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Post by 100andthirty on Jul 4, 2021 20:43:23 GMT
Trailer bogies on end cars and their effect on rail head contamination is quite limited where those axles have disc brakes - and I think CRossrail 345s are so. For the wheelset to "clean" the rail, the wheel tread itself needs cleaning, mulch builds up there too as much as it does on the rail head. Tread brakes do that cleaning, disc brakes do not. I'm not saying one way or the other what the friction braking on the new stock is, I really have no idea, just commenting the panecea answer about leading unpowered axles is not necessarily what it seems. One of the reasons BR SR and later incumbents has had an ever increasing increase in adhesion related incidents has been the change from tread braking to disc braking, starting from 508/455s and onwards. Sure the elimination of steam and subsequent allowing increased lineside vegation is an input, disc vice tread brakes is equally important but seldom mentioned. Even with tread brakes though, take a Thameslink 700, these have tread brakes on motor bogies and disc brakes on trailer bogies. The end cars of all 700s are all motors (FLU = MTMMTT+TTMMTM; RLU = MTMT+TMTM) so all end cars have tread brakes. But the tread brakes are minimal action anyway, 700s friction brakes only cut in on the last 2-3 mph down to stop. They are so little used that even after 5 years service no block or pad had been changed except for a very small number of items failing not directly related to brake cycles. They do just about enough wheel tread scraping to have a cleaning effect. Thameslink 700s and Crossrail 345s are designed for very similar duty, yet the very fact that these things are done differently kind of proves there are many differing inputs to what axles are or not motored, that that 345s have x1 because of y1 does not mean elsewhere x2 necessarily is the fix for y2. Braking and cleaning the railhead are two very complex subjects, made even more complex when ATP/ATO systems which require wheelset based odometry. Having the end bogies as trailer bogies and using the friction tread brakes to clean the wheels is a perfect solution if the braking is set up to give the friction brakes some work to do. As d7666 says, modern trains are set up to do very little friction braking. Indeed, that's why a 100mph EMU in the form of the class 700 "gets away with" tread brakes on motor cars; just as well really as there is no space for disc brakes on those inside frame bogies. The 2024 tube stock will have tread brakes and, with permanent magnet motors, the friction brakes are likely to do less work than on S stock. LU will, therefore, have to work out how to keep the friction surfaces in good order. Northern, Jubilee and all S stock, have a routine built into the trains such that they do a friction only brake application for a couple of stops on every run to keep the wheel/friction surface in good order. Achieving good adhesion between the wheel and the rail is not generally something that can be delivered by the train alone. Keeping the lineside clear of foliage is the first requirement, followed by the operation of Rail Adhesion Trains. The final ingredient is the use of sanders which are controlled by the wheelslide protection system. Sanders, are, these days, fitted to virtually all but the very oldest of main line trains and to S stock. Properly optimised sanders can deliver excellent braking in poor conditions. Final point, adhesion is affected by the ride quality of the trains. Modern trains ride better than older trains. The lateral motion of wheels on rails helped to clear leaf contamination, but I don't think anyone would want to swap the ride of a modern EMU for that of a 4-SUB!
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Post by 100andthirty on Jul 1, 2021 11:43:30 GMT
I notice that the middle motor car 5 sits in the middle of the train and is differently equipped to the others. This looks very neat, but if they ever build a Central line version with two cars added, the actual middle car will only be an intermediate car. Will the extra motor car be of type 1 or type 2, I wonder. Also pick-up shoes feed the traction case on the adjacent intermediate car, which feed the motor bogies either side. Thus there is no need for shoes on the middle motor car. Is this the reason the leading bogies are unmotored, because they are not adjacent to an intermediate car to receive this feed, or is it because they might help clear the rail head to reduce wheel spin/slide on following bogies? LU trains don't actually need to be all axles motored. 80% axles motored feels about right. Having two trailer bogies allows the possibility of one axle at each end being unbraked to provide always accurate speed/distance signals like on the Crossrail trains. In practice, trailer bogies are less able the clear railhead contamination as the adhesive mass tends to be lower. If you accept that trains don't need to have all axles motored, then Jimbo's suggestion that the end bogies are unmotored because there is no adjacent car to provide a feed sounds the most plausible explanation. Central line will, in all probability have an additional motor car with shoes feeding an intermediate car's inverters which in turn feeds the bogies on the adjacent motor cars. This would mean that car 5 (or 7) would still have the space for de-icing, track monitoring or the other features described in the article.
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ATO
Jun 30, 2021 15:03:53 GMT
Post by 100andthirty on Jun 30, 2021 15:03:53 GMT
Sometimes train accelerate up to the speed limit, then the speed limit changes to a lower value, and finally the speed limit rises again just before a station stop. For example, the journey from Bank to Liverpool St sees a typical train accelerating into Liverpool St station before it brakes to a stop. This is quite normal and is done to minimise headways.
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Post by 100andthirty on Jun 25, 2021 21:17:16 GMT
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Post by 100andthirty on Jun 25, 2021 20:39:19 GMT
I'm sure I've read previously on this site that by the time the Tubelines-era new Piccadilly line trains were cancelled, they were intended to be articulated and walk-through, and had almost reached the point of issuing an Invitation to Tender. I can't find the relevant post though. It was to be called 2012 tube stock, tender were invited and the requirement was a modern equivalent of the 1973 tube stock - 6-car train approx 106 m long, no inter-car gangway, no air conditioning. It was very unambitious. When the competition was cancelled I don't think anyone thought it would be another 10 years before a contract was eventually let.
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Post by 100andthirty on Jun 25, 2021 11:26:21 GMT
The thinking that led t the current Deep Tube programme goes back to circa 2003-5. Neither Tube Lines nor Metronet had any interest in innovation. There was a myth in government circles when PPP was formulated that public sector was conservative - with a small c - and the private sector was much more innovative. In practice the opposite was true, mainly because much of the PPP was funded by banks who really are conservative - with a small c again.
LU's ideas, building on the Space Train, were firmly rejected by the Infracos. Piccadilly line 2012 stock was to have been a modern version of 1995 tube stock - 6 cars, DM-T-M-M-T- DM formation. No one in Metronet worried about the Bakerloo line - it was far to far away.
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Post by 100andthirty on Jun 24, 2021 19:25:27 GMT
Accepting that these pre-production/prototype trains were scrapped and replaced, why were the numbers reused for the new trains, rather than just being added on to the end of the number series? The aim was to reinforce that the original vehicles had ceased to exist. There is little or no emotion about train numbers in LU; they were simply a means of identifying the trains/cars in the various databases.
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Post by 100andthirty on Jun 19, 2021 19:35:19 GMT
Do floating cars pivot off the inter-car connection, or off the adjacent bogie? In the latter case, I have trouble imagining movement in the inter-car corridor. But the former suggests that the weight is carried by the bodywork of the adjacent car. An article is expected to be in the next edition of Rail Engineer magazine giving more detail about the configuration of the train.
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Post by 100andthirty on Jun 19, 2021 19:33:37 GMT
There were two "pre-production" 2009 tube stock trains. When they were returned to Bombardier for upgrade to production standard, the carbodies were scrapped but bogies and a great deal of the equipment was transferred to new bodies. The first pre-production train didn't have a proper interior and was mainly used to test the ATO/ATP system which could not have been optimised on the 1967 tube stock due to the latter's comparatively poor performance.
The difference between the pre-production and production 2009 tube stock was quite significant although I don't recall details. The difference between the pre-production and production S stock was comparatively small. There were greater differences between S8 and S7 as the opportunity was taken to improve the design in a few places.
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Post by 100andthirty on Jun 14, 2021 6:10:29 GMT
I believe that Gordon Hafter succeeded Graeme Bruce as Rolling Stock Engineer(Railways) reporting to the Chief Operating Manager.
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Post by 100andthirty on Jun 12, 2021 19:55:39 GMT
"G Bingham was CME in 1969 when I started having replaced A W Manser shortly before. Graeme Bruce was the engineer responsible for all the depots before becoming Chief Operations Manager." That's what my memory tells me. However, in the 1970 Preface to "Steam to Silver" Graeme Bruce refers to G Bingham as "CME Design and Development" so it's possible that Graeme Bruce's title was something like "CME depots".
Perhaps a real expert will be along who has access to the TfL archives.
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Post by 100andthirty on Jun 7, 2021 14:54:37 GMT
For info. J Graeme Bruce was a very senior rolling stock engineer, but was never the CME. A W Manser followed Graff Baker from 1952 and G Bingham followed Manser in circa 1969. That take us to the early 1970s. S F Smith was next, I believe, and was certainly in post in 1979. Next came C W Hardie and G H Hafter - but I forget in which order. After that the post of CME was abolished and the nearest equivalent post - Principal Mechanical Engineer, Head of Rolling Stock Engineering of the Rolling Stock Engineer - was occupied in turn by A W Waterman, PD Longhurst, J W Vint, M H Dobell, G Neil and as of next month, I Rawlings. The current job title is "Head of Vehicles" and covers all TfL's vehicles including bikes and the Woolwich ferry!
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Post by 100andthirty on May 30, 2021 7:07:07 GMT
Modelling showed that there was a significant risk of derailment even at the nominal speed limit of the crossover. The solution was to provide a continuous check rail though the points. This is almost unique in the UK and was cribbed from a design used on the New York Subway and seen in Coney Island overhaul works. The feature can be seen in the photo in the post above.
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Post by 100andthirty on May 23, 2021 7:24:09 GMT
There is a well rehearsed process for hauling an unpowered 1992 tube stock from Ruislip to Acton. However, the track circuits that necessitate this arrangement will have to be replaced for the new Piccadilly trains, so if this is done, the 1992 tube stock might well be driven both ways, just needing tripcocks fitted for the journey.
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Post by 100andthirty on Apr 19, 2021 15:19:53 GMT
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Post by 100andthirty on Apr 19, 2021 8:36:42 GMT
First time I've noticed the blocked-off centre cab window; the colour scheme makes it very obvious! Is that the same on all the conversions, and what's behind it? It was a door in D stock days. Not required it would appear. Less chance of draughts in the cab. Checking photos all the trains so far have had the door removed. The former window area is painted black so not so obvious. Some strengthening of the body has been installed where the centre door used to be to help withstand the impact should a train hit a lorry on a level crossing.
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Post by 100andthirty on Mar 8, 2021 21:50:10 GMT
As for the route north of Finchley Road, will there still be an enforced stop for all trains - even when on what are supposed to be non-stop runs - at a location away from a station for swapping between manual and ATO? The next migration point on the MET will be in SMA 8 at Preston Road, station platform on the local line but alongside the platform on the fast lines. Does this mean that trains on the fast tracks will have to stop at Preston Road for the changeover?
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Post by 100andthirty on Mar 7, 2021 17:27:15 GMT
It's really good news that the SMA3 has gone live. Congratulations to everyone involved.
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Post by 100andthirty on Mar 6, 2021 21:27:47 GMT
Various points:
1) Normal laminated glass used for train window glazing is heavier than aluminium for equivalent strength. There is work going on in the light rail industry for light weight glazing. This is probably based on the sort of gorilla glass used on mobile phones as a tough outer layer for some sort of plastic core. If/when this is developed, it would have to pass the stringent fire safety standards for tube stock. As has been seen with building cladding, a composite material with a flammable core can produce some very undesirable results in a fire. 2) The car ends on 1992 tube stock were aluminium fabrications and aspects of the fabrication failed necessitating replacement. This was not as a result of body distortion. 3) The 1986 tube stock body ends were made from fibreglass and the connections between these and the bodies were poor. That's why aluminium was specified for the car ends of 1992 tube stock 4) The large curved glass windows were bonded to the body. The preparation of the metal frame and the quality of bonding was absolutely critical to the integrity of the bonding, and many failed leading to the glass falling out. A mitigation was a so-called shoulder test carried out during maintenance. This led to all the windows being replaced by framed windows where the glass is held in place with rubber mouldings and an aluminium trim screwed to the frame.
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Post by 100andthirty on Feb 1, 2021 11:47:01 GMT
Indeed, the accountants wanted to scrap spares to reduce working capital many years ago, despite protestations that the simplest thing to do was to revalue the items as £0. In the end a communication plan was set up to advise the fleet people that items that hadn't been in demand for years would be scrapped. Somehow, demand for these items surged!
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Post by 100andthirty on Feb 1, 2021 7:27:52 GMT
There are all sorts of spaces around the LU estate where things may be stored. For example many substations are housed in buildings designed for large rotary converters. Today's electronic cubstations occupy a tiny proportion of the space. I recall as a trainee visiting a substation, also designated as a sub-stores where they were keeping equipment for a cancelled major electrical upgrade of Q stock ....sorry, wandered off topic.
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Post by 100andthirty on Jan 30, 2021 7:59:43 GMT
Metman...... the use of two camshafts was to facilitate rheostatic braking, not ATO.
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Post by 100andthirty on Dec 31, 2020 16:08:10 GMT
For any city considering a Metro, they start with a few basics.
1) How many passengers per hour per direction 2) It will be powered by electricity 3) The tunnel will be big enough to accommodate trains that are roughly rectangular in cross section 4) There will probably be a side walkway 5) The trains will be tall enough to accommodate all the equipment and bogies under the floor without the wheels penetrating the floor to give maximum flexibility on interior and door layout. 6) The platforms will be level with the train floor and will be straight.
If this sounds like a deviation from the topic, all the above means that there will be space above the train for a conductor rail similar to that used on Crossrail and avoidance of ground based conductor rails, even very well insulated, is to be preferred. The above requirements, however, mean that there is no increased tunnel size to accommodate the overhead supply
Whether the power supply is AC or DC is somewhat moot. DC at 1500 V allows reasonable space between substations and is a metro standard. AC Traction are unpopular with the electricity distributors as they don't make balanced use of the three phases and the load can swing from 2-3 MW being taken from the supply to a similar amount of power being fed back into the supply all over a few seconds. Increasingly, two way power converters are being employed to avoid this problem. These take in three phase electricity and output single phase - and vice versa when trains are braking.
There is also a debate to be had as to whether regenerated energy is captured on train or all exported off train. On train energy capture would significantly reduce the load swings and reduce the power supply peak ratings. The external supply would provide power to the auxiliaries and for steady speed running with the battery (or other energy store device) providing top up for acceleration. Similarly, on braking, the regenerative brake would feed the auxiliaries and charge the battery with any surplus power going back to the line. Clearly there would be load swings, but not as severe.
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Post by 100andthirty on Dec 11, 2020 12:35:39 GMT
Class411 said: "Excessive cost/excessive disruption to services whilst work carried out/ownership of space required"
It was a combination of all those things, and the two latter points contribute to the first
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Post by 100andthirty on Dec 1, 2020 17:29:34 GMT
d76666 Are you able to provide a link to the drawing? As to your last point, there's no substitute for "go look see". I was recently looking for drawings of a train for another professional project and even the operator didn't have them. Instead they used a tape measure directly on the train!
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Post by 100andthirty on Dec 1, 2020 9:42:45 GMT
d7666.....Based on my knowledge of train configurations, the layout described in the Platform 5 document makes logical sense. I know for a fact that the bogie under driving cabs is a trailer bogie. Therefore the bogie at the other end is a motor bogie. It is therefore logical for the adjacent bogie on the PMS also to be a motor bogie, minimising cabling lengths and so on. It's also logical for the other bogie on the PMS to be a trailer bogie helping to manage weights as that car will have a heavy transformer. It also makes sense for the MS1 car to have two motor bogies otherwise there would have been a performance deficit on RLUs. Ans using the same logic as for DMS/PMS, it makes sense for the outer bogie on the MS2 car to be a motor bogie. Sorry it's not facts, but informed speculation apart, that is, from the trailer bogie under driving cabs.
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Post by 100andthirty on Nov 30, 2020 13:12:02 GMT
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Post by 100andthirty on Nov 22, 2020 18:29:12 GMT
As someone old enough to remember the transition from imperial to metric measurement, I have observed that people were much more precise with metric dimensions than with imperial.......probably me too! In the old days is someone stated that a dimension was, say, 4' 8 3/8" they might say that 'it's only 1/8" smaller than the right dimension". However in metric if someone says the dimension is 1432 mm, then the remark might be 'oh, that's 3 mm smaller than the right dimension', with an implication that 3 mm is a lot, despite the fact that its just 1/8"!
Another of the challenges with track is measuring the gauge with a train on the track will give a different result than if the track is measured unloaded. Coned wheels on inclined rails leads to a tendency to spread the gauge against the tension of the rail clips.
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Post by 100andthirty on Nov 22, 2020 8:29:03 GMT
Tom has highlighted one curve, but gauge widening is allowed and necessary on small radius curves.....the smaller the radius, the more widening. Apart from the circumstance I mentioned above, gauge tightening is never a good thing.
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Post by 100andthirty on Nov 19, 2020 7:54:07 GMT
As a postscript, there is one type of track on the underground where 'tight gauge is allowed and that's on depot roads where height setting is carried out to ensure the wheels are properly centred between the rails.
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