On 1 Nov, 16:25, "R.C. Payne" wrote:
AIUI, there hasn't been *any* EMU built [for UK rail use, pedantry
fans] since the 322s which isn't dual-voltage under the skin.

However, while all 750V stock is legally required to be easily
convertible to 25kV [see: panto spaces on the 444s and 450s' roofs],
there's no corresponding requirement for 25kV stock.

Who is responsible for this "law"? It seems a little silly to me, given
that units built for the Southern will almost certainly spend their
entire working lives on that system, and if they leave it, will need to
be replaced by something else that can work on that system.

Haven't got a cite to be honest - it's something I've picked up here
and from the Wiki (so it might be rubbish - but it is certainly true
that all DC EMUs post-465s are readily AC-able).

And It's already proven useful in the case of 350s (albeit that this
happened before they went into service) and 365s, not to mention
whatever's about to happen with the Electrostar reshuffles.

Certainly in the context of Crossrail, the 390s are a red herring, and I
suspect the only reason it would be difficult (apart from DC control
software not existing yet) to make them work on 3rd rail is because the
tilt gear (which has no purpose off the WCML and a few non-Southern
other bits) takes up the space that might otherwise be wanted for shoegear.

With the class 323, which is not a current design, asside, everything
else has been built either as a dual voltage unit, or as part of a
standard family that contains members of both sorts.

Obviously the 390s aren't going to be used for Crossrail, and agreed
100% that all new /suburban/ EMUs post-323s are readily AC/DC-able.

--
John Band
john at johnband dot org
www.johnband.org