[railguy]

I just discovered this issue on R105 of Monogame. When diesel locomotives are MU'ed together, the compressor only runs on the front and rear locomotives of the lashup. I discovered this because the compressors on the "middle" locomotives were not starting as they should. I checked the F5 display and the "middle" locomotives show no compressor at all in the display. Reservoir pressure shows, but no compressor. I've tried this with multiple locomotives with the same result. The OpenRails logs show no errors related to .eng files. Attached is a screenshot showing the F5 display. Note there are 4 locomotives on the head end and 2 DP locomotives on the rear. "Compressor" only shows on the lead loco and rear loco of the head end locomotives.

This also points out what I believe is another omission that has been present in OR loco operations with regard to air compressors. Prototypically, when locomotives are MU'ed together, ALL air compressors will run and feed air to fill the train pipe, etc.--their airflow is thus additive--more locomotives means more airflow. This also includes mid-train and rear distributed power--DP currently does not even respond to drops in train pipe pressure and start the DP air compressors. Again, this is not faithful to prototypical operation. Finally, I believe there should be a "main air reservoir leak rate" parameter available for each locomotive, in addition to the current TrainPipeLeakRate parameter. Main locomotive reservoirs do leak without affecting the train pipe, but will cause the compressor to run to replenish the main reservoir.

Thanks in advance for looking into this.

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[Csantucci]

Can you please check if these problems arise also in the OR Testing version?

[railguy]

I'm working on other projects and don't have time to check the test version, but the air compressor issue is not present in R103.1 of Monogame, so it must have been introduced into R105.

[Csantucci]

The modified braking features of rev. 105 stem from the testing version. Either the problem has been derived from the testing version, or within the process of getting the new features from the testing version a mistake has been made. Thus my question.

[Weter]

Quote

Main locomotive reservoirs do leak without affecting the train pipe, but will cause the compressor to run to replenish the main reservoir.

This is exactly correct!
At "Running" position (I mean real driver's valve now, not MSTS brake token) the pressure at BP is maintained on "normal" level, as well as at "Lap with feeding" position (keeps reduction step).
But leaks from both: brake and feeding networks are compensated by main reservoir's air deposite, so indeed MR's pressure decreases with time, causing compressor(s) to pump it up periodically.
WRT turned-off compressors, by default that must not be so, definitely!
Compressor can be turned off intentionally for saving its resource or for guarantee of having reserve, or may be so due to failure, but normally, all compressors are working together. Furthermore, it's complex to turn-off mechanical compressor - only by cut-off it from entry system by valve.

[Csantucci]

 railguy, on 22 September 2021 - 11:30 AM, said:

I'm working on other projects and don't have time to check the test version, but the air compressor issue is not present in R103.1 of Monogame, so it must have been introduced into R105.

As you can't find the 10 minutes needed, I had to test myself. Below is the result with the actual testing version

As can be seen, only for the first locomotive the compressor state is shown. With 1.3.1 the compressor state is shown for all three locomotives.
I'd ask our physics expert to examine the issue, to avoid having this bug in the 1.4 release.

[railguy]

Carlo, I did try to find the bug last night, but my computer had issues trying to compile the source code. I'm trying to sort that out now. My apologies for sounding like I'm trying to dump the problem on you. I confess that I'm not an expert on source code--but I do know something about railroading as I spent time working in the railroad industry. I have always appreciated all the effort you and the OR developers put into the OR program to make it a great simulator.

[Csantucci]

I appreciate that you tried to find the problem, case is closed :) . As written in my preceding post, I hope that the OR developer expert in physics checks this issue.

[Csantucci]

OK, waiting for others' intervention, I digged into the case and found out what causes the problem: at the beginning of September a change has been inserted in the official code, which causes that locomotives with mechanical compressor don't show the compressor state. This is true only for locomotives different from the player locomotive: the player locomotive always shows the compressor state. Accordingly to the added code comments mechanical compressors for diesel locomotives are always active.
In the test I did, the SLI ES44AC have a mechanical compressor accordingly to the .eng file, and so the state of the compressor is not shown (except for the player locomotive).

Moreover IMHO if mechanical compressors in diesels are always on, they should be shown in state ON in the HUD, rather than being not shown at all.

[Weter]

That's good, but would be better, if HUD will be fixed.