[gpz]

So on these locomotives there is an additional, separated dyn-brake controller? Does that set different dyn-brake forces at different speeds and controller positions, than the blended brake controller? So are there two different ORTSDynamicBrakeForceCurves needed to handle these?

[Csantucci]

Peter, I will ask for detail.

[Csantucci]

gpz, on 22 January 2015 - 03:34 AM, said:

So on these locomotives there is an additional, separated dyn-brake controller? Does that set different dyn-brake forces at different speeds and controller positions, than the blended brake controller? So are there two different ORTSDynamicBrakeForceCurves needed to handle these?

I got a reply.
Trainsets like the TAF that I mentioned in my above post, and that already can command different electric braking levels with the train brake lever, don't have another way to command the electric brakes.
Trainsets like the E464, built by Bombardier in 688 exemplars, that is the backbone of regional and interregional trains in Italy ( http://en.wikipedia..../FS_Class_E.464 ), and that have only one possible electric braking level commanded with the train brake lever, have also a classical traction-electric brake combined control lever. (In the case of the E464 there are two further levers that are used when automatic speed control is selected: one is used to set speed, and the other is used to set max tractive - electric braking effort to achieve the speed target, but that's another story :) ).

In the meantime Eugen R. reminded me that also SBB locos like the SBB460 have blended braking, at least looking at their parameters in the MSTS .eng file...

[gpz]

After some thinking on it, maybe only two additional information is needed for the train brake (TB) notch controller, for the dynamic brake (DB) is to be blended:

• the correspondence from TB to DB notch positions,
  
• a TB notch position to desired braking force interpolator,
  
• additionally, a DB notch position to desired braking force interpolator might be needed, see below.

The effective DB force in function of speed and notch position is already available in ORTSDynamicBrakeForceCurves, as implemented by Matej. As the force will decrease by the decreasing speed, we will have to know how much it is below the desired force, if at all, so that the necessary amount of air can be let in or bailed off the cylinder.

Certainly, some specialities are to be defined here:

• In (1) the corresponding DB notch position could be -1, to indicate the DB is to be disengaged. Explicit disengaging command must be possible, because re-engaging takes time on Diesels.
  
• There must be a way to blend TB into a combined throttle-DB controller. For this case a separate (3) must be defined. Using this one only instead of (2) above might not be adequate, since there could be a configuration, where e.g. tha max. DB force is assigned to multiple TB notch positions, but with different desired total brake forces.

[Matej Pacha]

Well,
first of all, OR code is not ready for such features. You need to create "levers" independent from "controllers". In modern traction, some important modules are allowed to command the controllers and the driver's levers are "untouched". For older locomotives, it is very easy to bind a lever with a controller to act like the one.
Second, a dynamic brake is not a safe brake, if it is line-voltage dependent. Based on this, you cannot make the system act like described in some previous posts. If you would command the dynamic brake as the main brake, in the case of failure, the air brake would start to act with some delay, what is not desirable. You need to command them at the same time to ensure the braking effect. If the dynamic brake response is OK, then you can bail-off the air brake.

Usually the dynamic brake is controlled by the locomotive brake pressure and bails-off the locomotive brake if the dynamic brake works fine. Level of the bail-off can be controlled by the dynamic brake feedback to replace the dynamic brake fade-effect at low or high speeds.
The first command usually comes from the train brake or the combined throttle lever. It can be an electric signal, but it is converted to a pneumatic signal (pressure) to ensure the train brake will always play a role. This pressure signal is converted back to an electric signal to command the dynamic brake controller. Based on the dynamic brake response, the bail-off command is executed to save the friction brake material. If the dynamic brake fades due to low or high speeds, the pneumatic brake replaces the brake effect. In case of the dynamic brake failure, the feedback is lost and the air brake covers whole brake effect. The description above is a brake system of Skoda and CKD locomotives since 1975 (more than 2000 locomotives with a dynamic brake).

In fact, it doesn't matter who or what commands the brake controller. It can be a driver or e.g. an automatic speed (cruise) controller.

And about the brake effect - the brake system must not cause the train to skid when braking. Thus, the dynamic brake must be marked as "safe" to be used with emergency braking. If it is not marked as "safe", it must be switched off when the emergency brake is engaged. The brake effect of the dynamic brake must not be higher than the pneumatic brake according to the latest TSI specifications (TSI - technical specifications for interoperability in EU). The brake effect mentioned in TSI must not be higher than adheasion factor 0.12, what means 0.12*9.81*85t = 100 kN for 85 ton locomotive. I'm not sure if we need to care about this, but definitelly it should be considered at least.

Matej

[gpz]

Matej Pacha, on 24 January 2015 - 06:42 AM, said:

Well,
first of all, OR code is not ready for such features. You need to create "levers" independent from "controllers". In modern traction, some important modules are allowed to command the controllers and the driver's levers are "untouched".

You could be surprised how much it is ready! :crazy: I have mentioned in various forum posts without details, that im my own repository I have already implemented some scripting, that is also capable to control the controllers. As part of this job, in the past 3-4 months, I have already cleaned up the notch controller code, and strictly separated the lever positions from the effective controller values. I have also committed these changes, so they are already in svn. I also accidentally committed some variables that are used only by my scripting code yet, but shows how the controllers can be adjusted without moving the levers, just look at e.g. the DynamicBrakeIntervention (ThrottleIntervention, etc.) variable, which can be used for this purpose. (It is not widely tested, beware :D )

First of all I would thank you for your valuable description. I think you are the only one in the team with such very detailed knowledge about the various locomotive systems. So I would like to ask you, if my following theory about the implementation possibility is right, because I can read about it on internet only, I'm not working for a railways related company.

So as I read, at the air brake part there is only a simple modification needed, that consists of two on/off valves:
1) A release valve, that releases (bails off) brake cylinder pressure in case the actual summarized (air+dynamic) braking force is higher than the desired force.
2) A holding/applying valve, that fills brake cylinder valve from main reservoir (bypassing the triple valve / distributor) in case the summarized force is less than the desired, and at the same time it holds air from being released by possible other "commands", much like an EP brake.

This setup would ensure that in case of a dynamic brake outage, the air brake cylinders would be started to be filled up immediately.

[Simon E]

Cool Work Guys.

So with all of this neat Braking logic now in place,

So is It pretty safe for me to say that it is now possible to properly implement Westinghouse's Westcode Braking on Our (Open Rails only) Melbourne, Australian EMU's models now? http://www.elvastower.com/forums/public/style_emoticons/default/pleasantry.gif

[Hamza97]

Yes......!!!! Implimenting blended braking will be really usefull. And marks a difference between old conventional locos and microprocessor controlled locomotives. Here on IR, blender braking feature is implimented in newer EMD/DLW & ABB/CLW locmotives. ATM I could not find the relavemt description of it, but will post it ASAP.

[Genma Saotome]

gpz, on 24 January 2015 - 12:11 PM, said:

So as I read, at the air brake part there is only a simple modification needed, that consists of two on/off valves:
1) A release valve, that releases (bails off) brake cylinder pressure in case the actual summarized (air+dynamic) braking force is higher than the desired force.
2) A holding/applying valve, that fills brake cylinder valve from main reservoir (bypassing the triple valve / distributor) in case the summarized force is less than the desired, and at the same time it holds air from being released by possible other "commands", much like an EP brake.

This setup would ensure that in case of a dynamic brake outage, the air brake cylinders would be started to be filled up immediately.

Peter, does that reflect real brake equipment or is it an Open Rails software solution to an Open Rails software problem?

[gpz]

It was a while I read after it, but as I recall, it works somelike similarly in real trains too.