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Reading Topic #24406
There has been a lot of discussion on changing brake values for freight cars for better realism, but have values for passenger cars been developed? I am looking for values for the period of the late 40s - early 60s that would work for the California Zephyr of the Super Chief. Also, I will be using FCalc2 for the friction values, so any suggestions on frontal area and drag values?
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Frank,If you have downloaded the 22 beta of EngMod, you will find some Australian passenger rolling stock physics files there.
Derek
EngMod@sgrail.org
www.sgrail.org
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I think these parameters would be appropriate:
EmergencyBrakeResMaxPressure( 110 )
TripleValveRatio( 2.5 )
MaxReleaseRate( 0.49 )
MaxApplicationRate( 1.15 )
MaxAuxilaryChargingRate( 0.28 )
EmergencyResCapacity( 8.7 )
EmergencyResChargingRate( 0.24 )
Note, I did not specify the brake force or cylinder pressure. Jean Louis may have some input on what values would work well for the following lines:
MaxBrakeForce( ?kN )
BrakeCylinderPressureForMaxBrakeBrakeForce( ? )
These are probably specified by the AAR somewhere, and he may have the data, as he is much more familiar with passenger trains.
For the friction calculations, a value of 10.0 sq. meters is probably good for the cars. The big error you will need to eliminate is the extra drag on the "B" unit diesels. Since Alco PA, and EMD F and E units, all have pretty good streamlining, I tend to use values like 0.92-0.93 for the drag coefficient for the front unit only. Since these fit very snuggly together as ABBA or ABA consists, I would use a drag coefficient of about 0.30-0.40 for the trailing unit locomotives. While not an issue in freight service, this error will definitely come into play on fast passenger trains, and I have noted this before when several others mentioned they could not get their F unit passenger trains to reach appropriate top speeds for the prototype, lowering the trailing locomotives put them right on target (if you use an updated physics set, or later verions of Marc's F units, geared for passenger service).
Bob Boudoin
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It's very hard to find good informations about the US passengers brake.
I think that 2.67 would be a better value for MaxReleaseRate() since the release is faster for passengers operations.
The EmergencyResCapacity( 8.7 ) value looks good since the total air capacity is bigger than for a freight car.I keep the 50 psi reference but the brake ratio is bigger for a passenger car, between 100% and 150% of the loaded weight.Jean-Louis
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