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Post by 100andthirty on Dec 28, 2022 17:36:56 GMT
At SMD it was Althsom’s responsibility to clear walkways. Do you mean Golders Green and Morden? Alstom were never responsible for maintenance at Stratford Market depot.
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Post by 100andthirty on Dec 27, 2022 20:18:27 GMT
It's been 19 yeas so a few day/sweeks/months won't make much difference!
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Post by 100andthirty on Dec 24, 2022 21:08:29 GMT
Tom,any chance you can photograph the bracket to identify the exact part?
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Post by 100andthirty on Dec 22, 2022 22:54:51 GMT
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Post by 100andthirty on Dec 14, 2022 16:26:22 GMT
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Post by 100andthirty on Dec 9, 2022 7:51:45 GMT
Thanks for the correction t697.
How do drivers change ATP systems from, say, SSR Seltrac to the Jubilee variety, or from tripcock to Northern Seltrac?
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Post by 100andthirty on Dec 8, 2022 22:09:52 GMT
d7666 and Tom have summed engineers trains up rather well! I believe some engineers trains have received Northern and Jubilee Seltrac kit. Similarly some have received SSR Seltrac kit. I don't know whether any have more than one type of equipment.
I vaguely recall that some engineers trains have Central line ATP - particularly the RATs.
No engineers trains have been fitted with the Victoria line ATP to the best of my knowledge.
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Post by 100andthirty on Dec 8, 2022 9:41:09 GMT
It's understandable that people think CBTC is a generic product. More accurately, its a concept. Each supplier of metro CBTC has its own product or products which are, almost without exception, incompatible with each other. So, for example, a Victoria line train wouldn't recognise any of the Seltrac system, but then again, an S stock wouldn't recgnise the Jubilee line flavour of Seltrac and a 1996 tube stock wouldn't recognise the 4LM version.
For this reason, when thoughts turned to go anywhere battery locos it all got rather complicated (typical British understatement).
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Post by 100andthirty on Dec 8, 2022 7:46:38 GMT
Which leads to- What's the rationale for placing the transponders? I don't think I was clear in my earlier post Following up Tom's and dstock7080's comments, each CBTC has its own rules: Dstock7080 cited the rules for RFID tags on the subsurface version of Seltrac. The Northern and Jubilee versions of Seltrac don't use RFID tags at all. They determine position by the wire loops crossing over every 25 m; these are called null points. On all these lines, the trains read the tags/null points to confirm their position ie to correct any inaccuracy that has built up in the odometry since the last tag or null point. These trains routinely report position to the shore side of CBTC. The system provides for a single missed tag/crossover to be ignored but the missed read is reported. No track circuits are necessary with Seltrac but LU closes to have some axle counters arranged in long blocks to help manage degraded conditions and movements of trains without Seltrac fitted (e.g. Bakerloo movements to/from Acton. Victoria is different. The shore system relies totally on track circuits for train detection. The large number is provided to allow trains to close up in places where they're expected to be close....around stations. The blockjointless track circuits have limits for both short and long lengths both of which are exploited. The RFID tags are read by and solely used by the trains to determine absolute position. Another feature of the Victoria line not shared with the Seltrac systems is automatic fine wheel size calibration which happens every time the trains leave the depot.
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Post by 100andthirty on Dec 8, 2022 7:14:19 GMT
Indeed so - zbang asked how CBTC establishes train position, which Dstock7080 and I replied to. Are you thinking about Siemens Traingard on the Elizabeth Line 100andthirty? No, Victoria line.......a Westinghouse/Invensys product unlike Trainguard MT which is a Siemens Germany product.
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Post by 100andthirty on Dec 7, 2022 7:39:08 GMT
Transponder tags fitted in the 4 foot provide the train with positional information. Which the train uses to report its position back to the control centre via radio link. I'm not sure that the train does report its position to control. In this respect it's not as sophisticated as Thales Seltrac. What follows is a simplistic mechanical engineers understanding Hence the need for all the track circuits which give the signalling system comparatively fine information about train location. The trains get told by broadcast radio how far they can travel. The train's ATC has has its own map of the line (including RFID TAG locations and IDs) and works out where it is from odometry (tachos and dopplar radar) and the tags position codes. The tags also correct any errors in the odometry. Using all this info the train equipment decides what to do. In comparison, with the Seltrac system, the shore system builds a picture of where all the trains are based on feedback from trains passing 'nul' locations where the inductive loops cross (RFID tags perform this on 4LM), and the control centre tells trains how far they're allowed to travel. In short, Seltrac train needs to be told where it is.
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Post by 100andthirty on Dec 6, 2022 16:19:51 GMT
Victoria line uses a lot of track circuits. To allow trains to close up around stations, some of them are very short - circa 40m. I'm sure Tom will be able to give a lot more detail.
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Post by 100andthirty on Dec 4, 2022 10:58:37 GMT
It is my understanding that the change boundary is just past where through trains go beyond the reversing sidings to the west of Paddington.
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Post by 100andthirty on Nov 30, 2022 7:45:43 GMT
Regarding the 1:19 at Kennington, I can confirm that this is the gradient value used in the Thales TBTC System data (for a 30m stretch of track shortly after departing platform 1). Well, you learn something every day!
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Post by 100andthirty on Nov 27, 2022 7:52:45 GMT
d7666...all good and valid points, but I would still expect to tell any supplier about such a gradient. They can then judge how much it matters e.g. for performance or for strength of couplings.
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Post by 100andthirty on Nov 26, 2022 18:41:29 GMT
I'm guessing that 1 in 19 is a typo. I've never seen a gradient that steep quoted as a requirement that the trains have to cope with.
Having checked just one sample specification, 1 in 30 is the steepest gradient quoted, but I expect that trains would cope with up to 1 in 25, as I expect thise aren't a train's length
The only 'teenage' gradient I'm aware of on the TfL estate is the one between the Bank branch and the viaduct on the DLR.
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Post by 100andthirty on Nov 24, 2022 20:34:51 GMT
As I understand it, the flowery shirt brigade (aka TfL design) wanted to maintain the dot matrix look and feel that's present on all the other fleets (and also going in on the Central line)
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Post by 100andthirty on Nov 6, 2022 18:10:48 GMT
Sandite is, indeed sand and some condictive particles bound together with something that has the consistency of wallpaper paste. It's the binder that helps the sandite persist after the first train has passed. The Network Rail railhead treatment trains aalso waterjet the rail head...think a Kercher pressure wash on max strength steriods. The pressure is some 1500 bar (22500 psi or 750 times the pressure in a small car tyre). The water jet cleans leaf debris and any other contaminents including rust and then sometimes sandite is applied afterwards. Chiltern trains have sanders operated by WSP. Sanders on main line trains are generally fitted in front of the 3rd axle.
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Post by 100andthirty on Nov 6, 2022 15:02:02 GMT
Adding to my previous post:
The 1973 tube stock's lowest brake rate is pretty high - just under 0.6m/s2. With this brake rate and no WSP it's not surprising there are wheel flats
Reponding to spsmiler: Rail adhesion trains are part of the process of managing adhesion levels on the Metropolitan line together with foliage management, and leaf clearance. WSP and sanders will do a good job unless the leaf film is very tough/the coefficient of friction is very low. Under those circumstances, neither sanders nor the action of WSP will help.
Lastly, one 1973 tube stock car has operated through the Central line routinely. It's the track recording car.
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Post by 100andthirty on Nov 6, 2022 13:03:02 GMT
This is a very complicated subject. The issue of DC motors vs AC motors is a red herring though. It is general LU practice on trains with WSP that, when wheelslide protection is activated, the dynamic brake is dumped and braking is carried out pneumatically.
WSP systems generally compare the speeds of all four axles on a car. If there's a significant discrepancy it determines there's slip. There's also another factor. If the system detects an unfeasibly high deceleration rate, the WSP determines that slip is occurring*.
The ATO/ATP systems add to the complexity.
On the axles with the ATP tachos, (two per train end) the system compares the speed between the two axles and looks for an unfeasibly high deceleration rate. If there's a discrepancy, in simple terms, the system decides it's lost and applies the emergency brake.
One of the reasons for a great deal of care of adhesion levels on the Central line is that it was LU's first ATO line operating in the open (ignoring the original trials on the District and Woodford Hainault). When originally delivered there was no WSP as it was believed that the dynamic brake would self correct in poor adhesion. In practice all trains tended to get wheel flats, and an excellent WSP was retrofitted. The original plan of open ATO was for the deceleration rate to be 0.75m/s2 which is very high for open running in leaf fall. Later an option for 0.6m/s2 was added - still high.
In comparison, Jubilee and Northern have much more control over braking rates and 0.4m/s is not uncommon. But, and there's a big but, these trains have a blended braking system. At low brake rates, the system tries to brake using the dynamic brake, and the trailer cars do little or no braking. But if wheel slip is detected, the dynamic brake is discarded and friction brake is applied to all cars. This means that brakes are suddenly applied on the trailer cars which can cause the issues described above with the ATP tachos.
Re S stock, a great deal of work has been done simulating the effect of sanders on S stock braking but as I understand it, sanding has yet to be commissioned. I hope I'm wrong!
And Elizabeth line trains always have a proper speed reference signal as the axles at the cab ends are unbraked.
* the very latest WSP systems have been further developed and they compare speeds of all axles on the train and operate dump valves appropriately. The very latest systems have another feature whereby the brake demand is adapted depending on the assessed adhesion which will vary along the train. The driver - or ATO - might be demanding a medium brake rate and the brake system will decide to apply a low rate at the front of the train, medium in the middle and high towards the rear. I don't know of any practical applications of this system but someone else might be along with more knowledge
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Post by 100andthirty on Oct 18, 2022 6:13:36 GMT
Chris L.....I mean Waterloo....the 'moving pavements' that ptovide the link between the Northern/Bakerloo and Jubilee lines.
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Post by 100andthirty on Oct 17, 2022 14:50:55 GMT
Last time I travelled though Waterloo (3/10/22), neither travolator was working and there didn't seem to be any "out of service" notices. Are there out of service long term and if so what is the problem?
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Post by 100andthirty on Sept 24, 2022 6:42:34 GMT
And Siemens made at least some of the C&SLR locos.
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Post by 100andthirty on Sept 16, 2022 12:47:28 GMT
Pullman Rail based at the low level of Cardiff Canton is a supplier to LU, having overhauled bogies and wheelsets for the 1996 and 1993 tube stocks.
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Post by 100andthirty on Sept 10, 2022 15:04:24 GMT
The best solution would be to deal with the ventilation problem a different way, and get rid of the doors completely. Talk about making a rod for your own back! Don't take the publicity (solely to manage wind speeds on platforms) at face value. They have provided and were always intended to provide safety benefits. The original publicity was intended to help manage pressure to retrofit the rest of the tube.
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Post by 100andthirty on Sept 8, 2022 15:38:26 GMT
Have you ever seen the size of the crowd at North Greenwich for an O2 event? Not a hope in hell of finding enough vehicles. To match the capacity possible on the Jubilee line after an O2 concert something over 400 buses would have to leave North Greenwich in the hour after the concert ended. Mod edit [Antharro]: Quote partially removed. Please be selective about the part of a post you wish to quote rather than the whole post verbatim, particularly if you are replying to the previous post in the thread.
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Post by 100andthirty on Sept 8, 2022 15:34:01 GMT
Driverless trains on London Underground, the Network Business Case dated August 2020 and leaked by ASLEF, suggested that current PEDs would be replaced when new trains are introduced. Presumably this is on the same basis that S8 dimensions did not follow A stock dimensions, limiting services for another 40 years by restricting them to the dimensions of the previous 40 years. I wonder if the recent closure of the Northern City branch for Bank reconstruction would provide a precedent for closure of the tunnel JLE stations for station modification to match a new fleet of trains. Hmmm. That sounds like one of those client requirement which are assumed to be deliverable once written on the sheet of paper. I don't recall the ASLEF leaked document but I'm assuming that it talked about new trains without describing them in detail. I think there are two basic choices: 1) replacing the trains. Assuming a replacement fleet is required to have the same properties as the new Piccadilly line trains, it will be impossible to lay out the doors to align with the existing PEDs. If the PEDs are to be replaced, this is a task that will take weeks, if not months and if laid out to suit the new trains they won't suit the old ones. The only viable option in my mind would be to close Westminster to North Greenwich, replace the PEDs whilst introducing the new trains on the other sections. This would be unpopular, I think (typical British understatement). 2) replace the PEDs like for like (I'd expect only the mechanisms and controls to need replacement/overhaul) and buy new trains in the with the same door layout as today (but with air con and gangways). This is straightforward and would require few if any closures. I've assumed that eliminating PEDs altogether wouldn't be acceptable. I know which option I'd choose.
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Post by 100andthirty on Sept 8, 2022 6:58:22 GMT
The scale of the factory at Goole is such that Siemens must have plans beyond the current TfL order. Paraphrasing a well known saying "train factories are for life, not for Christmas". Similarly, CAF have plans for their Newport factory beyond the current class 19X orders.
TfL always retain the right to tender for fleets where the order is not committed. The NTfL tender included priced options for Bakerloo, Central and Waterloo and City, but these would have to be exercised by agreed dates. I hope they still have time! Allowing the options to lapse before committing to the additional Piccadilly trains could well lead to a repeat of the Jubilee/Northern additional trains procurement which got cancelled (a job where I suspect the full story was never told). All that said, TfL's financial position in 2018 when the contract was let was quite healthy compared with where it is now.
It is a mistake to link the Jubilee and Central line fleets. All the factors that led to the Piccadilly line articulated train design (wide gangways, all double doors, air conditioning) do, of course apply to both, but the elephant in the room is the platform edge doors on the Jubilee which constrain that line's trains to the current layout. The gentler curves on the Jublilee might possibly allow gangways on the current two-bogie-car configuration that wouldn't be feasible on other lines. But it is unlikely they could be significantly bigger in profile than the Central line. Jubilee is constrained by the 1930s tunnels between Finchley Road and Baker St.
Mod edit [Antharro]: Quote removed. Please be selective about the part of a post you wish to quote rather than the whole post verbatim, particularly if you are replying to the previous post in the thread.
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Post by 100andthirty on Jul 26, 2022 6:59:41 GMT
I’ve noted all the valid points made by other contributors. It’s the nature of the forum that contributions will be added to and improved as knowledge is pooled.
The key point I was trying to make was that the formula would calculate that a conventional (e.g. 1973 tube stock) train would arrive at a signal at a speed that would rarely be achieved in practice. As the modern train’s traction package is much better controlled when emulating existing stock, its performance can be programmed to arrive at the signal at or closer to the calculated speed. This will give a modest performance increase.
I also note that I neglected to mention that effects of gradient are also taken account of in overlap calculations.
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Post by 100andthirty on Jul 25, 2022 12:16:50 GMT
In the New Tube for London thread there has been discussion about the performance of 1973 tube stock and how it had the capability to have a much higher acceleration rate which was never exploited. One of the issues identified was that LU trains and signalling systems are matched. This allows the best possible throughput for a given train performance. However it also limits performance improvements if only one part of the system is changed. (For completeness, the power system and track are also part of the system and do affect performance but will be ignored for this post).
Modern trains with solid state traction can, to a limited degree, break out of this. I’ll explain why.
Firstly, the signalling principles on London Underground work something like this – recognise though I’m not a signalling engineer!
1) The overlap for a given signal is determined by the worst case speed at which the train arrives at the signal and 2) The worst credible case distance to stop from that speed plus an allowance.
Point 1 is calculated for an empty train running on the highest voltage with the biggest wheels, and point 2 is calculated for a crush loaded train. This is safe but standardises the fiction, albeit one erring on the side of safety, that an empty train suddenly becomes full at the signal, and also that older train would go faster on higher voltage and when empty. Most trains don’t achieve that speed, so the best capacity is not delivered
Modern trains are programmed to deliver the same performance irrespective of voltage or load, and this allows trains such as the forthcoming 2024 stock to be programmed to take better advantage of the existing signalling layout than would be allowed with the 1973 tube stock. It's also true that modern trains tend to have a much smaller, load dependent variation, in stopping distance compared with older trains. T697 applied similar principles to optimise S stock on the existing signalling soon after it was introduced into service.
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