Wagon especs - Emergency applications and other Q's

[H222]

Hi guys, myself and a couple of others have been trying to improve some of our wagon/physics handling in Trainz. It is something that is severely underlooked at, and makes for a heck of a lot more immersive play when trains actually roll and brake a bit more prototypically. I have a couple of questions that some may or may not be able to help with.

Has anyone had any luck in "forcing" a train's BP/TP down to 0 quicker when an emergency application is made? Anyone know what Tag that is influenced by in the wagon's espec? Prototypically, most locos with a 26-L or newer can dump the entire train's brake pipe very, very quickly

The other question is in relation to the independent/bail off feature on loco's and avoiding it creeping up after you've bailed off the first time. Prototypically, once a minimum is made on a self-lapping brakestand and the bail off is held down for a couple of seconds, the independent will stabilize at 0, and will not creep back on unless you make a further reduction (then the expectation is you bail off again). In trainz, if the Train Pipe or Equalising Res is still reducing the independent will definitely reapply, and often it will reapply again even once your EQ and TP have equalized. Is there a tag in trainz that can increase the power or length of the #4 pipe/Bail off feature? Or is that something that may just need scripting to "force" one bail off command to last several seconds or something?

Cheers
Jamie

 

[2995Valliant]

I've done a very similar exercise for UK rolling stock not so long ago - look for a loco and wagon specs with VB in the title under my kuid (#248163) and try the values I've used in there as a starting point.

Although set up to replicate the sort of delays on a vac. system, I think you might find them closer to what you are looking for. Altering any tag with "vent" in the description to a larger value will help with the brake response time.

Also, getting the brake ratio values right is critical - the default 55000 is way over the top for most UK stock, but probably not so far out for the stuff I imagine you are looking at.

For a loco, take the weight on the braked wheels in kg and use somewhere between 85 - 100% of that figure. Wagons are more complicated as IRL modern wagons normally have different brake settings according to whether they are loaded or not, so It's either two different specs (at 100% of the respective weights) or just average the empty and loaded mass and use that figure. For steam era stuff in the UK that's close enough, but for modern high capacity bogie wagons it may not work so well.

 

[SHEPRom]

H222, I can try offering some insight into the pneumatic brake settings for a locomotive. See the spoiler in this post

throttle-power in enginespec

II have opened an Enginespec config file to edit. Under throttle-power I see which I think are sections for 0 (idle I assume) and 1-8 which I assume are notch positions. Under each notch, I see 2 colums of from 6 up to 11 lines of (I assume) parameters. Would someone explain what these...

forums.auran.com

 

[SHEPRom]

getting the brake ratio values right is critical - the default 55000 is way over

I'd like to know how you decided this value is the "default"? There's no direct indication of this in Wikipedia, and in my opinion, this is just an example...

For a loco, take the weight on the braked wheels in kg and use somewhere between 85 - 100% of that figure.

If I've translated and understood the expression correctly, then it follows that if a locomotive weighs 120,000 kg, then you're suggesting using the exact same value—120,000—in the brake ratio tag? Or am I misunderstanding something?

 

[2995Valliant]

I'd like to know how you decided this value is the "default"? There's no direct indication of this in Wikipedia, and in my opinion, this is just an example...


If I've translated and understood the expression correctly, then it follows that if a locomotive weighs 120,000 kg, then you're suggesting using the exact same value—120,000—in the brake ratio tag? Or am I misunderstanding something?

See here https://online.ts2009.com/mediaWiki/index.php/"Motor"_container

55000 is probably not uneasonable for large US or equivalent item of rolling stock, but for the sort of stuff I muck about with (UK mid 20th century) it is quite a bit too high. It was used in the original <kuid:-1:42004201> default wagon spec by Auran and as such has been widely re-used elsewhere.

Unless you have a brake force figure for the locomotive, 85-100% of the weight seems a reasonable figure based on data and text books for UK locos with modern braking systems. For steam loco's the rule of thumb was 65% of the weight on the drivers, early diesels in the UK could be as low as around 50%

 

[H222]

Locomotive independent brakes are generally much stronger than wagon brakes, partly due to their mass and partly due to the respective air pressure placed on their shoes. A figure around its weight seems right to me, as they are able to often hold entire trains just on their loco independents. There are many nuances between different locos too, especially as some (that I work on) have 2 brakeshoes per wheel and others only have 1. 134t locos with 2 brakeshoes per wheel hold significantly more on their independant than 134t locos with only 1 shoe per wheel.

My calculations and (LOTS of) testing lead me to believe a calculation between 0.5 and 0.75 of the wagon’s maximum gross weight gives you a reasonable “loaded” brakeratio figure. I.e. a freight wagon that’s maximum gross (loaded) weight is 100t would have a brake ratio between 50000 and 75000, depending on whether it’s a poorly braking or well braking vehicle. I have seen figures on builders diagrams that may or may not accidentally correspond with these figures. I have seen diagrams of Victorian Railways locos that have info on them that states “73% air” but i can’t really confirm what this relates to and whether it’s just a coincidence or if N3V got these Brakeratio figures from somewhere similar.

Unfortunately, on a lot of our tracks if I averaged it out between loaded and empty figures we would be running away down 1/33 (3%) gradients quite regularly. Zec and I are discussing how to easily (and in a performance friendly way) script the espec changing when a wagon detects that it is now loaded, either requiring 2 assets or if the Brakeratio tag can be taken from the espec and a tag can multiply or divide that figure. I’m pretty sure 2 especs will be easier - it really only is a change of 1, possibly 2 figures.
Scripting locos with an emergency brake valve opening and forcing the pressure down very quickly might be the go as well. Only in emergency does the brake pipe drop so rapidly.

Being a freight driver in real life and working on a variety of lines and wagon types/scenarios has been a real help for what is still educated guesswork - I guess that’s all the job is a lot of the time when it comes to the Westinghouse brake too.

Thanks for the input guys. Happy to hear from others as well

Jamie

 

[2995Valliant]

I think my vote would also be for two separate specs as that also allows other parameters to be adjusted more easily if required such as wind resistance and suspension settings which also may alter between empty and loaded wagons - for example empty hoppers have more wind drag than full ones, and a empty container wagon has very different characteristics to a double stack one.

If a script is going to be done, could it also include an option to set the handbrake?

 

[SHEPRom]

See here https://online.ts2009.com/mediaWiki/index.php/"Motor"_container

By default I mean that when a tag or its value is missing, calculations take some default value.

55000 is probably not uneasonable for large US or equivalent item of rolling stock, but for the sort of stuff I muck about with (UK mid 20th century) it is quite a bit too high. It was used in the original <kuid:-1:42004201> default wagon spec by Auran and as such has been widely re-used elsewhere.

Unless you have a brake force figure for the locomotive, 85-100% of the weight seems a reasonable figure based on data and text books for UK locos with modern braking systems. For steam loco's the rule of thumb was 65% of the weight on the drivers, early diesels in the UK could be as low as around 50%

Brake ratio isn't the braking force, nor is it the total pressure on the brake pads of a rolling stock unit. Wikipedia clearly states it—it's a coefficient... A coefficient can only be applied to the lever transmission, the gear ratio. There's no point in looking for official values for this, either, because the ultimate goal, the braking distance, will depend on a number of other factors. This will primarily be influenced by the operating speed of the air brakes on the entire train. Brake ratio should be determined based on actual testing in the game.

 

[2995Valliant]

By default I mean that when a tag or its value is missing, calculations take some default value.


Brake ratio isn't the braking force, nor is it the total pressure on the brake pads of a rolling stock unit. Wikipedia clearly states it—it's a coefficient... A coefficient can only be applied to the lever transmission, the gear ratio. There's no point in looking for official values for this, either, because the ultimate goal, the braking distance, will depend on a number of other factors. This will primarily be influenced by the operating speed of the air brakes on the entire train. Brake ratio should be determined based on actual testing in the game.

I disagree - I think as far as Trainz is concerned, regardless of the proper definition of the term, the value can be assumed to be the brake force. It certainly gives realistic results when compared to real world brake test stopping distances.

A further question: if it is a ratio, why is it such a high number - what is it a ratio of? Although no unit of measurement (eg mass) is specified, the fact the default is very conveniently around the brake force of a large modern rail vehicle rather than the magnifying force of a brake linkage on a brake cylinder (which would be single or low double digits) makes me even more inclined to think the tag is incorrectly named.

 

[SHEPRom]

My calculations and (LOTS of) testing lead me to believe a calculation between 0.5 and 0.75 of the wagon’s maximum gross weight gives you a reasonable “loaded” brakeratio figure. I.e. a freight wagon that’s maximum gross (loaded) weight is 100t would have a brake ratio between 50000 and 75000, depending on whether it’s a poorly braking or well braking vehicle. I have seen figures on builders diagrams that may or may not accidentally correspond with these figures. I have seen diagrams of Victorian Railways locos that have info on them that states “73% air” but i can’t really confirm what this relates to and whether it’s just a coincidence or if N3V got these Brakeratio figures from somewhere similar.

These are quite large values. I believe their use is due to the relatively low operating speed of the pneumatic brakes, both for the locomotive, the car, and the entire train. So, yes, to compensate for the low operating speed of the pneumatic brakes and maintain acceptable braking distances, such high values are necessary. With my pneumatic settings, the locomotive is at mass/2.75, and the car is at mass/3.25.

Scripting locos with an emergency brake valve opening and forcing the pressure down very quickly might be the go as well. Only in emergency does the brake pipe drop so rapidly.

In the train, the brake pipe doesn't operate separately from the equalizing reservoir; it doesn't fill or empty faster than the equalizing reservoir. And there are all the tags for adjusting all the equalizing reservoir modes, including emergency braking - equaliserventemergency . Everything works quite well. The main thing is to not be afraid to set a good value there.
And if you need to implement the emptying of the brake pipe only separately, then yes, only script control - settrainbrakepipeefficiency.

Of course, the default air brake settings, with most tags set to 0.1, are completely inadequate; they're too slow for modern trains, especially long trains. Perhaps these settings were acceptable for the early days of steam locomotives, when carriages were few and brake pipes were considerably shorter.

Again, who wants to get what from brake settings? Who expects what, and based on what information? For example, the time it takes for the brake cylinder of the 100th car in a train to fill to 95% of its maximum pressure, from the moment the brake valve is applied, in seconds, during full service braking, and during emergency braking, when the locomotives are only on one side of the train. The release time of the brake cylinder of the 100th car after full service braking, to a pressure of 0.5 atm (0.2 or 20 kPa in the game). I have all this information for our braking equipment, ex-USSR, from the literature.

 

[SHEPRom]

I disagree - I think as far as Trainz is concerned, regardless of the proper definition of the term, the value can be assumed to be the brake force. It certainly gives realistic results when compared to real world brake test stopping distances.

No, that's not a question, I completely agree with your arguments regarding this tag. Ultimately, it determines the braking force of the locomotive/car, whatever its name. If I may say so, I merely described my perception of this tag based on its name. Mathematically, or numerically, I agree that it most closely resembles the braking force: 30,000-50,000 kg for a 100-ton car. For the gear ratio, this should look like 15-20, and for the pressure on the brake shoes, 100,000-200,000 kg.

 

[SHEPRom]

Has anyone had any luck in "forcing" a train's BP/TP down to 0 quicker when an emergency application is made? Anyone know what Tag that is influenced by in the wagon's espec?

To answer this question specifically, yes, it is possible to reduce the brake line pressure to 0, but only when using the default pneumatic settings, without script control. This is determined by the tags in the container "pressure" . I write it like this:

  brakepipe                             0.00669
  brakeinitial                          0.00669
  brakefull                             0.00105

Ex-USSR train driver's brake valves, code numbers 394 and 395, allow this. They do not require the brake pipe pressure to be set at the equalizing pressure, approximately 3.8 - 4.0 atm. These valves also don't have an initial braking pressure as such.

 

[SHEPRom]

But not everything depends solely on the locomotive's air brake settings; the cars must also contribute. And that's where the fun begins...