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Post by Deleted on Apr 23, 2013 12:01:55 GMT
On a slightly lateral note, presumably higher voltages (3000 vs 640 say) are prefered because of lower requirements for the conducter cross-section? Higher voltages require less fixed equipment (sub stations etc.). High voltage is not suitable for third/fourth rail for various reasons such as safety. More particularly, the safe clearance required INCREASES with voltage - 3kV DV from a contact rail is feasible, but is it practical? For retrofitting into a tube environment - won't pass "GO" and certainly won't collect $200. But I do mull over whether conversion to modest voltage AC would be beneficial. For example, the safe clearances (air gaps) for 25kV AC and 1500vDC seem remarkably similar. So, could 5-11kV 50Hz AC be practically delivered by 3rd rail into our existing tube and SSLs?
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Post by phillw48 on Apr 23, 2013 13:46:03 GMT
Higher voltages require less fixed equipment (sub stations etc.). High voltage is not suitable for third/fourth rail for various reasons such as safety. More particularly, the safe clearance required INCREASES with voltage - 3kV DV from a contact rail is feasible, but is it practical? For retrofitting into a tube environment - won't pass "GO" and certainly won't collect $200. But I do mull over whether conversion to modest voltage AC would be beneficial. For example, the safe clearances (air gaps) for 25kV AC and 1500vDC seem remarkably similar. So, could 5-11kV 50Hz AC be practically delivered by 3rd rail into our existing tube and SSLs? There was a 1,000 volt 3rd rail DC system IIRC in Manchester until it was replaced by a Metro tram system.
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Post by norbitonflyer on Apr 23, 2013 17:21:10 GMT
the safe clearances (air gaps) for 25kV AC and 1500vDC seem remarkably similar. Some sections of the GE electrification operated at 6.25kV for many years to avoid the need to adapt bridges when converted from 1500V dc to ac. First generation ac emus were capable of operating on both voltages. There was a 1,000 volt 3rd rail DC system IIRC in Manchester until it was replaced by a Metro tram system. 1200V actually, but it was side contact (protected), rather like the DLR system.
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Ben
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Post by Ben on Apr 23, 2013 17:49:39 GMT
Just to clarify I was refering to the internal voltage links d7666 spoke of, not the third/fourth rail itself Though having said that, voltages in the thousands have been used for third rail systems before...
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Post by Deleted on Apr 23, 2013 23:00:10 GMT
the safe clearances (air gaps) for 25kV AC and 1500vDC seem remarkably similar. Some sections of the GE electrification operated at 6.25kV for many years to avoid the need to adapt bridges when converted from 1500V dc to ac. First generation ac emus were capable of operating on both voltages. The air gap for 25kV according to RSSB is 125mm. The air gap for 1500vDC in Sydney is 150mm. Probably with experience, BR was able to reduce the air gap requirement, rather than anything else - so phase out the 6.25kV sections. Essentially 6.25kV was used because of engineering conservatism than any other reason, and that is to be applauded when lives could be at risk.
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Post by Deleted on Apr 23, 2013 23:05:34 GMT
Just to clarify I was refering to the internal voltage links d7666 spoke of, not the third/fourth rail itself Though having said that, voltages in the thousands have been used for third rail systems before... The internal DC voltages for VVVF traction packs can be up in the 3000+ volt range. As for 3rd rail supply to conventional rail systems, can you cite examples higher than 1200v DC? I am aware of 3 phase AC and various exotic systems used for monorails, hover guideways and similar exotica that may or may not still be in existence.
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Antje
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Post by Antje on May 1, 2013 20:57:50 GMT
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Post by Deleted on May 2, 2013 7:54:03 GMT
I thought Hitachi would make something sensible but no even they've gone down the route of crazy whacky designs that look terrible and probably will be terrible. There is no hope for the Underground!
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metman
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Post by metman on May 2, 2013 8:23:04 GMT
Not much appears to have changed from the late 80s designs for the Northern and Central lines!
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Post by Chris M on May 2, 2013 9:12:59 GMT
Other than not enough doors I don't think that looks any of crazy, wacky or horrible!
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metman
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Post by metman on May 2, 2013 9:21:39 GMT
I think the leading car only has two doors so the front can partly be in tunnel. These will be 7 or 8 car trains I think.
The design is nothing special in my eyes but I would like to see something a little more retro, celebrating the 67/72 stock look but will a modern feel.
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Post by domh245 on May 2, 2013 16:15:10 GMT
How about a 38TS restyling, as suggested elsewhere on the sight? I knocked this model up quite quickly, after my GCSEs, I might do it up a bit
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Post by Deleted on May 2, 2013 19:27:38 GMT
Other than not enough doors I don't think that looks any of crazy, wacky or horrible! What happened to clean lines, good proportions and oh yeah a cab door?
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Post by Deleted on May 2, 2013 19:48:12 GMT
What I find amusing is that all of these "wacky" ideas are not new at all and always end up being trashed. More recently if you look at some of the proposals for the "new northern line stock" in the early 1990's, you could be forgiven that LUL wanted something with a little more je sais quoi (or SNCF if you like!). You only have to look at just how watered down and conservative in design the 95/96 stock and 09/S stock are compared with their proposals to see how this pattern occurs. I'd recommend "Underground Movement" by Paul Moss for this subject. The design is nothing special in my eyes but I would like to see something a little more retro, celebrating the 67/72 stock look but will a modern feel. There is something very special about the classic front end styling of the 67/72 stock, especially in unpainted ally finish, in my opinion one of the more underrated pieces of LT styling. The rubber sealing that was applied to the cab windows of the 72mkII stock on refurbishment does ruin the effect slightly though. A creation by the industrial designer Misha Black who also came up with the orange and brown moquette for LT among others, the timeless City of Westminster street sign format in 1967 which is still in use today. Like the new bus for London, some attention to styling by someone who knows what they're doing would be a nice step change for TfL who's predecessor was once so well known for it, more recent builds of train have given the impression that the powers that be have given up trying.
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metman
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Post by metman on May 2, 2013 21:05:31 GMT
Yup it was Paul Moss's book that got me thinking. The 1995/6 stock are very dull designs although the background behind the Jubilee design is known.
The 1967/72 design is in my opinion the best. The clean 'cigar tube' look was unparalleled for me.
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Post by Deleted on May 2, 2013 22:52:57 GMT
I thought Hitachi would make something sensible but no even they've gone down the route of crazy whacky designs that look terrible and probably will be terrible. There is no hope for the Underground! There isn't much showing, but from what little I can see, it apppears to be an articulated design concept. This is a pre-requisite (we are told) for the full width gangways shown. The aerodynamically efficient front end may have some "fashionable-ness" about it, but would still serve several purposes in a modest way (reduced drag, easier to clean through mechanical washers, maybe improved visibility in adverse weather). The externally hung doors means Hitachi aren't ready to bite the bullet on fast, guaranteed performance plug doors. They also neutralise the aerodynamic gains from the front end design.
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Post by Chris M on May 2, 2013 23:02:30 GMT
The externally hung doors means Hitachi aren't ready to bite the bullet on fast, guaranteed performance plug doors. They also neutralise the aerodynamic gains from the front end design. I reckon it must be possible to design exterior hung doors that are less aerodynamically inefficient than the slab-ended ones we currently have. It would need a closer fit to the bodyside than is current but that shouldn't be impossible,
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Post by norbitonflyer on May 3, 2013 5:45:59 GMT
The aerodynamically efficient front end may have some "fashionable-ness" about it, but would still serve several purposes in a modest way (reduced drag,,,,,,,,,,,,,,,,). Not necessarily - aerodynamics in tunnels are not the same as on the surface. Wasn't it discovered that the 1935 stock had significant problems in that department, and that a flat front that pushes the air down the tunnel is better than encouraging it to squeeze down the sides of the train? On the surface, aerodynamics are a minor concern at the speeds tube trains go.
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Post by revupminster on May 3, 2013 6:20:57 GMT
To be universal a new train cannot be longer than the shortest carriage already in use to negotiate the tightest bends. The Hitachi does look shorter and if articulated could get away with less but bigger doors.
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Post by Deleted on May 3, 2013 8:57:23 GMT
The externally hung doors means Hitachi aren't ready to bite the bullet on fast, guaranteed performance plug doors. They also neutralise the aerodynamic gains from the front end design. I reckon it must be possible to design exterior hung doors that are less aerodynamically inefficient than the slab-ended ones we currently have. It would need a closer fit to the bodyside than is current but that shouldn't be impossible, Plug doors are definitely not suitable for metro operation! Sliding pocket doors are the best for this kind of work.
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Post by class411 on May 3, 2013 11:42:18 GMT
Plug doors are definitely not suitable for metro operation! Sliding pocket doors are the best for this kind of work. Can you explain that a little further. They seem a definite advance, to me, (although I must admit I've never given the matter a great deal of thought).
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metman
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Post by metman on May 3, 2013 12:30:23 GMT
Plug doors are seen as unreliable for Metro operation was there are so many more operations per day than on outer sub. trains. Plug doors were considered for the S stock but rejected. The London overground units and their cousins on the SE line also have slide doors into pockets.
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Post by Deleted on May 3, 2013 13:12:08 GMT
Externally hung doors are preferred on deep level tube stock because sliding pocket doors take up more space inside the cars and LUL are hardly likely to order trains with less space for passengers.
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Post by Deleted on May 3, 2013 14:07:35 GMT
Externally hung doors are preferred on deep level tube stock because sliding pocket doors take up more space inside the cars and LUL are hardly likely to order trains with less space for passengers. The space saved is hardly used in a productive way though, look at all the stock with externally hung doors like 92ts or 09ts etc. The only one where the space saved is used is on the S stock but even on those the walls are so thick for some reason you could easily fit a pocket door there anyway.
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Post by Deleted on May 3, 2013 14:11:12 GMT
Plug doors are definitely not suitable for metro operation! Sliding pocket doors are the best for this kind of work. Can you explain that a little further. They seem a definite advance, to me, (although I must admit I've never given the matter a great deal of thought). The mechanisms for them are just abit too complex to ensure very reliable performance when they are opening and closing every 2mins for long periods of time. Also on places like the Underground or any other high frequency service where passengers are used to letting people off first when a train is nearly stopped the passengers mainly move past the yellow line and get very close to the side of the train allowing people off, A plug door would come out and hit people stood there. Also they are much slower.
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class411
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Post by class411 on May 3, 2013 15:40:11 GMT
Plug doors are seen as unreliable for Metro operation was there are so many more operations per day than on outer sub. trains. Plug doors were considered for the S stock but rejected. The London overground units and their cousins on the SE line also have slide doors into pockets. Externally hung doors are preferred on deep level tube stock because sliding pocket doors take up more space inside the cars and LUL are hardly likely to order trains with less space for passengers. The space saved is hardly used in a productive way though, look at all the stock with externally hung doors like 92ts or 09ts etc. The only one where the space saved is used is on the S stock but even on those the walls are so thick for some reason you could easily fit a pocket door there anyway. I thought that the S Stock did have plug doors (assuming I understand the term correctly - doors that slide and sit externally but form a smooth skin with the rest of the carriage when closed - as used on the Electrostars). There seems to be some disagreement.
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Post by Dstock7080 on May 3, 2013 17:04:01 GMT
I thought that the S Stock did have plug doors (assuming I understand the term correctly - doors that slide and sit externally but form a smooth skin with the rest of the carriage when closed - as used on the Electrostars). There seems to be some disagreement. '92, '95, '96, '09, S Stock have externally hung doors which do not close into the bodywork, they remain on the outside: www.railway-technical.com/95TS-doors-open-2.jpgPlug-doors will slide along the outside of the body, then close inwards to create a smooth bodyside: www.railway-technical.com/Plug-doors.jpg
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class411
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Post by class411 on May 3, 2013 17:32:33 GMT
Thanks. That clears up my confusion.
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Post by Deleted on May 3, 2013 18:58:32 GMT
The space saved is hardly used in a productive way though, look at all the stock with externally hung doors like 92ts or 09ts etc. The only one where the space saved is used is on the S stock but even on those the walls are so thick for some reason you could easily fit a pocket door there anyway. Really? When they started introducing the 09s they seemed noticeably more roomy inside when compared to the 67s running at the same time and I seem to remember noticing the difference when the 92s were replacing the 62s. Optical illusion?
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Post by Deleted on May 3, 2013 22:15:06 GMT
The space saved is hardly used in a productive way though, look at all the stock with externally hung doors like 92ts or 09ts etc. The only one where the space saved is used is on the S stock but even on those the walls are so thick for some reason you could easily fit a pocket door there anyway. Really? When they started introducing the 09s they seemed noticeably more roomy inside when compared to the 67s running at the same time and I seem to remember noticing the difference when the 92s were replacing the 62s. Optical illusion? What I mean is that if you look on 92ts between the seats there's quite a bit of space used/wasted by the air blower. 09ts have very thicks walls if you look at the window, from the glass to the back rest there is about 3 or 4 inches wasted/used space.
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