Elvas Tower: Guideline For Setting Open Rails Braking Parameters (Including Blended Braking) - Elvas Tower

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Guideline For Setting Open Rails Braking Parameters (Including Blended Braking)

#1 User is offline   jtr1962 

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Posted 24 April 2019 - 09:40 PM

I recently spent a few weeks playing with braking parameters in Open Rails and wanted to pass on what I learned. Rather than write an extremely long post, I thought it would be easier to just attach a .pdf file of my findings. This also helps keep the formatting the way I intended.

I will probably make a few spreadsheets to help with the calculations and attach those later.

Please give me any feedback, especially on things I'm either not sure of, or in error.

Attached File(s)



#2 User is offline   scottb613 

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Posted 25 April 2019 - 03:42 AM

View Postjtr1962, on 24 April 2019 - 09:40 PM, said:

I recently spent a few weeks playing with braking parameters in Open Rails and wanted to pass on what I learned. Rather than write an extremely long post, I thought it would be easier to just attach a .pdf file of my findings. This also helps keep the formatting the way I intended.

I will probably make a few spreadsheets to help with the calculations and attach those later.

Please give me any feedback, especially on things I'm either not sure of, or in error.


Hi...

While I can't help with more info - wow - just a huge thanks for the time and effort...

ORTS needs a library to save works like this and make them easy to find when you need them...

Peter has a brake force calculator on his "Coals To Newcastle" site - I don't know how that would play into your calculations...

Regards,
Scott

#3 User is offline   R H Steele 

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Posted 25 April 2019 - 07:28 AM

Just fantastic, brake settings have always been a puzzle to me, wonderful to have such a fine resource. Much appeciated. http://www.elvastower.com/forums/public/style_emoticons/default/sign_thank_you.gifhttp://www.elvastower.com/forums/public/style_emoticons/default/good2.gif

#4 User is offline   pnrailway 

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Posted 25 April 2019 - 07:40 AM

There are also three Exel sheets by Bill Hobbs under the name "MSTS Calculation Tools" over at TS that cover breaking, Steam loco, and couplers.

#5 User is offline   Genma Saotome 

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Posted 25 April 2019 - 08:03 AM

Minor comment. IMO MaxReleaseRate (6) is too low. I looked into this last year and concluding something in the range of 16-20 was likely correct. I asked and got numerous comments from engineers and many said what boiled down to almost instantaneously while others said a couple of seconds for the whole train. Based on that, I built a 60 car consist, set the brakes, released them (rinse and repeat) until the head of the train train took 5-6 seconds from showing released to hit zero. A fast release rate has no effect on how long it takes to pump up the line.

#6 User is offline   jtr1962 

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Posted 25 April 2019 - 09:07 AM

View PostGenma Saotome, on 25 April 2019 - 08:03 AM, said:

Minor comment. IMO MaxReleaseRate (6) is too low. I looked into this last year and concluding something in the range of 16-20 was likely correct. I asked and got numerous comments from engineers and many said what boiled down to almost instantaneously while others said a couple of seconds for the whole train. Based on that, I built a 60 car consist, set the brakes, released them (rinse and repeat) until the head of the train train took 5-6 seconds from showing released to hit zero. A fast release rate has no effect on how long it takes to pump up the line.

I recall reading your comment to that effect. Testing my values with a 60-car train, if I go to full service braking, it takes about 45 seconds for the last car's brake cylinder pressure to reach 64 psi. The first car takes about 11 or 12 seconds, which is about right given the 6 psi/sec MaxApplicationRate. As for release, it depends upon whether on not the Graduated Release Air Brakes box is checked in the options menu. If it's checked, it takes about 65 seconds before the last car fully releases (i.e. way too long). If it's not checked, which should be the case for freight trains, it takes about 16 seconds. This seems about right given the values I have. I figure about 11 or 12 seconds for the actual release, and about 5 seconds for brake propagation. Changing the MaxReleaseRate to something like 20 should get the brakes to release in under ten seconds. Also, you would probably have to change the TrainBrakesControllerMaxReleaseRate to something high enough to allow at least a 20 psi/s release rate. Based on a triple value ratio of 2.5, then means this parameter should be at least 8, not the 1.7 I was using.

That brings me to another thing I wish the Open Rails programming team would implement. A lot of people run both freight and passenger trains. For freight trains unchecking the Graduated Release Air Brakes box gives correct operation. For passenger trains the box needs to be checked. There should be a parameter in the .eng file which overrides this setting so you don't have to check it or uncheck every time you switch from passenger to freight. I suggest something like ORTSGraduatedReleaseAirBrakes. You would use ORTSGraduatedReleaseAirBrakes ( 0 ) for freight locomotives and ORTSGraduatedReleaseAirBrakes ( 1 ) for passenger locomotives.

EDIT:

I just tried changing MaxReleaseRate to 20 for both the freight cars and locomotive. I also changed TrainBrakesControllerMaxReleaseRate from 1.7 to 8. Now the brakes release on an entire 60-car train in about 6 seconds. That's probably about as fast as is possible unless you're using ECP brakes which transmit the brake signal electrically.

#7 User is offline   R H Steele 

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Posted 25 April 2019 - 09:17 AM

View Postjtr1962, on 25 April 2019 - 09:07 AM, said:

...

That brings me to another thing I wish the Open Rails programming team would implement. A lot of people run both freight and passenger trains. For freight trains unchecking the Graduated Release Air Brakes box gives correct operation. For passenger trains the box needs to be checked. There should be a parameter in the .eng file which overrides this setting you you don't have to check it or uncheck every time you switch from passenger to freight. I suggest something like ORTSGraduatedReleaseAirBrakes. You would use ORTSGraduatedReleaseAirBrakes ( 0 ) for freight locomotives and ORTSGraduatedReleaseAirBrakes ( 1 ) for passenger locomotives.


Good common sense idea, should be implemented. One request I have, would you consider sharing the formula you used to calculate the OR Dynamic force curves? I would like to make up a spreadsheet for calculating these values. Definition of terms for equation would be helpful.
Best Regards, Gerry


#8 User is offline   jtr1962 

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Posted 25 April 2019 - 09:31 AM

View PostR H Steele, on 25 April 2019 - 09:17 AM, said:

Good common sense idea, should be implemented. One request I have, would you consider sharing the formula you used to calculate the OR Dynamic force curves? I would like to make up a spreadsheet for calculating these values. Definition of terms for equation would be helpful.
Best Regards, Gerry

I already made a spreadsheet for that. I attached it. You enter the parameters in the red and yellow cells. Just copy and paste the output in blue into your .eng file. If you have any questions let me know.

Attached File(s)



#9 User is offline   R H Steele 

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Posted 25 April 2019 - 09:46 AM

Joe, if I may, this is a MOST welcome advancement for OR. Thank you just does not seem enough. ( okay I'll put away the butter knife - as my grandmother used to say )http://www.elvastower.com/forums/public/style_emoticons/default/hi.gifGerry
edit: for now, I gotta take some time, read the pdf, study the spreadsheet, get my mind in order...I'm sure there will be some questions.


#10 User is offline   dajones 

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Posted 25 April 2019 - 10:19 AM

I have some shop test procedure documents for ADB and DB-60 brake values that call for slower release times. The first document is in a file called Code-of-Test-for-ADB.pdf that I think I got from the Wabtec web site. The second is in a file called NYT-1199-C.PDF that I got from the New York Air Brake web site. The ADB release test calls for the pressure in the brake cylinder to drop from 40 psi to 20 psi in 8 to 12 seconds. The DB-60 document calls for 40 to 20 psi in 8 to 11 seconds. Both tests use a fixed 800 cubic inch reservoir to represent the brake cylinder and no retainer or retainer piping.

These documents also have a charging rate test. The ADB charging test calls for the brake cylinder pressure to increase from 0 to 60 psi in 4 to 6 seconds. The DB-60 charging test calls for 0 to 50 psi in 3 to 5 seconds. The charging tests use a 2500 cubic inch auxiliary reservoir and 800 cubic inch brake cylinder. The usual volume ratio for aux. res. to brake cyl. is 2.5, so maybe these times should be multiplied by 1.25 to adjust for the small brake cylinder.

Doug

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