"again, my questions are when switching one or more cars at a particular industry, moving cars between a spur and main (or whatever the spur is connected to). I'm wondering if the brake line pressure is restored after each car is switched."
Whether cars have air or not when switching local industries would depend on type of cars being switched (such as hazardous v. non-hazardous), or perhaps the "conductor's style". The local conditions might have something to do with it (are there any grades involved? You don't want cars just rolling off on their own). If it's only a car or two, sometimes it's easier to leave the air in it, rather than take the time to bleed it off.
Back in the days of the General Motors assembly plant in Tarrytown (NY), we'd switch the train at the Croton West Yard (north of the Croton-Harmon station). Typical engines might be two SW1500's. All the cars in the yard had no air. But I'd pull up a long string right out into CD interlocking, and give them "kicks" back into the yard while still in interlocking limits. I don't think they do that any more!
Once the train was together, the car inspectors would put the air in it and get it ready for the trip down to Tarrytown (only about 7-8 miles).
As soon as we got the train into the yard there, the cars would be bled off and we'd switch out the plant, 10-20 cars, no air at all. The two engines had enough braking power to handle it.
For the return train, it would get air and a brake test before we took it back north.
On the other hand, when placing a car or two at the Arnold Bakery in Greenwich (CT) on the New Haven line, the conductor would keep the air in. He would have had to hook it all up later back out on the main, anyway.
This was in the 1980's (I last worked freight in March 1991). I'll bet things have changed since then!
Depending on the condition of a car's air brake system air brakes may hold for many days or a few seconds - and you never know which it will be.
dehusmanA crew can safely assume that there is no air on a cut of cars (which is what I said).
I assumed nothing at cars in an industry.
It's safer if they have no air in them (means the handbrakes are holding), but I wouldn't assume it.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
BigJimWhat a bunch of malarky! You don't assume anything!
A crew can safely assume that there is no air on a cut of cars (which is what I said). That is right in line with what the rules say, that crews cannot assume that airbrakes on a cut of cars detached from an engine will hold. That's why crews have to apply hand brakes. Assuming the detached cut has no air brakes is the safest course.
BigJimYou put the air in the cars so that the brakes that are still on the cars will release and apply when you cut them off when switching.
But a crew can't count of the air brakes to hold the cut of cars when they cut away from them. Handbrakes have to be applied to hold a detached cut. We had a crew set over a cut of cars with air on them, cut away, putting it in emergency and relying on the train brakes to hold the cut while they set another cut over. After the derailment we tested those cars and the train brakes only held for about a minute before the air started to bleed off and the brakes released after a couple minutes. A crew can't rely on the train brakes to hold cars that are detached from an engine.
Dave H. Painted side goes up. My website : wnbranch.com
zugmannOur management took exception to that - so air up everything is now the name of the game.
A lot of that is era dependent too. How strictly the FRA and management apply the rules varies by era. Today is a lot more stringent than it was 50 years ago.
When I was a trainmaster the road foreman of engines rigged up a head end device to work off a cigarette lighter plug for an auto. He would bring that along for observations and dial in the EOT of the train and we could see the air pressure and leakage, the same as the engineer (OBTW, can't remember a crew failing a brake test out of the dozens we observed). 50 years ago, that technology didn't exist. You had to get on the caboose to see the pressure. Switching two industries at the same station without testing the cars between industries was no big deal. Today, maybe not so much.
The modern GCOR rule is 7.11 " Do not handle cars without charging the air brake system, unless the cars can be handled safely and stopped within the required distance. If neessary, couple the air hoses and charge the brake systems on a sufficient number of cars to control the movement." That does give some wiggle room, just depends on how a person feels about "safely handled". The air brake rules from the era when I hired on define the places where brakes tests have to be performed as "points" so a lot depends on how big a "point" is. Is the point the exact spot when any car is added, or is it when the last car is added? Seems like the modern interpretation is the former.
If it hasn't already been mentioned, the reason you DO NOT bottle the air is because the pressure gradient left in the trainline could equalize and cause the brakes to release. Then your cars could run away.
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dehusmanThe cars spotted at the industry have to be assumed to have no air on them, all the air pressure has bled off. The cars that came off the train have air on them. If you are switching around in the plant, you won't put air on the cars in the industry until you bring the pulls back out to the main and put them on the train. However if you are mixing cars from the train and cars at the plant, you may have to put air on them, or quicker, bleed the air off the cars from the train that you are switching around at the plant.
dehusmanHow would a crew know what pressure is in any individual car? All the crew knows is what the train line pressure is at the engine and at the point where the air gauge is.
You'll know when you make an application and don't get much - just a little weak hiss...
dehusman. If you are at a station that has 6 industries in close proximity, then you might switch all the industries before doing a brake test. If you are switching a bunch on industries on an industrial lead, you might not have air on the cut at all.
The other year there was a crew working on a branch near here. At the end of the line were 2 industries - with their respective mainline switches 50' apart. Normal move was to do both industries, swap ends, brake test and return.
When the conductor finished the first, then coupled back up to pull the train for the cut for the next industry (that was 50' away), the FRA jumped out and took exception. They wanted the crew to do the brake test before leaving that first industry. I can't remember if they took action or not... willful violation of a airbrake test is decertifiable.
Another industry I worked had a bunch of sidings along a branch. Normal practice was just to bleed out the cars and drag them around (saves a lot of time when you have 10 cars for 6 different places). Our management took exception to that - so air up everything is now the name of the game.
gregcwouldn't a gauge in the engine reflect this drop in brake line pressure?
Yes.
gregcpresumably the brake reservoir pressure in the cars previously coupled to the engine would be "full"
No. When you cut away from the cars on the main, you left the angle cock open, putting the cars on the main in emergency. So the train line of the cars on the main is at zero and the air systems may have some pressure in them, but is is way less than "full" because some of the air was used to apply the emergency application, plus the air leaks off over time.
gregcagain, my questions are when switching one or more cars at a particular industry, moving cars between a spur and main (or whatever the spur is connected to). I'm wondering if the brake line pressure is restored after each car is switched.
You are giving more details so it makes if easier to say what's going on.
The cars spotted at the industry have to be assumed to have no air on them, all the air pressure has bled off. The cars that came off the train have air on them. If you are switching around in the plant, you won't put air on the cars in the industry until you bring the pulls back out to the main and put them on the train. However if you are mixing cars from the train and cars at the plant, you may have to put air on them, or quicker, bleed the air off the cars from the train that you are switching around at the plant.
If you switch with are then any time you move any car you have to couple up the air hoses, then pump up the air to move the car and any time you uncouple a car you have to turn angle cocks, plus everything is shove to rest, you can't kick or roll anything. Most crews I worked with tried to avoid this if at all possible because its realllllllly slow to do. Its way quicker to switch without air.
If they were making a straight pick up or a straight set out, then they would spot the car with air. The car being piked up would be added to the train and while the conductor was spotting the car the brakeman would be lacing the hoses (and opening the angle cocks) on the car added to the train, so when they engine comes back to the train they can just couple in and start pumping air for the air test.
gregcof course the brake line pressure must be "correct" when the train travels back between separate industries or back to a yard.
There has to be a brake test when you want it to be a "train". That's the only time the air pressure has to be "correct" (and its not just pressure, its also leakage. If you are just switching around you just need enough air to release the brakes. Its possible if you have just one car attached to the engine, you can get 75 lbs of air in the train line with the angle cock on the other end of the car partially open. At whatever point you stop switching and the engine and cars becomes a "train" for movement, then you would do the brake test. If you are on the main moving between stations then you would do a brake test. Any time you have to move the rest of the train that has air on it you have to couple all the air hoses and pump up the brakes, but only have to actually do a brake test right before departing. If you are at a station that has 6 industries in close proximity, then you might switch all the industries before doing a brake test. If you are switching a bunch on industries on an industrial lead, you might not have air on the cut at all.
It depends on how close the industries are, how much switching around has to happen, whether or not the rest of the "train" has to be moved to do the switching, what the grades are, what's being switched, how heavy is it, etc., etc. An empty boxcar on flat ground may be handled differently than a 10 car cut of loaded chlorine tanks on a 1/4% grade.
To do a proper initial terminal brake test, a gauge on the rear of the train must show a pressure within 15psi of the feedvalve setting on the locomotive. So, if the rules require a feedvalve setting of 90psi, then the rear car must show 75psi. Once a brake test is complete (when the engineer releases the brake), the train can depart when the brakes actually release on the rear no matter what the pressure indicates. The trainline will continue to increase over time. How fast and how much depends on the air tempurature and the amount of leakage in the trainline (5psi/min. maximum as determined on the second minute of the initial brake test).
dehusmanDon't have a clue what you mean by "switch cars with partial brake line pressure".
gregcwhen one or more cars are coupled to the train and the brake hoses are connected and brake hose (?) valve opened, some of the air from the train immediately bleeds into the brakes lines of the cars being connected.
doesn't this mean the brake line pressure drops when the car is added and the brake valve opened on the car previously coupled to the engine?
wouldn't a gauge in the engine reflect this drop in brake line pressure?
presumably the brake reservoir pressure in the cars previously coupled to the engine would be "full"
again, my questions are when switching one or more cars at a particular industry, moving cars between a spur and main (or whatever the spur is connected to). I'm wondering if the brake line pressure is restored after each car is switched.
of course the brake line pressure must be "correct" when the train travels back between separate industries or back to a yard.
greg - Philadelphia & Reading / Reading
gregccan a train be operated if just one car doesn't have full brake pressure?
How would a crew know what pressure is in any individual car? All the crew knows is what the train line pressure is at the engine and at the point where the air gauge is. The crew has to meet certain requirements for train line pressure and leakage. The only "car" requirement is that the brakes release (or set, depending on what test is done.) The brakes will begin to release before the system is fully charged. You can physically move a car before the brake system is fully charged. Its just you probably can't do a properly do an air test becuase the pressure or leakage/air flow won't meet the requirements to pass the test.
gregcif it's ok to "switch" cars, not move a train on the mainline, with no brake line pressure using independent brake, why would it be illegal to "switch" cars with partial brake line pressure?
Don't have a clue what you mean by "switch cars with partial brake line pressure".
if it's ok to "switch" cars, not move a train on the mainline, with no brake line pressure using independent brake, why would it be illegal to "switch" cars with partial brake line pressure?
dehusman If you are switching a typical "Lance Mindhiem industrial spur", you might not even be putting air on the cars for the portion of the railroad he typically models.
so then the operator needs to recognize that he needs to use independent brakes on the loco which i believe will have less effect.
this is another interesting (?) aspect of micro-operation
mvlandswAccording to engineer training material from 1980 it takes 7 minutes to completely charge one car. A 150 car train takes 60 minutes.
we've read this before - http://cs.trains.com/trn/f/111/t/274313.aspx
can a train be operated if just one car doesn't have full brake pressure?
According to engineer training material from 1980 it takes 7 minutes to completely charge one car. A 150 car train takes 60 minutes.
The charging ports in the AB brake valves are restricted so that cars near the front of a train do not use all of the air coming through the brake pipe, but allow some to pass to cars to the rear of the train. This is not too important when initially charging a train, but it is important when releasing the brakes when moving. If the the cars near the front took up most of the air the pressuse on the rear would rise very slowly, causing the rear brakes to release slowly or maybe not release at all.
Mark Vinski
I would pick the longest time you want to wait and then work backwards from there. If you are switching a typical "Lance Mindhiem industrial spur", you might not even be putting air on the cars for the portion of the railroad he typically models. If you are just moving cars around form spot to spot at one industry then you might not have air on the cars.
thanks dave & ed
i'm thinking about micro-operation -- where you're focused on detailed operation of the train: proper speed, proper braking, ... i'm reading a minheim book where he discusses how time consuming switching cars can be. he's suggested simply waiting specific amounts of time to capture this when switching
the ProtoThrottle has an unused feature for specifying train tonnage (hi, med, lo, ...). i believe, that using physics, knowing loco horsepower and the # of cars (and approx weight) being moved can more realistically model train speed. modeling westinghouse brakes is a big part.
but if you can adjust the # of cars as they are un/coupled to model tonnage, you can also model the time to restore brake line pressure when cars are added.
rather than just watch a clock, a gauge on something like the ProtoThrottle can show the brake line pressure to know when it's ok.
a rough estimate of how long is necessary for each car is one approach. modeling the pump capacity and air volume in a typical car is another
Some larger yards (division points) would have "ground air" or shop-supplied air available at the departure tracks. The car inspectors would connect to this air line to charge the cut of outbound cars and using a test air brake valve. The "car knockers" would walk the train and check for leaks, bad hoses, piston travel, braker beams and shoes, etc.
This would save some time when the road engines were coupled, another "class 3" brake test would be done and the train can depart. I used to listen to the car department communicate to the engine crews on the radio saying "your air test is complete, you may depart on signal indication".
I remember when the engines would first couple on and the angle cock opened, the engineer would crank up the diesel to run 5 or 6 with the reverser in neutral so the air compressors would have some volume. I guess most new power has motor-driven compressors so this isn't a thing any more. I replicate this on the model RR by using the Loksound Drive-hold feature. I can ramp up the prime mover while the engines sit still.
This was back before EOTs so rules may have changed. The conductor used to read the brake pipe gauge in the caboose. Today, the EOT transmits the data to the engine. Air can be dumped from the EOT from the engine. It wasn't always this way and there were some runaways because of this.
Below you can see two cuts of cars being charged and tested here. The test valve is at the other end of the cut and this way the two cuts can be checked with one walk-by.
IC_Yard-Chicago_blue-flag by Edmund, on Flickr
IC_Yard-Chicago by Edmund, on Flickr
Good Luck, Ed
gregcfirst, am i correct, that when disconnecting the brake hoses between cars being uncoupled, that there is a valve that can be closed on the car still coupled to the train to prevent the loss of air from the train?
You close the valve on the cars coupled to the ENGINE.
You leave the valve on the cars being detached from the engine OPEN. When the engine and cars attached to it pull away, the detached cars go into emergency.
Turning the angle cock on the detached cars is called "bottling the air" and is against the rules on most rule books (and I only say "most" because there may be an 1800's rule book out there that permits it).
The engineer releases the train brakes after the coupling is made, the air hoses connected and the angle cocks opened. That charges the train line. If the cars have been off air for a while it can take 5-30 sec per car depending on temperature, types of brakes and how long they have been off air.
i'm curious how long it takes to pump up the brakes lines when uncoupling and coupling one or more cars when switching
first, am i correct, that when disconnecting the brake hoses between cars being uncoupled, that there is a valve that can be closed on the car still coupled to the train to prevent the loss of air from the train?
when one or more cars are coupled to the train and the brake hoses are connected and brake hose (?) valve opened, some of the air from the train immediately bleeds into the brakes lines of the cars being connected. does the engineer need to do anything or will the brake system immediately start recharging the brake line to max pressure?
how long would it take per car?