rincew1nd
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Junior Under-wizzard of quiz
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Post by rincew1nd on Nov 28, 2016 21:40:05 GMT
Doesn't the suspension make alterations to the train height? I seem to remember there's some cleverness such that a full train sits at the same height as an empty one.
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Post by domh245 on Nov 28, 2016 22:00:50 GMT
Doesn't the suspension make alterations to the train height? I seem to remember there's some cleverness such that a full train sits at the same height as an empty one. I can remember reading about this somewhere, but I want to say that it was something fitted to the C69 stock and that was removed eventually. Might be wrong of course!
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Post by drainrat on Nov 28, 2016 22:03:31 GMT
Doesn't the suspension make alterations to the train height? I seem to remember there's some cleverness such that a full train sits at the same height as an empty one. On a trip to Wood Lane control room during white city derailment investigation, they showed us how they can see the load weigh of each carriage. The information is downloaded from train to PAC at each station, and available to Wood Lane in order to make a decision. Doubt this is available to controllers on Picc
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Post by drainrat on Nov 28, 2016 22:07:42 GMT
Thats still some discrepancy between new and worn Hmm, it'd be a ~10% difference, which does seem quite high, but on the flipside, as long as there are ways of coping with the variations it'll allow them to use the wheelsets that bit longer, saving a bit of money as a result. I assume that there is a way of accounting for the varying wheel diameter in speedometer readings, but I'm not sure how you'd cope with an up to 40mm variation in the height of the train. Central line ATO measures distance to next station/stop by way of wheel revolutions. Wonder how much difference this would give in distance? Must be biggest diameter and would be fail safe as smaller diameter would equate to train stopping short
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Post by drainrat on Nov 28, 2016 22:13:01 GMT
.....if each axle is given individual info at the PAC, then wheels with smaller diameter would stop turning before other wider wheels, multiplied by many stops and those wheels with smaller diameter would be at higher risk of flats. Now I know the Picc doesn't operate same as ATO, but I'm thinking load weigh by increased passenger loading through increased braking on each wheel over a longer period of time. If one or more wheels go below minimum diameter, then they could be left hanging (unchecked) with not enough contact with rail head (minimal downward pressure), this would result in those wheels locking when brake applied and grinding down to flats whilst other wheels carry on rotating.
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metman
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5056 05/12/1961-23/04/2012 RIP
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Post by metman on Nov 28, 2016 22:22:42 GMT
Does the D stock not use the same traction motors and wheel sets to the 1973 stock? I hope they kept some spare wheels from the Undm?
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Post by drainrat on Nov 28, 2016 22:25:18 GMT
Undm, now that's a term I haven't heard I a while
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Post by fish7373 on Nov 28, 2016 22:40:29 GMT
Hi when you turn the wheels you have to adjust ever thing on the car speedo brake packing truck heights trip cock posi shoes and nege shoes and check car heights, and we do not use D78 Parts .
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roythebus
Pleased to say the restoration of BEA coach MLL738 is as complete as it can be, now restoring MLL721
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Post by roythebus on Nov 29, 2016 0:31:27 GMT
My son is a chief rolling stock engineer on the Southern; they have to scrap wheel sets when they get to the minimum diameter. In the old days you could re-tyre rail wheels, I don't know if this is still done. All the WSP sensors have to be re-calibrated to deal with the differing wheel diameters. Failure to do this would result in the WSP detecting wheels going at different speeds and constantly operating.
I don't think anybody anywhere in the world has invented a steel wheel that will brake on a steel rail during autumn without slipping!
Re the steel quality, that is a possibility. Back in the early 1970s there were a couple of incidents on the District of broken spokes on CP stock. This was found to have been on a batch of wheels made in Switzerland in the late 1920's! Metal failure is nothing new.
I would strongly suggest that the current problem is one of nature. Leaves+lots of rain=flat spots.
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Chris M
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Post by Chris M on Nov 29, 2016 3:24:15 GMT
Hi when you turn the wheels you have to adjust ever thing on the car speedo brake packing truck heights trip cock posi shoes and nege shoes and check car heights, and we do not use D78 Parts . How long does it take to do all that?
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Post by 100andthirty on Nov 29, 2016 10:11:39 GMT
for info:
Both wheels on an axle have to be the same diameter (very small tolerance) Both wheelsets on a bogie have to be similar in diameter (small tolerance) All wheelsets on a motor car have to be similar in diameter (small tolerance)
I have not mentioned tolerance number as a) they vary from stock to stock and b) I don't recall the actual numbers (but 1mm on a wheelset and 5mm to 10mm on a bogie/car come to mind).
All trains have a means to adjust the BOGIE height either by adjusting the yoke (the silver coloured item surrounding the axlebox on 1972 and 1973 stock) or by packing in the primary (axlebox) suspension.
All LU's service passenger trains except 1972 tube stock maintain reasonably constant motoring and braking performance by monitoring either secondary suspension deflection (1973 stock and 1996 stock) or by monitoring pressure in the air springs (all other stock) and using the signal obtained as an input to the brake/traction systems.
1972 tube stock maintains brake performance reasonably constant regardless of train mass using mercury in tube decelerometers.
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Deleted
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Post by Deleted on Nov 29, 2016 11:17:30 GMT
I'm puzzled about what has changed over recent years to bring about this situation. When I was driving in the sixties and seventies I never heard of a RAT. We did get flats and they would be reported on the trouble card and sometimes this wasn't acted on or it was noted as serviceable, or the original card was just replaced with a clean one! Maybe it was a game to manage the situation, but years went by and I was never aware of flats ever causing a shortage of stock, though there were the odd occasions of a m/m insisting on a change over after being frustrated by previous inaction. I have to wonder now if the potential for cancellation is not encouraging some drivers to be less careful, maybe with the added bonus of an RAT duty eventually being added to the roster.
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Post by chris11256 on Nov 29, 2016 12:59:41 GMT
Forgive a potentially stupid question, but what makes it worse for the Piccadilly Line than main line trains? Leaves and flats are a problem all over the place, but I've never seen flats on this scale before.
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North End
Beneath Newington Causeway
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Post by North End on Nov 29, 2016 13:09:28 GMT
Forgive a potentially stupid question, but what makes it worse for the Piccadilly Line than main line trains? Leaves and flats are a problem all over the place, but I've never seen flats on this scale before. Modern trains generally have better WSP systems which help to avoid the issue, although they don't eliminate it completely as sliding can still happen. It is often said that older trains making more use of friction braking tended to cope slightly better as this would clean the wheels, although they still suffered badly. The 73 stock falls between the two, no good WSP system and most braking done by rheostatic brake, meanwhile the Rayners Lane branch is a problem location because it has a comparatively infrequent service compared to other parts of the network. Having said all this, the situation on the Picc has deteriorated badly in the last couple of years -- so clearly at least one variable has changed somewhere. At present no one seems to have a definitive answer for what that might be.
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Post by mb2014 on Nov 29, 2016 18:29:23 GMT
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Post by 1018509 on Nov 29, 2016 20:28:07 GMT
Hi when you turn the wheels you have to adjust ever thing on the car speedo brake packing truck heights trip cock posi shoes and nege shoes and check car heights, and we do not use D78 Parts . How long does it take to do all that? IIRC from 2010 about 1 entire shift for a four man team if they are changing 12 pairs of wheels.
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Post by 1018509 on Nov 29, 2016 20:44:30 GMT
What aggravates the problem is insufficient trucks made up and ready to go when a train comes to depot with flats. When I retired some trucks were becoming available ready built but most trains are stripped down and wheels replaced and then built up again. A long job and only two roads available at Northfields (if the wheel lathe is not working). I don't know about Cockfosters. Definitely more space needed and staff solely on truck dismantling and re-building. What causes further delay is very little of the equipment needed to be removed to replace wheels is easily removable - no plug in motor wiring no bayonet fitting pipework - everything is large spanners on badly placed fillings. The blokes doing this job are heroes - I know - I worked with them. I believe one of the two wheel lathes at Northfields is out of action. Are there two wheel lathes at Northfields now? There was only one when I was there and that used one of the pit roads needed for wheel changing when being used and blocked easy access to the rest of the depot. Cheap design for wheel lathe building at Rolls Royce prices for a quick fix which has now come back to bite hard - who gets the blame? The poor buggers changing the wheels that's who.
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roythebus
Pleased to say the restoration of BEA coach MLL738 is as complete as it can be, now restoring MLL721
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Post by roythebus on Nov 29, 2016 21:55:37 GMT
The variables that have probably charged are the management. Weather has changed a bit this year but it tends to do that every 12 months. Management should be able to cope with it.
All railways the world over have trouble with poor adhesion in times of rain and autumnal leaf fall. as I said earlier, nobody has yet invented a way round the problem. Real railways tend to use power sanders on locos and motor coaches to try to lessen the problem. BR though they'd do away with them on modern stock (post508/455 etc) as WSP would provide the protection from slipping. Ha ha ha. In the past, the old stock could get away with lathe turning just the eraant wheels, maybe one ot two axles per train, these days the whole car load has to be done for reasons mentioned above.
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Deleted
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Post by Deleted on Nov 30, 2016 8:57:36 GMT
In mitigation, the leaf fall season was unusual this year. A mild autumn with few Atlantic storms meant the trees were still fully laden when the weather did finally break. A shorter, more intense leaf-fall season will always cause problems for operators.
Incidentally, if the Atlantic weather pattern doesn't wake up soon we could be in for a very cold Winter this year.
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Post by alpinejohn on Nov 30, 2016 9:45:14 GMT
So how do we fix this? - Perhaps its time for TFL to fund a staff suggestions prize?
Obviously management action is needed now to quiz staff (not just drivers) to try and identify the location of hot spots where most of these wheel slip events occur. (Instinctively these will be mostly on open section braking areas especially on downgrades).
Given repeated efforts to cut back swathes of lineside undergrowth have not fully solved the problem. It seems the current problems may increasingly be due to leaves being blown in from adjacent land? Sort of like drifting snow on the North of Scotland route, where drivers have helped identify the most prone areas allowing snow fences to be placed where necessary to protect the line.
Once LU identifies the most high risk stretches, perhaps LU should consider screens or planting low hedges to create some sort of natural retaining fence, or even incentivising neighbours to remove or prune back trees on their properties to minimise leaf fall on the tracks.
Given the significant financial impact on businesses in London caused by recent disruption to journeys, it might be reasonable for TFL to press the Mayor to fund a fair bit of preventative work to install screens to retain and keep most leaves off the tracks, and hopefully reduce the prospect of this thread being repeated next autumn.
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Post by nig on Nov 30, 2016 9:53:03 GMT
Forgive a potentially stupid question, but what makes it worse for the Piccadilly Line than main line trains? Leaves and flats are a problem all over the place, but I've never seen flats on this scale before. Modern trains generally have better WSP systems which help to avoid the issue, although they don't eliminate it completely as sliding can still happen. It is often said that older trains making more use of friction braking tended to cope slightly better as this would clean the wheels, although they still suffered badly. The 73 stock falls between the two, no good WSP system and most braking done by rheostatic brake, meanwhile the Rayners Lane branch is a problem location because it has a comparatively infrequent service compared to other parts of the network. Having said all this, the situation on the Picc has deteriorated badly in the last couple of years -- so clearly at least one variable has changed somewhere. At present no one seems to have a definitive answer for what that might be. the picc line had new wheels on the trains probably made from cheaper metal to save money thats why the problems started last year and carrying on worse this year as wheels are older
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Post by br7mt on Nov 30, 2016 9:59:57 GMT
the picc line had new wheels on the trains probably made from cheaper metal to save money thats why the problems started last year and carrying on worse this year as wheels are older Do you have evidence of this or is it uninformed speculation? Regards, Dan
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Post by nig on Nov 30, 2016 10:13:06 GMT
the picc line had new wheels on the trains probably made from cheaper metal to save money thats why the problems started last year and carrying on worse this year as wheels are older Do you have evidence of this or is it uninformed speculation? Regards, Dan well they didn't have the problem with the old wheels the unions reckon its that as well as some managers although tfl would never admit it even the 25mph speed limits in open sections couldn't stop this years fiasco
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Post by br7mt on Nov 30, 2016 10:43:50 GMT
well they didn't have the problem with the old wheels the unions reckon its that as well as some managers although tfl would never admit it even the 25mph speed limits in open sections couldn't stop this years fiasco So it's uninformed speculation then. Bear in mind the wheelset is a single point of failure and as such the materials and assembly of it is a very highly controlled and inspected process. Any changes to the materials used has to receive formal engineering approval either through the change process or as a concession, which, if it exists, will be found by those charged with investigating the service disruption. Regards, Dan
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Post by whistlekiller2000 on Nov 30, 2016 11:05:28 GMT
Mod Comment: All, please recognize that everything prior to the conclusion of the inquiry is speculation, whether presumed uninformed or otherwise. Let's try to avoid point scoring in advance of the facts.
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Post by trt on Nov 30, 2016 12:11:39 GMT
Wasn't there a problem of a similar nature on the Northern Line caused by changes in the braking system?
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Post by piccboy on Nov 30, 2016 14:24:02 GMT
Can't help but think that the 83 stock that sat in the sidings at South Harrow for years, should have been converted into a RAT for Piccadilly Line long time ago.
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Deleted
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Post by Deleted on Nov 30, 2016 15:04:58 GMT
They laid dormant for many years and were more then likely beyond saving
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Post by snoggle on Nov 30, 2016 16:57:43 GMT
They laid dormant for many years and were more then likely beyond saving There was no way they could be saved for anything. I understand they were in appalling condition and had "welded" themselves to the rails hence the involved palaver to remove them. Before I left LU I was involved in trying to push through the necessary paperwork etc to start the removal process. Others clearly managed to get the process through to completion.
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Post by stapler on Nov 30, 2016 18:23:05 GMT
Why were they not scrapped straightaway?
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