Locomotive Brake

[hf1001]

Why does the engineer on a locomotive press down the brake lever on the locomotive brake?

                                       ,HF1001

[silicon212]

Pressing down on the handle cuts the trainline brakes out on the locomotive, to allow the engineer to control the locomotive independant brakes.  You generally see this if a train goes into emergency, the engineer will press down on the handle so the locomotive wheels do not get flat-spotted.

[Randy Stahl]

This is called "bailing" off the locomotive brakes . Engineers are required to do this each time an automatic reduction is made on the brake pipe to prevent brake cylinder pressure on the locomotive from developing .  

[bakupolo]

In emergency braking, do all the wheels on the train lock up and develop flat spots>

[nbrodar]

Engineers will generally "bail off" any time there is an application of the automatice brake.  It keeps the brakes released on the locomotives, and is one way to control the slack action in the train.

It's also important when in dynamic braking, to keep the locomotive wheels turning.

Nick

[CSSHEGEWISCH]

In emergency braking, do all the wheels on the train lock up and develop flat spots>

Although this is a common visual device in movies and television, it doesn't actually happen.  Sliding wheels provide less braking than wheels that are still turning but being restrained by the brake shoes.

I've ridden several trains where emergency braking was applied, the train slowed and stopped rather quickly but there was no wheel sliding.

[WSOR 3801]

If there are a lot of empty cars, the wheels could slide in emergency. 

Engine wheels can and do lock up from braking.  Seems to be more common with clasp type brakes, as there are 2 brakeshoes grabbing each wheel.  Add a little moisture, and sliding is very possible.

[J. Edgar]

 

 most modern bathtub gons for coal have device that detects carload and will reduce braking force for empty cars....

[magicman710]

In refference to the wheels sliding, you dont have to be much of an expert to realize this (not saying the person who asked is stupid, afterall, I believed it myself before) Steel wheels sliding on steel track, you can imagine, wouldent do good. It would be like ice sliding down a slide, it slides for ever. But imagine if you were to add enough pressure on the wheels to almost the point of sliding, the train would be forced to stop, since theres no way out of it, there is strain on the train, lol, rhyme, which would cause braking quicker. I know my explanation is hard to understand, but its pretty much like this: F=VM/SP

[Anonymous]

Bathtub gons have them, also covered hoppers, rapid discharge coal cars, so that time is not spent after a unit train loads or unloads the carman has to set the retaining valves(is that what the retaining valve lever does?).

[CSSHEGEWISCH]

Bathtub gons have them, also covered hoppers, rapid discharge coal cars, so that time is not spent after a unit train loads or unloads the carman has to set the retaining valves(is that what the retaining valve lever does?).

It's a load/empty switch, quite different from retainers.

[khhogger]

Engineers will generally "bail off" any time there is an application of the automatice brake.  It keeps the brakes released on the locomotives, and is one way to control the slack action in the train.

It's also important when in dynamic braking, to keep the locomotive wheels turning.

Nick

You don't "bail off" when using dynamic brakes.

[Randy Stahl]

Engineers will generally "bail off" any time there is an application of the automatice brake.  It keeps the brakes released on the locomotives, and is one way to control the slack action in the train.

It's also important when in dynamic braking, to keep the locomotive wheels turning.

Nick

You don't "bail off" when using dynamic brakes.

You don't? please , explain why not ?

[clash]

I'm a locomotive  electrician for U.P. and this is how our locomtives operate...                         As soon as you go into dynamic brake setup, any automatic brake application will be bailed off the locomotive by energizing the dbi mag valve. The engineer never has to bail it off manually. If an engineer applies the independent brake while the locomotive is in dynamics one of two things can happen depending on the type of locomotive.  On EMD units, the extended range feature will be disabled. On GE units, dynamic power will be reduced to minimum effort. This is for dc type locomotives. I'm not sure how AC locomotives deal with it.

[Randy Stahl]

I'm a locomotive  electrician for U.P. and this is how our locomtives operate...                         As soon as you go into dynamic brake setup, any automatic brake application will be bailed off the locomotive by energizing the dbi mag valve. The engineer never has to bail it off manually. If an engineer applies the independent brake while the locomotive is in dynamics one of two things can happen depending on the type of locomotive.  On EMD units, the extended range feature will be disabled. On GE units, dynamic power will be reduced to minimum effort. This is for dc type locomotives. I'm not sure how AC locomotives deal with it.

An engineer is NEVER relieved from the responsibility to manually actuate the bail feature , this includes locomotives equipped with DBI's. Failure to do so is an operational failure. (at least on the railroads I worked for).

If your locomotive is operating the DBI in brake setup you should double check the system , it should only operate as soon as the handle is moved OUT of setup into braking.

[zapp]

I don't bail the air if I'm going into DB on the new units, but I do on our older units, because they say we don't have too. I got gigged when on the simulator for doing just that, so I quit doing it.

As far as the sliding wheels, that can, and does, almost always happen when the car is being switched somewhere, as opposed to going into emergency out n the road. Either someone will drag it out of a spot without bleeding the brakes, or an old-school railroader got up there and put his foot in the hand brake!

[jeffhergert]

I'm a locomotive  electrician for U.P. and this is how our locomtives operate...                         As soon as you go into dynamic brake setup, any automatic brake application will be bailed off the locomotive by energizing the dbi mag valve. The engineer never has to bail it off manually. If an engineer applies the independent brake while the locomotive is in dynamics one of two things can happen depending on the type of locomotive.  On EMD units, the extended range feature will be disabled. On GE units, dynamic power will be reduced to minimum effort. This is for dc type locomotives. I'm not sure how AC locomotives deal with it.

I'm a locomotive engineer for the UP and the train handling/air brake rules require you to bail off any automatic air brake application, even in dynamics.  We are not to rely on the dynamic brake interlock valve to keep the independent released during an automatic application when in dynamic braking.

Jeff

[csxengineer98]

i have never had to bail off my engin brakes while use ONLY dynmaic breaking to help maintain or reduse speed.. the only time i have ever bailed anything off while in dynamic is if i set an automatic application for more breaking force.. then yes.. i have bailed off..but with just dynamic.. never had done it..and have yet to see any brake cylinder PSI show up on my air gagues with just dynamic...

csx engineer 

[csxengineer98]

infact...even thow this totaly aginst the rules.. (on some stepper but not long grades) i have on some occations put 10 PSI independant brake and put sand down while in dynamic to help shave another MPH or 2 off the speed to help hold it back if the dynamic is weak or im in the 8th notch of it... ..it dose work..but they frown on it..and you dont want to go above 15psi or the dynamic brake interlock will kick in..and you lose all your dynamic untill untill you drop below the 15pis range agin... this was shown to me by an old head some years ago and have only ever used it a few times but it dose work to help keep your speed in check..totaly frowned appon..but sometimes you have to do what you have to do out there...

csx engineer 

[BigJim]

I'm a locomotive  electrician for U.P. and this is how our locomtives operate...As soon as you go into dynamic brake setup, any automatic brake application will be bailed off the locomotive by energizing the dbi mag valve.

Keep these things in mind fellas;
1) What clash didn't tell you is that on UP units, if for some reason you knock the dynamic off while the automatic is still applied, the independent brake pressure builds back up to the level it should be when the automatic was put on to begin with!

2) ALWAYS bail off in D/B if there is a BN unit in your consist. That is especially true for those Green & White units. They don't have a DBI!

[Railroad Paul]

WSOR 3801

If there are a lot of empty cars, the wheels could slide in emergency. 

Engine wheels can and do lock up from braking.  Seems to be more common with clasp type brakes, as there are 2 brakeshoes grabbing each wheel.  Add a little moisture, and sliding is very possible.

 

WSOR 3801

 

 

 

 Im a retired locomotive mechanic installing 26L in a big steam engine and I was wondering if the drivers or empty tender would slide wheels in emergency (If I remember correctly it might be 70 psi for a 45psi system) if the engineer forgets to bail off.

[RME]

Railroad Paul

Im a retired locomotive mechanic installing 26L in a big steam engine and I was wondering if the drivers or empty tender would slide wheels in emergency (If I remember correctly it might be 70 psi for a 45psi system) if the engineer forgets to bail off.

Ask Ed Dickens

Short answer: yes.  Drivers can slide very easily, and I think the problem can occur even if fairly sophisticated blended braking techniques are applied to the independent.  Flatting driver tires is an expense out of proportion to the gain in stopping effectiveness from aggressive use of the independent on driver foundation.

With respect to the tender: use one of the commercial devices used on centerbeam pulpwood cars and some others with radical loaded-to-empty weight ratios to adjust brake proportioning.  And be certain to put a placard in the cab indicating the range of derating for ranges of low fuel or low water.

[ATSFGuy]

Anytime you see sparks coming from the wheels whether it's in a movie or real life, it means the emergency brakes have been applied.

I've seen a few scenes where the emergancy brakes are applied and the wheels are still spinning.

[BigJim]

ATSFGuy

Anytime you see sparks coming from the wheels whether it's in a movie or real life, it means the emergency brakes have been applied.

Blanket statements like this make me just shake my head!

[DS4-4-1000]

BigJim

 

ATSFGuy

Anytime you see sparks coming from the wheels whether it's in a movie or real life, it means the emergency brakes have been applied.

 

 

Blanket statements like this make me just shake my head!

I totally agree with you BigJim.  I spent many an evening at the horseshoe curve and would watch the coal trains and ore trains coming down the hill with a ring of sparks encircling every wheel.  And no, ATSFGuy, they were not in emergency.  It was just everyday railroading on the hill.

[RME]

ATSFGuy

Anytime you see sparks coming from the wheels whether it's in a movie or real life, it means the emergency brakes have been applied.

The 'sparks' are a consequence of the brakeshoes doing what they're supposed to, helping to remove frictional heat from the wheels.  Modern composition brakeshoes can work similarly to ablative heat shields for orbital re-entry, and are generally 'better' than the old sacrificial cast-iron or matrix type.

Of course, the outgassing that goes along with the sparks can impede the actual friction that does the braking.  That is why a train that exceeds a speed of 23mph on parts of Seventeen Mile Grade will proceed to run away no matter what the brake-cylinder pressure is -- and yes, the wheels will still be "spinning" even as they are acquiring a beautiful blue oxide coat.

[Railroad Paul]

Thanks Ed,

If I remember right  26L goes to at least 70psi in emergency and when bailed off comes right back which would not be good for our steam engine engineer who has to worry about alot else in emergency.  As I recall #6 airbrake with the #6N distributing valve ( the Milwaukee 261 and the Calif 3751) has  a 55psi pop valve that prevents any brake cylinder pressure above that pressure.  I was wondering what our origional 8ET Westinghouse system did for brake cylinder pressure in emergency or your 844 if it has the old brake valves.

[urrSam]

Gentlemen- I was an ass't train master for 5 years back in the '70s for the Pittsburgh-area Union RR. I don't remember ever seeing any load sensors on any of the hoppers or covered hoppers we handled in & out of the 6 US Steel mills we serviced. Also, I never saw any of our "car knockers" adjust any brake rigging s as a car's shoes wore - they only replaced cpndemnable shoes with new ones. Are new hoppers typically equipped with load sensors, and if so do these merely detect spring compression or can they tell a "part-load"?

[RME]

Load sensors in the '70s did exist -- you can see some of them referenced in contemporary Car Builders Cyclopedias (and perhaps wanswheel can put a couple of them up to see, or provide live links to online content).  They were of course not something that would be put on lowly hoppers, even the simple mechanical kind that gauged the deflection of the truck springs; if I recall correctly, the only real place they were used (e.g. by some of the Canadians) was on relatively low-weight cars like centerbeams used for lumber shipment, where the actual braking ratio would change dramatically from loaded to unloaded and it would be comparatively rare for the car to operate partially loaded.

Modern 'adjustments of brake rigging' are handled by automatic slack adjusters (just as adjustments to shoe clearance in drum brakes have been done 'automatically' just by reversing, for a great many years) precisely to accommodate shoe wear, stretch and pin wear appropriately.  I have a suspicion that composition brakeshoes wouldn't be as cost-effective if this 'feature' weren't commonly provided.

There are some modern load-sensor devices that 'weigh' the car (and condition, debounce, etc. the signal) just as if it were sitting on load cells.  This is one of the kinds of data that the 'wireless train line' in last week's story would communicate.  I have my doubts that more than a few steps of resolution purely in car weight over a three-piece truck is going to give you highly different and more exact braking control in equal proportion.  That money would be much better spent in adaptive wheelslide control (which, I am finding, can be done in a foundation setup!)

The situation with modern 'hoppers' -- meaning mostly things like aluminum bathtub gons -- is a bit complex.  On the one hand these things have comparatively high payload and minimized tare, so they need some sort of accommodation of brake strength; on the other hand, they almost always run in unit trains, so (as in Australian ore practice) you can have a simple control in the cab that switches the braking-effort profile from 'loaded' to 'empty' or back when you dump or load, and don't need a fancy proportional system or the assured robust  communications to implement it.

[urrSam]

RME- thanks for the reply. So, today if I buy a unit train's worth of regular 110-ton mixed-use bottom-drop hoppers for use on the US, will either load sensors or automatic brake rigging adjusters come as standard feature?