[Traindude]

Hi. I have been modifying my existing rolling stock with the new brake shoe friction parameters, but whenever I try to specify High-Friction Composite Brake shoes either like this:

ORTSBrakeShoeType ( Hi_Friction_Composite ) (as suggested by the ORTS Manual)

or like this:

ORTSBrakeShoeType ( High_Friction_Composite ) (as suggested by the CTN website)

...I get an error in the log file that looks like this:

Information: Unknown BrakeShoeType set to OR default (Cast Iron) with a MaxBrakeForce of 117.0 klbf

So there seems to be some ambiguity in how the HFC brake shoe tag is spelt or something. Am I doing anything wrong, and if I am, what is it that's wrong?

[R H Steele]

Remember this thread >>> Brake Shoe Composition OR does not appear to recognize any of the brake shoe types and always defaults to cast iron....I cannot count the number of ways I spelt and wrote the phrase --- did not help.
I hope you get an answer, thanks for asking again.

[pschlik]

Huh the manual is just wrong. The options for brake shoe types are these:

        {
            Unknown,
            Cast_Iron_P6,
            Cast_Iron_P10,
            Disc_Pads,
            High_Friction_Composite,
            User_Defined,
        }

(Though I would guess using ORTSBrakeShoeType( Unknown ) wouldn't do much, all the other options have their uses.)

Never had any trouble using this feature myself, got plenty of things using the composite option, some disc braked equipment, and a couple things with cast iron, all of which have worked with the intended unique performance characteristics.

What I actually think is going on here is that you need to define your brake forces using ORTSMaxBrakeShoeForce, which is a requirement for using the new brake shoe setup. If the brake force is defined using the classic MaxBrakeForce, the sim will refuse the selected brake shoe type as the new system needs to simulate the brake shoe force and won't know what to do without being given a brake shoe force. Just remember that the 'actual' brake force will always be quite a bit lower than the brake shoe force, so it's not as simple as swapping "MaxBrakeForce" with "ORTSMaxBrakeShoeForce".

[R H Steele]

Would appreciate a critique of the following, I put it together from reading the forums and Joe Realmutos brake OR pdf...I know nothing about brakes/braking.Thanks in advance.

Comment ( Standard Single Pipe AB Freight Brakes with Retainers )
Comment ( Composition Brake Shoes )
Comment ( Car Weight to Brake Ratio -- 38% )
Comment ( Mass -- Weight -- of empty car assumed to be 30t - metric )
Comment ( MaxBrakeForce Calc --- 30t = 66139lb Mt weight x 38% Car Weight to Brake Ratio x 0.49 composition brakes C.F. )

    BrakeEquipmentType ( "Handbrake, Triple_valve, Auxilary_reservoir, Emergency_brake_reservoir, Retainer_4_Position" )
    BrakeSystemType( "Air_single_pipe" )
    ORTSBrakeShoeType ( High_Friction_Composite )
    ORTSMaxBrakeShoeForce( 12.3kN )
    ORTSBrakeShoeFriction ( 0.0 0.49 8.0 0.436 16.1 0.4 24.1 0.371 32.2 0.35 40.2 0.336 48.3 0.325 56.3 0.318 64.4 0.309 72.2 0.304 80.5 0.298 88.5 0.295 96.6 0.289 104.6 0.288 )
    MaxHandbrakeForce ( 25kN )
    NumberOfHandbrakeLeverSteps( 100 )
    EmergencyBrakeResMaxPressure( 110 )
    TripleValveRatio( 2.5 )
    EmergencyResVolumeMultiplier ( 1.461 )
    MaxReleaseRate( 6psi/s )
    MaxApplicationRate( 6psi/s )
    MaxAuxilaryChargingRate( 20 )
    EmergencyResCapacity( 0.973ft^3 )
    EmergencyResChargingRate( 20 )
    ORTSEmergencyDumpValveRate( 15psi/s )
    BrakeCylinderPressureForMaxBrakeBrakeForce( 77 )
    BrakePipeVolume ( 0.46ft^3 )

[R H Steele]

 pschlik, on 07 November 2023 - 07:47 AM, said:

...

What I actually think is going on here is that you need to define your brake forces using ORTSMaxBrakeShoeForce, which is a requirement for using the new brake shoe setup. If the brake force is defined using the classic MaxBrakeForce, the sim will refuse the selected brake shoe type as the new system needs to simulate the brake shoe force and won't know what to do without being given a brake shoe force. Just remember that the 'actual' brake force will always be quite a bit lower than the brake shoe force, so it's not as simple as swapping "MaxBrakeForce" with "ORTSMaxBrakeShoeForce".

Phillip, https://www.elvastower.com/forums/public/style_emoticons/default/sign_thank_you.gif reading that solved my problem, I hope it also solves Traindudes problem.
Using all three parameters

 ORTSBrakeShoeType ( High_Friction_Composite )
    ORTSMaxBrakeShoeForce( 12.3kN )
    ORTSBrakeShoeFriction ( 0.0 0.49 8.0 0.436 16.1 0.4 24.1 0.371 32.2 0.35 40.2 0.336 48.3 0.325 56.3 0.318 64.4 0.309 72.2 0.304 80.5 0.298 88.5 0.295 96.6 0.289 104.6 0.288 )

together produces no warnings or errors in the log and the brakes work as expected. Now my question is -- as I stated above -- am I using realistic values in the parameters, checked my math, appears okay. Thanks again for the help with the code. Much appreciated.

[pschlik]

Well I'd say a 38% braking ratio is incredibly high, higher than what's allowed by the AAR I think, wouldn't expect to see that on anything with composite brake shoes. But the exact value depends on the train car anyway. Whatever the case, 12.3 kN brake shoe force is not a 38% braking ratio. Going off of the assumption of a 30 metric ton car, 30,000 kg * 9.81 m/s^2 (gravity) = 294,300 N vehicle weight, 294,300 N * 0.38 (braking ratio must be applied to the vehicle weight, not mass) = 111,834 N. Also, braking ratio is usually calculated from brake force at full service, so for OpenRails you must adjust this brake force to the force at BrakeCylinderPressureForMaxBrakeBrakeForce. In this case that's 111,834 N * 77 psi/64 psi = 134,550 N. If you actually want a 38% braking ratio ORTSMaxBrakeShoeForce should be that 134.6 kN number.

Also, ORTSBrakeShoeFriction is not needed if the built in brake shoe types are used. (That can still be used if ORTSBrakeShoeType is User_Defined.)

[R H Steele]

Would 38% braking ratio make sense for cast iron shoes? I think that's where I got the figure. Thanks for the critique, gives me some work to do...excellent.

[pschlik]

Yeah 38% empty braking ratio could show up on some steam era equipment with regular cast iron shoes. The lower friction coefficient of the metal brake shoes necessitated more extreme braking ratios to get the same deceleration. Use the same braking ratio with composite brake shoes and instead of getting better stopping power you risk locking up wheels. As such, most things these days will end up in the 20-30% empty braking ratio range.

[R H Steele]

Thanks.

For members reading this thread >>> more brake information can be found in this discussion>>>
Automatic Air Brakes

[R H Steele]

Attached is a Union Pacific pdf entitled: "TESTING FOR CURRENT FREIGHT CAR BRAKING RATIOS ON UNION PACIFIC RAILROAD" for those interested.

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