6Y99 Posted January 23, 2011 Share Posted January 23, 2011 In the wee small hours at work this morning I was talking to an old of the old hands just after he been on the H.O.B.C. and I was doing a bit research an asked him this question why did all Air Braked freight stock in the 1970s have both Yellow (Main Res) and Red (Brake pipe) pipes fitted and I showed him a pictures taken out of the book BR Freight services in focus this showed BBA 910064 HAA hoppers Vans and Tank with them fitted. The old hand who has been since 1972 didn't know why and I'm wondering why? With modern coal and stone wagons the Yellow Main Res pipe is used to operate the bottom discharge doors but in the 1970s HAA hopper doors was opened by the line side equipment in the in power stations and the BBA and other vans and steel wagons I can't see why they need it they don't use them now and as far as I'm aware they have always run in the Air Goods brake setting and not Air Passenger setting. You help on this is appreciated. Link to post Share on other sites More sharing options...
Pennine MC Posted January 23, 2011 Share Posted January 23, 2011 My understanding of this is that when adopting the air brake for widespread use, BR considered the two pipe system more effective than the single pipe system as in use in Continental Europe. However as the 70s progressed and more privately owned and foreign (via the train ferries) wagons found their way into the air braked network, it became increasingly pointless trying to maintain any useful amount of dual piping. Link to post Share on other sites More sharing options...
Fat Controller Posted January 23, 2011 Share Posted January 23, 2011 The second pipe was used to keep the main reservoir pressure up, so that the wagon brakes could be released more quickly. This meant that restarting after a stop could be done more quickly, a useful feature on a heavily trafficed system. I believe air-braked passenger stock, both in the UK and on main-land Europe, still uses a twin-pipe system. Certainly, Eurotunnel's trains, which draw heavily on French practice, have a 'Conduite Principale' (which exclusively serves the brakes) and a 'Conduite Generale' (which recharges the reservoirs and provides the air for auxilary systems like doors) Link to post Share on other sites More sharing options...
Rugd1022 Posted January 23, 2011 Share Posted January 23, 2011 Not all freight services in this country are twin piped, although many are. Twin piping allows a more evenly distributed application of the brakes down the full length of the train. On heavy, singled piped trains, when you apply the brake for a speed restriction (for example) it takes a little longer for those on the rearmost vehicles to apply, and when recharging the brake and taking power once the restriction has been passed, you sometimes feel a drag or a 'snatch', as the brakes take a little longer to release at the back of the train. Careful driving can avoid this but if you're losing time and facing a steep gradient right after the speed restriction, you really need to 'get into them' and keep the momentum up. Twin piping helps no end in these circumstances. HTH Nidge Link to post Share on other sites More sharing options...
Edwin_m Posted January 23, 2011 Share Posted January 23, 2011 I think twin piping also reduces the risk of the system running out of air after multiple brake applications. Passenger stock is certainly twin piped and I've noticed the two pipes on some intermodal wagons. If the reservoir pipe isn't connected, for example if wagons near the front of the train only have single pipe, then the twin-pipe system works as a normal single pipe system. Link to post Share on other sites More sharing options...
6Y99 Posted January 23, 2011 Author Share Posted January 23, 2011 Thanks for all the replies thank you, The lad at work I though he would know the answer as at the time he was a second man at Healey Mills and was always coupling up and un-coulpling trains that was twin piped but he didn't have a clue why tho! But thanks for the replies and Nige I am aware that not all trains are twin piped it's my fault the post should have made it more clear that most coal and some aggregates run twin piped for the purpose of operating there bottom discharge doors I have worked many trains that are single piped in the Air Goods setting your right you do need to get into them to keep momentum up and also empty the pipe to stop at times and for some new starters they can be a bit frightened by the fact that you put the brake on and nowt happens and then you or them give it the lot and nearly go through the cab window when the brakes bite! Link to post Share on other sites More sharing options...
RMweb Gold The Stationmaster Posted January 23, 2011 RMweb Gold Share Posted January 23, 2011 Not all freight services in this country are twin piped, although many are. Twin piping allows a more evenly distributed application of the brakes down the full length of the train. On heavy, singled piped trains, when you apply the brake for a speed restriction (for example) it takes a little longer for those on the rearmost vehicles to apply, and when recharging the brake and taking power once the restriction has been passed, you sometimes feel a drag or a 'snatch', as the brakes take a little longer to release at the back of the train. Careful driving can avoid this but if you're losing time and facing a steep gradient right after the speed restriction, you really need to 'get into them' and keep the momentum up. Twin piping helps no end in these circumstances. HTH Nidge And that is exactly why it was adopted in the first place of course - plus various things as mentioned above but the main aim was to get a far quicker brake release than would be possible with a single pipe. I think it possible than some of the Mendip stone trains might still work on the 2 pipe system as that is somewhere that it would pay dividends for train handling but it's an awful long time since I had anything to with them so am well out of touch. The main reason for doing away with it as a general thing on freight stock was the oldest and simplest one of all - cost; 2 pipe systems are more expensive to provide and they cost a bit more to maintain and the BR decision was that the extra cost simply wasn't worth it for freight. That perhaps wasn't too much of a problem with a Class 56 on a 45 wagon mgr formations as that meant a loco with enormous compressor power on a relatively short train - very different thing with a stone train more than twice as long and twice the weight. And over those sort of lengths the difference in brake release can be measured in seconds and on an undulating route there is a risk with shackle type couplings of breaking a coupling, notwithstanding they are designed for a 50 tonne rating. (The worst we ever managed - admittedly with the 12,000 tonne test train - was breaking a loco drawhook on the mid-train 'helper' when the rear end of the train stretched out due to gradient profile at the same time as the brakes were still releasing at the back, and that was with 2 pipe working). Link to post Share on other sites More sharing options...
Rugd1022 Posted January 23, 2011 Share Posted January 23, 2011 Most of our stone trains from Bardon Quarries are twin piped Mike, they need to be with most of them heading down the mountainous Midland Mainline to Cricklewood. The 'big dipper' between Harpenden ans St Albans is especially trickey with the Thorney Mill train which usually loads to 26 bogies, equal to 2,400 tonnes. In complete contrast is the 'Drain Train' I was working last night out of Bletchley, consisting of two converted freightliner flats and a fan wagon for working in Kilsby Tunnel..... all up weight including the loco was 220 tonnes! Nidge Link to post Share on other sites More sharing options...
Steadfast Posted January 23, 2011 Share Posted January 23, 2011 This is an interesting read guys - thanks for posting this stuff. I knew about keeping the resevoir pressures up, and using the pipe to run discharge doors, but I didn't realise the effect it had on braking was so great! I've checked my photos, and Mendip stuff is still twin pipe btw, even the new Nacco IIA hoppers in use have two pipes. I presume the doors are opened mechanically like MGR stuff of old? The HOBC has two pipes too, makes sense given the length cheers jo Link to post Share on other sites More sharing options...
Mick Boyd Posted January 23, 2011 Share Posted January 23, 2011 The main reservoir (yellow pipe) only effects the rate of release (as far as braking is concerned), not the rate the brake pipe is discharged. Regards, Mick. Link to post Share on other sites More sharing options...
6Y99 Posted January 24, 2011 Author Share Posted January 24, 2011 Once again thank you for all your replies I've only worked on the freight side of the railway for 10 years! and to be honest I can never remember being told the true purpose of the two pipe system or if I was I've probably forgotten in the mist's of time! But once again guy's thank you for all your replies on the subject it has cleared a lot of things up Link to post Share on other sites More sharing options...
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