Neillw001 wrote:
Excuse my ignorance, but why in the 21st Century are saftey-critical
devices on one of the most heavily-used urban metro systems in the
World reliant on a bit of string?

If there was indeed a "bit of string" instead of a great thick rope, we
probably wouldn't have the current problem. We'd just have bits of
string breaking occasionally when drivers tried to reset the tripcock,
but that wouldn't affect safety.

--
Richard J.
(to e-mail me, swap uk and yon in address)

It's not a piece of string, it's quite a substantial piece of rope, which
adds to the resetting difficulty. The trains were originally part of a super
line upgrade so the tripcock reset cord was installed as a temporary measure
until ATP/ATO was introduced.
The cord itself goes through several tight bends from the loop that the
driver pulls in the offside cabinet down to the trip itself. The bends and
cord thickness have been a problem since we first tested train set 1 on the
test track at Washwood Heath.

Whilst conducting the conversion training for the drivers we used to tell
them to stick their J Door Key through the loop to get better leverage and
failing that, get out of the cab and attempt a reset pulling where the cord
is visible (about 6 inches from the trip).


"Neillw001" wrote in message
oups.com...
Excuse my ignorance, but why in the 21st Century are saftey-critical
devices on one of the most heavily-used urban metro systems in the
World reliant on a bit of string?

Neill

Neillw001 wrote:
Excuse my ignorance, but why in the 21st Century are saftey-critical
devices on one of the most heavily-used urban metro systems in the
World reliant on a bit of string?

Maybe you are the kind of person who would fit a complex, unknown system
to a train saying `Its the latest hi-tech system`, it is what you need,
string is so 18th century?

If a piece of string works, then what is the problem?


You could put in electronics, a button, introduce a software controlled
system and a processor.

The simple fact is that the mechanical properties of a piece of string
have been understood for centuries.

(although, according to another thread, this still means people are
silly enough to buy the wrong sized string )

Tim