On Oct 25, 11:51*pm, Charles Ellson wrote:

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 ?

No, but the clearances are minimal, and 319s sit lower on their
suspensions than 321s do (I guess 377/5s do comoared with other 377s
but have yet to find this data).

Some of the track was lowered by using slab track - the usual reason
stated for slab track in the tunnels is reduced maintenance - which
is of course true - but overall it is lower height than sleepered
track allowing shoe horning of OLE.




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.


That depends how you look at this.

Other statements that " xx volts" are difficult to install in tunnels
are incorrect without qualification. There is no difficulty in
installing anything in tunnels provided the tunnel is big enough, so
if you go back in time to when these ideas were proposed the
underground network was a lot smaller, and, in the case of the Met.
and Dist. that already existed far easier to have altered than today
- you don't have huger tower blocks foundations straddling the railway
making for impossible obstructions. Cut and cover lines could have
been more easily dug out then but imagine trying to do that now with
todays road traffic ... and road lobby.


I'd say if it had been done at the time it was proposed it would have
required alterations of larger extent than today because they'd need
larger clearances than todays modern insulation standards allow, and
those alterations would have been far far less disruptive than
attempting it today.

--
Nick