PGtrips
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Post by PGtrips on Jan 11, 2008 0:24:57 GMT
Apologies if any of this has been asked before.
There has been discussion in previous threads about the 72TS train on the Bakerloo formed with 2 UNDMs. What modifications were required, if any, to the UNDM in the 4 car unit to achieve this?
Also, as the 4 car 72TS units could couple either end onto a 3 car unit, presumably that makes the UNDM end of a 3 car as equally reversible as a 4 car? Therefore would it be possible to couple two 3 car units back to back and has this ever actually been done for any reason?
Similarly, has an 8 car 72 TS ever run with two 4 car units?
Finally, with regard to the C Stock, I understand that 8 car operation was designed in for implementation sometime in the future. But has a C stock ever run as either 4 or 8 cars for any reason?
I appreciate that if any of this did happen, it would almost certainly not be in passenger service due to platform length issues, but I wonder if any of the above has ever occurred with empty stock moves, etc.
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towerman
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Post by towerman on Jan 11, 2008 0:53:43 GMT
Since installation of PEA's and later of OPO,the reversible facility in 72TS 4 car units was lost around the late 80's.As for the UNDM on 3299 unit,it would've had to be turned and the inter-car jumpers rewired.I don't think 72TS has ever run as 8 cars even when they worked the Jubilee.Don't think 8 car C stocks have ever run,but plenty of 4 car stock moves.
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Colin
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Post by Colin on Jan 11, 2008 1:27:37 GMT
I don't really know much about 72ts specifically, but I'll apply my C stock knowledge and see where that leads.......... Apologies if any of this has been asked before. Firstly, welcome to the forum; secondly, you'll never know if you don't ask! There has been discussion in previous threads about the 72TS train on the Bakerloo formed with 2 UNDMs. What modifications were required, if any, to the UNDM in the 4 car unit to achieve this? I thought that they where all 7 cars, with a 4 car double ended unit (proper cab at each end) coupled to a 3 car single ended unit (proper cab cab one end, UNDM other end). On that basis, you'd only have one UNDM per train - if I'm wrong and there are two UNDM's in a train, well it's academic really as it makes no overall difference to how a train works. The basic answer (got there in the end! ;D) is that no modifications are necessary when two UNDM's are coupled together. Also, as the 4 car 72TS units could couple either end onto a 3 car unit, presumably that makes the UNDM end of a 3 car as equally reversible as a 4 car? Yes & no! ;D ;D As I mentioned, the 4 cars (again, AIUI) have a proper cab at each end - meaning it's a complete train in it's own right - a three car unit with an UNDM at one end is not a complete train (hence why it's called a unit) as the UNDM is simply for use in depots to shunt around. Can you see the answer to your next question? Therefore would it be possible to couple two 3 car units back to back and has this ever actually been done for any reason? Yes it's possible - that's how you make a train! The D stocks on the District are all three car units, does that help your understanding? I don't know whether two 3 car 72ts units have been coupled, but like I say, there's no technical reason not to (well there may be one - see the C stock answer for more ). Similarly, has an 8 car 72 TS ever run with two 4 car units? Pass - but again it's equally possible (and again, the C stock answer may equally apply). Finally, with regard to the C Stock, I understand that 8 car operation was designed in for implementation sometime in the future. But has a C stock ever run as either 4 or 8 cars for any reason? They have run as 12 cars - one train assisting another ;D ;D ;D The optimum design for C stock is 6 cars, but yes, I believe 8 car operation was factored in. The reason the optimum is 6 cars (and here's the link with the 72ts I mentioned above) is the braking system. Both stocks are fitted with similar braking systems - EP (electro-pneumatic) which is not fail safe, and Westinghouse (pure air only) which is fail safe. The EP brake is the normal service brake and uses retarders & rheostatic energy (the motors) as part of the service brake - these retarders & rheostatic characteristics are set up specifically for a set number of factors and if they're varied wildly [by using a different number of cars] the braking effect will be noticeably affected. Because the fail safe secondary brake - the Westinghouse - uses pure air only, cases like that above where you end up with a 12 car train, mean that the EP brake has to be cut out as it would not work as intended. Cutting out the EP brake isn't really a problem as we're trained & tested in the use of Westinghouse (in fact some would say, and I'm among them, that the Westinghouse is a better & more reliable brake anyway) - but the loss of the EP brake does create a problem...................the emergency passenger alarm relies on EP to stop the train ;D ;D ;D So if the EP is cut out, the train goes out of service - the only other reason why trains of different lengths can't operate is as you acknowledge: due to platform length issues but I wonder if any of the above has ever occurred with empty stock moves, etc. Given the number of years these trains have been around, it's almost a forgone conclusion that it's happened. EDIT: towerman posted while I was typing, so some of what I have said is wrong - if anyone else has corrections, feel free to make me look daft ;D ;D
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Post by c5 on Jan 11, 2008 3:18:35 GMT
I know of a number of stock moves to Acton Works that have only been formed of 4 cars of C Stock. Interestingly, 4 cars of C stock is still shorter than 8 cars of A Stock, by 6m (unless me maths is all wrong!).
I do also know of a 24 car A Stock once-upon-a-time!
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Oracle
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Post by Oracle on Jan 11, 2008 8:03:27 GMT
This has got me trying to think whether 8-car trains have ever worked on the Picc? The only one I recall was the Victoria line tour. I, in common with many people, have seen 2 x 3-car 38TS units coupled together as against a usual 7-car.
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Post by Deleted on Jan 11, 2008 9:37:29 GMT
Cutting out the EP brake isn't really a problem as we're trained & tested in the use of Westinghouse (in fact some would say, and I'm among them, that the Westinghouse is a better & more reliable brake anyway) - but the loss of the EP brake does create a problem...................the emergency passenger alarm relies on EP to stop the train ;D ;D ;D So if the EP is cut out, the train goes out of service - Isn't it also the case that with the EP cut out the train has to run at reduced speed, because the blow-down valve won't operate? My 72 stock knowledge is rather rusty but there are one or two other things about this rattling around in my head, I may come back to it later when I've mulled it over a bit more.
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metman
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Post by metman on Jan 11, 2008 13:04:05 GMT
When the C69 stock was first delivered it was tested as a 4 car unit on the District line I believe. As has been said 3 car 72ts units could couple but there could be a few difficulties as all (bar 3299) are A ends to aid shunting in Stonebridge Pk depot. Remember that until the early 80s Mk1s and Mk2s were incompatable. I imagine that in a couple of years 3299 will be converted back into an A end UNDM and replaced by a 1967ts DM, but that is all to come....
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PGtrips
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Post by PGtrips on Jan 11, 2008 14:37:44 GMT
The EP brake is the normal service brake and uses retarders & rheostatic energy (the motors) as part of the service brake - these retarders & rheostatic characteristics are set up specifically for a set number of factors and if they're varied wildly [by using a different number of cars] the braking effect will be noticeably affected. Please would you explain why this is the case a bit further? To the uninitiated, if you couple a further 2 cars onto an exisiting 6 car C stock, yes the train is now 2 cars longer and heavier, but is there not now 2 cars more braking kit available to stop it? So, given the foregoing, what is it that means that braking performance of an 8 car is different to a 6 car (or even a 4 car)?
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PGtrips
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Post by PGtrips on Jan 11, 2008 14:40:02 GMT
I do also know of a 24 car A Stock once-upon-a-time! So how did that come about then?
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metman
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Post by metman on Jan 11, 2008 15:10:12 GMT
Probably in the Chilterns in icy weather! This happened to a couple of 115 units, where a 4 car down train got stuck at Chalfont and was assisted by another 4 car 115 which failed! The next 8 car 115 had to them help and all 16 cars went on to Aylesbury!
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Colin
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Post by Colin on Jan 11, 2008 15:41:31 GMT
Isn't it also the case that with the EP cut out the train has to run at reduced speed, because the blow-down valve won't operate? My 72 stock knowledge is rather rusty but there are one or two other things about this rattling around in my head, I may come back to it later when I've mulled it over a bit more. That is my understanding Please would you explain why this is the case a bit further? To the uninitiated, if you couple a further 2 cars onto an exisiting 6 car C stock, yes the train is now 2 cars longer and heavier, but is there not now 2 cars more braking kit available to stop it? So, given the foregoing, what is it that means that braking performance of an 8 car is different to a 6 car (or even a 4 car)? The main change is with regard to the retarders - they basically consist of liquid metal (was mercury but I don't know if that's now changed) which moves between two contacts. If the train brakes too heavily, and the liquid moves far enough, the brakes will release and will reapply as the motion of the train allows the liquid to flow back. If you have travelled on a C stock and felt it 'rocking' as it brakes to a stand, you will have felt the retarders doing their job. The retarders are therefore set up to work on the basis of six cars - if you then add more cars (or take some away), you change the characteristics such that the retarders become over/under responsive. As the retarders are a primitive version of ABS (anti-skid, if you will), it's important they are set up correctly.
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Post by Deleted on Jan 11, 2008 17:12:57 GMT
The main change is with regard to the retarders - they basically consist of liquid metal (was mercury but I don't know if that's now changed) which moves between two contacts. Mercury is the only metal which is liquid at room temperature.
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Post by tubeprune on Jan 11, 2008 17:56:52 GMT
I hate to disagree with you Colin but the retarders do not need to be adjusted if the length of the train is changed. We used to couple and uncouple various stocks in service with retarders ranging from Qs to As. The retarders are set to a specified angle according to the designed brake performance of the stock.
Also, on 67/72 and C Stocks the blowdowns are reversed so that if the e.p supply is lost they still allow max brake cylinder pressure. However, IIRC the reduced speed is required to prevent trains with failed e.p and thus without the benefit of retarder control from getting flats due to over braking with the Westinghouse.
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Colin
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Post by Colin on Jan 11, 2008 22:28:23 GMT
As I said before, any corrections to my understanding are welcome - especially from you, Tubeprune ;D In my defence, even though I'm still qualified on C stock (and will be re-certified in March, hopefully ;D ;D) - I haven't actually been near one since I transferred to Upminster last July (well, apart from a single trip to Wimbledon last October for my last six monthly driving check).
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solidbond
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Post by solidbond on Jan 12, 2008 0:11:35 GMT
A few comments on this thread I have worked a 4 car C stock from Hammersmith Depot to Edgware Road and back to Hammersmith Depot on a test run, although that was back in the early 1990's ;D The reason why the EP is cut out if an assisting C stock is needed (making a 12 car train) is that there is a risk of the MCB tripping, due to the additional cars all now taking the electrical feed from the same cab. The time when the retarders cause the EP to be cut out is when the train is being driven in reverse from the rear cab, as the retarders are now not going to work correctly, as the mercury will now be going the opposite way to normal Colin - I would be willing to do your C stock refresher in March, but since I'll still be training for my new role at Loughton, that may prove a bit awkward ;D ;D
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Colin
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Post by Colin on Jan 12, 2008 0:32:43 GMT
Colin - I would be willing to do your C stock refresher in March, but since I'll still be training for my new role at Loughton, that may prove a bit awkward ;D ;D Well as one of our colleagues said in a different place, you really are being most inconsiderate indeed ;D ;D ;D ;D I'm just praying I don't end up on a one to one job with whoever does do it - that could be interesting ;D ;D
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Post by 100andthirty on Jan 12, 2008 18:50:11 GMT
I had a very scary moment when I saw this thread; a C stock and 72ts would be a REALLY unusual formation
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Post by dannyofelmpark on Jan 12, 2008 22:49:13 GMT
Getting back to the point at the top of the page regaurding four car units of C stock......
Four car trains have run in customer service - for steam on the met, on the Chesham branch i.e. the Yellow pages train in 1998.
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PGtrips
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Post by PGtrips on Jan 13, 2008 21:33:32 GMT
The reason why the EP is cut out if an assisting C stock is needed (making a 12 car train) is that there is a risk of the MCB tripping, due to the additional cars all now taking the electrical feed from the same cab. So if I understand this correctly, it makes no difference to braking performance how many cars are coupled, but if an excessive number are coupled, the additional power required to operate the EP brake circuits will cause a circuit breaker to trip. Is that right? On that basis, would 8 cars be within the permitted current consumption for these circuits, but anything longer require the EP to be cut out?
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Post by District Dave on Jan 16, 2008 17:13:05 GMT
I had a very scary moment when I saw this thread; a C stock and 72ts would be a REALLY unusual formation Oh - I don't know! Where there's a will there's a way!! (Rolls up sleeves and looks for coupler adapter lying around )
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Oracle
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Post by Oracle on Jan 16, 2008 17:58:41 GMT
I am sure that it never happened but there was of course the theoretical possibility that 1972 Stock and C Stock could have been one behind the other when C Stock ran to / from Neasden via the #-over south of / 'loop' north of Finchley Road. I wonder what the rules were regarding a train breakdown then? The Class 503 [?] DC trains had a coupling bar to enable a 1938 or presumably 1972 Stock to be pushed but the other way round was banned.
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metman
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Post by metman on Jan 16, 2008 18:03:11 GMT
It'd be one hell of a coupler! Did 59ts ever run (or could they) as a 6 car train with 2 x 3 car units?
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Oracle
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Post by Oracle on Jan 16, 2008 18:15:17 GMT
I never saw such a train but have at least one Bakerloo 1938 Stock 2 x 3-car (and photo'd one in train and bus red at Wembley Park). Tubeprune may confirm if any 2 x 3 car 1959 Stock was returned to the Picc from the Northern after loan say, or sent to Acton Works.
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Post by Deleted on Jan 16, 2008 18:22:47 GMT
never have I seen a 1959 or 62 stock coupled with a 1956 stock
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Post by Oracle on Jan 16, 2008 18:46:23 GMT
Were the 1956 Stock units coupled with 1959 Stock at any time or were they unable to so couple? I never paid much attention to this aspect when Hounslow West was the terminus and 1938, 1956, 1959 and 1962 Stock all mixed in service on the Picc!
The Aldwych shuttle 1962 Stock (Unit 1751) was used in main line service coupled to another unit and film exists of such a train at Turnham Green. Indeed the last Picc 1959/1962 Stock working was on 5th October, apparently with 1219 + 1728.
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metman
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Post by metman on Jan 16, 2008 19:14:23 GMT
I believe the 56s and 59s could and did work together. This was carried on when they transfered to the Northern Line. Whether the 56ts was part of the allocation sent to the Bakerloo in the 80s I don't know. All I know is as a child I did travel on a 56ts (I was into my trains even as a 6 yr old and noticed the headlights were different!) and all 21 cars of 56ts were scrapped when some 62 stock was transfered to the Northern in the mid 90s.
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Oracle
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Post by Oracle on Jan 16, 2008 19:27:10 GMT
The cab roof ends also looked different, and the cars had more wood than the 1959 Stock
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towerman
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Post by towerman on Jan 16, 2008 22:13:58 GMT
56,59 & 62TS were coupled indiscriminately when on the Northern.BTW only 59TS were ever on the Bakerloo.
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metman
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Post by metman on Jan 16, 2008 22:58:07 GMT
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Post by Deleted on Jan 16, 2008 23:26:54 GMT
Reasons for out of service if EP cut out off the top of my head are no blowdown retarders, no pass alarm brake, no SCAT (speed control after tripping) brake, no runback protection brake.
Also; I heard recently that the Vic's 67's won't be going to the Bakerloo when the 09ts comes in due to the cost of works to change them from auto to manual working. Looks like the Watford extension knackered then... unless they can fit some 92's down there when the central gets new stock.
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