Deleted
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Post by Deleted on May 26, 2014 19:30:07 GMT
Talking to someone in Upgrades last week, they said that the brief was to be a walk-through design. To cope with the Sth Ken bends the idea of shorter carriages in a TEN car formation was mentioned. We shall see....in around 18 years time at this rate....hopefully
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Ben
fotopic... whats that?
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Post by Ben on May 26, 2014 19:45:31 GMT
Makes a lot of sense. With the need for cabs to be in platform for cctv gone, the limit becomes siding length, Cockfosters platforms, and the need for one door of each end carriage to fit in other platforms.
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Post by causton on May 27, 2014 0:09:00 GMT
Makes a lot of sense. With the need for cabs to be in platform for cctv gone, the limit becomes siding length, Cockfosters platforms, and the need for one door of each end carriage to fit in other platforms. How much needs to be added to Cockfosters? Seems easy to extend the platforms a few feet into the concourse as it is quite big... you could always demolish the ticket office
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Post by railtechnician on May 27, 2014 8:43:09 GMT
If a semi-walkthrough DLR train can negotiate tight "S-bend crossovers", and a modern walkthrough Paris metro trains can negotiate 20m curves, then I'm sure it will cope! I'm sure that Paris Metro tunnels have more clearance than the tube tunnels on the Piccadilly. Negotiating the curves isn't the problem; it's the ends of the carriages fouling the tunnel wall. However the 92 stock manage to make it round the Caxton curve, so I'm sure the problem has a solution. No it's the whole carriage! If the ends of the cars foul the tunnel so will the centres of the cars, simple geometry. When mounting equipment in the tunnels we would gauge the curves with the tried and tested 33' dead straight length of string held tight on the running rail at each end and a tunnel gauge to measure the deviation at the centre of the string.
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Deleted
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Post by Deleted on May 27, 2014 18:07:03 GMT
... you could always demolish the ticket office Lol, cheeky!
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Post by norbitonflyer on May 31, 2014 10:22:23 GMT
No it's the whole carriage! If the ends of the cars foul the tunnel so will the centres of the cars, simple geometry. The actual clearance required also depends on the distance of the bogie pivots from the end of the car, and from each other - the closer together they are - and the further from the car ends - the less overthrow in the centre and the greater overthrow at the ends. Also, the car ends would foul the outside of the bend, the car middle would foul the inside - it would be quite possible for the track to be aligned in such a way that only one of them is fouled - in practice of course you need extra clearance on both sides.
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Post by railtechnician on May 31, 2014 23:00:24 GMT
No it's the whole carriage! If the ends of the cars foul the tunnel so will the centres of the cars, simple geometry. The actual clearance required also depends on the distance of the bogie pivots from the end of the car, and from each other - the closer together they are - and the further from the car ends - the less overthrow in the centre and the greater overthrow at the ends. Also, the car ends would foul the outside of the bend, the car middle would foul the inside - it would be quite possible for the track to be aligned in such a way that only one of them is fouled - in practice of course you need extra clearance on both sides. It is highly unlikely that the track would not be centred in a tube tunnel, the sleepers are concreted in and as equipment can be fitted on both sides of a tunnel and on both inside and outside of curves it would be poor practice. The length of the string used for gauging must be as long as the distance between the bogie centres if you think about it and in all my years on the system it was AFAIK 33' so I guess all the stocks had bogies at the same centres although I stand to be corrected. Due to the smaller diameter tunnels on the Central there was less clearance but AFAIR we used the same tunnel gauge in all the tube tunnels when hanging relay cases, transformers, signal heads etc. The Vic the Jubilee and the west end of the Picc were built with more room and I can't recall any problems with equipment etc but in places on the Picc, the Bakerloo, the Central and the Northern I can recall badly installed cables being clipped by trains over the years.
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Post by phillw48 on Jun 1, 2014 8:46:53 GMT
Are tube curved tracks 'canted' like main lines, and would there be any advantage in doing so?
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Post by norbitonflyer on Jun 1, 2014 11:41:13 GMT
the distance between the bogie centres if you think about it and in all my years on the system it was AFAIK 33' so I guess all the stocks had bogies at the same centres although I stand to be corrected. As I understood it, a six-car 1973, 1983, 1995 or D stock train is approximately the same length as the seven car 1959, 1972 and R stock trains they replaced, but whether this translated into a longer distance between bogie pivots or a longer end overhang I don't know.
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Post by Dstock7080 on Jun 1, 2014 12:04:10 GMT
A recent incident on the District Line has highlighted this very issue.
between bogie centres on Stock (DM cars): C 10820mm D 11885mm S7 10820mm '59 10211mm '73 11124mm '72 10338mm '83 11124mm
length of car (DM cars): C 16030mm D 18372mm S7 17439mm '59 15926mm '72 16091mm '73 17473mm '83 17726mm
width of car (DM car): C 2920mm D 2850mm S7 2920mm '59 2604mm '72 2642mm '73 2630mm '83 2630mm
leading bogie centre to cab end (DM car): C 2540mm D 3370mm S7 3562mm '59 2980mm '72 2934mm '73 3073mm '83 3326mm
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Post by railtechnician on Jun 1, 2014 15:29:14 GMT
Are tube curved tracks 'canted' like main lines, and would there be any advantage in doing so? There is very definitely an obvious cant on many tight curves and AFAIK it is the practice to cant the curves but it's difficult to see on gentle sweeping curves. AIUI the cant is to as far as is possible keep the centre of gravity as vertically near the centre of the four foot as possible. A train negotiating a flat curve at speed will tend to pivot on the outer rail as centrifugal force attempts to throw it in an opposite direction e.g. a train taking a right hand curve will be thrown to the left. Thus the left hand rail is raised with respect to the right hand rail to cant the track and gravity will act to keep the train on the track. I don't know what cant angles are used but I assume there is a table with preferred values according to maximum line speed, radius of curve etc. The rails themselves are of course canted inward at 1 in 40 IIRC but that is all to do with the smooth passage of axles around curves, the train wheels being cone shaped to match the rails rather than cylinders. This assists the ride by allowing the axles to move horizontally and mitigates to some extent the rail wear that would otherwise occur.
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Post by phillw48 on Jun 1, 2014 20:18:33 GMT
Thanks railtechnician, As rail cant effectively increases the radius of a given curve could it be used to enable tube stock to 'fit' the tube? An added bonus as the radii of curves is effectively increased this would enable an increase in line speeds.
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Post by railtechnician on Jun 2, 2014 2:36:05 GMT
Thanks railtechnician, As rail cant effectively increases the radius of a given curve could it be used to enable tube stock to 'fit' the tube? An added bonus as the radii of curves is effectively increased this would enable an increase in line speeds. I'm not quite sure what you are getting at there, the radius is the same but in a different plane i.e. the track and train have been rotated off the horizontal and the tube tunnel diameter is a fixed parameter. Line speeds are selected to suit the geometry of the track, canting the track on a curve allows a train to run a little nearer to the speed on the straight but of course the tighter the curve the more friction and natural braking. If you want higher line speeds you need straighter runs and long sweeping curves as well as wider tunnels as there is more roll at high speed effectively tightening the gauge with respect to tunnel mounted equipment and cabling.
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Post by crusty54 on Jun 2, 2014 5:40:22 GMT
It should be remembered that the early 73 stock was too high to fit in the tunnels and the grabrails had to be modified to pull the roof down on all the trains.
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Post by norbitonflyer on Jun 2, 2014 9:19:22 GMT
It should be remembered that the early 73 stock was too high to fit in the tunnels and the grabrails had to be modified to pull the roof down on all the trains. I thought it was the 1983 stock that had that problem - apparently because the smaller door openings didn't increase the body stiffness as much as it had been calculated it would.
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Post by railtechnician on Jun 2, 2014 12:49:27 GMT
Some tube platforms had to be lowered to take 1995 stock on the Northern, I recall Hampstead as one of those because I had to survey the site for the comms cable diversions that were required as a result.
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Post by crusty54 on Jun 2, 2014 15:38:19 GMT
It should be remembered that the early 73 stock was too high to fit in the tunnels and the grabrails had to be modified to pull the roof down on all the trains. I thought it was the 1983 stock that had that problem - apparently because the smaller door openings didn't increase the body stiffness as much as it had been calculated it would. no it was 73 stock which was lighter than predicted. The grabrail design was changed to pull the roof down and bits were shaved off the tunnel fixtures and fittings.
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