Train speed calculation

[ingmarins]

I'm playing with mods that change trains, so I was wondering what would be a good locomotive/cargo wagon ratio. The wiki page of Locomotive explains something about maximum speed, but there are some constants involved that I'm not sure about the meaning of.

Why is there a 10 here?:

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train_speed = train_speed + (10 × number_of_locomotives_in_moving_direction × fuel_acceleration_bonus ÷ train_weight)

Is that the vanilla 600kW divided by 60 ticks/s? So for a modded locomotive I would replace the 10 with the modded consumption / 60?

Why is there a 1.2 here?:

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max_speed = 1.2 * fuel_top_speed_multiplier

Is that the vanilla top speed in m/tick? So for a modded locomotive I would replace the 1.2 with the modded top speed in m/tick?

[DaveMcW]

The constants are historical values that were picked randomly, then followed precisely during 7 years of development to avoid any breaking changes. You can use math to give them different meanings, but you can't change them.

For example, let's rearrange the locomotive speed formula.

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train_speed = train_speed + (number_of_locomotives_in_moving_direction × (fuel_acceleration_bonus × 10) ÷ train_weight)

Now it is saying that the fuel_acceleration_bonus is expressed in units 10x smaller than normal.


Or we can move it to another position.

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train_speed = train_speed + (number_of_locomotives_in_moving_direction × fuel_acceleration_bonus ÷ (train_weight ÷ 10))

Now it is saying that train_weight is expressed in units 10x larger than normal.

Either way, fuel_acceleration_bonus and train_weight are using units that differ by a factor of 10.