On Mon, 11 Feb 2008 22:16:10 GMT, wrote:

And what about trains running fast on the Metropolitan Line? I heard that
the A62s could do close to 70 miles before they started to discover cracks
in the bogies.

Many years ago when I was just starting with LT I had a run out to
Amersham. On the way back I got a cab ride and certainly saw 70 mph on
the speedometer. It was a bit "shake, rattle and roll" as well but great
fun.
--
Paul C


Admits to working for London Underground!

On 13 Feb, 15:05, "Peter Corser" wrote:
set maximum and then draw that current until maximum speed is attained.
This means that acceleration at speeds above 10 to 15 mph is considerably
enhanced on the modern stock.

Interesting post, thanks for that. Certainly on the central line the
acceleration is pretty impressive but I can't say I find the northern
or jubilee stocks anymore impressive performance wise than the stocks
they replaced. I used to live in finchley and travel on the northern
when the 59 & 72 stocks were still being used and they used to floor
it on the open air section from east finchley to finchley central no
doubt because its well over a mile of almost straight track. When
travelling on the 95 stock though it seemed all rather sedate. Perhaps
its just psychological because theres no screaming motor sounds and
the windows didn't sound like were about to fall out but even so , its
certainly nowhere near as quick as the 92 stock.

B2003

Boltar wrote:
On 13 Feb, 15:05, "Peter Corser" wrote:
set maximum and then draw that current until maximum speed is
attained. This means that acceleration at speeds above 10 to 15 mph
is considerably enhanced on the modern stock.

Interesting post, thanks for that. Certainly on the central line the
acceleration is pretty impressive but I can't say I find the northern
or jubilee stocks anymore impressive performance wise than the stocks
they replaced. I used to live in finchley and travel on the northern
when the 59 & 72 stocks were still being used and they used to floor
it on the open air section from east finchley to finchley central no
doubt because its well over a mile of almost straight track. When
travelling on the 95 stock though it seemed all rather sedate. Perhaps
its just psychological because theres no screaming motor sounds and
the windows didn't sound like were about to fall out but even so , its
certainly nowhere near as quick as the 92 stock.

B2003
Boltae

The actual performance of modern stock is electronically controllable (a set
of EPROMS on the Central Line). If you are running mixed stock and/or the
signalling has not been updated the new stock has to match (or not better)
the old in performance terms if the overlaps are not to be compromised.

It may also be necessary to ensure that any regen is limited to ensure that
the performance of the old stock is not significantly improved.

Peter
--
Peter & Elizabeth Corser
Leighton Buzzard, UK


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On 13 Feb, 22:57, "Peter Corser" wrote:
The actual performance of modern stock is electronically controllable (a set
of EPROMS on the Central Line). If you are running mixed stock and/or the
signalling has not been updated the new stock has to match (or not better)
the old in performance terms if the overlaps are not to be compromised.

But the old stock is long since gone to the depot in the sky. Surely
they could turn the wick up a bit on the new stocks by now? I can see
how the signalling would affect max line speed but I don't see why it
should limit the acceleration though.

B2003

On Feb 14, 10:27*am, Boltar wrote:

But the old stock is long since gone to the depot in the sky. Surely
they could turn the wick up a bit on the new stocks by now?

Maybe they don't want an increase in their energy bill (and carbon
emissions) ? But I suspect a lot of this is simply to do with varying
track/bogie quality.
Tim

Boltar wrote:
On 13 Feb, 22:57, "Peter Corser" wrote:
The actual performance of modern stock is electronically
controllable (a set of EPROMS on the Central Line). If you are
running mixed stock and/or the signalling has not been updated the
new stock has to match (or not better) the old in performance terms
if the overlaps are not to be compromised.

But the old stock is long since gone to the depot in the sky. Surely
they could turn the wick up a bit on the new stocks by now? I can see
how the signalling would affect max line speed but I don't see why it
should limit the acceleration though.

B2003
Boltar

I'm not sure what the current status of the signalling is, but with
"traditional" LUL signalling increasing the rate of acceleration of the
train without modifying the signalling (probably requires complete new
layout, in practice) can mean that the train can arrive at any intermediate
signal travelling significantly faster than the signalled overlap speed.
The potentially increased speed aproaching the next station could compromise
the safety of the home signal.

Conventional signals were laid out based upon the speed-distance curves
supplied by the Rolling Stock Engineer. Later (more recent) practices took
more account of worst case variations in performance and gradients. There
were even some blanket overlaps (nominally 100 km/h, although the practical
application included ISTR 97 km/h overlaps to physically fit the layout) on
the original Heathrow Extension west of Hounslow West.

Peter
--
Peter & Elizabeth Corser
Leighton Buzzard, UK


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