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Author Topic: 1850-1880's passenger car constraints (brake carriages)  (Read 347 times)

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Offline Vladki cz

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1850-1880's passenger car constraints (brake carriages)
« on: January 05, 2019, 05:06:31 PM »
I have a question about how passenger cars of the 19th century should be combined into train.
I can see front/rear brake cars (of various classes), mail brake cars and then cars without brakes.
Please correct me, but from some previous discussions I understand that passenger cars had a brake guard's compartment at the end. So the custom was to put a brake car at each end, one with the brake compartment towards each end of the train. And the guard was only in the rear carriage. If the brake car did not carry passengers but mail, it was not important which way it was turned. (maybe it had suitable compartment at both ends?)
I see that this sort of arrangement is enforced with constraints for e.g. LNWR six wheel (radial) carriages, and Metropolitan 8-wheel carriages, but not for the various 4-wheel carriages of 1850-1870's. Is that intended?
I see also the the 6 and 8 wheel carriages are constrained so that they cannot be combined with others, but the 4-wheel cars can

Offline jamespetts gb

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Re: 1850-1880's passenger car constraints (brake carriages)
« Reply #1 on: January 05, 2019, 07:52:16 PM »
The way in which trains were made up on real railways was actually fantastically complicated and we can only attempt at a very general approximation with the very limited constraint system that we have in Simutrans.

First of all, before the mid 1870s, most passenger trains lacked continuous braking. The only braking came from brakes manually applied in the brake carriages. Each train would have had multiple brake carriages and each brake carriage would have had a guard (one head guard and one or more underguards) who would manually apply the brakes in each brake carriage. The locomotive whistle would be used to communicate when the brakes should be applied. All other carriages would not have any kind of braking, although the locomotive's tender (or the locomotive itself if a tank engine) would have a brake, applied by the fireman on the driver's command.

When continuous braking was introduced, only one guard per train was needed, but a guard's compartment was usually maintained at each end of the train so that the guard could be at the rear of the train no matter which way that the train was facing. In more modern times (1960s or so onwards, very approximately), this was not considered important, and a single guard's compartment anywhere in the train was thought to suffice.

The front/rear brake constraints were formerly enforced for the earlier four wheel carriages, but given that there is now an actual mechanism which gives realistic operational/economic consequences of not having enough brake force (trains have to start braking much sooner, reducing their average speed), it seemed not worthwhile to maintain this enforcement in the constraints given the very large amount of work that maintaining the constraint set took (and also some railway companies, notably the LSWR, did in fact use only one brake carriage per train even when there was no continuous braking).

Offline Vladki cz

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Re: 1850-1880's passenger car constraints (brake carriages)
« Reply #2 on: January 06, 2019, 06:11:36 PM »
Thank you for nice explanation. I was then wondering how differently are cargo trains implemented than passenger trains?
If I have a cargo train with one brake van at the end, it will swap with the engine when reversing.
But if the train consists of pax/mail carriages with brake van at the end, it will stay in place, and after reversing the brake van will be right behind the engine.

Offline jamespetts gb

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Re: 1850-1880's passenger car constraints (brake carriages)
« Reply #3 on: January 06, 2019, 06:16:13 PM »
Yes - generally, passenger trains were not remarshalled at the end of each journey to turn around the brake carriage, whereas goods trains were.

Offline Vladki cz

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Re: 1850-1880's passenger car constraints (brake carriages)
« Reply #4 on: January 06, 2019, 08:15:56 PM »
OK. is there any special processing of cargo trains that moves the brake car to the rear?
Just asking so that I know when adjusting pak128.cs for extended.

Offline jamespetts gb

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Re: 1850-1880's passenger car constraints (brake carriages)
« Reply #5 on: January 06, 2019, 08:47:55 PM »
Yes - have a look at the way in which the Pak128.Britain-Ex brake vans are configured. There is an algorithm for detecting brake vans.

Offline Vladki cz

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Re: 1850-1880's passenger car constraints (brake carriages)
« Reply #6 on: January 08, 2019, 11:43:50 PM »
Hmm, I see that pure brake vans have nonzero brake_force and zero capacity (cargo=books).
Now I tried to make a mixed cargo/passenger/mail train with mail brake van at one end and passenger brake van at the other, and it gets quite mixed up, with the cargo (unbraked) car at the end and both brake vans right behind the engine. So the question is - is it just dat definitions, or is there some special piece of code that detects cargo trains and does the shunting of brake vans?

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Re: 1850-1880's passenger car constraints (brake carriages)
« Reply #7 on: January 08, 2019, 11:47:35 PM »
There is code that detects brake vans specifically - but that detection is based on the .dat file parameters. I am slightly confused by the distinction that you imply between being a special piece of code and being based on .dat file parameters, however - can you elaborate?