Air Brake Blueprint Assistance needed

[nsl714]

Is there anyone out there who knows their way around a brake blueprint? I'm trying to tweak down the air brakes on the North Shore car to something realistic. The real life cars use a Westinghouse M23 brake valve and a U-4 Triple valve in a Control Pipe system. On the M23 valve you have 5 positions: Release, Handle Off, Lap, Apply, and Emergency. In normal service the train line is charged to 70psi. A 20psi reduction in the brake pipe should set up a 50psi pressure in the brake cylinder. Due to the equalization point of the train line and the Auxiliary Reservoir, there should be no further increase in the brake cylinder beyond 50psi in a full service application. An Emergency Application should put approximately 70psi into the brake cylinder. I have tried to replicate this in the brake blueprint. I tell it that a normal service application is no greater than a 20psi drop in the train line, and that full service pressure is 50psi. However, when normally applying the brakes, the brake cylinder keeps gaining air to 70psi. I want to be able to cut the service brake application off at 50psi and let the emergency application put 70psi in the cylinder. What am I missing?

Thanks,
Zach

[Ericmopar]

"minimum reduction pressure" should be 3 to 6.

"max force percent of vehicle weight" should be between 50 and 60.

"proportional brake" should always be checked.

I didn't see a maximum system or line pressure setting?
Those are usually around 90.

"normal full release pressure" should be the same as the maximum line pressure.

The retainer should be off "eFalse"

"Pressure used from pipe per pound gained" doesn't look right to me, but I have no access right now to look at some of my own brake blueprint files.
I keep thinking that it's %100 but I'm not sure.

This is confusing, I've never seen brakes settings displayed like that. I've always seen them as a text file in RW_Tools.

You can also have problems with the control settings in the "Engine" bin.

[JohnS]

where you have Max cylinder pressure and pressure for max force in the Brake Control Blueprint, change them to 50psi and you should be good.

[nsl714]

John: I set max cylinder pressure and pressure for max force to 50psi, and still it went above 50psi. I changed the "Emergency Application Pressure" down to 50 and the brake cylinder doesn't pass 50.

Eric: I'll respond to each line

1. Changed to 6.

2. This is set at 82.5 to match a braking curve done by the North Shore Line in 1940. I've done testing on a straight drag strip with 100' increments marked off to come to this value. It has been tweaked down to 80. The curve is attached.

3. I have checked "Proportional Brake" now. The Dev Docs don't explain this one. What does it do?

4. As with most railroads in the first part of the 20th century, the North Shore ran a train line pressure of 70psi.

5. The retainer option is set to "No Retainer"

6. These two are undefined in the Dev Docs. I simply kept the 2.5 ratio (with it's inverse for pressure used from the pipe over pound gained in the cylinder).

7. This is an excerpt from the Blueprint editor. I'm editing source files, rather than backfeeding through RWTools.

8. I've checked the Engine.bin. It's got 5 points on the brake handle, which are correct according to the Dev Docs.

So now this comes back to the braking curve. All the above settings produce a behavior roughly close to the curve in full service applications. However, there is no improvement in stopping distance for Emergency. It follows the service curve, with a slight gain for quicker application. Having run one of these in real life and having dumped the air while doing so, it is a quick, shuddering stop, much as the curve suggests. I'm a bit unsure where to go from here. At the very least, the service portion functions a bit more like it is supposed to now.

Thanks,
Zach

[JohnS]

That's odd. I didn't try it myself but I will do some experiments and let you know

[BNMike]

HI....

New guy here. I just stumbled onto this conversation while looking for a piping diagram for my M23 valve. Air brake is my "thing" since about 1960. I can offer advice or information if I know what you're looking for. is this a discussion about the 'real thing" or a computer simulation of the air brake action?

Thanks,

Mike

[JohnS]

I set max cylinder pressure and pressure for max force to 50psi, and still it went above 50psi. I changed the "Emergency Application Pressure" down to 50 and the brake cylinder doesn't pass 50

after reading this I'm leaning toward the positions of the brake valve in the engine bin file may be wrong if setting Emergency to 50psi sets the brakes to 50psi in normal application. If you want to, Send me the files and stuff so I can edit and test as I go.