On Jan 19, 6:13 pm, Mizter T wrote:
On 19 Jan, 17:50, Edward Cowling London UK



wrote:
In message , asdf
writes

On Sat, 19 Jan 2008 12:44:10 +0000, Edward Cowling London UK wrote:

While we're taking about the Victoria Line can someone fix the computer
to make the breaking less last minute and less fierce. It's the only
line that seems to routinely try to throw everyone on the floor !

Please don't; I'd rather have the faster journey times. More
grab-rails can be installed if necessary.

I'm getting on a bit (brings out violin) and my back doesn't like all
the excitement of the unplanned roller coaster ride the Victoria Line
can be.

Roll on the invention of inertial dampers :-)

Fair enough, I see your point - and yes, I suppose the Victoria line
can be a bit jerky. Perhaps the new stock on the upgraded line will
manage to do the job in a smoother manner, without sacrificing the
speed.

Isn't the upgrade actually going to increase the speed?
http://news.bbc.co.uk/2/hi/uk_news/e...on/5186896.stm says
journey times will improve by 16%.

On Sat, 19 Jan 2008 19:13:55 +0000, Edward Cowling London UK wrote:

Hi fellow brother of the damned, I do the same awful route :-) I've
lost track of the times I've started to move towards the doors, only to
have the train stop dead and chuck me about. I don't get this on the
Piccadilly line.

Plus the trains don't wait at the platform like the human driven trains
do if there is a bad morning with the trains up ahead. They just stop in
the bloody tunnel.

All in all give me a human being at the wheel any day.

It's still a human being that presses the buttons to close the doors
and start the train moving.

That's like calling the guy in the space capsule a pilot :-)

My point was that whether or not the trains wait in the platform when
there's a delay up ahead is still entirely human-controlled.

On Sat, 19 Jan 2008 19:24:58 +0000, Tom Anderson wrote:

Fair enough, I see your point - and yes, I suppose the Victoria line
can be a bit jerky. Perhaps the new stock on the upgraded line will
manage to do the job in a smoother manner, without sacrificing the
speed.

That seems perfectly possible - they could lower the rate of change of
deceleration, without significantly sacrificing the magnitude of the
deceleration.

You beat me to it! The rate of change of acceleration [1] is known as
'jerk rate',

[1] The fourth derivative of position with respect to time - fourth!

Third, surely?

"Tom Anderson" wrote in message
h.li...
On Sat, 19 Jan 2008, asdf wrote:

On Sat, 19 Jan 2008 10:13:13 -0800 (PST), Mizter T wrote:

I'm getting on a bit (brings out violin) and my back doesn't like all
the excitement of the unplanned roller coaster ride the Victoria Line
can be.

Roll on the invention of inertial dampers :-)

Fair enough, I see your point - and yes, I suppose the Victoria line can
be a bit jerky. Perhaps the new stock on the upgraded line will manage
to do the job in a smoother manner, without sacrificing the speed.

That seems perfectly possible - they could lower the rate of change of
deceleration, without significantly sacrificing the magnitude of the
deceleration.

You beat me to it! The rate of change of acceleration [1] is known as
'jerk rate', and it's primarily that, rather than the magnitude of the
acceleration, which determines passenger comfort. Well, until the
acceleration is a significant fraction of gravity, but i don't think we're
likely to see that - normal braking is usually on the order of 1 m/s^2, i
think. You can indeed reduce the jerk rate while maintaining the same
deceleration; it means it'll take a little longer to come up to full
braking, but the extra time is negligible compared to the time then spent
at full brake. The jerk rate is entirely limited by the sophistication of
the control system, i believe; the primitive computers on the current
Victoria line trains probably don't make any attempt to control it, and
just switch between acceleration rates as quickly possible. I'd hope the
new stock makes more effort here.

tom

[1] The fourth derivative of position with respect to time - fourth!

Velocity is the first derivative, and acceleration is the second derivative.
What are you regarding as the third derivative if you are calling the rate
of change of acceleration the fourth derivative?
--
David Biddulph

On Sat, 19 Jan 2008, asdf wrote:

On Sat, 19 Jan 2008 19:24:58 +0000, Tom Anderson wrote:

Fair enough, I see your point - and yes, I suppose the Victoria line
can be a bit jerky. Perhaps the new stock on the upgraded line will
manage to do the job in a smoother manner, without sacrificing the
speed.

That seems perfectly possible - they could lower the rate of change of
deceleration, without significantly sacrificing the magnitude of the
deceleration.

You beat me to it! The rate of change of acceleration [1] is known as
'jerk rate',

[1] The fourth derivative of position with respect to time - fourth!

Third, surely?

Fourth if you start counting at zero!

[runs away]

tom

--
Things fall apart - it's scientific

In article ,
(Edward Cowling London UK) wrote:

In message , asdf
writes
On Sat, 19 Jan 2008 17:48:17 +0000, Edward Cowling London UK wrote:

Hi fellow brother of the damned, I do the same awful route :-) I've
lost track of the times I've started to move towards the doors, only
to have the train stop dead and chuck me about. I don't get this on
the Piccadilly line.

Plus the trains don't wait at the platform like the human driven
trains do if there is a bad morning with the trains up ahead. They
just stop in the bloody tunnel.

All in all give me a human being at the wheel any day.

It's still a human being that presses the buttons to close the doors
and start the train moving.

That's like calling the guy in the space capsule a pilot :-)

Say what you like, but the trains always felt safer and seemed to
run better when they had a driver and a guard.

The Victoria Line has never had any other driving system than the one it
has today. So it's hard to make sense of your remarks. It is designed for
higher speeds than older lines so greater acceleration and braking is to
be expected.

--
Colin Rosenstiel

In article
,
(Mizter T) wrote:

On 19 Jan, 17:30, asdf wrote:
On Sat, 19 Jan 2008 12:44:10 +0000, Edward Cowling London UK
wrote:

While we're taking about the Victoria Line can someone fix the
computer to make the breaking less last minute and less fierce.
It's the only line that seems to routinely try to throw everyone on
the floor !

Please don't; I'd rather have the faster journey times. More
grab-rails can be installed if necessary.

I'm with you on that. One of the great things about the Victoria
line is that it is fast.

Up to 50 MPH instead of 30 on older lines.

--
Colin Rosenstiel

On Sat, 19 Jan 2008 21:41 +0000 (GMT Standard Time),
(Colin Rosenstiel) wrote:

In article ,
(Edward Cowling London UK) wrote:

[Victoria line]

Say what you like, but the trains always felt safer and seemed to
run better when they had a driver and a guard.

The Victoria Line has never had any other driving system than the one it
has today. So it's hard to make sense of your remarks. It is designed for
higher speeds than older lines so greater acceleration and braking is to
be expected.

Absolutely right in that it has always been automatic so the comparative
comment is wrong. However the thread has set me thinking and I believe
that there was a fairly recent change to the control system to remove
coasting and allow more accelerated running between stations. Given the
trains and the control system are near the end of their life there *may*
be some deterioration in performance when asset age and the removal of
coasting are combined.

Still the new trains will certainly accelerate and brake much more
quickly so I think it will definitely be a case of "hang on tight".
Part of me is looking forward to a faster and hopefully reliable journey
but I will miss 67 stock given the years I've been using it.

--
Paul C


Admits to working for London Underground!

On Jan 19, 12:39 pm, "David Biddulph" groups [at] biddulph.org.uk
wrote:

Velocity is the first derivative, and acceleration is the second derivative.
What are you regarding as the third derivative

Which - as was posted above - is ''jerk'' which does exactly what it
says on the label.

I had noticved this on the Vic. too.

Agreed the Central does seem to have got that bit right ... although
the whole was a long time coming.

Had I not taken the job I have now I *would*have been on the Victoria
line resignalling project and no doubt might have been able to offer
some insight into comments in this thread. But I'm not, so I can't.

That job was with Metronet so I dodged than one ... phewww ... )



--
Nick

On Sat, 19 Jan 2008 20:09:35 +0000, asdf
wrote:

On Sat, 19 Jan 2008 19:24:58 +0000, Tom Anderson wrote:

Fair enough, I see your point - and yes, I suppose the Victoria line
can be a bit jerky. Perhaps the new stock on the upgraded line will
manage to do the job in a smoother manner, without sacrificing the
speed.

That seems perfectly possible - they could lower the rate of change of
deceleration, without significantly sacrificing the magnitude of the
deceleration.

You beat me to it! The rate of change of acceleration [1] is known as
'jerk rate',

[1] The fourth derivative of position with respect to time - fourth!

Third, surely?

"In the fall of 1972 President Nixon announced that the rate of
increase of inflation was decreasing. This was the first time that a
sitting president used the third derivative to advance his case for
reelection." - Hugo Rossi, Mathmetician.