Chris M
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Post by Chris M on Jun 25, 2015 17:46:05 GMT
Even better than rail blue and grey was the original Great Western livery (before First got their mits on it) - green and ivory. It would need some tweaks to meet RVAR but it was simple and classy.
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Post by stapler on Jun 25, 2015 20:57:33 GMT
Chris M, agree re GW. Or GER royal blue would be OK
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Post by pridley on Jun 26, 2015 1:54:08 GMT
www.railway-technology.com/news/newsbombardier-secures-260m-london-overground-train-contract-from-tfl-4607224"London mayor Boris Johnson said: "This brand new fleet of trains will enable London Overground to carry a growing number of passengers more reliably and speedily than ever." Is this a throwaway comment, or do they actually plan to speed up services? NLL is not yet faster than it was in the 1980s. Will West Anglia really be sped up? I would like to think so. Certainly, with greater reliability the on-peak services can rise without new trains. off-peak journeys are a few minutes faster, with on-peak trains being slower, presumably to deal with dwell time and disruptions that maybe more reliable and easier to board trains will resolve? Also, maybe TFL is better at managing dwell times with its underground experience? For example, it can take 32mins from Edmonton Green to Liverpool Street on-peak, whereas the same journey is 27mins on the off-peak. A huge 18% difference. Even the semi-fast peak service from Cheshunt is 29mins from Edmonton Green, by-passing Stamford Hill, Cambridge Heath and Bethnal Green. It should be more like 24mins. Does anybody know what could be possible for the new trains? Are higher speeds and better acceleration and breaking possible? Do the tracks need upgrade to cope? Would higher speeds facilitate greater frequencies? Can the disparity between on-peak and off-peak frequencies be removed? ----------- From the Crossrail stats: Key technical aspects of the trains : • Maximum Length – 205 metres • Top Speed – 145 kph (90mph) • Acceleration – up to 1 m/s2 (comparable to metro trains) ----------- Wiki says that the existing 315s have a top speed of 75mph. Acceleration: 0.75 (0-10ms-1 ) ----------- 33% faster accelleration. (presumably breaking is just as improved). 20% faster top speed. Back of a fag packet, split the two, and you get 26.5% improvement. The preset off-peak time of 27mins from Edmonton Green to London Liverpool Street could then be 19.854mins. That would be just over 2mins faster than the existing Hertford East "fast" trains. A little birdie tells me that Cheshunt trains will soon be running to Hertford East. Off peak Enfield Town services cut from 32mins to 24mins. Cheshunt trains reduced from 39mins to 28mins, to match the present "express" trains on the West Anglia Mainline. In short, a game changer, and they justify devolution elsewhere right there.
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Post by stapler on Jun 26, 2015 7:07:38 GMT
Some Chingford journey times are now worse that before electrification...so improvement should not be difficult
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Post by snoggle on Jun 26, 2015 8:09:57 GMT
www.railway-technology.com/news/newsbombardier-secures-260m-london-overground-train-contract-from-tfl-4607224"London mayor Boris Johnson said: "This brand new fleet of trains will enable London Overground to carry a growing number of passengers more reliably and speedily than ever." Is this a throwaway comment, or do they actually plan to speed up services? NLL is not yet faster than it was in the 1980s. Will West Anglia really be sped up? I would like to think so. Certainly, with greater reliability the on-peak services can rise without new trains. off-peak journeys are a few minutes faster, with on-peak trains being slower, presumably to deal with dwell time and disruptions that maybe more reliable and easier to board trains will resolve? Also, maybe TFL is better at managing dwell times with its underground experience? For example, it can take 32mins from Edmonton Green to Liverpool Street on-peak, whereas the same journey is 27mins on the off-peak. A huge 18% difference. Even the semi-fast peak service from Cheshunt is 29mins from Edmonton Green, by-passing Stamford Hill, Cambridge Heath and Bethnal Green. It should be more like 24mins. Does anybody know what could be possible for the new trains? Are higher speeds and better acceleration and breaking possible? Do the tracks need upgrade to cope? Would higher speeds facilitate greater frequencies? Can the disparity between on-peak and off-peak frequencies be removed? ----------- From the Crossrail stats: Key technical aspects of the trains : • Maximum Length – 205 metres • Top Speed – 145 kph (90mph) • Acceleration – up to 1 m/s2 (comparable to metro trains) ----------- Wiki says that the existing 315s have a top speed of 75mph. Acceleration: 0.75 (0-10ms-1 ) ----------- 33% faster accelleration. (presumably breaking is just as improved). 20% faster top speed. Back of a fag packet, split the two, and you get 26.5% improvement. The preset off-peak time of 27mins from Edmonton Green to London Liverpool Street could then be 19.854mins. That would be just over 2mins faster than the existing Hertford East "fast" trains. A little birdie tells me that Cheshunt trains will soon be running to Hertford East. Off peak Enfield Town services cut from 32mins to 24mins. Cheshunt trains reduced from 39mins to 28mins, to match the present "express" trains on the West Anglia Mainline. In short, a game changer, and they justify devolution elsewhere right there. We don't even know what the trains will be so why run away with the notion that they're going to offer vastly faster journeys? Boris is well known for using flowery and exaggerated language in press releases which is why it's worth ignoring at least 50% of what he says. I'd also argue that the performance requirements for Crossrail are rather different to those for West Anglia. When the contract is signed off I am sure Bombardier will release a press release - they haven't done so yet as I've just checked. I simply don't believe that the new trains could offer anything like the journey time reductions you've postulated. They will probably accelerate faster than the 315s simply because the latter are old and knackered. However they will still have to slot between slower trains and there will be issues like signal sighting and track speeds to consider. Your point about dwell times may well be true but the other aspects to consider are door open and close cycle times, stepping distances and heights and obviously door widths, stand back space and the numbers of people at any given stop. I suspect there may be some marginal dwell time improvements but the substantive issues relate to the infrastructure and not the trains and you aren't going to see platforms with curves, poor step heights or gaps to the platform edge suddently being fixed. The other factor in the longer term will be more people in wheelchairs or otherwise encumbered using the services when trains with wheelchair bays enter service and more stations are made accessible. The need to deploy ramps for these users will always mean longer dwell times. Obviously not a factor on every trip but some will be affected and therefore the timetable has to have allowances for this. The final point to make is that TfL practice is not to create timetables that are so tight that they require "grand prix" type speeds and driving techniques with minimal turnround times. In fact just the opposite is true because it makes it easier to hit performance targets and is probably better for passenger comfort. That's demonstrably the practice on the original Overground lines and I see no reason for West Anglia to be any different. I know everyone on rail forums wants trains running at max speed everywhere but that's not how it's done on a stopping Metro type service.
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Dom K
Global Moderator
The future is bright
Posts: 1,819
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Post by Dom K on Jun 26, 2015 10:29:20 GMT
Signs are up (with black tape on) at Hackney Central for the connection to Hackney Downs. Some workmen working on the gate from the platform too!
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Post by norbitonflyer on Jun 26, 2015 11:05:20 GMT
From the Crossrail stats: Key technical aspects of the trains : • Top Speed – 145 kph (90mph) • Acceleration – up to 1 m/s2 (comparable to metro trains) ----------- Wiki says that the existing 315s have a top speed of 75mph. Acceleration: 0.75 (0-10ms-1 ) ----------- 33% faster accelleration. (presumably breaking is just as improved). 20% faster top speed. Back of a fag packet, split the two, and you get 26.5% improvement. There are some huge assumptions here. Firstly, that braking (not breaking!) is as good as acceleration. Even if it is, a greater margin needs to be allowed in case of greasy rails, brake wear etc. Secondly, that acceleration is constant throughout the speed range (rarely the case, note that the figure for a 315 is only valid at low speeds for up to 10metres /sec (22 mph) and that quoted for the 345 is only a maximum figure: "up to" 1m/s^2) Thirdly, that line speed would permit 90mph running throughout Fourthly, that you could actually get to even 75mph between stops. Lastly, that splitting the difference between improvements in acceleration and top speed is in any way meaningful - it depends on how much time you spend accelerating and how much time at top speed. Just to illustrate the likely actual time savings, let's look at the average distance between stops on the Enfield line: according to the GBTT the distances range from 0.5 to 1.25 miles, but with 14 stops in 10.75 miles the average distance between stops is 0.77 miles or about 1230 metres. I will assume, for want of any better information to hand, that your first three assumptions are correct. Using s=ut+(at^2)/2, and setting s as half the average distance between stations (615m) we can see how long it will take a 315 at maximum acceleration to cover that distance (we are assuming it can brake just as fast, and therefore will cover the other half of the distance in the same time. Given u=0, a=0.75 and s= 1230/2 = 615m gives t=40.5 seconds. Thus start to stop is 81 seconds. Applying the same formula to a 345 clone, we get an acceleration over half-distance of 35 seconds - start to stop in 70 seconds - a saving of 11 seconds. 11 seconds times 14 stops is 154 seconds or about three minutes saved end to end, from 33 minutes to 30 minutes, about 9%. This assumes ideal conditions, with acceleration and braking rates equal, and constant over the speed range, and with no external constraints on speed. As for the maximum speed, setting v=u+at, the 315 will hit 0.75x40 = 30m/s (108kph, or 67mph), whilst the 345 will hit 1x35=35m/s (126kph or 78mph), so top speed is largely irrelevant over such short distances. For the longest stretch (Lower Edmonton to Bush Hill Park, or Liverpool Street to Bethnal Green, both 2km, and again assuming no speed restrictions over the junctions (!)) Class 315: 44 seconds to reach 120kph: distance covered 733m, same distance to stop, leaving 534m at 33m/s top speed = 16 seconds - total 104 seconds Class 345: 40 seconds to reach 145kph: distance covered 816m, same distance to stop, leaving 368m at 40m/s top speed = 9 seconds - total 89 seconds - a saving of 15 seconds. EDIT corrected arithmetic
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Post by whistlekiller2000 on Jun 26, 2015 11:50:48 GMT
Using s=ut+(at^2)/2, and setting s as half the average distance between stations (615m) we can see how long it will take a 315 at maximum acceleration to cover that distance (we are assuming it can brake just as fast, and therefore will cover the other half of the distance in the same time. Given u=0, a=0.75 and s= 1230/2 = 615m gives t=40.5 seconds. Thus start to stop is 91 seconds. If 40.5 seconds is the halfway mark wouldn't it be 40.5 x 2 = 81 seconds for the start/stop, not 91 seconds? Apologies if I've missed something critical here but wouldn't that mean that the improvement is even less?
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Post by norbitonflyer on Jun 26, 2015 12:20:39 GMT
If 40.5 seconds is the halfway mark wouldn't it be 40.5 x 2 = 81 seconds for the start/stop, not 91 seconds? Apologies if I've missed something critical here but wouldn't that mean that the improvement is even less? Indeed, now corrected - good job I showed my working. This also shows, as you would expect, that the advantage is marginally greater on the longest stretches, where (in theory at least) the newer units can make use of their higher maximum speed. (on most stretches they wouldn't reach it before it's time to slow for the next stop)
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Post by snoggle on Jun 26, 2015 13:50:18 GMT
If 40.5 seconds is the halfway mark wouldn't it be 40.5 x 2 = 81 seconds for the start/stop, not 91 seconds? Apologies if I've missed something critical here but wouldn't that mean that the improvement is even less? Indeed, now corrected - good job I showed my working. This also shows, as you would expect, that the advantage is marginally greater on the longest stretches, where (in theory at least) the newer units can make use of their higher maximum speed. (on most stretches they wouldn't reach it before it's time to slow for the next stop) Good work on the maths (beyond me!) and it shows the danger of just applying a simple rule of thumb to something that's very involved. Even if the trains can perform very well there are still, as you say, a shed load of other factors that come into play when determining a likely journey time saving. From a pure guess (so treat that with the caution it deserves) I'd say that targeted works to raise line speeds across junctions and to improve the platform train / interface (lower stepping heights and reduced stepping distances) would probably yield as much benefit as making the trains run a bit faster. Also creating more access and egress capacity and wider platforms at places like Seven Sisters would help spread loadings and reduce dwell times. You really need a very thorough and systematic review of train operation over a long time period in varying conditions to build an accurate picture of what is going on and to develop targeted strategies to improve journey times etc. This, of course, assumes that reducing journey time is your key objective and I wouldn't say that is TfL's key objective at the moment. It will be to get the operation to be reliable and dependable and then to build patronage and then capacity.
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Deleted
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Post by Deleted on Jun 26, 2015 15:22:18 GMT
good job I showed my working. 4 marks out of 5 - with the potential to receive full marks on any subsequent part where the error is carried forward
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Post by whistlekiller2000 on Jun 26, 2015 15:57:06 GMT
good job I showed my working. 4 marks out of 5 - with the potential to receive full marks on any subsequent part where the error is carried forward It was pretty cool though wasn't it? I remember sailing through that sort of stuff at school although not so much nowadays thank god! It just goes to show that, despite the slight error, norbo must have used a cuban cigar box for his calculations instead of pridley's fag packet. Class will out..........
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Deleted
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Post by Deleted on Jun 26, 2015 16:10:13 GMT
I did that sort of thing in "M1" (Mechanics 1). Got a U (29%) first time and an A (98%) second time
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Post by norbitonflyer on Jun 26, 2015 16:37:20 GMT
It just goes to show that, despite the slight error, norbo must have used a cuban cigar box for his calculations instead of pridley's fag packet. Class will out.......... Why thank you. A-level maths was forty years ago for me - maybe the fact it was less than a month ago for one of my kids has more to do with recalling the formulae correctly.............. And for my next trick I'll put in a more plausible acceleration and braking profile.
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Post by pridley on Jun 26, 2015 16:56:11 GMT
For enfield Town, if 70 seconds is the average travel time between the 14 stations on the new trains, that is 980 seconds or, 16.3 minutes. Add 1min at each station, 14mins, and you get 30mins. A saving of 2mins. But in reality, wouldn't dwell times be no more than 30 seconds, making it a 23mins journey saving 9minutes.
Though I do not believe that the train would be breaking for anywhere near the same amount of time that it accelerates.
The bigger issue is, that if the maximum of around eight trains per hour at Edmonton Green all save a small amount per journey you can squeeze in more frequency.
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class411
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Post by class411 on Jun 26, 2015 17:13:07 GMT
Acceleration is most definitely not constant throughout the speed range.
To accelerate a train you have to increase its energy and e = mv^2.
Since e is constant(ish) (i.e. what electrical power is drawn), you can see that the acceleration will vary dramatically from low speed to near top speed.
Similarly, braking from high speed is dramatically slower for a given braking system than breaking at low speed, for much the same reasons, except here it is the amount of energy you have to dissipate.
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Post by pridley on Jun 26, 2015 18:26:30 GMT
Wait a second, S Stock accelerates at 1.3m/s2. What is going on there?! Would that not be better, despite lower speeds?!
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rincew1nd
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Post by rincew1nd on Jun 26, 2015 18:39:51 GMT
What has the acceleration rates and accompanying formulae got to do with the transfer of lines from AGA to LO?
There have been numerous reminders from various forum staff regarding thread drift, as the lines have now transferred I think it's padlock time.
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