Elvas Tower: Compressor and main reservoir - distributed power units - Elvas Tower

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Compressor and main reservoir - distributed power units Rate Topic: -----

#1 User is offline   istvanek 

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Posted 05 February 2017 - 07:25 AM

I would like to raise this issue again. I do remember that Carlo switched off DPUs (not multiple units, this perform ok) main reservoir connection with a train main air line on request. I do not remember why sombody asked for this feature because I am not able to find orginal topic on this forum (could anybody find it and give a link?). But in my opinion current OR setup for how DPUs are acting with a train air line is wrong. Charging a main air line is one of the most importand DPUs feature because it is reducing significantly time needed to recharge it. And for very long trains, DPUs reduce the likelihood of breaking a coupler beceuse they charging an air line (and so cars start releasing brakes) from two points in a train. In a long train this would matter as main air line will not charge instantly but an air pressure will rise form the nearest main reservoir. If we have main reservoirs only at the begining of the DPU equipped train (as it is in current OR setup), we will end with brakes releasing from the front to the end which is not prototypical for DPU equipped trains.

And this problem does not affect only DPU trains. Push-pull passenger trains (common both in Europe and America) behave the same way, as usually steering car do not have compressor nor main reservoir. So if we have this setup:

<Steering car + car + car + ... + pushing engine< (.eng+.wag+.wag+...+.eng)

our train in OR will not recharge main air line unless we equip steering car with a fake compressor and main reservoir.

I can not imagine train setup with powered units equipped with main reservoirs which are cut off from the main air line. Probably it is possible to cut off main reservoir in a locomotve but only because of failure.

This do not apply to 'short strech pushers' (called helpers in North America?) but as far as I know this locos are not connected to main air line (brake hose remains unconnected) so they do not charge the main air line nor they respond to pushed train train brake. They have they own crew who communicate with pushed train crew by radio or signals (sound or others).

Could you please consider to restore DPU main reservoirs feature? If current OR behavoir in this matter is needed mayby it will be a good choice to create an option under OR Options menu? (or better under train F9 window)

Artur

#2 User is online   Csantucci 

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Posted 05 February 2017 - 08:59 AM

Hi Artur,
I don't think I switched off something. If I remember well, I asked if the operation as it was at that moment (which was already as it is now, that is only engines directly connected with the front engine contribute to air recharge) was correct or not (I believed it wasn't), and after some discussion it was considered better to leave as it was, even if this does not cover all situations, as you mention. Someone posted also a table with all cases about this. Probably having an additional selection line under the Car Operation Window (e.g. Reservoir connected/disconnected) would be the best way to have more possibilities open. However probably simply setting a flag wouldn't do the job, as also the physics should be upgraded to consider the brake pipe pressure propagation in the opposite direction. I'm not an expert in this.

#3 User is offline   Coolhand101 

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Posted 05 February 2017 - 10:09 AM

View Postistvanek, on 05 February 2017 - 07:25 AM, said:

And this problem does not affect only DPU trains. Push-pull passenger trains (common both in Europe and America) behave the same way, as usually steering car do not have compressor nor main reservoir. So if we have this setup:

<Steering car + car + car + ... + pushing engine< (.eng+.wag+.wag+...+.eng)

our train in OR will not recharge main air line unless we equip steering car with a fake compressor and main reservoir.



It is possible atm for the rear compressor to charge the front cab car providing the whole trainset is using "air_twin_pipe". I have a push pull unit, 8 coaches and diesel engine. The compressor is on the diesel engine. This will charge the main res pipe through out the train. OR by default will always use a compressor on the front engine (cab car ). By using this setup, the compressor will never work and act as if that coach has no compressor.

AirBrakesAirCompressorPowerRating( 0 )
AirBrakesMainMinResAirPressure( 0 )
AirBrakesMainMaxAirPressure( 100 )
AirBrakesMainResVolume( 20 )
AirBrakesAirCompressorWattage( 0 )
AirBrakesCompressorRestartPressure( -90 )
AirBrakesAirUsedPerPoundsOfBrakePipePressure( 4 )
AirBrakesHasLowPressureTest( 1 )
AirBrakesIsCompressorElectricOrMechanical( 0 )

This is what i use, until the compressor will work on air_single_pipe or until the aux. reservoir will not recharge under air_twin_pipe until the train brake is the release position.

Thanks

#4 User is offline   istvanek 

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Posted 05 February 2017 - 11:47 AM

View PostCsantucci, on 05 February 2017 - 08:59 AM, said:

Hi Artur,
I don't think I switched off something. If I remember well, I asked if the operation as it was at that moment (which was already as it is now, that is only engines directly connected with the front engine contribute to air recharge) was correct or not (I believed it wasn't), and after some discussion it was considered better to leave as it was, even if this does not cover all situations, as you mention. Someone posted also a table with all cases about this. Probably having an additional selection line under the Car Operation Window (e.g. Reservoir connected/disconnected) would be the best way to have more possibilities open. However probably simply setting a flag wouldn't do the job, as also the physics should be upgraded to consider the brake pipe pressure propagation in the opposite direction. I'm not an expert in this.



I'm sorry Carlo. I remembered it this way and the memory is sometimes unreliable. Probably I read something wrong. Please excuse.

I have found similar topic here Multi-part locomotives and the air compressor

and Peter explanations:

View Poststeamer_ctn, on 28 August 2016 - 12:25 AM, said:

I think that this makes sense, as in a single pipe system, the train pipe provides the control signals for the brake operation, and mostly the main reservoirs of trailing locomotives would be isolated from the brake pipe. If they weren't isolated then they could give "funny" pressure readings behind the controlling locomotive due to them injecting air into the system.

Twin air pipe systems overcame this problem, as one pipe could be used for control purposes, and the other one to link all the reservoirs together to create a "super reservoir", without impacting on the train pipe pressures.

There are probably a number of scenarios in regards to multiple locomotive operation that could be considered:
i) Steam (especially older units) - only had single pipes, and the reservoirs on trailing locomotives would have been switched out
ii) Older diesels may not have been set up for multiple operation for brakes, and thus their reservoirs would have also been switched out.
iii) New Diesels would have been set up for multiple operation with multiple air hoses and electric control
iv) Modern Diesels appear to mostly use wireless and electronic control.



In normal operation, with the exception of option iv), above it would be unlikely for locomotives separated by wagons (WAG files) or tenders to operate in MU and have their reservoirs "connected". I agree that OR doesn't appear to cater for option iv) at the moment.

I think that the real question to ask is, should we use "dummy" WAG and ENG files to get around issues with articulated or multiple part locomotives? Is this solving the problem or making it more complex?


That explains the problem.

For now we have MU front locomotives with operating main reservoirs and compressors, so there is a code which simulates electrical connection beetween locomotives and main reservoir remote control. Am I right?

What will happen when all trailing units in a consist will behave as front MUs? How the train air line (in OR) will behave? It is clear that we need a switch here to enable/disable this feature. I am just curious if it is possible to implement without significant changes in OR braking behavior. I am avare of the brake pipe pressure propagation in the opposite direction problem.

Artur

#5 User is offline   istvanek 

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Posted 05 February 2017 - 11:54 AM

View PostCoolhand101, on 05 February 2017 - 10:09 AM, said:

It is possible atm for the rear compressor to charge the front cab car providing the whole trainset is using "air_twin_pipe". I have a push pull unit, 8 coaches and diesel engine. The compressor is on the diesel engine. This will charge the main res pipe through out the train. OR by default will always use a compressor on the front engine (cab car ). By using this setup, the compressor will never work and act as if that coach has no compressor.

AirBrakesAirCompressorPowerRating( 0 )
AirBrakesMainMinResAirPressure( 0 )
AirBrakesMainMaxAirPressure( 100 )
AirBrakesMainResVolume( 20 )
AirBrakesAirCompressorWattage( 0 )
AirBrakesCompressorRestartPressure( -90 )
AirBrakesAirUsedPerPoundsOfBrakePipePressure( 4 )
AirBrakesHasLowPressureTest( 1 )
AirBrakesIsCompressorElectricOrMechanical( 0 )

This is what i use, until the compressor will work on air_single_pipe or until the aux. reservoir will not recharge under air_twin_pipe until the train brake is the release position.

Thanks


Thank you Coolhand. I did not realize that twin piped systems would solve this problem. But yes, we have there second air line for charging. Unfortunatelly this system behaves differently when braking/releasing brakes so I prefer fake compressor in my steering cars and single pipe system.

#6 User is offline   railguy 

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Posted 05 February 2017 - 12:43 PM

This is good reading on how US locomotives are set up for MU operation, with some paragraphs on air brakes.
http://www.railway-t...m/us-musp.shtml

It is my opinion that MU units should be set up with the default that all MU'ed locos contribute air to recharging the train line. Possibly, the connect/disconnect MU cable function could have the added functionality isolating the locomotive compressor's air contribution. Similarly, I would think that the default for DPU/helper locomotives should be that their compressors contribute air to charging the train line. The default DPU control in the US is for the DPU locomotive (and whatever MU locos are connected to it) to respond in kind to the engineer's operation of the lead locomotive's controls. The exception is when the engineer "builds the fence" that allows him/her to make control commands to the DPU's independently from the controls of the lead loco and its connected MU locomotives. In the sim world, Run 8 already does this.

#7 User is offline   Coolhand101 

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Posted 05 February 2017 - 01:00 PM

View Postistvanek, on 05 February 2017 - 11:54 AM, said:

Unfortunatelly this system behaves differently when braking/releasing brakes so I prefer fake compressor in my steering cars and single pipe system.


For me, i lost the ability to charge the aux.reservoir once the train brake handle is in the release position.

How different is the braking/releasing for you compared to air single pipe?

Thanks

#8 User is offline   istvanek 

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Posted 05 February 2017 - 02:59 PM

View PostCoolhand101, on 05 February 2017 - 01:00 PM, said:

For me, i lost the ability to charge the aux.reservoir once the train brake handle is in the release position.

How different is the braking/releasing for you compared to air single pipe?

Thanks


The biggest difference is that with double piped system you have auxiliary reservoirs always charged. This makes the brake 'inexhaustible'. Quite a difference during mountain railroading with old push-pull consist and engine not equipped with dynamic brakes.

#9 User is offline   SP 0-6-0 

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Posted 05 February 2017 - 03:25 PM

It would be cool if the Southern Pacific air repeater cars can be modeled correctly. SP Air Car

More info My link

SP air car at TS.com aircarsp.zip

Robert

#10 User is offline   istvanek 

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Posted 05 February 2017 - 03:49 PM

View PostSP 0-6-0, on 05 February 2017 - 03:25 PM, said:

It would be cool if the Southern Pacific air repeater cars can be modeled correctly. SP Air Car

More info My link

SP air car at TS.com aircarsp.zip

Robert


Very interesting units. This cars did what DPUs do today. I guess there were no radio nor electrial connection with lead engine and it was controlled only by pneumatic signals from main pipe.

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