[darwins]

For a mechanical compressor definitely the rate of charging must depend on engine rpm and not be constant* like an electric compressor.

What I would suggest that will cover all eventualities would be this:

If the eng file includes

AirBrakesCompressorRestartPressure( x )

Then it must operate as described by Erik and use existing start and stop and sound triggers as previously.

If the eng file does not include

AirBrakesCompressorRestartPressure( x )

Then operation could be continuous as for the new patch.


What does surprise me about the information provided by Erik is that large diesel electric locomotives in USA have mechanical compressors (rather than electric). I had assumed these might only be found on small shunting locomotives or diesel railcars with mechanical or hydraulic transmission. In these cases part of the reason for using a mechanical compressor would be simplicity. With that in mind I would expect them to be more simple in operation. Does anyone have operational details of a compressor for say a Budd RDC, small shunting locomotive (or even the compressors used on a truck or bus which would be similar)?


*it has been pointed out that for both electrical and mechanical compressors the rate of charging should decrease as reservoir pressure increases, but this seems to be beyond the scope of the present OR model.

[BB22210]

Hi, is anybody tested successfully the Cabview 3D features with release 1.4 ?

[quresh sk]

that's great


waiting for the update

[Csantucci]

I've tested steamer_ctn's latest patch in the Unstable release for mechanical compressors, and it's OK to me. Now compressor sound changes (or goes on and off) as it should.
It would be nice if ErickC and/or railguy test it too.

[superheatedsteam]

 BB22210, on 27 September 2021 - 10:47 PM, said:

Hi, is anybody tested successfully the Cabview 3D features with release 1.4 ?

I have tested my 3D cabs in v1.4rc3 . All dials, digital numbers, wipers, control levers, buttons and state indicators work as expected. I do not have any SOLID style gauges so can't report on these.

Cheers,

Marek.

[Weter]

@Darwin
USSR mainline diesels until 1970-th had mechanic driven compressors too.
ТЭ2 to ТЭ10, M62, ТЭП60, soviet&chekh 1200+ hp switchers...
Only after 1970 with ТЭП70, 2ТЭ116 with separate generators for auxiliary machines, compressors became electric.
So far, this work with code is a lot actual for many projects.

I think, the reason was not simplicity (mechanic transmission could include hydro-clutches), but less weight of transmission and less care, in compare with collector DC motors. Plus more compact size.

As I see, buses have device to load-off compressors too. That saves fuel and decreases wearing of rotating parts, cylinder-piston pairs and valves.

Some old trams (2-axle, rigid base/single bogey) had pure MECHANICAL compressors, driven by wheel axle. No moving-no air.

[railguy]

 Csantucci, on 27 September 2021 - 11:36 PM, said:

I've tested steamer_ctn's latest patch in the Unstable release for mechanical compressors, and it's OK to me. Now compressor sound changes (or goes on and off) as it should.
It would be nice if ErickC and/or railguy test it too.

I did a quick test of this in Unstable release 0321 earlier this afternoon. It appears that everything is working, with only one possible (and maybe unrelated) exception. It appears that applying the Independent brake does not deplete air from the main reservoir as it should on an independent brake application. Either that, or the flow rate is so slow that depletion goes almost unnoticeably. The compressor sound triggers, both for electric and mechanical compressors, worked correctly for me.

[pschlik]

Out of curiosity, does anyone know how the sim is determining the main reservoir fill rate with these changes to mechanical compressors? I only know of the ability to enter one value for the rate at which the compressor refills the MR in psi/s. For a mechanical compressor, is that number treated as the recharge rate at maximum RPM, minimum RPM, or something else? And with only one value entered, how is the sim determining what charge speed to use for other RPMs? I would assume a linear relationship has been coded between engine RPM and compressor speed, but I don’t know for sure.

Personally I would prefer to be able to define my own table of psi/s vs RPM as that would give a lot more room for realism. For example, something like a GE Dash 8 does have an electric compressor, but the speed of the compressor is not constant. The power to drive the compressor’s AC motor comes from the auxiliary alternator, which produces an AC frequency which depends on engine RPM. But it doesn’t behave like a mechanical compressor because the compressor can run at either twice engine speed, or run in sync with the engine, depending on the current engine RPM and throttle setting. Consequently, a constant air flow rate nor a linear rate is appropriate for this situation. The best way to model that is with hand-picked data points.

And then, from what I understand, pumping rate isn’t going to be linearly related to speed on a mechanical compressor, either. There isn’t really a one size fits all simulation in this case.

[Weter]

Tip from colleague: as it has intercooler, low speeds drives it less efficient. While electric drive makes its installation more flexible (no need of mechanical shafts/gears. Plus, in case of emergency, it can be turned off, or turned on directly-depending on the case.

[steamer_ctn]

 pschlik, on 28 September 2021 - 12:42 PM, said:

Out of curiosity, does anyone know how the sim is determining the main reservoir fill rate with these changes to mechanical compressors? I only know of the ability to enter one value for the rate at which the compressor refills the MR in psi/s. For a mechanical compressor, is that number treated as the recharge rate at maximum RPM, minimum RPM, or something else? And with only one value entered, how is the sim determining what charge speed to use for other RPMs? I would assume a linear relationship has been coded between engine RPM and compressor speed, but I don’t know for sure.

The existing recharge rate is equated to Max RpM, and then a linear relationship is adopted to vary the charging rate.

Do you have manufacturers graphs or tables for the RPM vs output air volume?