Current US Freight physics

**scottb613** · 12-15-2021, 12:28

Hi Shawn,

Just my understanding - so take with a grain of salt.

I believe the following is not needed or used in ORTS.

Code:

InertiaTensor ( Box (3.2004m 5m 17m) )

	Buffers (
		Spring (
			Stiffness ( 1e6N/m 5e6N/m )
			Damping ( 1.3e6N/m/s 3.8e6N/m/s )
			r0 ( 0m 1e9 )
		)
		Centre ( 0.5 )
		Radius ( 1 )
		Angle ( 0.5deg )
	)

I'd suggest changing "NumWheels ( 8 )" to "ORTSNumberAxles (4)".

I'd also suggest trying to use "include" files as it will make any future changes soooo much easier to make. The things such as brakes and friction that remain the same for freight cars of the same weight are moved to common include files.

I just got done writing a script to convert all my rolling stock to ORTS only.

Typical Wag Script Output

Code:

SIMISA@@@@@@@@@@JINX0D0t______

Wagon ( ATSF_XM_138464_LD
	Type ( Freight )
	WagonShape ( ATSF_XM_138464.s )
	Name ( "BLW/ZT Box ATSF 138464 LD" )
	Size ( 3.00m 4.53m 13.23m )
	Mass ( 50.4t )
	WheelRadius ( 33in/2 )
	ORTSNumberAxles (4)
 
	Coupling (
		Type ( Automatic )
		Spring (
			Stiffness ( 2e1N/m 5e6N/m )
			Break ( 5.1e7N 5.1e7N )
			r0 ( 5cm 8cm )
		)
	)
 
	Coupling (
		Type ( Automatic )
		Spring (
			Stiffness ( 2e1N/m 5e6N/m )
			Break ( 5.1e7N 5.1e7N )
			r0 ( 5cm 8cm )
		)
	)

	include ( "../../Include/SCO_4F50_Friction.inc" )
	include ( "../../Include/SCO_4F50_Brake.inc" )

	Sound ( "genfreightwag1.sms" )
)

Friction Include

Code:

Comment ( #### 55 Ton (4) Axle FrictionBearing Freight Car - - - Friction #### )

	CentreOfGravity_Y ( 1.4 )
	ORTSTrackGauge ( 4ft 8.5in )
	ORTSRigidWheelbase ( 6ft 0in )
	ORTSUnbalancedSuperelevation ( 6in )
	ORTSBearingType ( Friction )
	ORTSDavis_A ( 187.49lbf )
	ORTSDavis_B ( 2.4750lbf/mph )
	ORTSDavis_C ( 0.005000lbf/mph^2 )

Brake Include

Code:

Comment ( #### 50 Ton (4) Axle FrictionBearing Freight Car - - - Brakes #### )

	BrakeEquipmentType ( "Handbrake, Triple_valve, Auxilary_reservoir, Emergency_brake_reservoir" )
	BrakeSystemType ( "Air_single_pipe" )
	MaxBrakeForce ( 33.0kN )
	MaxHandbrakeForce ( 33.0kN )
	TripleValveRatio ( 2.5 )
	MaxReleaseRate ( 20 )
	MaxApplicationRate ( 15 )
	MaxAuxilaryChargingRate ( 1.684 )
	EmergencyResCapacity ( 2.604 )
	EmergencyResChargingRate ( 1.684 )
	BrakeCylinderPressureForMaxBrakeBrakeForce ( 50 )
	ORTSBrakeShoeFriction ( 0 0.31 1 0.30 2 0.28 3 0.27 4 0.26 5 0.25 7 0.24 8 0.23 9 0.22 12 0.21 14 0.20 17 0.19 20 0.18 24 0.17 29 0.16 34 0.15 40 0.14 47 0.13 55 0.12 66 0.11 84 0.10 115 0.09 160 0.09 )
	BrakePipeVolume ( 0.37*(ft^3) )

I broke my include files down by ton rounded off to the nearest 5 tons (10,15,20,25).

So SCO_4F50_Friction.inc - is the Friction file for a (4) axle Friction Bearing that uses the weight of 50 Tons. All cars within 2.5 tons either side of 50 tons uses it.

Regards,
Scott

**Vince** · 12-15-2021, 13:47

coupler break force?

The coupler break force ( 5.1e7N ) seems a bit much. A typo?

regards,

**scottb613** · 12-15-2021, 14:08

Originally posted by Vince

The coupler break force ( 5.1e7N ) seems a bit much. A typo?

regards,

Hi Vince,

I probably picked it up somewhere - I know I didn't come up with the number myself. I see Shawn uses 750kN - I didn't know we could use kN there - would that be a more plausible value? That's the beauty of taking the time to automate conversions via script - I can change that value for my entire fleet very easily.

UPDATE: Oh - that's the value included with the BLW/ZT payware set.

Regards,
Scott

**CSRX** · 12-15-2021, 15:14

Scott,
The included file seems handy to work with, however considering modern freight can range from 100 total US tons to 143 total US tons, I'd be in need of four or five "included" files to work with, end result would still be about the same when it comes to editing each file.

750kN seems to work okay for me, had a knuckle break once with that value, but I think that was a fluke on my part.

I think I will give a go on the included files, however, considering your values are based off older generation freight cars, I would take a guess the values I am using are closer to modern equipment.

**R. Steele** · 12-15-2021, 15:18

I'm not anywhere near an expert on brakes...those parameter values were copied from the best values I could find in the forums -- at that time.

Best source would be from Joe Realmuto's paper on OR brake values -- which I would place much confidence in --- it was attached to a thread at Elvas ...I can provide copies of it to anyone that asks. it is too large to attach a zip here --- forum rules.

There are AAR guidelines for railcar design and specifications & brakes -- I've found several papers on this stuff. Also I've been finding all sorts of design plans for locomotives and railcars, which contain all the measurements necessary for the new derailment code modifications.

"Mild Rant": To my mind there is no such thing as "current US Freight physics" --- there are current design standards certainly, but physics are formulas, maths, and calculations derived from the long term scientific study of natural forces...railroad physics are the same in the US as they are in Austrailia, China, England...anywhere. The natural forces acting on a train do not change...only the circumstances under which those forces act, and the object upon which they are acting ( short light weight train --- long heavy train ). The train has a mass, it has power, it has friction, resistance, etc.. all those values can be found or derived and calculated. Change the train, values change. Physics is the science of studying and determining those values.

And most certainly I am not finding fault with Shawn's choice of words, I have too much respect for his professional capabilities to do that. I just like clarity.

Concerning North American railcar and locomotive design standards there are certain constants...one obvious one would be track gauge--which would affect the design and measurements of the wheels, wheel sets & trucks ( bogies elsewhere ). Standard Gauge is defined as 1,435 mm (4 ft 8+1â„2 in in the U.S. -- which is actually 1435.1mm -- to be "Spockish"about it ) -- so there are some constants and the designs/specs that flow from certain standards...track gauge being one of them.

Recently, I've been digging in the web and pestering folks about finding plans and specifications for railcars. There is definitely a variety depending upon who is designing them...although I'm quite positive I'll find some constants the more information I gather.

Here's an example: plans for a 3 bay Trinity covered hopper and plans for a Pullman Standard 3 bay covered hopper

Trinity>>> bandicam 2021-12-15 13-08-30-037.jpg PS-2 >>> bandicam 2021-12-15 13-10-24-978.jpg

Now...find the similarities and the differences in measurements...remember, the data you put into a simulator like OR drives the simulation...at least when you are using Advanced Adhesion...and it appears to me that OR is moving in the direction of two different modes, that of simple physics and that of advanced physics. Nothing wrong with both modes co-exisiting, some days I just want to jump in and run the train ( Lionel style -- or more like venerable MSTS ) but other times, I want more realism, more challenge and more learning.

Shawn, if this seems confusing to you...think what it looks like to me...I'm fairly new to this hobby, most certainly a LOT LESS experienced than you. It's not for nuthin' that I have a tagline that reads: "Forever ridin' drag in railroad knowledge"!

**CSRX** · 12-15-2021, 15:37

Gerry,
If what I am using, are the current best values, then I will keep plugging away using those specific values for me current and future releases.

I do like Scott's method, and could be something I'd give a go, as a release for future NVLW products.

**scottb613** · 12-15-2021, 16:26

Hi Shawn,

Sounds good - if you try an include file - remember the first line of an include file needs to be blank and it's a good practice to make the last line blank as well.

Hi Gerry,

Great stuff - sir.

Also Peter's Coals to Newcastle is an excellent resource as he is the ORTS Physics guy now and has written much of the code - I've spent a great deal of time with it.

Coals to Newcastle | Physics

http://www.coalstonewcastle.com.au/physics/

Describes the testing approach for locomotives, wagon and other rolling stock run in Open Rails train Simulator. Provide relevant tools and guidance to support performance testing of rolling stock, including a test route.

Regards,
Scott

**R. Steele** · 12-15-2021, 16:41

Originally posted by scottb613

...Also Peter's Coals to Newcastle is an excellent resource as he is the ORTS Physics guy now and has written much of the code - I've spent a great deal of time with it.

Coals to Newcastle | Physics

http://www.coalstonewcastle.com.au/physics/

Describes the testing approach for locomotives, wagon and other rolling stock run in Open Rails train Simulator. Provide relevant tools and guidance to support performance testing of rolling stock, including a test route.

Regards,
Scott

Could not have said it better...!! A most valuable resource!

If any OR users want to support his web site, there is a donation page...please think about it.

**R. Steele** · 12-15-2021, 18:31

Here's the values and parameters I'm currently using, couplers and brakes are always being adjusted as I learn more about them --- comments, advice, new data, and "Oh go soak yur head!" accepted thankfully. The specific dimensions are taken directly from plans published by BNSF which are shown in post#6.

The include wag file is from the OpenRails folder...msts wag file one level up is the unedited default file.

The path string to the include file is long ( include ( "..\\..\\..\\..\\..\\Common.inc\\ ) because I got tired of making junction links. When I got a laptop I reorganized my ORTS profiles ( miniroutes) as shown in the attached screenshot. All the common folders - sound, cabview, and OR "common.inc" are 5 levels above the trainset folders in all the profiles. A change in any of the common folders affects all 47 of the profile folders.

Yup, I changed all of the paths, everything -- cvf, sms files, alias stuff, etc to read "..\\..\\..\\..\\..\\Common.blah blah. I still have to use junction links to the SOUND & GLOBAL folders which are common to all the profiles. I wish OR would be coded to look for these two folders, other than the default MSTS location --- then we wouldn't have to use any sort of junction or other types of OS links.

Folders with green checks indicate I've completed converting all equipment to OR parameters, and have checked for sound and cabview errors...and activity errors ( using, of course, Ged's (Slipperman) excellent utilities. ) The whole folder "ORTS_Profiles" is backed up to a usb SSD drive ( multiple backup drives are used ).

Code:

include ( "..\\CSX_259970_LD.wag" )
Wagon (
	Mass ( 100.5t )
	include ( "..\\..\\..\\..\\..\\Common.inc\\Fleet\\Couplers\\Std_Freight_Coupler.inc" )
	include ( "..\\..\\..\\..\\..\\Common.inc\\Fleet\\Brakes\\Std_Freight_Brakes.inc" )
	ORTSAdhesion ( ORTSCurtius_Kniffler ( 7.5 44 0.161 0.7 ) )
	ORTSNumberAxles ( 4 )
	ORTSNumberBogies ( 2 )
	ORTSLengthBogieCentre ( 13.9446m )
	ORTSLengthCarBody ( 17.5006m )
	ORTSLengthCouplerFace ( 18.3007m )
	ORTSWheelFlangeLength ( 19.1516mm )
	ORTSMaximumWheelFlangeAngle ( 1.308996rad )
	ORTSBearingType ( Roller )
	ORTSDavis_A ( 1061.68 )
	ORTSDavis_B ( 16.5353 )
	ORTSDavis_C ( 1.748934 )
	ORTSWagonFrontalArea ( 157.3724ft^2 )
	ORTSTrackGauge ( 1435.1mm )
	ORTSRigidWheelBase ( 1.778m )
	ORTSUnbalancedSuperelevation ( 2.56in )
	Comment ( ORTS Dimensions for 3bay covered ribbed hopper 4750 cubic ft - Trinity )
	Comment ( Lightweight = 29.3t Load Limit Range 236K-286K = 90t - 100.5t )
	Comment( == Assumptions -FreightCar Standard - speed - 65mph (105km/h), Roller Bearing, 4 axles, frontal area - 14.6m2, WagonWeight - 100.5 ton (metric) == )
)

Code:

	Comment ( Standard Couplers for all freight cars )
	Comment ( include ( "..\\..\\..\\..\\..\\Common.inc\\Fleet\\Couplers\\Std_Freight_Coupler.inc" ) )

	Coupling (
		Type ( Automatic )
		Spring (
  			Stiffness ( 1e6N/m 5e6N/m )
   			Damping ( 1e7N/m/s 1e8N/m/s )
			Break ( 1850kN 1850kN )
			r0 ( 5cm 8cm )
		)
		Comment ( CouplingHasRigidConnection ( 0 ) )
		Velocity ( 0.1m/s )
	)
	Comment ( front coupling )
	Coupling (
		Type ( Automatic )
		Spring (
  			Stiffness ( 1e6N/m 5e6N/m )
   			Damping ( 1e7N/m/s 1e8N/m/s )
			Break ( 1850kN 1850kN )
			r0 ( 5cm 8cm )
		)
		CouplingHasRigidConnection ( 1 )
		Velocity ( 0.1m/s )
	)

Code:

Comment ( Standard Single Pipe AB Freight Brakes with Retainers )
	Comment ( Braking Ratio -- standard 38% maximum empty car braking ratio )
	Comment ( Mass -- Weight -- of empty car assumed to be 35t - metric )
	Comment ( Composition Brake Shoes )
	Comment ( include ( "..\\..\\..\\..\\..\\Common.inc\\Fleet\\Brakes\\Std_Freight_Brakes.inc" ) )

	BrakeEquipmentType ( "Handbrake, Triple_valve, Auxilary_reservoir, Emergency_brake_reservoir, Retainer_4_Position" )
	BrakeSystemType( "Air_single_pipe" )
	MaxBrakeForce( 76.9kN )
	MaxHandbrakeForce ( 35kN )
	NumberOfHandbrakeLeverSteps( 100 )
	EmergencyBrakeResMaxPressure( 110 )
	TripleValveRatio( 2.5 )
	EmergencyResVolumeMultiplier ( 1.461 )
	MaxReleaseRate( 6 )
	MaxApplicationRate( 6 )
	MaxAuxilaryChargingRate( 20 )
	EmergencyResCapacity( 0.839ft^3 )
	EmergencyResChargingRate( 20 )
	BrakeCylinderPressureForMaxBrakeBrakeForce( 77 )
	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)
	BrakePipeVolume ( 0.46ft^3 )

bandicam 2021-12-15 16-02-38-481.jpg

**scottb613** · 12-15-2021, 19:19

Hi Gerry,

Good post - as sometimes getting definitive answers on physics is tough.

So - I was going to put my couplers into an "include" but I noticed many cars have different values for [r0] (the coupler slack). I was also under the impression that ORTS used but a single coupler definition. Someone on Elvas recently mentioned that the second block is only needed when the car is reversed - a concept I haven't tested myself. I've added the second coupler block back into my files. I see you have [CouplingHasRigidConnection ( 1 )] - I thought that was only needed for the bar between steam locomotives and a tender and would negate the [r0] values freezing slack movement of the connection?

I initially used Peter's Brake Force Calculator to set the Max Brake Force value - but - it seems to produce values that are astronomically high as the train would stop unrealistically fast. I came up with my own way - just using .65 of the freight cars mass in (US-T) - so far it seems to work pretty well. So a 50 ton car uses a brake force of 33kN (rounded) where Peter's calculator suggested 133.453kN. Perhaps I'm using his calculator wrong.

Regards,
Scott

**steamer_ctn** · 12-16-2021, 00:49

Originally posted by CSRX

Scott,
750kN seems to work okay for me, had a knuckle break once with that value, but I think that was a fluke on my part.

It will depend upon the age and type of car.

See this table for some examples - https://www.coalstonewcastle.com.au/...ouplers/#break

So older cars that are used in shorter trains would probably more likely be at the lower end of the scale, say 0.75MN (750kN).

For more modern unit or longer trains, the value maybe at the higher end of the scale, say 2.54MN (2540kN) (Some research is required rather then putting a huge number in just to "fix a breaking problem")

I think that this discussion in this thread raises two other points that would be good to consider:

i) Creation of a Physics repository - the question of what physics should be used is often asked, and whilst my CTN site attempts to give some general guidance in relation to how to configure OR, it cannot provide detailed specification information (such as Gerry sometimes shares) for all stock. So the question is, can we establish a "physics" repository of some description? I would be potentially happy to host this type of information, however not in the form of a huge number of documents or drawings, etc. So it would require people to contribute to a repository in some form (not sure how at the moment). Perhaps it could be "standard" piece of ENG/WAG file code that users could cut and paste into their files. This would save others spending lots of time researching, and also ensure some level of consistency of operation.

ii) Content Providers - I think that content providers need to consider a strategy to either maintain their products up to date, or alternatively lock them to a fixed version, such as v1.4, or whatever. If they consider an upgrade strategy, it probably should only apply to major OR upgrades, ie v1.3, v1.4, v1.5, etc. An upgrade strategy might be easier to maintain with the use of INC files (though I don't have a great deal of experience using them), as it may be possible to change one INC file (say, for the brake system), and then this would ripple through all physics configurations.

The use of an INC file might also be shared between content providers and thus reduce the amount of effort required to produce an upgrade. For example, if a brake change for a 24-RL was required this could be common to all content providers using this brake system type, if they are willing to collaborate.

Anyway perhaps some food for thought.

**scottb613** · 12-16-2021, 06:33

Hi Peter,

I like your ideas - there are just so few of us left who produce anything - getting any kind of mass compliance to a standard seems difficult. Heck - if I knew someone had good values - I'd happily use them.

Also - I think you used to have the table with coupler parameters on your website - I think when you updated some of your "Advanced Coupler" parameters - the reference table like you have for all the other parameters - disappeared. Do you still have it or am I imagining something that was never there?

Hi Folks,

Just more on the coupler strength - did some digging - came across this info from someone who seems to know what he's talking about.

The strength of couplers is based on the type of steel used, and how they are heat treated. Many years ago, couplers were made of grade B steel, and were rated at 250,000 lb. These couplers should be all gone by now, except perhaps on some museum equipment.

Grade C steel couplers are the minimum allowable these days, rated at about 350,000 lb.

Grade E steel couplers are typically used on unit train equipment, and are rated at about 500,000 lb. (Note that Type E couplers describes the shape of the coupler, and not the grade of steel used to make them.)

You will also see grade E couplers that have been heat treated for better wearing properties. These are often identified by something like E50QT cast into the metal. The "QT" standing for quenched and tempered.

The problem with the ratings is that they are only a nominal rating based on a typical casting. Casting is not an exact science, and many couplers will have problems with weaknesses like bubbles, inclusions, or other metallurgy problems when they are made. Further, as a coupler ages, it will get progressively weaker due to fatigue cracking. As a result, most railroads will only design train services using something lower than the coupler ratings. As an example, it is rare to see a train service using more than about 350,000 lb. with grade E couplers, even though they are "rated" at 500,000 lb.

What's the conversion to make these figures useable for us? Since I model the 40's/50's - just curious on which value I should use - since he didn't define when the changes took place.

More on NumWheels from Peter:
Capture.JPG

Regards,
Scott

**scottb613** · 12-16-2021, 07:24

Hi Folks,

Oh - I was thinking lbs and kN were two different units of measurement - which they are - but if the numbers I quoted above are actually pounds force (lbf) - the conversion is easy.

Coupler Break Strength:
250,000 lbf = 1112.0554 kN
350,000 lbf = 1556.87757 kN
500,000 lbf = 2224.11081 kN

Regards,
Scott
250,000

**CSRX** · 12-16-2021, 12:20

Thanks for all the insists! Being I mainly model in the current era (2015-2021), I think newer cars are what I am going to base on.

All good information, will take it all in, and go from here.