Thank you UP

First item to to tell if brakes are applied or not on truck mounted brake equipment.

@Lehigh Valley Railroad posted:

First item to to tell if brakes are applied or not on truck mounted brake equipment.

And how do you tell?  I'd assume any residual air pressure had leaked out by now.  The car has been sitting there almost a week and the hand brakes are definitely applied.  And, I might guess that the air brakes were bled when the car was dropped off for safety reasons?

I also assume the containers are empty otherwise the shippers might get a bit peeved that their stuff is just sitting there.

I think the item is an empty/load adjuster.  If the car is loaded, the truck springs compress and the bolster will drop in relationship to the sideframe.  As it drops the arm pivots as it makes contact with the top of the frame, activating something in the brake system to reflect the weight of the car.

I suspect that on the car side above the appliance, it will say something like "EMPTY/LOAD 1/4 ADJ. BLOCK".

Photos are my own.

Jim

@rdunniii posted:

And how do you tell?  I'd assume any residual air pressure had leaked out by now.  The car has been sitting there almost a week and the hand brakes are definitely applied.  And, I might guess that the air brakes were bled when the car was dropped off for safety reasons?

I also assume the containers are empty otherwise the shippers might get a bit peeved that their stuff is just sitting there.

There would be no reason, especially for safety that the car was bled off.

If the piston is down, the brakes are applied, it up, released.

Loaded or not, depending on the defect it could be possible that it CANT be moved until repaired.

@Lehigh Valley Railroad posted:

There would be no reason, especially for safety that the car was bled off.

If the piston is down, the brakes are applied, it up, released.

Loaded or not, depending on the defect it could be possible that it CANT be moved until repaired.

The angle cock was left open when they left the car, I didn't include that pic

So regardless it was bled off.

@big train posted:

I think the item is an empty/load adjuster.  If the car is loaded, the truck springs compress and the bolster will drop in relationship to the sideframe.  As it drops the arm pivots as it makes contact with the top of the frame, activating something in the brake system to reflect the weight of the car.

I suspect that on the car side above the appliance, it will say something like "EMPTY/LOAD 1/4 ADJ. BLOCK".

Photos are my own.

Jim

Thanks, if the car is still there tomorrow I'll look for that.  I knew it had something to do with the brakes and that makes a lot of sense.  From the looks of some of those wheels it is possible that it malfunctioned and the brakes acted like the car was loaded when it was not and the brakes locked up.  Does the shipper adjust that when they load/unload the car?

@rdunniii posted:

The angle cock was left open when they left the car, I didn't include that pic

So regardless it was bled off.

How do you know it was bled off? When a car is “cut away” it’s not bled off.

@big train posted:

I think the item is an empty/load adjuster.  If the car is loaded, the truck springs compress and the bolster will drop in relationship to the sideframe.  As it drops the arm pivots as it makes contact with the top of the frame, activating something in the brake system to reflect the weight of the car.

I suspect that on the car side above the appliance, it will say something like "EMPTY/LOAD 1/4 ADJ. BLOCK".

Photos are my own.

Jim

What? The brakes on a freight car operate the same loaded or empty.

@Lehigh Valley Railroad posted:

What? The brakes on a freight car operate the same loaded or empty.

Well, apparently there is a recognition that the braking force required for an empty car is significantly less than that required for a loaded car.  The empty/load sensor identifies an empty or loaded car and regulates the air pressure to the brake cylinder accordingly. 

Here's some links for anybody interested.

New York Air Brake (click through to the technical documents/component write-ups for additional info)
NYAB Technical Guide (has a schematic showing how the sensor is integrated into the brake system plumbing)
Wabtec Empty/Load top page

There's also a slope sheet mounted sensor which serves the same purpose, although it seems specific to hopper cars.

I was wrong about how the sensor works.  By default, the lever on the sensor does move closer to the truck sideframe as the loaded car settles on the springs, but it doesn't make contact with the sideframe at that point.  Instead the lever is retracted when brakes are released, and extends to the sideframe when air is applied.  How far the lever travels dictates how the air is proportioned to the brake cylinder.  It obviously has further to go when the car is empty.

So in that sense, the device would in fact indicate by it's position whether brakes are applied or released.  It's not the primary purpose, but it does happen by default.

What I'm curious about is why in both examples in this thread, the sensor levers appear to be extended, when there ostensibly isn't any air in the system.  The Trinity hoppers in my photos are empty cars that have been stored without moving for at least five years.  Even with the angle cocks closed, doesn't the air bleed off eventually?

@Lehigh Valley Railroad posted:

How do you know it was bled off? When a car is “cut away” it’s not bled off.

You are of course correct that when a fully charged brake line is parted and loses pressure from its source the brakes go into emergency from the pressure stored in the reserve canisters.  But when all the pressure is lost within the car the brakes release.  And in this case the only brakes applied are the hand brakes, which I thought I said originally.  Sorry.

@big train posted:

Well, apparently there is a recognition that the braking force required for an empty car is significantly less than that required for a loaded car.  The empty/load sensor identifies an empty or loaded car and regulates the air pressure to the brake cylinder accordingly.

Here's some links for anybody interested.

New York Air Brake (click through to the technical documents/component write-ups for additional info)
NYAB Technical Guide (has a schematic showing how the sensor is integrated into the brake system plumbing)
Wabtec Empty/Load top page

There's also a slope sheet mounted sensor which serves the same purpose, although it seems specific to hopper cars.

I was wrong about how the sensor works.  By default, the lever on the sensor does move closer to the truck sideframe as the loaded car settles on the springs, but it doesn't make contact with the sideframe at that point.  Instead the lever is retracted when brakes are released, and extends to the sideframe when air is applied.  How far the lever travels dictates how the air is proportioned to the brake cylinder.  It obviously has further to go when the car is empty.

So in that sense, the device would in fact indicate by it's position whether brakes are applied or released.  It's not the primary purpose, but it does happen by default.

What I'm curious about is why in both examples in this thread, the sensor levers appear to be extended, when there ostensibly isn't any air in the system.  The Trinity hoppers in my photos are empty cars that have been stored without moving for at least five years.  Even with the angle cocks closed, doesn't the air bleed off eventually?

If there is pressure held on the system and the line pressure is zero that pressure would be used to apply the brakes.  That is how the failsafe works.  But yes, eventually it will leak out.  How long that takes depends on the seals on the individual car and a few PSI might remain for a long time.  If you look at the truck cylinders (not attached to the handbrakes) and they are applied then either there is residual air pressure or there is something wrong with the brakes and that is why they are sitting there.

Got any more pics of the end frame areas?

@rdunniii posted:

If there is pressure held on the system and the line pressure is zero that pressure would be used to apply the brakes.  That is how the failsafe works.  But yes, eventually it will leak out.  How long that takes depends on the seals on the individual car and a few PSI might remain for a long time.  If you look at the truck cylinders (not attached to the handbrakes) and they are applied then either there is residual air pressure or there is something wrong with the brakes and that is why they are sitting there.

Got any more pics of the end frame areas?

I don’t know a ton about train brakes, but it’s sort of interesting that the emergency failsafe on railroad cars isn’t more like those in tractor-trailers.  There a spring applies the brakes until enough air pressure is generated to lift the “parking brake” off of the actuating rod.

Any rapid loss of air pressure results in the spring returning and applying pressure to to the control rod, which rotates the S-cam through an actuating rod.  The design of the cam allows the brakes to be held on with almost no effort by the spring.

@rplst8 posted:

I don’t know a ton about train brakes, but it’s sort of interesting that the emergency failsafe on railroad cars isn’t more like those in tractor-trailers.  There a spring applies the brakes until enough air pressure is generated to lift the “parking brake” off of the actuating rod.

Any rapid loss of air pressure results in the spring returning and applying pressure to to the control rod, which rotates the S-cam through an actuating rod.  The design of the cam allows the brakes to be held on with almost no effort by the spring.

That would have been my guess as well

@rplst8 posted:

I don’t know a ton about train brakes, but it’s sort of interesting that the emergency failsafe on railroad cars isn’t more like those in tractor-trailers.

Why?

There a spring applies the brakes until enough air pressure is generated to lift the “parking brake” off of the actuating rod.

No springs needed on railroad cars, since the air pressure from the individual air reservoirs on ever car, is used to apply the brakes.

Any rapid loss of air pressure results in the spring returning and applying pressure to to the control rod, which rotates the S-cam through an actuating rod.  The design of the cam allows the brakes to be held on with almost no effort by the spring.

Springs on such heavy railroad equipment would be a high maintenance item. The current train lined air brake system used by virtually all railroads, has worked successfully since developed by George Westinghouse,  well more than 100 years ago.

@Hot Water posted:

Why?

No springs needed on railroad cars, since the air pressure from the individual air reservoirs on ever car, is used to apply the brakes.

Springs on such heavy railroad equipment would be a high maintenance item. The current train lined air brake system used by virtually all railroads, has worked successfully since developed by George Westinghouse,  well more than 100 years ago.

Why? I’m taking the other posters at their word, but a cut of cars that are sitting could eventually leak the air pressure required to hold the brake on.

Also, after doing a little Googling, apparently an over application of the train brake can deplete the air and lead to the inability of the triple-valve to detect an emergency condition.  
https://en.m.wikipedia.org/wik...ir_brake#Limitations

On a tractor trailer, you lose air, your truck stops.  The brakes are applied and don’t let off until air is restored.

@rplst8 posted:

On a tractor trailer, you lose air, your truck stops.  The brakes are applied and don’t let off until air is restored.

Truck brakes aren't perfect.  According to the Federal Motor Carrier Safety Administration, brake failures are the number one reason for crashes, making up 29% of all large truck crashes.

Rusty

@Rusty Traque posted:

Truck brakes aren't perfect.  According to the Federal Motor Carrier Safety Administration, brake failures are the number one reason for crashes, making up 29% of all large truck crashes.

Rusty

First, that study used data from about 900 crashes and extrapolated that to the estimated 140,000 commercial trucks that were involved in an accident over the same period.

Second, brakes are NOT the number one reason, they're the number one associated factor.

The number one cause is the driver, representing 87% of all crashes.  Vehicle issues are about 10% of all causes, with brake failures representing some fraction of that.

For example, if the driver rides the brake pedal down a long steep grade and melts the brake shoes off, you can hardly blame the air brake design for that.

You have some valid points.  Train brakes are not mean't to be applied and released over and over as the reservoirs can deplete and not provide adequate pressure for a solid brake application if needed.  Train brakes are actually designed to operated at much higher temperatures so '"riding" the brakes down a grade is normal.  Engineers can modulate the pressure to fine tune the application depending on where they are, minimize air consumption and keep the slack out.  That is a reason why "knowing" the territory can be so critical.  After an emergency application it can take several minutes for the system to recover and pump off the brakes, especially on these longer trains so common today.  Each individual car's reservoir has to recover.  I think it takes about 90 PSI throughout the train to release all the brakes,

The reason dynamic brakes are so great is they take some of the pressure (no pun intended) off the air brakes.  A 5-10% reduction in air brake line pressure can be kept steady by modulating the dynamic brakes as grade vary.  Grades for trains are much smoother over long distances where truck brakes might get a chance to cool (a bit) going more up and down shorter grades whereas train brake applications can last for many miles.

As I understand it full air braking releases the dynamic brakes for reasons I don t really understand.

@rplst8 posted:

Why? I’m taking the other posters at their word, but a cut of cars that are sitting could eventually leak the air pressure required to hold the brake on.

Also, after doing a little Googling, apparently an over application of the train brake can deplete the air and lead to the inability of the triple-valve to detect an emergency condition.  
https://en.m.wikipedia.org/wik...ir_brake#Limitations

On a tractor trailer, you lose air, your truck stops.  The brakes are applied and don’t let off until air is restored.

Correct

@rdunniii posted:

You have some valid points.  Train brakes are not mean't to be applied and released over and over as the reservoirs can deplete and not provide adequate pressure for a solid brake application if needed.  Train brakes are actually designed to operated at much higher temperatures so '"riding" the brakes down a grade is normal.  Engineers can modulate the pressure to fine tune the application depending on where they are, minimize air consumption and keep the slack out.  That is a reason why "knowing" the territory can be so critical.  After an emergency application it can take several minutes for the system to recover and pump off the brakes, especially on these longer trains so common today.  Each individual car's reservoir has to recover.  I think it takes about 90 PSI throughout the train to release all the brakes,

The reason dynamic brakes are so great is they take some of the pressure (no pun intended) off the air brakes.  A 5-10% reduction in air brake line pressure can be kept steady by modulating the dynamic brakes as grade vary.  Grades for trains are much smoother over long distances where truck brakes might get a chance to cool (a bit) going more up and down shorter grades whereas train brake applications can last for many miles.

As I understand it full air braking releases the dynamic brakes for reasons I don t really understand.

In an penalty or emergency application, the pneumatic control switch, will cut either power or dynamic, a full service application does not.

To basically put it, when using air, you cannot simply “let up” on the brakes once they have been applied, if you take too much of a reduction, the only way to recover from that is to full release of the brakes.

Some yard service uses 75 PSI, most freight uses 90 PSI as regular service and passenger 110.

Most roads, the dynamic is the first priority brake.

Pending train size, equipment and ambient temperature, it can take a very long time to charge the train, and to get a proper reading on the rear of the train to perform a proper brake test.

@Lehigh Valley Railroad posted:

In an penalty or emergency application, the pneumatic control switch, will cut either power or dynamic, a full service application does not.

That depends on the railroad, as many western railroads, having such long steep mountain grades, have a feature as part of the PC Switch, that allows full dynamic braking for so many seconds/minutes after a penalty or emergency brake application.

To basically put it, when using air, you cannot simply “let up” on the brakes once they have been applied, if you take too much of a reduction, the only way to recover from that is to full release of the brakes.

Or, as some western railroads have as part of their operating rules, simply go back into power from dynamic brake, and pull the train down the grade.

Some yard service uses 75 PSI, most freight uses 90 PSI as regular service and passenger 110.

Most roads, the dynamic is the first priority brake.

Pending train size, equipment and ambient temperature, it can take a very long time to charge the train, and to get a proper reading on the rear of the train to perform a proper brake test.

I owe a huge apology to Lehigh Valley Railroad.  I was under the erroneous viewpoint that this car had a single airbrake system.  Wrong, It has two apparently independent systems and indeed there is still air pressure in the 2nd applying the brakes to both ends of car A.  

@big train posted:

I think the item is an empty/load adjuster.  If the car is loaded, the truck springs compress and the bolster will drop in relationship to the sideframe.  As it drops the arm pivots as it makes contact with the top of the frame, activating something in the brake system to reflect the weight of the car.

Jim

And you are correct!  You receive a tip of my hat.

The actual purpose is to provide higher brake cylinder pressure when the car is loaded, and to provide reduced brake cylinder pressure when the car is empty.  You will see these devices on cars which are very heavy when loaded and very light when empty -- coal hoppers, double-stack container cars, etc.

This prevents sliding the wheels and causing flat spots when train brakes are applied and the cars are empty.  It is possible to have both empty and loaded cars that are equipped with load/empty devices, in the same train

Was wondering where all those flat wheels I hear in freight trains come from !