Elvas Tower: Vacuum Braking Update - Elvas Tower

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Vacuum Braking Update

#1 User is offline   steamer_ctn 

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Posted 11 July 2019 - 02:19 PM

As a result of a request from one of my testers I will be making some changes to vacuum braking functionality.

These changes will aim to correct a small number of errors identified, and to add additional functionality, such as a working Large Ejector on some brake combinations.

A blueprint has been raised for this work.

More to follow.

#2 User is offline   roeter 

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Posted 24 July 2019 - 04:48 AM

I'm using two vacuum-braked DMU. These used to work reasonably well.
I haven't run these trains for some time, but I now find that one destroys the vacuum immediately when even only applying 1% brake, whilst the other doesn't brake at all.
No idea what the parameters should look like, so can someone please either tell me what's wrong or provide a proper example?

The one that immediately destroys the vacuum :
Attached File  Class122.eng (38.88K)
Number of downloads: 26

The one that does not brake at all :
Attached File  DLW_Single.eng (27.96K)
Number of downloads: 22

Regards,
Rob Roeterdink

#3 User is offline   darwins 

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Posted 24 July 2019 - 01:06 PM

There are lots of ifs and buts with 1st generation dmu from UK.
The best set of (workaround) parameters to use at present looks something like this:

In the wagon section: Comment (******************************* Brakes ********************************************* Included in this section - Type, Force, Reservoir, Applicatiion, Release. etc
************************************************************************************)
BrakeEquipmentType ( Vacuum_brake, Auxilary_reservoir, Handbrake )
BrakeSystemType ( Vacuum_single_pipe )
MaxBrakeForce ( 129kN ) Comment (* braked @ 83.5% tare - Railcar.co.uk *)
MaxHandbrakeForce ( 30kN )
BrakeCylinderPressureForMaxBrakeBrakeForce ( 21inHg )
BrakePipeVolume ( 1.33ft^3 ) Comment (* from CTN calculator *)
ORTSBrakeCylinderSize ( 21in )
ORTSNumberBrakeCylinders ( 2 )
ORTSAuxilaryResCapacity ( 4.41ft^3 )
MaxReleaseRate ( 10 )
MaxApplicationRate ( 5 )
ORTSDirectAdmissionValve ( 1 )


In the engine section: Comment (*************************** Brake System ********************************************* Included in this section - Compressor, Reservoir, Application rates, etc
**************************************************************************************)

Comment (*** Braking systems ***)
BrakesTrainBrakeType( vacuum_single_pipe )
ORTSBrakeServiceTimeFactor ( 80 )
ORTSBrakePipeTimeFactor ( 0.01 )
TrainPipeLeakRate ( 0.04 )

Comment (*** Exhausters ***)
ORTSBrakePipeChargingRate ( 0.64 )
Comment (* ORTSBrakePipeChargingRate Assumes rapid charging from reservoir pipe *)
Comment (* Mechanical exhausters - depend upon engine speed - charge vacuum reservoir - twin pipe system - not modelled in OR *)
Comment (* Unit fitted with quick release twin pipe vacuum brake system - brakes section should be updated if this becomes functional in Open Rails *)

Comment (*** Brake Valve Combined ***)
TrainBrakesControllerMaxReleaseRate ( 2 )
TrainBrakesControllerMaxApplicationRate( 1 )
TrainBrakesControllerMaxSystemPressure ( 21inHg )


and in the controllers section: Brake_Train ( 0 1 0.2 0.4 NumNotches( 3
Notch(0 0 TrainBrakesControllerReleaseStart )
Notch(0.4 0 TrainBrakesControllerSelfLapStart )
Notch(0.6 0 TrainBrakesControllerApplyStart )))

I have attached a complete eng file for your perusal. I think it goes as far as OR can at the moment with trying to recreate the engine and gearbox on these things.

There is anyway some discussion about the gears in another thread http://www.elvastowe...l-transmission/

Attached File(s)



#4 User is offline   darwins 

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Posted 24 July 2019 - 01:36 PM

These are very popular models and were very common in UK, but have a lot of unusual features, many of which are not in OpenRails and may not even be planned for future versions.
( 1 ) They had a manual gearbox transmission - which seems to have a few bus in OR - check the other thread for descriptions
( 2 ) The two-car sets of which there were many consisted of one motor and one trailer. At present in MSTS we can not drive from the trailer end without the old MSTS work around of changing into a motor car. This is a problem on the to do list as Commuter Cab cars or as Driving Trailers / Push Pull cars depending on what you call them!
( 3 ) They have twin pipe vacuum brakes not single pipe. The work around above gives you a fast release with single pipe, but we miss another fun aspect of this whole system...
( 4 ) The vacuum was provided by mechanical exhausters driven by the engine crankshaft charging a high vacuum reservoir (connected to the reservoir pipe) up to 28 in Hg. When the train was driving along the reservoir got charged, but when coasting to a stop it did not. So like the early Westinghouse brakes you could not apply and release too many times or you would run out of vacuum... which leads to...
( 5 ) Ideally we would be able to write the brakes controller as
Brake_Train ( 0 1 0.2 0.4 NumNotches( 3
Notch(0 0 TrainBrakesControllerRunningStart )
Notch(0.2 0 TrainBrakesControllerSelfLapStart )
Notch(0.4 1 TrainBrakesControllerApplyStart )))
At the moment this is not possible. Firstly because the "Running" position does not currently release the brakes on diesel and electric trains as it does on the real thing and secondly because so far it has proved challenging to set up an "Apply" token for vacuum brakes that works like a valve rather than like a switch. Ideally if you push the valve far into apply the vacuum drops quickly and if you only go a short way into apply the vacuum drops slowly.
Possibly these things are so difficult to sort out because the vacuum brake code was derived from the air brake code - and they work rather differently. I am sure Peter can explain more about the problems - and the headaches I am giving him even talking about vacuum brakes.
Another Trello card for the distant future asks for a complete rewrite of air brake code. When then happens I hope some brave coder with lots of time to spare will agree to write a completely separate code block for vacuum brakes.


#5 User is offline   darwins 

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Posted 24 July 2019 - 11:43 PM

Although going a bit off topic I should add for anyone who is interested, that there is lots of good information on the net including:
video of how to drive
driver's manual
good practice -
2 seconds delay before changing gearsfor coasting throttle back and go into gear 4 no matter what your speeduse lap to hold about 15 in Hg when brakingput gear into neutral before stopping - below about 10 or 15 mph


and almost every thing else you might want to know about them at
railcar.co.uk
as to having very sharp brakes you will find brake forces and percentages at the last site - they were commonly braked to around 90% of their tare mass


#6 User is offline   darwins 

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Posted 25 July 2019 - 10:33 PM

Hello Rob

Using the data from Railcar.co.uk I have tried to make new Open Rails eng files for your dmu. Give them a try and let me know how they are.Thankfully I found out the Derby Lightweight single car had the "standard" 4-speed manual gearbox.

The earlier Derby Lightweights had a transmission that would be impossible to model in OR at present. It worked something like this:Driver had a gear change lever with three positions N (Neutral), C (Converter) and D (Direct)
To set off the driver put the gear into C and powered up - the train was then driven by a three stage torque converter.
At 35 mph the driver throttled back and moved the gear to D - then opened the throttle one notch at a time - the train being in direct drive from the engines like a normal DMU in 4th gear. (Top speed 60)

Anyway that is another variation under making Diesel Hydraulic transmission fully functional in OR.

Attached File(s)



#7 User is offline   roeter 

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Posted 29 July 2019 - 07:03 AM

Thanks for the updated engine files.
Tested the 122 and it works a lot better. Not yet got round to testing the DLW.
One small issue : when defining a ORTSDieselEngines block, all parameters in that block must be defined otherwise the full block is ignored. The example above did not include all parameters, I added the missing ones using the values as shown in the manual. Not sure if that makes sense but at least it works.

Regards,
Rob Roeterdink

#8 User is offline   darwins 

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Posted 01 August 2019 - 12:07 PM

View Postroeter, on 29 July 2019 - 07:03 AM, said:

Thanks for the updated engine files.
Tested the 122 and it works a lot better. Not yet got round to testing the DLW.
One small issue : when defining a ORTSDieselEngines block, all parameters in that block must be defined otherwise the full block is ignored. The example above did not include all parameters, I added the missing ones using the values as shown in the manual. Not sure if that makes sense but at least it works.

Regards,
Rob Roeterdink


I have been having great difficulty getting OR diesel engines to work. In another thread I was able to get some help putting together a working OR engine file. Getting a good final product seems to involve trial and error with obscure input parameters!
Anyway the outcome of that is a file with OR diesel engines. (I suspect this is pretty much what you get if you add the values in the Manual anyway.)


Attached File(s)



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