[cesarbl]

Maybe an additional parameter is required for maximum pressure during EP operation.
For air brakes, higher brake forces for emergency braking can be achieved without additional parameters:
BrakeCylinderPressureForMaxBrakeBrakeForce is set to the maximum pressure at emergency.
MaxBrakeForce is adjusted to brake force in emergency.
TripleValveRatio is adjusted so TripleValveRatio=ServiceBrakeCylinderPressure/FullServiceReductionPressure

[darwins]

Thanks. Just tried that out for the first example above using:


Train Pipe Pressure - 70 psi

Emergency BC Pressure - 60 psi = BrakeCylinderPressureforMaxBrakeForce ( 60psi )

TrainBrakesControllerFullServicePressureDrop( 24psi )

Service BC Pressure - 50 psi

Service BC Pressure / Full Service Pressure Drop = 50 / 24 = TripleValveRatio ( 2.083 )



It works! For both difference in pressure and difference in brake force.

[Weter]

Quote

Maybe an additional parameter is required for maximum pressure during EP operation.

Indeed.
As long, as Due to EP application, BC pressure equalized almost to BP normal pressure, instead of normal BP/2.5 at Pneumatic braking.
So max brake force should be at EPT. This way it should be encreased, compared to pure-pneumatic brake force.

EP application doesn't cause any effect to BC pressure now.
It remains at zero.
Which settings are needed exept EPFullservice token?

[pschlik]

America is a bit odd for making independent braking work in multiple, and one of the many odd situations the system must handle is different locomotives being designed for different brake cylinder pressures. Many old locomotives were only designed with 45 psi as max independent braking, while more modern ones use 72 psi due to changes in brake rigging.


I find that usually content creators just avoid this, opting to set everything to the same locomotive brake pressure, regardless of the brake rigging. Unsatisfied with that, I have had a go trying to replicate real-life in Open Rails, but the sim just can't handle this correctly. Controlling from a newer locomotive will allow any connected old locomotives to over-apply to 72 psi instead of 45 psi. And vice versa if the older locomotive is in charge; it'll only apply the brakes to 45 psi on the modern locomotive at most, instead of allowing 72 psi. As far as I can tell, MSTS brake logic just assumes the locomotive brake pressure has to apply equally on all connected units, and there is no way to bypass this.


Problem is, that's just not correct. In real operations, each locomotive will apply its appropriate level of brake pressure regardless of the type of brakes on the controlling unit. This is achieved by using a common 0-45 psi signal for locomotive braking. Even the newest locomotives will still only put out 45 psi to connected locomotives, it's just that this 45 psi signal is multiplied or divided by the locomotive systems (J type relay valve) to produce the desired brake cylinder pressure. This allows locomotives working in multiple to develop completely different brake cylinder pressures appropriate for that locomotive's specific configuration, while still maintaining proportional control from the independent brake handle. (So, a better assumption is that the reference pressure, not the brake cylinder pressure, is equal on connected units. But I don't think this reference pressure exists at all in the sim.)




It seems that Open Rails would need some parameters for the maximum reference pressure in the locomotive brake system and some 'relay valve factor' to multiply or divide this reference pressure for purposes of setting the brake cylinder pressure. Rather than using the unusual MSTS EngineBrakesController behavior, Open Rails could instead just set the target brake cylinder pressure to be the reference pressure multiplied by the relay factor. All connected locomotives would receive the same reference pressure (rather than receiving the same target brake cylinder pressure), and the reference pressure would be determined by the position of the engine brake handle. Of course, as broken as the MSTS style is, leaving it in would be needed for compatibility, so additional options would work fine as ORTS____ settings.


And as a side note, some relay valves are also used to divide the brake cylinder pressure that results from a train brake application, not just a locomotive brake application, so an ability to define this behavior would also be handy. (Currently, the only option for influencing train brake applications is to change the triple valve ratio, which isn't a very realistic way to represent this.)

[darwins]

Quote

America is a bit odd for making independent braking work in multiple, and one of the many odd situations the system must handle is different locomotives being designed for different brake cylinder pressures.

There are a number of issues arising out of that.

1. The simple case of using the train brakes - each locomotive should apply its own brake in proportion to the train braking - although sometimes the relationship between train brakes and loco brakes was a bit more diverse. For example on GWR steam locos fitted with steam brakes, the steam brake did not apply until the vacuum in the train pipe had fallen to 10 in Hg. (Although vacuum brakes on the cars would start to apply as soon as the vacuum dropped from 25 in.)

2. The case you mention of locomotives working in multiple. I assume you are talking about only applying the independent brake and not the train brake. I do not know the situation in other countries but will try to find out. There would seem to be a logic to all locos connected and working in multiple all applying loco brakes at the same time.

3. The case of double heading without multiple unit operation - then obviously the independent brake can only be used on the leading loco.


However independent loco brakes need to be completely changed in OR to make them realistic. The present OR code has copied the mistake of MSTS and treated the independent brakes as being identical to train brakes and working in an identical way. In reality they are not the same. If we ignore handbrakes and dynamic brakes, which are treated separately in OR, there were only ever two kinds of "independent" brakes - steam brakes and straight air brakes. Steam brakes are now working in OR, but could be further improved. Straight air brakes are not yet available in OR.

The following combinations existed:

Train: Vacuum Single Pipe Independent: Steam Brake
Train: Vacuum Single Pipe Independent: Straight Air Brake

Train: Air Single Pipe Independent: Steam Brake
Train: Air Single Pipe Independent: Straight Air Brake
Train: Air Twin Pipe Independent: Straight Air Brake
Train: EP Independent: Straight Air Brake


Because loco brakes are always direct brakes they do not require things like triple valves, auxiliary reservoirs and emergency reservoirs. (Although in the case of vacuum brakes there was sometimes an auxiliary reservoir that acted as a control reservoir for the proportional valve to control the steam brake or straight air brake.)


In addition there were some situations, mostly where railways were dual braked, where the train brakes acting on the locomotive were of a different type to the train brakes acting on the train.

These are examples that I know of:

Train: Vacuum Single Pipe Non-independent brake worked by train brake: Steam Brake

Train: Vacuum Single Pipe Train brake on loco: Air Single Pipe

Train: Air Single Pipe Train brake on loco: Vacuum Single Pipe

There was also at least one example where the locomotive and train brakes worked totally independently without any interaction, with the driver having to manipulate two different valves to brake both together.

[MMax]

In Germany, most locomotives have a standard air brake as train brake and a straight air brake as independent. For normal operation, only the train brake is ever used, even when running locomotive only. The independent brake is controlled separately and may only be used when standing to hold the train in place, while shunting or in special cases when running locomotive only, the train brake is set for freight operation and you have to apply the emergency brake.

[Weter]

Bailing-off IB saves locomotive's brake-shoes, as real-life drivers suggest.
This may be done by LB handle too.

[Weter]

EPonly and EPFullService tokens don't give any effect on testing version.
Which wagon and engine parameters should I check?

[Traindude]

Sorry to bump this thread again, but I have another idea that may be worth implementing--variable main reservoir charging rates for diesels. On many diesels the air compressor was driven by the diesel engine, and consequently the rate at which the compressor pumps varies with prime mover speed. So if we add parameters ORTSMainResChargingRateAtIdle and ORTSMainResChargingRateAtMaxRPM, then we could potentially model this.

[darwins]

Quote

EPonly and EPFullService tokens don't give any effect on testing version.
Which wagon and engine parameters should I check?

Please can someone from development team clarify if recent changes to brakes in unstable versions have been included in most recent testing version?

Quote

Sorry to bump this thread again, but I have another idea that may be worth implementing--variable main reservoir charging rates for diesels. On many diesels the air compressor was driven by the diesel engine, and consequently the rate at which the compressor pumps varies with prime mover speed. So if we add parameters ORTSMainResChargingRateAtIdle and ORTSMainResChargingRateAtMaxRPM, then we could potentially model this.

This thread is still very much unfinished business. A lot of work has been done on train brakes recently. Hopefully that will be followed up with some work on locomotive brakes. It may be possible to add some other features. It is interesting to read about crankshaft driven compressors, as a similar situation exists for vacuum exhausters for vacuum brakes. There are three types of exhauster used on diesel and electric traction: ( a ) Normal Speed / Fast Speed continuously running exhausters driven by electric motors - found on large, modern, diesel and electric locomotives - this is the only type currently modelled in Open Rails
( b ) On / Off exhausters driven by an electric motor controlled by a pressure switch (for brake pipe vacuum) - found on some older electric multiple units
( c ) Crankshaft driven exhausters - used to exhaust high vacuum reservoirs on first generation diesel multiple units with twin pipe vacuum brakes. (Similar exhausters also I believe used on some small shunting locos.)