[steamer_ctn]

I have raised a blueprint to add some additional features to the air brake which appear to have been included(?) in MSTS, and apply to "prototype" brakes.

The first one that will be added, will be to allow for air leakage from the train brake pipe, as very few trains operated with a perfectly sealed air brake system. Coupling hoses between cars were potential sources for leakage.

Most railway operating companies had standard tests to check the amount of leakage in the train brake pipe, and it appears that a leakage rate of approximately 5 psi/min was an acceptable amount.

The air leakage amount will be set by using the existing MSTS parameter - TrainPipeLeakRate.

Thus when the train brake pipe is connected to the main reservoir (eg, when the brake controller is in the LAP position), a constant air pressure will be maintained in the train pipe, despite the leaks from the train pipe. The main reservoir will decrease over time

However when the brake pipe is isolated from the reservoir (eg, when the brake controller is in the Running position), then air will slowly leak out of the train pipe (at the rate indicated in the ENG file), thus applying an increased BC pressure, and applying the brakes harder.

[atsf37l]

Peter, I think you have Lap and Running reversed. Lap is all ports closed and status quo where no action is being taken in the system and the most recent action is 'held.' Running is used to keep the brake line charged at the running pressure through the equalizing valve and reservoir. The main reservoir is only connected to the brake line through the other components and is usually 20-30 psi greater than the train line pressure.

[steamer_ctn]

Hi Herb,

atsf37l, on 10 July 2016 - 11:23 PM, said:

I think you have Lap and Running reversed.

You are indeed correct.

Thanks for pointing that out, and sorry about the confusion.

[atsf37l]

You're welcome and we probably don't have to worry about the workings of the equalizing valve and reservoir for purposes of the sim. It's another of those "do this and magic happens" components.

[Coonskin]

And even with the so-called "self lapping" brake valves (such as a 26L): Every now and then you will get one that the EQ leaks (so it will not "maintain" a set), so it continues to draw off air on a set at an ever so slow (or not so slow if it's a bad leak), complicating dropping off long grades. Only way to overcome such a situation is:

* Use the PASS setting if the 26L has a 3-position cut-out.

* Use the Regulator Valve if the globe valve knob is still in place.

Either way, I'm not sure MSTS or OR either, needs the complication of the above. The above was just a general FYI from one that has had to fight such brake valves for over a decade.

[ATW]

Will there be a air flow indicator to determine BP leakage? Are we talking about adding eng/wag parameters that are like a hole size for air to escape an determine an excess of leaks based on the number of cars in a train?

I tend to purposely get leaks whether on rear or head end by making some cars bleed the air. But it sounds good to add a parameter instead of bleeding.

[TSCraftsman]

Looking forward to having a BP leakage feature which would make simulating winter time railroading for cold parts of Canada and the US much more realistic due to cold shrunken gaskets etc. Especially on empty autoracks when the slack comes in and the tendency to leak and setting the brakes harder.

[copperpen]

Additions to the airbrake system are very nice and welcomed, but when are we going to get a working ejector for vacuum systems.

[steamer_ctn]

ATW, on 12 July 2016 - 01:12 AM, said:

Will there be a air flow indicator to determine BP leakage? Are we talking about adding eng/wag parameters that are like a hole size for air to escape an determine an excess of leaks based on the number of cars in a train?

The existing MSTS parameter - TrainPipeLeakRate will be used. This parameter is in the ENG file, and it is expected that this value would be set at < 5psi/min.

copperpen, on 12 July 2016 - 10:20 AM, said:

Additions to the airbrake system are very nice and welcomed, but when are we going to get a working ejector for vacuum systems.

Do you have any detailed information on how the ejector works? Is there a manual with specifications available?

Info like steam usage rates, vacuum creation rates, etc.

[copperpen]

MSTS vac eng files have usage rates for large and small ejectors. The small ejector was used to take care of brake pipe leakage, the large ejector was used to give a fast increase to the vacuum when releasing the brakes. The small ejector on GWR engines was mechanical, driven as the engine was moving. I will do some research into the details. Until we have working ejectors, the vac brake system is not really useful.

[copperpen]

After a lot of digging in various books and trawling the internet, the only figure I can find is for steam usage of the small ejector of the Gresham & Cravens Dreadnought which is given as 300lb steam per hour. However, as the ejector could be varied over a small range to maintain a vacuum, the average for a train of the 1930's in Britain is stated as about 400lb per hour. The large ejector would of course use a lot more, but was not in continual use. The there is the mechanical pump used by the GWR in particular which was driven by the crosshead and maintained the vacuum in the trainpipe. The pipe itself was of 2 inch internal diameter pipe and the system was almost as fast in application and release as the air brake systems.

Given the above, it can be reasonably assumed that the figures for steam usage of ejectors in various MSTS eng files can be taken as about right. On that basis the other figures for the vac system in MSTS files should not be far from what is required.

[steamer_ctn]

Version #3600 now includes the capability to specify train air brake pipe leakage rate.

To enable this capability the following parameter must be entered into the ENG file.

TrainPipeLeakRate ( 0.0833 )

The default unit of measure is psi/s. Other units can be bar/s, inHg/s or kPa/s.

Normally the train air pipe leakage rate accepted by most railways was around 5psi/min.

In most brake positions the air leakage will be replaced instantaneously with air from the main reservoir to maintain the set pressure. However, in older braking systems, such as the A6ET system, the train brake pipe was isolated from the main reservoir when in the LAP position, and thus the pressure in the brake pipe could reduce, thus applying the brakes.

Most modern locomotive brake systems had a self-lap position which maintained the set brake pipe pressure regardless of the train pipe leakage.

[Icik]

Hello Mr. Steamer_ctn,

I found a bug when in options the language set to Czech language, then pipe leakage is from main reservoir but not from brake pipe.

Please fix that.

[steamer_ctn]

Icik, on 09 August 2016 - 02:41 AM, said:

I found a bug when in options the language set to Czech language, then pipe leakage is from main reservoir but not from brake pipe.

Can you please explain why you think that there is a bug.

Depending upon the brake controller setting, train pipe leakage will cause the main reservoir to drop in pressure over time.

What symptoms are you getting?

Thanks

[Icik]

When I set the language to English, the leakage is just from brake pipe (controller is in lap position). Compressor is off, just triple_valve go to apply and begin to brake.
When I set the language to Czech, the leakage is just from main reservoir (controller is also in lap position). Compressor is on, triple_valve is in release position.