John Rowland wrote:
"Mark Brader" wrote in message
...
Benjamin Nunn:
I thought the W&C tunnels were big enough to take regular stock...

John Rowland:
No, in fact they had to be enlarged slightly to take the 92 stock.

CULG gives the Waterloo & City Line tunnel diameter as 3.70 m
(12' 1.75"), which if I remember correctly was taken from Rails
Through the Clay. This is *larger* than the nominal 11' 8.25"
of the Central Line, so what had to be enlarged?

The metal ribs (I don't know the correct name) on the inside of the
rings had to be trimmed on some of the curves. This may be more to do
with the length of the 92 stock than their width, or it may be to do
with their kinematic envelope differing from that of the previous
stock. Perhaps the Central Line already used larger rings on some or
all of the curves.

The degree of curvature is also relevant, i.e. the tighter the curve the
further the car overhangs the track. IIRC some of the track had to be
realigned to take the 92 stock.