[FRDF] How to decide how many wagons you can have in a train

[Zuu]

ON TOPIC ONLY

from Hellfires list:

# Capacities: The maximum number of cariages should not be the amount of empty carriages that the loco can pull but the maximum amount of full carriages. What is the use of transporting a bulk load of empty carriages?

If you can, as written as optional in the FRD, attach and deattach wagons from a train at stations it can be usefull. Then you can have a loco that driving back empty wagons from a factory to a source. Well I cant give a good example where this is usefull, but I hope you got the point.

The FRD wrote:

Optional features:
...
* Locomotives are a seperate vehicles that can pick up bundles of wagons for example at a farm, and drop them then at the factory, where the locomotive then picks up some goods wagons to bring them to a city.
...

However, if you cant order a train to attach/deattach wagons at stations it would be useless to be able to attach more wagons then that you can pull all full loaded.

[Arathorn]

If a train could attach/detach carriages, the case could exist that a train has too many carriages, is able to bring them to a loading station and is then unable to depart again. I would vote for the ability for trains to attach/detach carriages but carry only a number of carriages based on the weight of full ones, to avoid such problems. It might bring a little more gameplay fun for control freaks to be able to pull more carriages but a huge amount of annoyance to a lot of other players.

[Zuu]

I think you have a point. Since the attach/deattach concept is quite coplicated, so we have to wach out, so we don't make it more complicated than nececcary.

[PJayTycy]

I don't think we need something as "maximum number of carriages". If we just drop that, wouldn't that be easier?

When a player is setting up a schedule, and the game notices the train won't be able to pull the maximum possible load at a certain station, give a warning and don't allow the player to click OK on the schedule.

The only thing we need to do then is set for each wagon you add wheter it can be loaded or will always be empty and for each loco wheter it will help pulling or if it's just a wagon. We probably want / need those things anyway.

I think the idea of a "maximum number of carriages" is unneeded. A loco might have a maximum weight it can pull, wheter that load is 100 empty carriages, 20 full carriages or a mix of both doesn't matter.

[Hyronymus]

You sound like you're contradicting yourself, Pjaytycy. If you do want a feature that warns when the train gets to heavy isn't that the same as setting a limit on the amount of vehicles? I think what you mean is that you don't want a general, preset maximum but a locomotive-based maximum. Correct me if I'm wrong. A locomotive-based maximum is what I would like. At first it may seem difficult to implement but with known (or estimated) values as power, tractive effort and friction we should be able to sort that out. Just as the DBsetXL works in TTD.

[Mek]

You sound like you're contradicting yourself, Pjaytycy. If you do want a feature that warns when the train gets to heavy isn't that the same as setting a limit on the amount of vehicles? I think what you mean is that you don't want a general, preset maximum but a locomotive-based maximum. Correct me if I'm wrong. A locomotive-based maximum is what I would like. At first it may seem difficult to implement but with known (or estimated) values as power, tractive effort and friction we should be able to sort that out. Just as the DBsetXL works in TTD.

i believe Pjaytycy doesn't want the maximum based on the number of vehicles, but the weight of them, so if some kind of vehicles are empty a lot heavier than others, you can pull less of them.

[Zuu]

I think the idea of a "maximum number of carriages" is unneeded. A loco might have a maximum weight it can pull, wheter that load is 100 empty carriages, 20 full carriages or a mix of both doesn't matter.

That was what the idea was about. The problem is whether you should use the empty or full weight of the carriages in the calculation of the train weight.

I suggest that we should warn the user when the train weight, full loaded, extends the max weight, and when the weight, empty, exteds the max weight.

In the later case we can hinder the user from proceed. But we have to make sure that users cant miss the first warning.

Or, shall we realy hinder the user? As the result will not be a train that cant drive, but a train that will be so much slower than the specified max speed, so that the braking distance wont be altered. And the acceleration will offcorce be bad. On the other hand do we need that complexity. The possibility to create that long train? (I might have missed some physics that tells how long train ca be.)

[PJayTycy]

OK, maybe I don't know enough about TTD then, so first some other questions:

1) Do all wagons have equal empty-weights?
2) Do all wagons have equal full-weights?
3) Do all loco's have equal pulling power?

About the discussion wheter to count a wagon's full or empty weight:
If the wagon can be loaded => use full weight
If the wagon is forced empty => use empty weight

For example: you are driving coal wagons from a coal mine to a power plant, then return with wood from a forest to a furniture factory. Your train would require coal wagons and wood wagons. The wood wagons are forced empty when going in one direction while the coal wagons are forced empty when going in the other direction.

This "force empty" setting could be just an extension of the departure settings (eg: wait for full load, wait for any load, don't care, force empty, ...)

If we skip this "force empty" idea, I vote for Zuu's idea : impossible to exceed maximum weight with empty carriages. When loading the train in the game, we could stop loading more wagons once the maximum weight is reached. However, this moves the problem (from the player's view) from some settings in the schedule to possible glitches in a user's network (trains waiting for full load can't depart because another train didn't deliver all of its promissed cargo).

[edit][OT]

...braking distance...

Braking distance usually doesn't increase that much with longer trains, usually each wagon has it own set of brakes. So if you add twice as much wagons, your train weight is doubled, but its braking power is doubled too. The only increase is the time it takes for the brake signal to travel to the last wagon.[/edit]

[Zuu]

OK, maybe I don't know enough about TTD then, so first some other questions:

1) Do all wagons have equal empty-weights?
2) Do all wagons have equal full-weights?
3) Do all loco's have equal pulling power?

1) No
2) No
3) No
(have checked to be sure)

About the discussion wheter to count a wagon's full or empty weight:
If the wagon can be loaded => use full weight
If the wagon is forced empty => use empty weight

For example: you are driving coal wagons from a coal mine to a power plant, then return with wood from a forest to a furniture factory. Your train would require coal wagons and wood wagons. The wood wagons are forced empty when going in one direction while the coal wagons are forced empty when going in the other direction.

This "force empty" setting could be just an extension of the departure settings (eg: wait for full load, wait for any load, don't care, force empty, ...)

If we skip this "force empty" idea, I vote for Zuu's idea : impossible to exceed maximum weight with empty carriages. When loading the train in the game, we could stop loading more wagons once the maximum weight is reached. However, this moves the problem (from the player's view) from some settings in the schedule to possible glitches in a user's network (trains waiting for full load can't depart because another train didn't deliver all of its promissed cargo).

I think that "force empty" allready exist in TTD. But is called "Unload". What it does is "force unload of whole train".

But what you are saying is that the game should read the schedule to decide if a train is vaild or not. Not that it would be complicated to program, but. hmm But I think it might be difficult to give a clear message to the user what is allowed, and what not if it depends on to much.

[PJayTycy]

I think it might be difficult to give a clear message to the user what is allowed, and what not if it depends on to much.

See screenshot, that seems like a clear a message to me...

[Hyronymus]

This calls for a simple example with fictive numbers I guess. To summarize, I suggest that we use a locomotive-based maximum amount of wagons. How could that possibly be put to work in TE?

Code: Select all

Train 1
Max. speed: 100 km/h
Max. TE: 150 kN

Train 1 is heading from Station A to Station B and back. You put 30 empty self-dischargers behind Train 1 at Station A, to be fully loaded there. It unloads at Station B. Train 1 can easily 'leave the depot' with 30 empty self-dischargers but when fully loaded at B it can not pull the load. Although the empty wagons are not a problem you do warn the player that Train 1 will be unable to pull the train when fully loaded.

Code: Select all

Train 2
Max. speed: 80 km/h
Max. TE: 250 kN

Train 2 is heading from Station B to Station D and back. You put 30 empty self-dischargers behind Train 1 at Station B, to be fully loaded there. It unloads at Station D. Train 1 can easily 'leave the depot' with 30 empty self-dischargers and also easily pull the 30 fully loaded wagons. Because neither the empty nor the fully loaded wagons are a problem you don't warn the player.

Code: Select all

Train 3
Max. speed: 100 km/h
Max. TE: 150 kN

Train 3 is heading from Station C to Station D and from there to Station A. When Train 3 leaves Station C it easily pulls 10 fully loaded timber wagons. When it arrives at Station D the timber is unloaded and 7 fully loaded goods wagons are loaded, still no problem. However, when Train 3 arrives at Station A it will be loaded with 20 log (unprocessed wood) wagons. This is a too heavy pull for this engine and therefore you warn the player in advance that it will not be able to pull the train from Station A.

Please note that I made a few assumptions. I wrote leaving the depot and I know we're not sure if that's how trains will enter a service. Train 1 and Train 3 are both from the same imaginairy Turtle-class but the example illustrates that the maximum number of wagons depends on engine type AND wagon type.

[Zuu]

Yes, you're right. It won't be that difficult.

[uzurpator]

I think this discussion is unecessary. I mean - shouldn't the player decide how to build his trains?

From a coder standpoint we should simply use the fastest and memory conservative way to store vehicles consists. What player does in a game is only for the player to decide.

Imho 128 vehicles in a consist as max is enough.

PJayTycy: Your proposition might work in a flatlands, but once grades are put into the model - it fails. For example:

BR103 can pull 30 empty hoppers, but has problems with 30 full but if we run empty uphill and full downhill then it is ok since the gravity does most of the work.

[Hyronymus]

128 max for ALL locomotives? That's very unrealistic IMO, it would render obsolete one of the main things that make it interesting to choose between trains: Tractive Effort! In TTD you only look at speed (although Patchman succesfully added TE to the info) but speed alone is complete parc (read backwards). That's like allowing The Rocket to pull 128 fully loaded coal wagons. Besides, what it so much more difficult in reading 1 line (v=100) than reading 3 lines (v=100, P=1000, TE=250).

[PJayTycy]

PJayTycy: Your proposition might work in a flatlands, but once grades are put into the model - it fails. For example:

BR103 can pull 30 empty hoppers, but has problems with 30 full but if we run empty uphill and full downhill then it is ok since the gravity does most of the work.

Damn. Didn't think of that...

[uzurpator]

Hyronymus: Tell me - which of the laws of physics disallows attaching one of the BHP mines ore trains to a Rocket? (FYI - BHP runs the heaviest trains in the world usually 330 cars and 6 locomotives - railroading ausse way ^^).

It is true that Rocket will not be able to haul 126 carworths of coal - but I see no reason to disallow the player to build such train.

Besides - I was more concerned about technical limits. The loco data will cut this to size in no time.

EDIT: After all - 128 coal cars from 1830 - each 5 tons of capacity is slightly different from 128 Bethgons - each with 100 tons of capacity ^^

[Steve]

Besides, what it so much more difficult in reading 1 line (v=100) than reading 3 lines (v=100, P=1000, TE=250).

Well, it's 3 times more difficult

Plus, not everyone knows what TE is and how it relates to power. I think it's generally well known (and easy to explain) that speed it top speed and power affects acceleration and maximum carry capacity. But TE is stranger and i can't personally explain it to you.

A message on train creation that it won't be able to pull the Fully Loaded wagons would be nice. Or if the weight is going to affect acceleration greatly, make the figure in the details below flash red to show the drop is efficiency.

The uncoupling of different carriages is a complex idea, i presume it's largely left out of games because of it's complexity. I don't think we can really feature it until someone (A) Makes a good system for trains knowing how to pick up trains without crashing (B) Make a user system so they can easily show what carriages are getting picked up on each route. Then you need to consider what happens if there isn't any wagons left for them to take back. Wait? Leave anyway? Crash the computer?

[Hyronymus]

To be the best solution seems:

• take into consideration the distinctive features of a locomotive
• take into consideration the weight of the different type of wagons at different eras
• warn when the maximum load for a specific locomotive type is reached pulling a specific type of wagons

I imagine you use one formula to determine it:


With:

• - Nwagon = max. number of wagons
  - TE = Tractive Effort of locomotive type (in N)
  - g = gravity (in m/s^2)
  - Mwagon = weight of wagon type (in kg)

[Zuu]

Can someone explain what TE is? Is it the force that the loco pulls with?

[Hyronymus]

Tractive Effort is the force that a locomotive can produce on the rims (edges) of the wheels. It's determined by the power of the engine, the number of driven axles and gear ratio (this is for electric locomotives). For steam engines it's the bore of the piston * the diameter of the piston * 0,85 boiler pressure IIRC.