Braking on SMEE equipment

[eaglestar]

I understand that the SMEE equipment utilizes "straight air" for normal service braking. I would appreciate some assistance in fully understanding how they work in practice. 

 

1. Are the brake valves on the SMEE equipment continuously adjustable, or do they have "steps"? In other words, would it be possible to take 15 pounds of air, then 18, then 21, then 30, and so on? Or can a T/O only take 5-10 pounds at a time?

2. On newer automatic brake valves (such as are used on FRA-regulated railroads), there is typically a minimum amount of air that has to be set initially (called a minimum reduction, usually results in roughly 15 pounds of brake cylinder pressure.) Do the SMEE brake valves also have this requirement, or can any amount of air, however small, be taken as a first set? It would seem that the latter would only be possible if the brake valves were "continuously adjustable."

3. Are the SMEE's equipped with "graduated release" brakes? Meaning, if the T/O took a bit too much air, would they be able to partially release the train brakes, or would they have to come all the way off and then "go back after it?" 

4. This is the silliest question of the bunch, but the SMEE's are equipped with dynamic braking, yes?

Thanks again for your information!

[Fan Railer]

8 hours ago, eaglestar said:

I understand that the SMEE equipment utilizes "straight air" for normal service braking. I would appreciate some assistance in fully understanding how they work in practice. 

 

1. Are the brake valves on the SMEE equipment continuously adjustable, or do they have "steps"? In other words, would it be possible to take 15 pounds of air, then 18, then 21, then 30, and so on? Or can a T/O only take 5-10 pounds at a time?

2. On newer automatic brake valves (such as are used on FRA-regulated railroads), there is typically a minimum amount of air that has to be set initially (called a minimum reduction, usually results in roughly 15 pounds of brake cylinder pressure.) Do the SMEE brake valves also have this requirement, or can any amount of air, however small, be taken as a first set? It would seem that the latter would only be possible if the brake valves were "continuously adjustable."

3. Are the SMEE's equipped with "graduated release" brakes? Meaning, if the T/O took a bit too much air, would they be able to partially release the train brakes, or would they have to come all the way off and then "go back after it?" 

4. This is the silliest question of the bunch, but the SMEE's are equipped with dynamic braking, yes?

Thanks again for your information!

1. The service range is continuous. You can take any amount of application and adjust it as finely as you possibly can.

2. Yes, there is a minimum brake application. It is somewhere between 5 and 10 lbs of straight air. There is a spring in the brake handle from min brake and running release; if you're not careful and don't pull the brake handle far enough back, it will spring back from min app into running release.

3. Yes, SMEE braking is graduated release.

4. Yes, SMEE braking has integrated dynamic braking.

This web page should give you more in-depth info on the workings of the SMEE brake system: http://www.thejoekorner.com/cars/brakes.htm

And if you're interested, the traction system on pre-NTT cars: http://www.thejoekorner.com/cars/carpow.htm

[INDman]

On 1/25/2018 at 12:07 AM, Fan Railer said:

1. The service range is continuous. You can take any amount of application and adjust it as finely as you possibly can.

2. Yes, there is a minimum brake application. It is somewhere between 5 and 10 lbs of straight air. There is a spring in the brake handle from min brake and running release; if you're not careful and don't pull the brake handle far enough back, it will spring back from min app into running release.

3. Yes, SMEE braking is graduated release.

4. Yes, SMEE braking has integrated dynamic braking.

This web page should give you more in-depth info on the workings of the SMEE brake system: http://www.thejoekorner.com/cars/brakes.htm

And if you're interested, the traction system on pre-NTT cars: http://www.thejoekorner.com/cars/carpow.htm

1. Kinda sorta, I would not describe it as continuous though.

2. Correct, as “snow brake” is the first application position on a brake valve (ME42/A/43) and that would register about  a 10lbs  straight air application. The is however, no spring in the brake stand. I can only guess that your only experience with SMEE equipment is 6688 and the brake valve on that is well out of adjustment and not typical of an ME42.

3. Yes

4. Yes, except on all post GOH equipment there is only a dynamic brake application until speed is reduced to 10mph at that point dynamics fad out and only pneumatic brakes ratarde the speed of the train. This is why a train traveling at 10mph or less will give a rougher stop than a train at say 30mph being brought to a stop. Pre-GOH equipment had what is called “in shot air” where a train traveling above 10mph would recive an actual pneumatic application as well as a dynamic brake application, resulting in a smoother and quicker stop.