Elvas Tower: Steam Locomotive Vacuum Brake Ejectors - Elvas Tower

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Steam Locomotive Vacuum Brake Ejectors

#1 User is offline   dennisat 

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Posted 11 June 2015 - 08:36 AM

I notice that the steam locomotive model continues to be developed. Could I therefore draw someone's attention to bug 1391449 that has been outstanding since 11th Nov 2014. This bug documents that Vacuum Brake Ejectors (not Injectors as quoted in the bug report) are not yet implemented in OR. They were implemented in MSTS, control "J". This means that a number of British steam locomotive models currently have no means of releasing their brakes. The brake controllers in the models, and in reality, do/did not have a Release sector on the brake controller.

I believe there were generally 2 Ejectors on a vacuum braked steam locomotive. There was a "Large" Ejector which was used to rapidly exhaust the brake system when the brake controller was set to Release. Alternatively, the Large Ejector control could be operated directly if there was no Release sector on the brake controller. There was also a "Small" Ejector which could be left running to compensate for leakage while the train was in motion and thus avoid dragging brakes.

If these Ejectors were purely mechanical, I would have had a go at writing a patch myself. However, they do/did use boiler steam and I don't have the knowledge to build that into the steam model. Would a steam expert be prepared to tackle this? It is after all an as-yet unimplemented feature of MSTS. In the bug report is a suggested workaround patch which could be used to get the affected models moving but it does not emulate reality. This patch is being independently tested at the moment to see if the workaround is acceptable to those running the affected models.

Dennis

#2 User is offline   cjakeman 

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Posted 11 June 2015 - 10:34 AM

Hi Dennis,

Since this is new functionality for Open Rails (though not for MSTS), would you please add a blueprint to our tracker (https://blueprints.launchpad.net/or). You can link your blueprint back to your own post to provide the details.

Blueprints help us developers to stay focused, keep track of what is needed and what is ready for inclusion in the project.

Thanks,

#3 User is offline   James Ross 

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Posted 11 June 2015 - 01:36 PM

View Postcjakeman, on 11 June 2015 - 10:34 AM, said:

Blueprints help us developers to stay focused, keep track of what is needed and what is ready for inclusion in the project.

You can also link the bug report to the blueprint, to keep everyone in the loop.

#4 User is offline   dennisat 

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Posted 12 June 2015 - 11:01 AM

View Postcjakeman, on 11 June 2015 - 10:34 AM, said:

Since this is new functionality for Open Rails (though not for MSTS), would you please add a blueprint to our tracker (https://blueprints.launchpad.net/or)

View PostJames Ross, on 11 June 2015 - 01:36 PM, said:

You can also link the bug report to the blueprint, to keep everyone in the loop.


Blueprint now added.

Dennis

#5 User is offline   copperpen 

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Posted 12 June 2015 - 12:32 PM

The diesel and electric locomotive equivalent was the exhauster, high speed to create the vacuum, low speed to maintain it. I wonder if it would be better to link the operation of the locomotive ejectors and exhausters to the brake handle positions. Release activates the large ejector/exhauster, running does the same for the small ejector/exhauster. Diesel railcars were slightly different in that the exhauster was driven by the engine and thus ran slowly at idle when stopped. To counter this they had a twin pipe system to speed up release.

That would free up a key assignnment for other usage.

#6 User is offline   dennisat 

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Posted 12 June 2015 - 12:48 PM

View Postcopperpen, on 12 June 2015 - 12:32 PM, said:

I wonder if it would be better to link the operation of the locomotive ejectors and exhausters to the brake handle positions.

This was the normal way except for some locomotive classes which had no Release sector on the brake controller and used the Ejector valve directly to release the brakes. Hence the problem with some, seems to be particularly GWR, models.

Dennis

#7 User is offline   D&RGW 

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Posted 12 June 2015 - 03:14 PM

View Postdennisat, on 12 June 2015 - 12:48 PM, said:

This was the normal way except for some locomotive classes which had no Release sector on the brake controller and used the Ejector valve directly to release the brakes. Hence the problem with some, seems to be particularly GWR, models.

Dennis


I believe some LMS locomotives (the 3F, I think, comes to mind?) had separately controlled ejectors as well. To release the brakes, the brake handle was moved into the 'off' position, isolating the brake pipe from the atmosphere, and the small ejector was opened to build a vacuum.

#8 User is offline   dennisat 

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Posted 23 June 2015 - 12:21 AM

Thank you for adding the Ejector control to the Blueprint list Steam Ejector Blueprint. Since the implementation of this blueprint is obviously subject to time and availability of qualified programmers, I wonder if the temporary patch at Bug 1391449 comment 12 could be applied. This allows brake release from the Running sector if there is no Release sector. This would enable locos currently affected by the lack of an Ejector control to at least be driven. The patch would be reverted when the Ejector control is implemented.

Dennis

#9 User is offline   copperpen 

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Posted 23 June 2015 - 01:45 AM

Dennis

I am intrigued by the fact that you find some vac braked engines undrivable. I have not found one so far. Could you perhaps say which ones are affected?.

#10 User is offline   dennisat 

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Posted 23 June 2015 - 02:42 AM

View Postcopperpen, on 23 June 2015 - 01:45 AM, said:

I am intrigued by the fact that you find some vac braked engines undrivable. I have not found one so far. Could you perhaps say which ones are affected?.


Two examples I have personal experience of are 7820 and 7828 on the West Somerset Railway. The locos in File ID 30443 on UKTRAINSIM apparently have the same problem. Not being a dedicated steam person, I don't really know how widespread the problem is. The odd gripe about this pops up every now and then on UKTRAINSIM. Apparently some users are resorting to amending the eng files but not many people are confident about doing this.

Dennis

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