Descending Grades and Throttle

E

Eboy87

Member
I’m running ‘22, but this is something I’ve wondered at for years. When my entire train is on a downhill of, say, -.4%, I still have to be in notch 5 or 6 to maintain track speed (usually 35-45 mph). This is with HP/t of 2 and train lengths (almost all JR content) of 4-5k feet.

is there something going on under the hood that explains this, or is the physics engine really that bad? I realize it’s not Run8, but still…
 
There is an awful lot of resistance with 4-5k feets worth of rollingstock, and hp/t of 2 is very, very low. -0.4% isn't exactly a particularly steep grade either
 
H222 said:
There is an awful lot of resistance with 4-5k feets worth of rollingstock, and hp/t of 2 is very, very low. -0.4% isn't exactly a particularly steep grade either
Click to expand...

Whilst I would grant that .4 is light compared to 1.4, I still shouldn’t have to be in notch 6 with a mostly empty train entirely on the downhill. I guess it doesn’t detract entirely from the game, but it doesn’t exactly help make the jump from “game” to “sim.”
 
Eboy87 said:
Whilst I would grant that .4 is light compared to 1.4, I still shouldn’t have to be in notch 6 with a mostly empty train entirely on the downhill. I guess it doesn’t detract entirely from the game, but it doesn’t exactly help make the jump from “game” to “sim.”
Click to expand...

I'm simply pointing out that there is an incredible amount of rolling resistance in 100+ wagons. Your train is still severely underpowered. 2hp per ton is absolutely nothing. Especially bearing in mind that the tons in game are Metric Tonnes, not US Tons. Your train being empty, if anything, makes it worse, as there is even more resistance in an empty train with more wagons than there is in a train the same weight with less wagons and less bogies. It's also worth noting that a lot of JR's wagons use default wagon specs which are often set up incorrect as well
 
The resistance to movement in the game does not correspond to the realities of today, and is taken at the beginning of steam locomotive times.Although the calculation itself corresponds to the literature, but due to the coefficients, the resistance turns out to be large, both for cars and for locomotives.And yes, an empty train has a higher resistance to movement, with the same number of cars.
 
Eboy87 said:
I’m running ‘22, but this is something I’ve wondered at for years. When my entire train is on a downhill of, say, -.4%, I still have to be in notch 5 or 6 to maintain track speed (usually 35-45 mph). This is with HP/t of 2 and train lengths (almost all JR content) of 4-5k feet.

is there something going on under the hood that explains this, or is the physics engine really that bad? I realize it’s not Run8, but still…
Click to expand...

Is this a general "downhill" problem you are seeing or a specific set of circumstances? (Particular downhill grade and consist perhaps?) I know there are many times I need to use dynamics to maintain control going downhill. You got me wondering now.. I'll run some consists on a -0.4% or such. I don't suppose you have a particular Route/Session where you see this?
 
1611mac:

It’s pretty consistent for me across routes and consists, no matter the author, and that’s with long downhills where the entire train is on the grade. I’ve noticed I need to be in power up to around a .8 descending grade, then it quickly goes to needing dynamics and air to control my speed, which I would expect needing over 1.8 or so. I generally chalked it up to bad physics modeling/rolling resistance and imprecise engine specs.

Full disclosure, I’m not a railroader. I’ve had the opportunity to run a couple engines on flat track, but I compare to run8 a lot for train handling.
 
Eboy87, I can suggest trying to drive with the following wagon engine specifications: 584469:37:5, 584469:73:5, 584469:75:5. To them choose the cars of the author 506034 Weersprada. The main thing is that the car should have one of the indicated traction units, and, well, a full load of the car. All of the above is on DLS.
If you want to unsubscribe about the difference in behavior.
 
Justin Cornell (Norfolksouthern37) put together an Engine HP calculator spreadsheet. You enter in the tonnage, average grade, curve degree, and line speed along with the number of cars and axles per car and the spreadsheet will return with the number of locomotives needed.

I don't remember where I got it though. He may have posted a link to the spreadsheet on the forums here, or maybe on the JR website.
 
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