Discussions

[MCDemuth]

Freight Cars do not require a locomotive to be attached for the brakes to be applied. Each car has a reservior air tank on them. When there is a LOSS or REDUCTION of air in the main brake pipe, then the reservior air tank releases whatever air is stored inside the tank to apply the cars brakes. This is why when the line BREAKS and/or a train seperates in to TWO or more parts while the train is in motion, the train will come to a sudden stop for safety reasons.

What the locomotive does, is to SLOWLY lower the pressure to apply the brakes a little bit, as the reservior air tank tries to maintain an equal amount of pressure with the pressure in the main brake pipe. If the pipe is LESS then there are MORE brakes. If the pipe is suddenly emptied, the brakes are fully engaged. Only if the pressure in the main brake pipe INCREASES will the brakes on the cars RELEASE.

https://en.wikipedia.org/wiki/Railway_air_brake

Charging these reservior air tanks may be done by the main brake pipe, or a secondary air system. The idea is to keep these reservior air tanks fully presurized. If there is no air in them, then then brakes can not be applied.

The air in the line being applied directly to the, brake shoes or whatever, from the reservior air tanks may eventually leak out over time. This has nothing to do with the locomotives. The locomotives only affect the operation of the reservior air tanks.

[derekmorton]

>The air in the line being applied directly to the, brake shoes or whatever,

And this is clearly what I am trying to clear up.
The train pipe charges the Aux reservoir through the triple valve,
Then a reduction of air in the train pipe moves the triple valve to apply and the air from the aux reservoir applies the brakes.

[MCDemuth]

>The air in the line being applied directly to the, brake shoes or whatever,

And this is clearly what I am trying to clear up.
The train pipe charges the Aux reservoir through the triple valve,
Then a reduction of air in the train pipe moves the triple valve to apply and the air from the aux reservoir applies the brakes.

Not to nit pick, but you didn't give a technical name for, and clear things up, what is actually being pressed against the wheels, or the hose for that matter that sends the air from the aux reservoir to those things that is actually being pressed against the wheels.

I don't know their technical names, and that is what my "whatever" was referring to...

That "hose" may leak air releasing the pressure from the "Brake Shoes" against the wheels.

Sorry for the confusion there.

[ragtimer]

Vince,exactly what I said!!!!!.The engineer would not have reduced the brake pipe to zero because that way,it is guaranteed the brakes will eventually release because the brake pipe which is the source of air for a single pipe train is empty.The engineer would have made a set to give the maximum application (refer to Al Krug again) because any further reduction in brake pipe pressure gives no more application pressure. quote from his article:

But what happens if you make a 26 psi reduction from a 90 psi brake pipe? 90 minus 26=64 psi in the brake pipe. Remember the triple valve moves to the apply position and allows service reservoir air to flow into the brake cylinder until the service reservoir pressure lowers to equal the brake pipe pressure. As the service reservoir pressure flows into the brake cylinder the brake cylinder pressure rises. Because of the 2.5 to 1 ratio of volumes, when enough air has flowed into the brake cylinder to lower the service reservoir 26 psi the BRAKE CYLINDER PRESSURE IS 64 psi !!! (2.5 times 26 =64) This air came from the service reservoir which is NOW AT 64 psi ALSO. Since the reservoir pressure and the brake cylinder pressure ARE EQUAL no more air will flow into the brake cylinder.
This condition is called a FULL SERVICE brake application because even reducing the brake pipe further, below 64 psi, WILL NOT INCREASE the amount of brake cylinder pressure. Even if you reduce the brake pipe pressure to zero psi the reservoir and brake cylinder pressure will still be 64 psi., the same as it was with only a 26 psi reduction. This full service or "equalisation of pressures" occurs at 64 psi for a 90 psi charged system. It occurs at 71 psi for a 100 psi charged system resulting in higher full service brake effort. It occurs at 57 psi for an 80 psi charged system resulting in lower full service braking effort. The corresponding brake pipe REDUCTIONS are 26 psi for the 90 psi brake pipe, 29 psi for the 100 psi brake pipe, and 23 psi for the 80 psi brake pipe.

With the brake pipe at zero,whether or not the loco is "supplying" air,eventually all the air in the cars will leak away.If the loco is shut down the same applies,however the brakes were set.

[E444.005]

I think is not a matter of one pipe versus two pipe, but of triple valve system, with only the auxiliary reservoir ,versus "ditributor" system (also built by Westinghouse company) with auxliary and "command" (reference) reservoirs.
In the first case, as far as I know, the equilibrium is between brake pipe and brake reservois, in the secon case the equilibrium is between brake pipe plus brake cylinder and "command" reservoir; if I understand weel in the second case the auxiliary reservoir can be keep at brake pipe pressure (one pipe system) or at "constant" pressure (two pipe system). This is done to achieve the "inexhaustibility"requirement of the system. Inexhaustibility means that, during normal operation, when a train has his brakes released it has in the auxiliary reservoir enough air for at least one more brake application.

[rdamurphy]

The windows on the space shuttle do not move. Neither do the doors, other than when they're sealed and opened.

The moving parts of a railway car move constantly, causing wear and tear on the parts.

The space shuttle windows are not subject to weather, other than for short periods on takeoff and landing.

The brake system of a railway car are in the weather, the dust, the dirt, the water, the snow, and anything kicked up off of the roadbed.

The comparison isn't valid.

Robert

[markus1996]

To ll who were trying to explain it, and did it correctly: A member of ElvasTower Forum who has a book on this Topic published by Wentsinghouse Company ITSELF confirmed to me, thiese drawings are simple, but correct. (see here



So, to all: take a closer look on them and everything on normal operations will be cleared out.

And another Thing to "durable" air-brake applications: (don´t confude with normal operations!)
And as for a full Service application: Practically thinking, there´s no Advantage in reducing the BP further than to 64 psi, as that´s the pressure of full Service application and you qouldn´t get out more by reducing further. From a technical approch, a running locomotive would now try to maintain this BP pressure, so it doesn´t leak away. The pressure in the AR and BC, however, does nevertheless bleed off. Thus, the Reservoir (and BC) pressure will at one Point just naturally become lower than the BP, resulting in a release.
This implicates - no matter, if this is allowed or not on any railroad - that if you want to hold a Train for a longer time just with the air Brakes, one should reuce the BP to Zero, just to be sure. Remember: if the Reservoir leaks below the air line pressure, the air line then is higher than the Reservoir, causing the triple valve to go to release!

Yours, markus

[ragtimer]

Markus,you really do not get it.If you reduce the brake pipe to zero in a Westinghouse single pipe system,the brakes are going to leak off pretty quick because there is no air supply to anywhere on the cars to keep the brakes applied because the replacement air for leakages must come from the brake pipe.If there is no air in the brake pipe....no replacement air!And you get no extra brake force than with a reduction to 64 psi!

[markus1996]

Im´m no expert (forgot to mention it: proof me wrong, if I am), and I´d be gald if you could tell me what you mean with your last post, ragtimer

I don´t get, how replacement air should flow to the AR or the BC, if the BP has to be lower pressurized than the AR / BC for keeping the Brakes applied. there´s just no pipe for this replacement air to get there, if the triple valve is in apply Position. Also, how to get some air in tere, the pressure of the Input air must be higher than the one in the AR. That in turn would release the Brakes...

Yours, Markus