On Thu, 25 Oct 2012 10:44:49 +0100, wrote:

On Thu, 25 Oct 2012 09:12:12 +0000 (UTC), d
wrote:

On Wed, 24 Oct 2012 20:02:23 +0100
Charles Ellson wrote:
present with the opportunity for future (whole/part) conversion of the
Met to 25kV when the DC equipment is beyond saving, possible use of

Brilliant idea. So who gets to rebuild the circle line tunnels so the
catenary can fit?

Is that a certainty with the lesser clearances that are now known to
be needed ? Was there any significant rebuilding on the Widened Lines
when 25kV was installed ?

To go off on a complete tangent does any one know if the 3000 volt 3
phase system the Metropolitan railway considered would have been
straightfoward to install, or would that have required some tunnel
alterations.

So maybe conductor rail electrification was already seen as not the
way to do it back then ? ITYF the cut and cover construction of the
tunnels would at the least have given a more horizontal tunnel roof to
work with.
http://www.gracesguide.co.uk/Metropolitan_Railway
refers to (in 1900) the Met favouring OHLE and the District favouring
DC conductor rail with a tribunal recommending the DC system; in turn
the article refers to :-
http://www.localhistory.scit.wlv.ac....MetRailway.htm
although there does not seem to be specific mention of the number of
AC phases proposed.

http://www.tubeprune.com/history.html
suggests that the DC choice was influenced by Yerkes's takeover of the
District Railway.

http://www.casebook.org/victorian_lo...l?printer=true
also mentions OHLE proposals but again no specific mention of 3-phase.

Mention is made however of Ganz which IMU infers 3-phase but according
to Wonkypaedia :-
http://en.wikipedia.org/wiki/K%C3%A1...A1n_Kand%C3%B3
there was also a modified system using a single-phase OH supply with
conversion to 3-phase on the locomotive used in Hungary; the wlv.ac.uk
article referred to above mentions the "an overhead conductor" so the
Met. might only have wanted one piece of wet string.
Either way it suggests that the Met. saw OHLE as a viable proposition
without apparent mention of clearances etc. although that doesn't
inevitably mean that clearances were related to tunnel roof height
rather than locomotive/carriage roof height.