Power vs tractive effort/force in opentdd

[GrandSeverus]

So locomotives differ when it comes to power vs tractive effort they have.
For example, Big Boy from NARS grf, has 6378 power and 600 tractive effort while PRR Class Q2 has 8098 power and 437 tractive effort.
So when I am transporting goods which statistic is more important in opentdd? The same question goes for passenger/mail, which is more important.
So if a locomotive has 6000 power and 600 kn how do I calculate what is the optimal weight of the train?
Thanks for the help,
Cheers,

[Eddi]

so the rough importance of engine stats is:

• tractive effort: least important. you need just enough tractive effort to overcome the friction of the wagons. acceleration might be slow for the first few seconds, but it doesn't really matter much in the scale of openttd. tractive effort only ever matters if you're accelerating from a standstill, and there are some fallback mechanisms that prevent trains from being completely stuck.
• top speed: medium important. travelling at high speeds is what earns you the most money over longer distances, if you can avoid stopping inbetween. (the game mechanics kinda overexaggerate the importance of speed on non-spoiling cargos like ore and coal)
• power: most important. if your rails are flat, you need just enough power to counteract drag and resistance. have some spare to reach top speed quicker. if you're going on hilly routes, you need significantly more power to maintain top speed (try to avoid going uphill when you're just starting up)

there probably are formulas to tell you exactly how much you need of each, but you can mostly just eyeball it.

[GrandSeverus]

so the rough importance of engine stats is:

• tractive effort: least important. you need just enough tractive effort to overcome the friction of the wagons. acceleration might be slow for the first few seconds, but it doesn't really matter much in the scale of openttd. tractive effort only ever matters if you're accelerating from a standstill, and there are some fallback mechanisms that prevent trains from being completely stuck.
• top speed: medium important. travelling at high speeds is what earns you the most money over longer distances, if you can avoid stopping inbetween. (the game mechanics kinda overexaggerate the importance of speed on non-spoiling cargos like ore and coal)
• power: most important. if your rails are flat, you need just enough power to counteract drag and resistance. have some spare to reach top speed quicker. if you're going on hilly routes, you need significantly more power to maintain top speed (try to avoid going uphill when you're just starting up)

there probably are formulas to tell you exactly how much you need of each, but you can mostly just eyeball it.

I am remember reading about opentdd that tractive effort is more important for cargo trains and power is more important for passenger trains.
So tractive effort is only needed to move if i am getting you right?
Since i am using a lot of grf's i have a lot of locomotives. Due to this fact, i have large number of locomotives that have small tractive effort but high power.

[Auge]

Hello

I am remember reading about opentdd that tractive effort is more important for cargo trains and power is more important for passenger trains.
So tractive effort is only needed to move if i am getting you right?
Since i am using a lot of grf's i have a lot of locomotives. Due to this fact, i have large number of locomotives that have small tractive effort but high power.

If you are using train sets, that mirrors real trains, you can see, that locomotives, that are intended for fast passenger services, have mostly a fair amount or high power but – in comparision to locomotives for freight services – low tractive effort. The high tractive effort is mainly needed to speed up. Its importance increases with more hilly or mountainous terrain and with heavier loaded trains. And these are typically freight trains.

So yes, your assumption is generally correct.

Tschö, Auge

[edit]Splitted the sentence "… high tractive effort is mainly needed to speed up[split /] its importance increases …" to make it better understandable.[/edit]

[Eddi]

in short: high power is needed to get (comparatively lighter) passengers to high speeds, but to get a freight train to speed, you need both power and tractive effort.

[odisseus]

The train acceleration is affected by the tractive effort only at low speeds, which can occur only when starting from a standstill, or on a very long slope.

I have run some analysis in Wolphram Alpha, and got the following chart. It shows that power begins to dominate when the train has reached a certain speed. This cutoff speed lies in the range of 50-60 km/h for freight engines to 100 km/h for high-speed passenger engines.

The source formulas can be found in the wiki.

The chart shows that the tractive effort becomes completely irrelevant when the speed exceeds 50-100 km/h.

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