Why didn’t BR order class 455s for South Eastern?

61653 HTAFC said:

They sort-of were, though with a 321-style cab. Also they had toilets from new which were removed by Southern.

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And they were built at the same time as the 321's.

Dr_Paul said:

That must explain the part of the side of one carriage which has no windows, except a little one at the end. Judging by the length of it, it must have been a pretty large khazi!

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They wouldn't have been big enough for next year, if they hadn't been ripped out!

Surprising that they didn't replace the window with a standard one though.

61653 HTAFC said:

They sort-of were, though with a 321-style cab. Also they had toilets from new which were removed by Southern.

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They also had 321-style seats, which were much better than the ghastly low-backed seating fitted to 455s.

AY1975 said:

The South Eastern has historically been tight for gauge clearance, so I believe that there are also issues to do with restricted clearances on some routes on the SE that would preclude the operation of 455s, 456s or other Mark 3-based stock, hence the decision to order the Class 465/466 Networkers rather than a Class 455/456 derivative.

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The Networkers needed a LOT of gauging work to be carried out before they could operate throughout the South Eastern suburban network. It was all part of the upgrade package, but I remember a Daily Mail "British Rail orders trains too big for tunnels!" headline at the time.

Are the Networkers to big for the Central? You often see signs around the Battersea/Victoria area that say “Networker X” where the eastern and central connects.

Sad Sprinter said:

Are the Networkers to big for the Central? You often see signs around the Battersea/Victoria area that say “Networker X” where the eastern and central connects.

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That's more an electrical interference issue than anything else. Networkers use an early form of three-phase AC motors, and the control equipment produces interference at a particular frequency that can affect signaling. A lot of immunization was needed on the routes where they operate.

Journeyman said:

That's more an electrical interference issue than anything else. Networkers use an early form of three-phase AC motors, and the control equipment produces interference at a particular frequency that can affect signaling. A lot of immunization was needed on the routes where they operate.

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The problem is actually the control equipment rather than the motors. Networkers use GTO thyristors that can only switch a few hundred times a second, within the range of frequencies used by track circuits and other equipment. Later EMUs have IGBTs that can switch much faster so have much less scope to interfere. I don't think there's any reason why the older traction motors couldn't be controlled by the IGBTs (they are on 323s but only at the original switching frequencies - not sure whether the Hitachi-powered Networkers got new motors).