[darwins]

Quote

And here in North America, we have the opposite behavior: On the F40PH, the minimum reduction position engages the air brakes exclusively, while subsequent positions engage the dynamics in addition to that.

Considering the wide range of blended braking behaviors, and the frustration that content creators like pschlik have with one-size-fits-all algorithms like "ORTSDynamicBlendingForceMatch", I propose that we introduce a lookup table that maps brake cylinder pressure to dynamic brake application. Content creators would thus have complete control over the blend.

That answer covers the North American situation, but does not seem to provide the brake controller that is needed for Europe (and possibly not for multiple unit trains as opposed to locomotive hauled trains).


Rather than mapping to the loco brake cylinder pressure could I suggest the addition of suitable brake controller tokens instead.

Looking at a British example (the Italian one is similar):

The braking system would be:

BrakesTrainBrakeType ( "EP" )
BrakesEngineControllers ( "Train, Blended" )


The controller for this has the following notches:


1 Release or Running

2 Holding

3 Regeneration 1

4 Regeneration 2 and EP

5 Lap Air

6 Service Air

7 Emergency


This is similar to the controller I would use for the Westinghouse Type A electro-pneumatic brake that is


Brake_Train ( 0 1 0.05 0.1
NumNotches ( 6

Notch ( 0 0 TrainBrakesControllerReleaseStart )

Notch ( 0.1 0 TrainBrakesControllerEPHoldStart )

Notch ( 0.2 0 TrainBrakesControllerEPFullServiceStart )

Notch ( 0.7 0 TrainBrakesControllerHoldStart )

Notch ( 0.8 0 TrainBrakesControllerFullServiceStart )

Notch ( 0.9 0 TrainBrakesControllerEmergencyStart )))


You can see compared to the real thing it has one missing step. What is needed would be something like


Brake_Train ( 0 1 0.05 0.1NumNotches ( 7

Notch ( 0 0 TrainBrakesControllerReleaseStart )

Notch ( 0.1 0 TrainBrakesControllerEPHoldStart )

Notch ( 0.2 0 TrainBrakesControllerDynamicFirstServiceStart )

Notch ( 0.3 0 TrainBrakesControllerEPFullServiceStart )

Notch ( 0.7 0 TrainBrakesControllerHoldStart )

Notch ( 0.8 0 TrainBrakesControllerFullServiceStart )

Notch ( 0.9 0 TrainBrakesControllerEmergencyStart )))

Now in this case as the dynamic brake is applied when brake cylinder pressure is zero then I do not see how you would control this using brake cylinder pressure.

On the other hand you probably could simulate the North American version by adding an appropriate brake token something like

Brake_Train ( 0 1 0.05 0.2 NumNotches ( 5

Notch ( 0 0 TrainBrakesControllerFullQuickReleaseStart )

Notch ( 0.1 0 TrainBrakesControllerReleaseStart )

Notch ( 0.2 0 TrainBrakesControllerAirFirstServiceStart )

Notch ( 0.3 1 TrainBrakesControllerContinousServiceStart )

Notch ( 0.9 0 TrainBrakesControllerEmergencyStart )))

[YoRyan]

Csantucci, on 31 October 2020 - 01:29 PM, said:

I thought more about a mapping from brake controller position to brake cylinder pressure and dynamic brake percent.
If you map brake cylinder pressure to dynamic brake application I don't think it is possible to consider the case of dynamic brake only, because in our case both the case of zero dynamic brake (release position of brake controller) and full dynamic brake(first apply position) correspond to 0 cylinder pressure.

Oh yes, of course, my mistake. The controller position would cover all of the cases we've discussed.

darwins, on 31 October 2020 - 01:29 PM, said:

What is needed would be something like


Brake_Train ( 0 1 0.05 0.1NumNotches ( 7

Notch ( 0 0 TrainBrakesControllerReleaseStart )

Notch ( 0.1 0 TrainBrakesControllerEPHoldStart )

Notch ( 0.2 0 TrainBrakesControllerDynamicFirstServiceStart )

Notch ( 0.3 0 TrainBrakesControllerEPFullServiceStart )

Notch ( 0.7 0 TrainBrakesControllerHoldStart )

Notch ( 0.8 0 TrainBrakesControllerFullServiceStart )

Notch ( 0.9 0 TrainBrakesControllerEmergencyStart )))

I think a single "the dynamics kick in here" instruction would be too limited. Content creators would want full control over the application curve. That's why I suggested a full lookup table, rather like the ORTSDynamicBrakeForceCurves instruction, just from cylinder pressure controller position to dynamic brake force.

[darwins]

From the format of the brake controller I have described - I think that the dynamic brake probably operated like the EP and air brakes - the longer the controller was left in that position - the greater the dynamic brake application.

Moving the handle back from APPLY to HOLD keeps the application at the same strength. It is hard for me to tell as this controller is historical and I am not sure what records survive - other than a simple description.

Possibly having a description of the present day Italian controller from Carlo might help inform you.

[cesarbl]

There seems to be two different approaches to dynamic brake blending:
In some trains, especially MUs, depending on the controller position, dynamic brakes and/or air brakes are applied proportionally. For these controllers, mapping controller position to dynamic brake intervention is a good solution. In fact, train brake controller acts here as both air and dynamic brake controller. Blended dynamic brake signal should be MUed to the train.

However, some other brake controllers are not self-lapping, so dynamic brake force cannot be proportional to controller position. An example of such type of controller is Serana's PBL2 brake controller, which has 3 positions: Release, Hold and Apply. After a release or application is commanded, the controller returns to the Hold position by means of a spring. In this case, dynamic brake force has to be proportional to brake pipe depressure (if dynamic braking causes bail-off) or cylinder pressure (if bail-off eliminates dynamic braking). This is already implemented in OR, and it would be pretty straightforward to add an option to use cylinder pressure instead of brake pipe's. I suppose that this type of blending shouldn't affect dynamic brake application in other locomotives (I might be wrong though), but changing it would require much more work.

[Weter]

The other example is automatic substitution of faded dynamic brake by pneumatic brake.
Or manual, if the last (highest) braking position of combined control applies pneumatic (or EP) brakes, wich is released after returning the handle to zero or to the first throttle notch. This is used for bringing trams and EMUs to complete stop by single handle operation.

[steamer_ctn]

Can I suggest that some research of different locomotive operating manuals be undertaken to ensure the most realistic outcome. There are a number available on the Internet, an example being these two, this and this. There are other ones as well.

Having a quick look at then suggests that dynamic brakes were set up with different features on different locomotives (in particular, depending upon the locomotive generation). For example some had safety interlocks for the set up delay, whereas others didn't, etc.

It would be then appropriate to model a number of representative models.