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Post by metropicc on Mar 12, 2008 19:43:32 GMT
The recent thread about the riding qualities of the A stock mentioned that not so long ago speed limits on the Met main were higher in places.
Does any one have a overall picture of where the limits have been reduced and does anyone know why this has been the case. Worn out track?, Worn out trains, lower maintenance standards?
Surely the push should be for higher speed limits in order to increase capacity. Will the resignalling see a higher line speed?
I am very surprised that the new Watford South Junction has a 25 mph limit crossing from local to main and vice versa. At present service trains will not use it with any regularity but should that change in a future timetable recast surely this will be an unecessary and self-imposed limitation.
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metman
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Post by metman on Mar 12, 2008 20:37:33 GMT
In the old days of the MET/GC joint line, very high speeds could be reached. The local lines were designed for 60mph and the fast line 70mph. Pre-war limits such as: Harrow-Northwood Hills 70mph, to Chalfont 60mph, 70mph to Gt Missenden and 75mph thence to Quainton Road! Higher speeds were regularly achieved too!
10 years ago the A stock bogies started to show signs of metal fatigue on the bogies (although they developed bogie cracks when introduced-thankfully sorted early doors). The track was rubbish-although its being improved. So probably a bit of a mixture of factors.
The S stock is only designed for 62mph, which is a bit poor IMO! If or when the resignalling is carried out may mean improvments.
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Ben
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Post by Ben on Mar 12, 2008 20:57:44 GMT
Is th S stock designed for 62mph at 630 volts or 750?
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Post by Deleted on Mar 12, 2008 23:19:05 GMT
Is th S stock designed for 62mph at 630 volts or 750? I would imagine it will get there eventually on either voltage, I can't see how the voltage can affect maximum speed, only acceleration. |
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Post by Deleted on Mar 13, 2008 5:59:20 GMT
Is th S stock designed for 62mph at 630 volts or 750? I would imagine it will get there eventually on either voltage, I can't see how the voltage can affect maximum speed, only acceleration. Higher line voltage means a higher motor speed before the "balancing point" is reached, at which back EMF from the motor equals line voltage. Of course, that assumes that the control gear provides full line voltage across the motors. |
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Post by Deleted on Mar 13, 2008 10:00:49 GMT
Is th S stock designed for 62mph at 630 volts or 750? The S-stock has to be designed for a compromise between running between closely spaced stations where acceleration/decceleration is important (e.g Circle), and fast express running where max speed is more important (e.g Met). |
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metman
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Post by metman on Mar 13, 2008 11:06:46 GMT
Which is why the A and C stocks were designed with different motor field strengths!
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Ben
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Post by Ben on Mar 13, 2008 13:47:43 GMT
Is th S stock designed for 62mph at 630 volts or 750? The S-stock has to be designed for a compromise between running between closely spaced stations where acceleration/decceleration is important (e.g Circle), and fast express running where max speed is more important (e.g Met). Indeed, forgive me for being dense though, but I don't understand how that relates to my question!   |
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metman
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Post by metman on Mar 13, 2008 15:20:29 GMT
The S-stock has to be designed for a compromise between running between closely spaced stations where acceleration/decceleration is important (e.g Circle), and fast express running where max speed is more important (e.g Met). Indeed, forgive me for being dense though, but I don't understand how that relates to my question! The S stock will be designed to operate at 630 volts because that is the current system. If, 750v is used in the future they would be upgraded for it. |
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Post by signalfailure on Mar 15, 2008 2:39:33 GMT
Well as stated above on the old MPH limit to Chesham. Considering its now 35mph. Thats pretty shitty.
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Post by trainopd78 on Mar 15, 2008 11:10:59 GMT
Won't the sustations have to be upgraded anyway as per Southern region to cope with the draw from the AC motors, air con etc? The S stock will have to be capable of running from 750 volts as soon as the C&H get their delivery as the Wimbledon road from Putney Bridge is 750v.
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Post by c5 on Mar 15, 2008 14:38:04 GMT
Well Croxleyhall already can't cope with too many trains on the Watford branch! And I hear that the breakers at Finchley Road are also set quite high.
It is/was quite common for traction current to go off and on due to overload on a number of sections.
Is the upgarde provided for in the PPP or EDF Powerlink PFI???
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Post by Deleted on Mar 27, 2008 18:47:12 GMT
Well as stated above on the old MPH limit to Chesham. Considering its now 35mph. Thats pretty shitty. I wouldn't want to go faster than 35mph as its pretty scary at that speed let alone any faster. The track is pretty poor quality and you get thrown around alot. |
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Post by Deleted on Mar 27, 2008 18:53:52 GMT
Which is why the A and C stocks were designed with different motor field strengths! A stock has the flag switch, (weak field). Finchley road to Aldgate with the flag down A stocks can match the acceleration of C stocks. |
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metman
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Post by metman on Mar 27, 2008 18:55:00 GMT
Yup thats true! Until that track is replaced, Chesham is always at risk of closure too!
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Post by Deleted on Mar 27, 2008 19:02:00 GMT
To answer the original question ;-) With the brand new track in place the ride qualities have improved. Most noticeable improvements is the new layout at Croxley junction. High speed points at 4 points (local to main, north curve triangle and Ricky cross-over) insures smooth running. The old rollercoster section, northbound, level with Wilesden Green siding has been sorted out aswell. Not sure how but the tamper might of had something to do with it. ;-)
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