer and Computers and is more complex than you might think, you see my Father invented it, for the Union Switch & Signal for use on the newer Diesel Engines/Trains and the 1st Magnetic Train Brakes were actually purchased in Japan, for their high speed Railroad Engines.  These Magnetic Train Brakes are now used all over the world, on just about every modern train on the tracks today, the new technology even inspects itself and reports wear problems on individual engines & rolling stock.  Every time I hear a Trains whistle, I know who's engineering stops those trains!  His US&S Seth Thomas Retirement Clock, sits in my Dinning Room.

PCRR/Dave

Anyone(no railroaders) want to guess what a Thousand miler is and what OCS means?

Thanks for the further explanations as well. I knew the brake operation would have been thoroughly thought out and there were reasons for everything that was implemented. Now I understand it a little better.  

Also enjoyed reading the stories of your experiences from all of you that posted them. Very interesting.

The anecdote about an undesired release being caused by a rear-end crewman tooting the caboose whistle at his girlfriend brings up a bit of a puzzle. My RR museum participation had wound down before I had an opportunity to take an air-brake class where the question might've been answered.

I do recall an entry in the NORAC rulebook about not making reductions smaller than a certain amount as they could cause an unintentional release. A friend of mine who volunteered with me on these RMNE trips (he was conductor, I did brakeman duty) was puzzling over that quote and related an incident where he caused a brake application with the backup hose whistle (part of these trips were via a reverse move since that end of the trip lacked a runaround track, and the backup hose whistle was used to signal for a couple of minor grade crossings).

So, what sort of fluke of the system causes a small reduction to result in an unintended release? 

---PCJ

 

So, what sort of fluke of the system causes a small reduction to result in an unintended release? 

---PCJ

For lack of a better term... A" tapered train" line   where there is a difference in air pressure  at each end.. .    The air  will eventually try  to  even out and it doesn't take much to active a brake release.     The brakes release  really fast.   Probably around 7 or 8 seconds for a good size  train.

I can see where the momentary drop in pressure initiated somewhere other than the locomotive (with the brakes applied) can trigger a release when this momentary drop is "corrected" by locomotive end. That part was the missing info--previously I wasn't aware that the locomotive's air system would counteract any further reductions coming from elsewhere in the brake line once the brakes had been set.

The long-standing question mark in my mind was the entry in the rulebook about making a reduction less than a certain amount (I want to say 6 lbs but I'll have to re-visit the book for the rule as stated) could trigger an unintentional release. From the wording of the rule it sounds like this applies to an additional reduction on top of an existing application. That if you needed to add more braking effort, you need to take a fairly sizable bite (say, another 10 pounds) to avoid a surprise release.

Edit: from reading the supplied link, it appears that taking the air-brake class would have addressed at least the first question (or at least I would have brought it up during the class). The answer to the second question appears to have something to do with the quick-service feature, but exactly what that is I haven't found yet.

---PCJ

Great stuff!

Peter