[Genma Saotome]

How does the OR code determine a sequence of units is actually a set of locomotives in multiple unit operation? Is it just the obvious -- a set of locomotives coupled together? Or is there something else that is used?


The reason I ask is this: There are situations where the locomotive is actually a sequence of .wag and .eng files and AFAICT when that occurs OR does not recognize there should be MU operation... at least not with triggering the air compressor to pump up the brake line. There might be other things that fail as well.

On the assumption the simple/obvious answer is the correct answer to my question could this idea be the fix: Crate a new parameter that goes in those .wag files that indicates the unit can function as-if it could pass MU signals to the next unit in line. Call it MU_Passthru( Y ) for lack of a better name. It is still a .wag for all other purposes (e.g., dead weight) but now can serve as a signal to the software to check if there is another locomotive next in line (or possibly another MU_Passthru unit.

A consist might look like this:

PT-L-PT-PT-L-PT-PT-L-PT-W-W-W-W-W-etc.

Where the L refers to three locomotives in MU operation connected by a number of PT wags.

[Traindude]

 Genma Saotome, on 02 December 2021 - 07:13 PM, said:

The reason I ask is this: There are situations where the locomotive is actually a sequence of .wag and .eng files and AFAICT when that occurs OR does not recognize there should be MU operation... at least not with triggering the air compressor to pump up the brake line. There might be other things that fail as well.

If I recall correctly, many diesel and electric MU lashups have additional air hoses to tie the capacity of the main reservoirs of all units together so that all the compressors on all the units serve to pump the Main Reservoirs and Brake Pipe in tandem. Similarly, the sanders on all units are linked together with air hoses so they all work in tandem, and when locos are coupled back-to-back, the rear sanders of the trailing unit are connected to the front sanders of the leading unit. Is this something you're referring to?

[Genma Saotome]

Air pumps, yes. I do not know what other ordinary locomotive functions are disabled by this situation but I am sure there is a failure of the air pumps in trailing units to kick in and assist in pumping up the air in the brake line. I would not be at all surprised if all of the functions normally controlled by MU operation are disabled.

[darwins]

 Traindude, on 02 December 2021 - 08:05 PM, said:

If I recall correctly, many diesel and electric MU lashups have additional air hoses to tie the capacity of the main reservoirs of all units together so that all the compressors on all the units serve to pump the Main Reservoirs and Brake Pipe in tandem. Similarly, the sanders on all units are linked together with air hoses so they all work in tandem, and when locos are coupled back-to-back, the rear sanders of the trailing unit are connected to the front sanders of the leading unit. Is this something you're referring to?

This system of working, was probably invented by Westinghouse in USA for electric trains at the start of the 20th century. From there it pretty much spread around the world on electric multiple unit trains. This is modelled in OR as Air_Twin_Pipe. It differs from more modern twin pipe systems in that the only function of the second pipe is to connect the main reservoirs and compressors together. This *should* be possible to model in OR using Triple_Valve or Graduated_Release_Triple_Valve as these *should* only work in the same way as a single pipe system with air from the brake pipe supplying the auxiliary reservoirs and brake cylinders as in the standard Air_Single_Pipe system. From this beginning EP, SMEE and modern twin pipe systems were developed. In the modern twin pipe system air from the main reservoir pipe rather than the train brake pipe is used to recharge the auxiliary reservoirs. In OR this *should* require the use of a Distributor rather than a triple valve.

[engmod]

>the rear sanders of the trailing unit are connected to the front sanders of the leading unit.

Sanders only ever work on the leading unit.
When the second unit gets to the lead unit position, the sand is still there!!

[Traindude]

 darwins, on 03 December 2021 - 12:10 AM, said:

This system of working, was probably invented by Westinghouse in USA for electric trains at the start of the 20th century. From there it pretty much spread around the world on electric multiple unit trains. This is modelled in OR as Air_Twin_Pipe. It differs from more modern twin pipe systems in that the only function of the second pipe is to connect the main reservoirs and compressors together. This *should* be possible to model in OR using Triple_Valve or Graduated_Release_Triple_Valve as these *should* only work in the same way as a single pipe system with air from the brake pipe supplying the auxiliary reservoirs and brake cylinders as in the standard Air_Single_Pipe system. From this beginning EP, SMEE and modern twin pipe systems were developed. In the modern twin pipe system air from the main reservoir pipe rather than the train brake pipe is used to recharge the auxiliary reservoirs. In OR this *should* require the use of a Distributor rather than a triple valve.

That's nice to know. Even if the loco MU system may be "twin pipe" by OR standards, the freight or passenger cars the lash-up is hauling would still be single-pipe. IIRC this arrangement (twin pipe for the MU connections and single pipe for rolling stock) is not currently modeled in OR.

[Laci1959]

 Traindude, on 03 December 2021 - 07:33 AM, said:

That's nice to know. Even if the loco MU system may be "twin pipe" by OR standards, the freight or passenger cars the lash-up is hauling would still be single-pipe. IIRC this arrangement (twin pipe for the MU connections and single pipe for rolling stock) is not currently modeled in OR.

I don't think this needs to be modeled separately. It is enough if the locomotives are designed for twin pipes and the wagons for one pipe, as in reality.
I would do that. But then the professionals will write the solution.

[pschlik]

I once attempted to give locomotives the twin pipe brake type while keeping the rolling stock single pipe, at which point OR decided that the locomotives should have gradual release air brakes, which they should not. And one of the lovely (and entirely inaccurate!) aspects of the graduated release code in OR is that you can not keep the brakes bailed off on a locomotive with gradual release brakes. Let go of the bail off switch and the brakes come right back up (which is not what happens in real life)!

So that ruined that idea. Made it useless to handle freight trains, defeating the purpose entirely. Now maybe that’s changed in the last few months, it’s been a while since I tried.

[Genma Saotome]

I don't know about 1 vs. 2 pipes. What I do know is the lead and trailing set of wheels on these locomotives are defined as .wags, whereas the middle two are defined as one .eng and the result is only the lead unit contributes to pumping up the air. I would not be at all surprised to discover that only the lead unit contributes power to move the train.

It basically comes to down the question I asked -- what defines a set of locomotives that will operate under one control? Obviously a set of diesel locomotives coupled together do this perfectly well. Swap out diesels for a trio of steam locomotives... does that work as one? If it does, how does the software know to do that?

[darwins]

 pschlik, on 03 December 2021 - 01:00 PM, said:

I once attempted to give locomotives the twin pipe brake type while keeping the rolling stock single pipe, at which point OR decided that the locomotives should have gradual release air brakes, which they should not. And one of the lovely (and entirely inaccurate!) aspects of the graduated release code in OR is that you can not keep the brakes bailed off on a locomotive with gradual release brakes. Let go of the bail off switch and the brakes come right back up (which is not what happens in real life)!

So that ruined that idea. Made it useless to handle freight trains, defeating the purpose entirely. Now maybe that’s changed in the last few months, it’s been a while since I tried.

With regard to the mixture of twin and single pipe - please could you test again now. Hopefully the problem of gradual release has been solved with last year's work on brakes by cesarbl and steamer_ctn. In order to work properly you must have an appropriate brake controller in your loco eng file. For a modern US diesel the controller is likely to be the Westinghouse 26L . For a freight train the engine should have the brake controller in "freight" mode:

Brake_Train ( 0 1 0.1 0.1

 NumNotches ( 5

 Notch ( 0.0  0 TrainBrakesControllerReleaseStart ) Comment ( RELEASE / RUNNING )

 Notch ( 0.1  1 TrainBrakesControllerGraduatedSelfLapHoldLimitedStart ) Comment ( MINIMUM REDUCTION >>> FULL SERVICE )

 Notch ( 0.8  0 TrainBrakesControllerSuppressionStart ) Comment ( SUPPRESSION )

 Notch ( 0.9  0 TrainBrakesControllerNeutralHandleOffStart ) Comment ( NEUTRAL HANDLE OFF )

 Notch ( 1.0  0 TrainBrakesControllerEmergencyStart )Comment ( EMERGENCY ) ) )

This should not give graduated release either with single pipe or if used in twin pipe to work in multiple with other locos. I have attached a document with some suggestions other brake controllers. With regard to bail off, coming from this side of the Atlantic I get annoyed for the other reason. Bail off works when it should not. Anyway, bail off is a function of independent locomotive brakes and at the moment there remains much work to be done to get them working properly in Open Rails. In reality independent brakes are almost always different to the train brakes. Train brakes are generally automatic air brakes or automatic vacuum brakes, whereas locomotive brakes are generally straight air brakes (or steam brakes). So not sure if there will be any improvement in the bail off yet. A question here is there a "bail off button" in loco cabs in USA? (As opposed to there being a RELEASE position on the loco brake controller that will release loco brakes without releasing train brakes.)

Attached File(s)

•  Brake Controllers 2.pdf (103.39K)
  Number of downloads: 213