Train acceleration and speed

[terror_gnom]

Hi,
is there any known formula to calculate the topspeed and acceleration of trains?

Google didnt help much for long trains I´ll probably need more than 2-6-2

[Optera]

empiric data for train speed:
https://www.reddit.com/r/factorio/comme ... comotives/
https://www.reddit.com/r/factorio/comme ... xperiment/

The formulas used for acceleration and top speed are not realistic.
Acceleration seems to be mostly a function of max_power and total weight ignoring friction_force and weight of the locomotive.
A train with 100ton can be accelerated by a mere 1ton locomotive if you give it enough max_power which is nonsense as it's wheels would only spin.

Top Speed has a hard limit with max_speed and a calculated limit derived of total weight, total max_power and total air_resistance. air_resistance seems to factor in more at higher speeds which is at least somewhat realistic.

[terror_gnom]

Thanks I know those tests, but it doesnt help me, how much cargo wagons a 3-x-3 can handle I hoped, the devs did post something or anyone who knows how checked it in the gamefiles

[Optera]

Thanks I know those tests, but it doesnt help me, how much cargo wagons a 3-x-3 can handle I hoped, the devs did post something or anyone who knows how checked it in the gamefiles

What do you mean by "can handle"? accelerate to max speed? If so in what time?
As far as I know the devs never published the train fomula. Here's a really nice one proving L-C is not equal to LL-CC in terms of acceleration

Edit: After doing some testing with 0.14.21 myself I think the formulas have changed since those test I linked. They seem more realistic now.
L-CC accelerates faster than CC-L, used to be the opposite
L-C-L accelerates faster than L-backwards L - C

[terror_gnom]

Thank you, so I´ll do some tests of my own. I just hoped, there are some (known) formulas to to see how the numbers changes and finding a "sweet spot"

[RoddyVR]

I'm still using L-CC trains because the last time i looked into this topic, the answer was:
1 locomotive by itself = highest accell and top speed.
1 loc per 2 cars (or reverced loc) second best.

I dont remember exactly where or what i read back then, but my impression was that a LL-CCCC train would be as fast as an L-CC train, and same as LL-CC-LL (where the other LLs face wrong way and are dead weight).

so for same speed i would assume that if you want bidirectional trains, it would be LLL-CCC-LLL to match the speed of L-CC trains.
If you dump more cars between the two sets of locos then there are locomotives on each side then the train will have less then a 1/2 ratio of "working locos"/pulled weight and be slower then a LCC

This was the main reason i decided that LCC with roll on roll off turning around would be way and i've built all my train systems that way since. If i ever make a real large base, and need insane amounts of trains coming in from far away, then i'll probably go to a LLCCCC system for far away outposts and have a transfer system betweeen the long distance 2-4 trains and the short range 1-2 trans

[Optera]

I'm still using L-CC trains because the last time i looked into this topic, the answer was:
1 locomotive by itself = highest accell and top speed.
1 loc per 2 cars (or reverced loc) second best.

I dont remember exactly where or what i read back then, but my impression was that a LL-CCCC train would be as fast as an L-CC train, and same as LL-CC-LL (where the other LLs face wrong way and are dead weight).

so for same speed i would assume that if you want bidirectional trains, it would be LLL-CCC-LLL to match the speed of L-CC trains.
If you dump more cars between the two sets of locos then there are locomotives on each side then the train will have less then a 1/2 ratio of "working locos"/pulled weight and be slower then a LCC

This was the main reason i decided that LCC with roll on roll off turning around would be way and i've built all my train systems that way since. If i ever make a real large base, and need insane amounts of trains coming in from far away, then i'll probably go to a LLCCCC system for far away outposts and have a transfer system betweeen the long distance 2-4 trains and the short range 1-2 trans

I was under the same impression that 2L-4C = L-2C in acceleration and top speed, but that's not true (anymore).
When testing locomotive parameters for this thread i built a very basic test track. Here's the results:

L-2C vs 2L-4C

L-2C vs 2L-4C start

2017-01-27-09-23-26-6695280.jpg (458.94 KiB) Viewed 7774 times

2L-4C starts pulling ahead

2017-01-27-09-23-30-7227598.jpg (457.17 KiB) Viewed 7774 times

2L-4C is done with the turn before L-2C even enters it

2017-01-27-09-22-46-5972360.jpg (90.1 KiB) Viewed 7774 times

2L-4C wins

2017-01-27-09-23-59-3633980.jpg (459.53 KiB) Viewed 7774 times

[Xeanoa]

snip

Well, that actually makes sense, because both trains should experience roughly the same amount of air pressure, and that will affect the single locomotive more.