Tom Anderson wrote on 13 August 2009 18:32:19 ...
On Thu, 13 Aug 2009, Basil Jet wrote:

Bruce wrote:
On Thu, 13 Aug 2009 12:22:13 +0100, "Recliner"
wrote:
The ever-reliable Wiki source says that the 2009 stock is 2.68m wide
and the 1973 stock 2.629, so the 2009 stock is apparently 5cm or 2"
wider. It also says that, "Unlike the 1967 Tube Stock, the trains
are built 40 millimetres (1.6 in) wider to take advantage of the
Victoria line's slightly larger than normal loading gauge compared
to the other deep level tube lines."

Ironically, one of the reasons why the Victoria Line tunnel was built
to a larger diameter was to reduce air resistance. ;-)

It's not unreasonable to build the first stock for the line small to
reduce air resistance, and then build subsequent stock large to push the
hot air along.

If the air's hot, then building the train bigger means there's less of it
surrounding the train, so the train won't get heated up by it so much.

On the contrary, the bigger train has more surface area so is in contact
with a greater area of hot air. Also, the smaller gap between train and
tunnel will increase the frictional heating effect.

--
Richard J.
(to email me, swap 'uk' and 'yon' in address)