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1. TOPS brake codes - a thread for railway modellers!
(Nerd alert!
)
(Nerd alert!
)
1a. A thread after a conversation with @NSE_Latchmere earlier today - for anyone looking to understand how brakes affected (largely BR era) train formations.
It's easy to forget it wasn't always like today, when everything had matching brakes.
It's easy to forget it wasn't always like today, when everything had matching brakes.
1b. And a caveat - I'm very much coming at this from a late BR point of view...
Also trying to keep it simple, so apologies to anyone for any "teaching granny to suck eggs" moments.
Also trying to keep it simple, so apologies to anyone for any "teaching granny to suck eggs" moments.
2. Quick historical context - whilst passenger trains got continuous brakes, up until BR times freight trains generally did not - they were "unfitted" - most wagons had a handbrake worked by a lever on the side but nothing more.
(Getting a lever on both sides took a while!)
(Getting a lever on both sides took a while!)
3. This was the reality for more than a century, it forced freight trains to run slowly - 25mph max - as only the brakes on the loco, tender and brake van wheels could be operated by the train crew whilst the train was in motion.
4. The brake van at the back was also critical as if there was a coupler failure the two halves of the train would *not* automatically come to a stand, so the guard on the brake van would have to try and stop the rear of the train with just the van handbrake. 
5. In it's early years BR did at least make a start to improve things, but built a real mix of vacuum brake ("fitted,") and unfitted wagons, and by the late 60s with a need for freight trains to be even fasted, they also started introducing air braked wagons into the mix.
6. Vac and Air "fitted" wagons both allowed for more powerful braking and so faster train speeds (up to 75mph with some wagon types in the case of air) but were incompatible with each other, however they needed to be used together at times for practical reasons.
7. Whilst you could just add a brake van to any combo and run it unfitted at 25mph, you could also run "partially fitted" if you had enough of one type AND marshalled them behind a loco with compatible brakes, increasing braking power available.
8. And to add to those 3 basic brake types, through pipes were added to the mix - some wagons were fitted with a vacuum or air pipe that didn't connect to the brakes on that vehicle, but would allow the pipe to reach the vehicles behind.
9. That allowed (for example) a nominally air braked wagon to run as an unfitted wagon a vacuum braked train, whilst passing the vacuum brake from the loco through to the wagons behind it to allow the whole train to run as fitted.
10. So by the 70s there was a whole heap of things staff had to consider when putting a train together - and mistakes potentially had big consequences - crews expecting more brake power than they actually had was an underlying theme in several accidents of the time.
11. So by the time BR's shiny new computer system, TOPS, came about in the 70s, BR was running unbraked, vacuum braked and air braked wagon fleets, plus some wagons were also fitted with through pipes to give them a basic compatibility with some other fleets.
12. Under TOPS all wagons got a 3(*) character code, these were both carried on wagon data panels and appeared in train consist paperwork.
(In the case of this Dogfish, the code is ZFV, visible just above the running number.)
(*OK 4, but the 4th is rarely carried...)
(In the case of this Dogfish, the code is ZFV, visible just above the running number.)
(*OK 4, but the 4th is rarely carried...)
13. TOPS codes are an absolute boon for period modellers to help build plausible rakes of wagons, as you don't need to guess what brakes wagons have.
So what brakes codes were there?
So what brakes codes were there?
14. There's a good TOPS coder primer online here: https://www.ltsv.com/w_ref_codes_tops.php
As Tom is reworking his site presently and I can't find the equivalent page on the new version yet I'll include a quick grab of his brake code table for continuity if that link stops working.
As Tom is reworking his site presently and I can't find the equivalent page on the new version yet I'll include a quick grab of his brake code table for continuity if that link stops working.
15. As you can see - a lot of variations, so lets simplify & put add a late BR context.
By the late 80s whilst the capability for unfitted was still there (brake vans hanging around in strategic locations) the reality was that trains were being built as vac or air braked.
By the late 80s whilst the capability for unfitted was still there (brake vans hanging around in strategic locations) the reality was that trains were being built as vac or air braked.
16. Side note for loco capabilities, whilst some are easy (56, 58, 59, 60 are all airbrake only) some are harder - earlier built types may have been built as vac only or as dual, and may have been converted to gain/lose capabilities over the years!
17. From memory, the Platform 5 spotters books used to list which individual loco's had which brakes fitted - if so then a tip would be to try and hunt down one of those for the year you are modelling!
18. The most common codes in a late 80s context are the basic A and V. Most wagons will just have one of those two.
Keeping those two on different trains from each other is a good first step.
Keeping those two on different trains from each other is a good first step.
19. So at a very basic level a train of all A (all air brake) pulled by an air brake fitted loco is fine.
20. And a train of all V (all vac brake) with a vac brake capable loco is fine.
21. And lots of trains will be that simple - but from a modelling point of view how do we use the information from the other codes?
Lets break (sorry
) it down by the two braking systems - a reminder of the list:
Lets break (sorry
) it down by the two braking systems - a reminder of the list:
22. So if you're building an air brake train then A is air brake - but so are B, H, and X - all those can work together in a fully air brake train.
23. And then G, Q, R, W have air through pipes - so you can put some of those in an air brake train *provided* you have enough air braked wagons marshalled behind them in the train to stop the back half from running away if it breaks away.
And i'm going to take a break (sorry!!!!!) here - will conclude later...
24. Just to wrap it up - in a similar vein to the Air mix - on a Vac braked train as well as the basic V, you can also include F, G, H, W and X.
And as piped wagons in a vac train, you can add codes B, P, R.
And as piped wagons in a vac train, you can add codes B, P, R.
25. Once you start looking at them you'll probably remember the most common. I'd struggle to remember exactly what G is off the top of my head for example. 
Hope this has been useful!
