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London Tubes: Unexpected locations of underground trains
On 2015\06\21 03:01, Recliner wrote:
Charles Ellson wrote: On Sun, 21 Jun 2015 02:41:35 +0100, Basil Jet wrote: IIRC Drayton Park has both fourth rail and overhead, although obviously not for much distance. The fourth rail might not be doing a lot unless it has been left connected but dropped onto the sleepers as done between Harrow and Watford. It's certainly not a functional fourth rail, and nor would 313s connect to a centre rail anyway. So why aren't all of the water pipes near the GN&C corroding merrily, which is the problem 4th rail was invented to solve? |
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London Tubes: Unexpected locations of underground trains
Basil Jet wrote:
On 2015\06\21 03:01, Recliner wrote: Charles Ellson wrote: On Sun, 21 Jun 2015 02:41:35 +0100, Basil Jet wrote: IIRC Drayton Park has both fourth rail and overhead, although obviously not for much distance. The fourth rail might not be doing a lot unless it has been left connected but dropped onto the sleepers as done between Harrow and Watford. It's certainly not a functional fourth rail, and nor would 313s connect to a centre rail anyway. So why aren't all of the water pipes near the GN&C corroding merrily, which is the problem 4th rail was invented to solve? There's plenty of third rail track in tunnels around the world and, indeed, in London. Just think of the ELL. |
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London Tubes: Unexpected locations of underground trains
On Sun, 21 Jun 2015 02:07:28 +0000 (UTC), Recliner
wrote: Basil Jet wrote: On 2015\06\21 03:01, Recliner wrote: Charles Ellson wrote: On Sun, 21 Jun 2015 02:41:35 +0100, Basil Jet wrote: IIRC Drayton Park has both fourth rail and overhead, although obviously not for much distance. The fourth rail might not be doing a lot unless it has been left connected but dropped onto the sleepers as done between Harrow and Watford. It's certainly not a functional fourth rail, and nor would 313s connect to a centre rail anyway. So why aren't all of the water pipes near the GN&C corroding merrily, which is the problem 4th rail was invented to solve? Probably nothing more than a lack of leakage current. If the tunnels are fairly dry and the traction bonds are in good condition then the leakage will be minimal. Many of the water pipes "upstairs" will now be plastic or interrupted by plastic sections which will further limit the flow of leakage currents through them; they're only going to corrode "merrily" when you have a combination of water and metal touching a different metal or other conducting material. On various LU lines, the only reason for 4-rail electrification is for standardisation. There's plenty of third rail track in tunnels around the world and, indeed, in London. Just think of the ELL. |
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