Air Brake Physics

[generalpalmer]

Hello;

I don't post here very often but I hope that the guys here may be able to help. I am looking for technical info regarding US air brakes, in particular application and release rates, I like to find real world data to use as a starting point for implementing realistic physics in Open Rails.

I came across this document: https://www.rssb.co.uk/rgs/standards...%20Iss%204.pdf (See table 3 on page 58) This gives application and release times for UK/European air brakes.

With that in mind are there similar standards to which US air brakes must comply? I've searched about on the net but cannot find any specific data or actual figures relating to the application and release times.

The figures used for most US stock in the FL give an application time of about 120s and release time of about 60s (Based on a BC pressure of 64psi) While the application is much slower, the release time is quite similar to European freight trains. It would be interesting to compare if anyone knows of any prototype data relating to this?

Regards;

-Paul Burton

[superheatedsteam]

Hi Paul,

Have a look at the following link which delves into some of the details and issues in creating a dynamic train brake simulation for a single pipe air brake system as used on US freight.

http://computationalnonlinear.asmedi...icleid=2618478

It's an interesting read in itself but the references at the end would probably be a good starting point. Mechanical engineers who work/study in the railway industry are the type of people that not only have the ability and opportunity to instrument and record train performance but in turn publish the methods and data I suspect you are looking for.

Other options are to approach railway companies themselves for this data. It could be deemed commercially sensitive or just to much trouble to give that data to you so don't be surprised if you are ignored or rejected.

Cheers,

Marek.

[geekman]

If my memory serves me right, didn't Al Krug publish a rather extensive synopsis on US air brakes? I just tried his web site but it's no longer active, but possibly someone here might have downloaded and saved it.

Edit: I found it, thanks to Google. Someone saved it for posterity!

http://hm.evilgeniustech.com/alkrug.vcn.com/

Click on Railroad Facts and Figures and you will find a 2 part essay on "How RR Air Brakes Work"

[=FI=Ghost]

Al Krug's text, as well as many others on the subject, can also be found here: http://www.railway-technical.com

[=FI=Ghost]

I have several PDF documents that explain the real-life train operating procedures. One of them is named "Air Brake and Train Handling Rules" by Union Pacific Railroad. Maybe it could be of help to you. If you can't find it online, send me a message.

[ebnertra000]

I've been looking high and low for some ABTH rules, so I tried again and found a bunch this time, including a BNSF version here:

https://www.google.com/url?sa=t&source=web&rct=j&url=http://1405.utu.org/Files/%5B4889%5DBNSF-AirBrake-TrainHandle-updated.pdf&ved=2ahUKEwiD_8-tpfDfAhUCJt8KHYecAgMQFjAAegQIARAB&usg=AOvVaw1uMiiJSDPXIYMHNJ1zaTAR

There are versions for several railroads out there

[generalpalmer]

Hello;

Thank you for the replies. From the paper Marek posted the link to there are some very good references and technical data.

Taking data from the various Figures and Tables here are some rough figures...
Full service application time approx: 35s
Emergency application time approx: 8-10s
Full service release time approx: 25s

From this we can calculate the MaxApplicationRate/MaxReleaseRate (in psi/s) for .eng and .wag files. OR does a good job of simulating the propagation of changes in brake pipe pressure along the length of the train so the brakes don't all apply and release simultaneously.

Thanks also for the links to the archive of Al Krug's old website, there is some great data there. The BNSF ABTH rules is a great resource too.

These figures would be for modern freight cars with 90psi pipe pressure, with quick application/release features described in the paper. I guess times would be slower for older types of triple valve and faster for passenger trains which i believe allow for a graduated release similar to European air brakes. There may be differences between locomotives and freight cars and of course independent brakes which would have much quicker release times.

Thanks

-Paul Burton