Coal Car Physics.

[Ericmopar]

Are there any fixes for the strange behavior of Coal cars on Cajon Pass?
I've tried other coal cars from other routes and the best ones on Cajon seem to be the Donner Pass cars, but they all have a strange problem that doesn't seem to affect any other U.S. stock.
They behave exactly the same on a 1.5-2% grade as on level track.
Unit oil trains when loaded, accelerate slowly on level ground and the train slows dramatically on any type of uphill grade.
Unit coal trains on the other hand, accelerate slowy when loaded on level ground, but when you reach a grade, they cruise right up like there is nothing in them. For that matter, they behave on an uphill grade almost like the cars aren't even there.
I'm wondering if there is a .bin fix, and if so, what is the file path, and what am I looking to adjust?
Thanks, Eric

[dfcfu342]

I ran into this issue when I was messing with physics on cars. As far as I can tell its an integer overflow that causes the resistance to go from negative to positive and push the train up the hill. It would take 3 ES44's to start it rolling but once I hit a grade notch 1 would haul right up at 40 no problem.

These were my final adjusted values that worked well:

Drag:

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<DragCoefficient d:type="sFloat32" d:alt_encoding="000000000000F03F" d:precision="string">1</DragCoefficient>
               <RollingFrictionCoefficient d:type="sFloat32" d:alt_encoding="000000A0A8DE4A3F" d:precision="string">0.00082</RollingFrictionCoefficient>


Car mass:

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<Mass d:type="sFloat32" d:alt_encoding="0000000000003A40" d:precision="string">26</Mass>


Brake Force:

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<MaxForcePercentOfVehicleWeight d:type="sFloat32" d:alt_encoding="0000000000805040" d:precision="string">66</MaxForcePercentOfVehicleWeight>


Cargo Capacity:

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<Capacity d:type="sFloat32" d:alt_encoding="0000000000405D40" d:precision="string">117</Capacity>


[Ericmopar]

Thank you for putting me on the right track. Those numbers are better than OEM, but after setting me in the right direction, so I knew finally where to look, I came up with some great numbers.
The other numbers I left at default values.
I used a test train of 65 Donner Pass "brown" coal hoppers, with 5 default (Cajon Pass) SD40-2s. Those hopper's .bin file is labled "coal_hopper_Def2"
I drove it over the summit from Victorville and had a blast.
I was in notch 5 to 8 almost all the way up to the top, and the braking was very good on the way down to the Cajon crossover.

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<DragCoefficient d:type="sFloat32" d:alt_encoding="0000000000001040" d:precision="string">4</DragCoefficient>

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<Mass d:type="sFloat32" d:alt_encoding="0000006066D65640" d:precision="string">91.35</Mass>

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<RollingFrictionCoefficient d:type="sFloat32" d:alt_encoding="000000C07493583F" d:precision="string">0.0015</RollingFrictionCoefficient>


[dfcfu342]

Have fun with it and don't be afraid to mess around with other cars as well. The sim play is much better and "feels" more real and as a bonus the AI trains behave like actual trains rather than like Ferrari's going 0-50 in 10 seconds.

My only suggestion would be to lower your values for drag coefficient to either 1 or 2 depending on the size of the car. The drag coefficient is to simulate the frontal area of the car and increases drag on the car in proportion to speed. Too high of a coefficient will cause your train to be more difficult to pull at speeds above ~45-50 mph even on flat ground where weight is irrelevant to speed. You can compensate for the decreased drag by increasing mass to keep the overall handling effect the same and retain more realistic handling at speed.