More Realistic Brake Force Settings on Freight Cars?

[GreatNortherner]

Hi,

A little question about the brake physics of the freight car models (US stock).

Except for the hand brake, they don't have a "fixed" brake force setting, instead they use the" Max Force Percent Of Vehicle Weight" value, which sets the brakeforce in kN. According to the Wiki, a 100t car would then have 70kN max brake force with the default 70% setting of this.

Now my question is this: 70kN for a 100t car seems to be (quite a bit) too much.

Some of the state-of-the art MSTS brake settings (by Bill Prieger) have these values:
100t rail car, comp brake shoes, max. brake force: 23.8kN (that's a THIRD of the RW car!!!)
27.5t rail car, comp brake shoes, max. brake force: 12.2kN

Now, trying to get a single % value from these two numbers is a bit tricky. The loaded car would have 24% MaxForcePercentOfVehicleWeight, but the mt car would have 44%.

So what do you think would be the most sensible approach here when we have only one percentage number available in the RW wagon BIN file? Overbreak the loaded car, or underbreak the empty car by using the % value of the ld car?

Edit: I don't know how an actual train 'handles', nor do I understand much of maths and physics, so I can't properly test these tweaks. My only point of reference is how a fine-tuned MSTS train feels like (in general: much heavier, more 'sluggish' than anything RW can offer). Maybe somebody else can pick up here?

If I may daydream a little: if a sort of "realistic brake physics consensus" could be reached in the community, maybe it would even be possible to create a tool that could automatically edit a big number of cars' BIN files in one go? (If such a tool is even possible, my programming skills are on par with my maths skills )

Thanks,
Michael

PS: Here's how a modified brakes section could look like:

Code: Select all

               <TrainBrakeAssembly>
                  <EngineSimulation-cTrainAirBrakeBlueprint d:id="21415960">
                     <BrakeType>
                        <EngineSimulation-cTrainAirBrakeDataBlueprint d:id="21784744">
                           <EquipmentType d:type="cDeltaString">eAirSinglePipe</EquipmentType>
                           <MaxForcePercentOfVehicleWeight d:type="sFloat32" d:alt_encoding="0000000000805140" d:precision="string">24.0000</MaxForcePercentOfVehicleWeight>
                           <Control/>
                           <Handbrake>
                              <EngineSimulation-cHandbrake d:id="16118080">
                                 <MaxForce d:type="sFloat32" d:alt_encoding="000000000070C740" d:precision="string">57000.0000</MaxForce>
                              </EngineSimulation-cHandbrake>
                           </Handbrake>
                           <GraduatedRelease d:type="cDeltaString">eTrue</GraduatedRelease>
                           <ProportionalBrake d:type="cDeltaString">eTrue</ProportionalBrake>
                           <MaxReleaseRate d:type="sFloat32" d:alt_encoding="000000608FC2ED3F" d:precision="string">0.9300</MaxReleaseRate>
                           <MaxApplicationRate d:type="sFloat32" d:alt_encoding="00000000295CDF3F" d:precision="string">0.4900</MaxApplicationRate>
                           <MaxCylinderPressure d:type="sFloat32" d:alt_encoding="0000000000004940" d:precision="string">50.0000</MaxCylinderPressure>
                           <PressureForMaxForce d:type="sFloat32" d:alt_encoding="0000000000004940" d:precision="string">50.0000</PressureForMaxForce>
                           <MaxSystemPressure d:type="sFloat32" d:alt_encoding="0000000000805640" d:precision="string">90.0000</MaxSystemPressure>
                           <MinSystemPressure d:type="sFloat32" d:alt_encoding="0000000000000000" d:precision="string">0.0000</MinSystemPressure>
                           <Distributor/>
                           <EmergencyBraking>
                              <EngineSimulation-cBaseAirBrakeBlueprint-cEmergencyBraking d:id="16125440">
                                 <TriggerRate d:type="sFloat32" d:alt_encoding="0000000000002440" d:precision="string">10.0000</TriggerRate>
                                 <ReservoirPressure d:type="sFloat32" d:alt_encoding="0000000000805640" d:precision="string">90.0000</ReservoirPressure>
                                 <ReservoirCapacity d:type="sFloat32" d:alt_encoding="000000A03A810040" d:precision="string">2.0631</ReservoirCapacity>
                                 <ReservoirVolumeMultiplier d:type="sFloat32" d:alt_encoding="00000000295CF73F" d:precision="string">1.4600</ReservoirVolumeMultiplier>
                                 <ApplicationRate d:type="sFloat32" d:alt_encoding="0000000000002440" d:precision="string">1.0000</ApplicationRate>
                                 <ChargeRate d:type="sFloat32" d:alt_encoding="0000004033330340" d:precision="string">1.6800</ChargeRate>
                              </EngineSimulation-cBaseAirBrakeBlueprint-cEmergencyBraking>
                           </EmergencyBraking>
                           <AuxiliaryBraking>
                              <EngineSimulation-cBaseAirBrakeBlueprint-cAuxiliaryBraking d:id="23275320">
                                 <MaxChargingRate d:type="sFloat32" d:alt_encoding="000000E0A370CD3F" d:precision="string">0.2300</MaxChargingRate>
                                 <MaxReservoirPressure d:type="sFloat32" d:alt_encoding="0000000000005940" d:precision="string">100.0000</MaxReservoirPressure>
                              </EngineSimulation-cBaseAirBrakeBlueprint-cAuxiliaryBraking>
                           </AuxiliaryBraking>
                           <PressureUsedFromPipePerPoundGained d:type="sFloat32" d:alt_encoding="000000403333D33F" d:precision="string">0.3000</PressureUsedFromPipePerPoundGained>
                           <PressureGainedFromOnePipePounds d:type="sFloat32" d:alt_encoding="0000000000005940" d:precision="string">100.0000</PressureGainedFromOnePipePounds>
                           <RetainerType d:type="cDeltaString">eNoRetainer</RetainerType>
                           <TripleValve d:type="cDeltaString">eTrue</TripleValve>
                           <TripleValveRatio d:type="sFloat32" d:alt_encoding="0000000000000440" d:precision="string">2.5000</TripleValveRatio>
                           <RetainerSlowReleaseRate d:type="sFloat32" d:alt_encoding="0000000000002E40" d:precision="string">15.0000</RetainerSlowReleaseRate>
                        </EngineSimulation-cTrainAirBrakeDataBlueprint>
                     </BrakeType>
                  </EngineSimulation-cTrainAirBrakeBlueprint>
               </TrainBrakeAssembly>


[Kali]

I did a lot of experimenting on this ( it's all in the Dodgy Physics thread ) - the idea is to end up as something like 12-13% when the car is loaded, so you have to do a little maths to work out what proportion of the empty weight to use that ends up as 13% when it's full. Unless it's not loadable, and then 13% is fine.

I got that particular figure straight out of a Wabtec document, rather than my backside :P Wabtec were talking about how 13-14% was a really nice increase over previous brakes, which is a bit worrying.

Programming a tool would be possible, but your tool would have to load all the XML in first and check if the car is loadable.

I believe the figures in the wiki are all for european stock - I'm not sure even european stock will have 70% brake effectiveness but even if they have clasp brakes rather than disk, they have two shoes per wheel ( unless it's the Thrall-built coal hoppers EWS use, which appear to have US trucks and single brakepipes. NIce step backwards, guys ).

[Rich_S]

Hi Michael,
A Kilo-newton is one of those measuring systems that I don't understand. I know it has to do with mass in motion but that is the extend of my knowledge The one thing I can tell you is, at a full application of the automatic brake handle each cars brake cylinders will have approx. 63 - 65 lbs of pressure. If the empty car is light enough or if the track is wet / icy the wheels will actually slide. When you do get a skating condition, you'll actually pickup speed because of the loss of friction, but that's a little off topic for this thread. If the car is loaded, then everything will slowly come to a halt. Under ideal conditions a empty train will stop in a shorter distance with a lower brake application than a loaded train, so my way of thinking is to setup the cars for loaded weight, then maybe back that value off a percent or two as an adjustment for the empty weight?

Regards,
Rich S.

[Kali]

A Newton is the amount of force it takes to accelerate 1kg at 1m/s^2 - so in terms of brakeforce it's just that force in the direction away from movement. You can rewrite it as kg-m/s^2 if you want, it's equally valid.

[Rich_S]

A Newton is the amount of force it takes to accelerate 1kg at 1m/s^2 - so in terms of brakeforce it's just that force in the direction away from movement. You can rewrite it as kg-m/s^2 if you want, it's equally valid.

Hi Kali,
I've read the formula before and it states:

A Newton is equal to the amount of net force required to accelerate a mass of one kilogram at a rate of one meter per second squared.

So I guess my question is, what are we accelerating? The brake cylinder piston, the brake beam lever, the air in the brake pipe, or the freight car itself. I really am being serious, I'm not trying to make a joke. I understand maximum velocity is 1 meter per second squared, which is the fastest any object can fall on earth. So I slightly understand that part of the formula, but I don't understand what we are trying to accelerate and what that has to do with the braking system? I would think we would somehow need to figure the foot lbs of force required to slow or stop the wheel from revolving under different load condition and friction conditions. Like I said earlier, I can read that equation all day and it still does not make much since to me. Good thing I never tried to pursue a career as a scientist or mathematician, we'd all be in a heap of trouble

Regards,
Rich S.

[nigel]

So I guess my question is, what are we accelerating? The brake cylinder piston, the brake beam lever, the air in the brake pipe, or the freight car itself.

In this case we are talking about the acceleration (or deceleration if you prefer) of the freight car itself due to the brakes. How the brakes actually work is not relevant here as far as I am aware, just the effect they have on the car. The acceleration of an object for a given force acting on it is the force divided by the mass of the object.

I understand maximum velocity is 1 meter per second squared, which is the fastest any object can fall on earth.

Metres per second squared is a measure of acceleration, not velocity. Falling objects on Earth accelerate at about 10m/s^2 until air resistance becomes significant and reduces the acceleration and eventually they reach terminal velocity - how fast this is depends on the shape / density of the object. None of this has much to do with brakes.

[Kali]

The handbrake is less confusing than the train brake setting; "MaxForcePercentOfVehicleWeight", what is that meant to mean? how is a force a percentage of a weight, ffs?

You can assume it's at full brake pressure so you can ignore any multiplier from that, so there must be some acceleration constant... which we're not given, anywhere.

[PapaXpress]

Just to go out on a limb... but perhaps if we ask RSC what "MaxForcePercentOfVehicleWeight" means they might reply?

[Kali]

Well, actually, weight is a force I guess - it's mass which isn't. Weight is just mass * local gravity. That is assuming they meant weight and not mass :p

[Rich_S]

The only thing you can find on the Rail Works Wiki page is the following:

Max Force Percent of Vehicle Weight
On disc brake vehicles, Brake Force in kN is usually roughly equivalent to the vehicle weight in Tons. So for example a 100 ton loco would be expected to have around 100kN Maximum Brake Force. Altering this figure is the easiest way of adjusting the maximum brake force of the locomotive. For example, if your locomotive weighs 100 tons and you want a maximum Brake Force of 80kN, set this parameter to 80%.
For tread brake vehicles, the braking force is slightly less than the weight and thus a figure of 60-70% is more accurate.

So I guess the question is, does a fully loaded 100 ton 3 bay hopper really have a Brake Force of 100 kN? Or do you go with it's empty weight and set the Brake Force to 29.15 kN?

Regards,
Rich S.

[Kali]

That is not true for NA stock. That's not even very true for euro stock tbh. As I mentioned above I pulled data from Wabtec ( and I've seen a report into US freight car braking which I can't find ) - and 13-14% is what they talk about as the maximum % of loaded. Brakes self-adjust so it'd be something like that empty also, but unfortunately RW doesn't self adjust for loads.

I think I ended up with 45% or so for the coal hoppers - they're 20ish tons unladen & over 100 fully loaded.

[g_nash]

Hi,

A little question about the brake physics of the freight car models (US stock).

If I may daydream a little: if a sort of "realistic brake physics consensus" could be reached in the community,

Try these .. http://www.bnsf.com/customers/equipment/ .. Since we can't have Bill or Bobs figures ( to play with and adjust as neccessary ) in RW , I based configs for my modern era stock on this info , not the same or as good as elsewhere but better than nothing , and TBH a "one size fits all approach" is not what I was looking for .

.

[Rich_S]

Hi G_Nash,
Are you using the braking ratio for the loaded weight or empty weight? Also has anyone verified that when you do load a car in Rail works, does it actually change the cars weight or is loading just a visual effect only?

Regards,
Rich S.

[g_nash]

Using both . Since I could never get a clear answer to any question and dialogue between Bob Boudin and RS on the values used and how to translate for us out here was never finished , what I did was adopt the MSTS method and use LD/MT stock and disregard the visual loading in RS/RW . Doing it this way , I could clearly define a known weight ( partial load/full load mesh on wagon ) to a given car and add the required braking percentage in the xml , empty cars are easy to set anyway . Not the best solution by any means , but my way of doing things allowed for at least some close to correct numbers in the available xml slots .

That's it

Cheers

[Ghettofab75]

I kinda like the LD/MT idea like msts. You may loose the visual loading in RS, but how often do train crews wait around to watch cars get loaded?

Kevo