I've noticed recently that the frighteningly wobbly stretch of DLR
from Mudchute to Crossharbour now seems to have a speed restriction,
although it still manages to wobble a surprising amount at very low
speed. I wonder if an opportunity will be taken during the works that
are about to start to fix whatever the problem is, or whether the
whole line will progressively be progressively reduced to a crawl.

Also, I wonder if this new speed restriction is due to the wobbling
actually having been unsafe, or was just to stop complaints from
alarmed passengers.

On Fri, 27 Jun 2008 06:31:22 -0700 (PDT), MIG
wrote:

Also, I wonder if this new speed restriction is due to the wobbling
actually having been unsafe, or was just to stop complaints from
alarmed passengers.

Have the DLR still not worked out how to deal with that issue? I
heard it was due to the use of tram-profile wheels on mainline-profile
rails. If that is the case, can't they just progressively replace or
reprofile the wheelsets?

Do the new sets have the same problem?

Neil

--
Neil Williams
Put my first name before the at to reply.

On 27 Jun, 17:11, (Neil Williams)
wrote:
On Fri, 27 Jun 2008 06:31:22 -0700 (PDT), MIG

wrote:
Also, I wonder if this new speed restriction is due to the wobbling
actually having been unsafe, or was just to stop complaints from
alarmed passengers.

Have the DLR still not worked out how to deal with that issue? *I
heard it was due to the use of tram-profile wheels on mainline-profile
rails. *If that is the case, can't they just progressively replace or
reprofile the wheelsets?

Do the new sets have the same problem?


I hope not, but I don't think any are in service yet. I haven't seen
any.

On Fri, 27 Jun 2008 06:31:22 -0700 (PDT), MIG
wrote:

I've noticed recently that the frighteningly wobbly stretch of DLR
from Mudchute to Crossharbour now seems to have a speed restriction,
although it still manages to wobble a surprising amount at very low
speed. I wonder if an opportunity will be taken during the works that
are about to start to fix whatever the problem is, or whether the
whole line will progressively be progressively reduced to a crawl.

Also, I wonder if this new speed restriction is due to the wobbling
actually having been unsafe, or was just to stop complaints from
alarmed passengers.

Is it not to do with the fact that works are underway at Mudchute to
create a longer siding? It's fairly typical practice to reduce train
speeds near work sites.

The other interesting point about this stretch of track is that it is
where the boundary point between the core network and the Lewisham
extension concessionaire area is. I wonder if something daft has
happened in terms of the track structure / design or the maintenance
process?

--
Paul C


Admits to working for London Underground!

On Jun 27, 6:50*pm, Paul Corfield wrote:
On Fri, 27 Jun 2008 06:31:22 -0700 (PDT), MIG

wrote:
I've noticed recently that the frighteningly wobbly stretch of DLR
from Mudchute to Crossharbour now seems to have a speed restriction,
although it still manages to wobble a surprising amount at very low
speed. *I wonder if an opportunity will be taken during the works that
are about to start to fix whatever the problem is, or whether the
whole line will progressively be progressively reduced to a crawl.

Also, I wonder if this new speed restriction is due to the wobbling
actually having been unsafe, or was just to stop complaints from
alarmed passengers.

Is it not to do with the fact that works are underway at Mudchute to
create a longer siding? *It's fairly typical practice to reduce train
speeds near work sites.

Not sure about that. It must have been a work site while they were
removing the siding, but that was going on for a long time before the
current speed restriction.

However, the nature of the work has changed now that they are
installing the new platform (and extension presumably), so there might
be an explanation involving a particular kind of work.


The other interesting point about this stretch of track is that it is
where the boundary point between the core network and the Lewisham
extension concessionaire area is. *I wonder if something daft has
happened in terms of the track structure / design or the maintenance
process?

--
Paul C

Admits to working for London Underground!

On 27 Jun, 17:11, (Neil Williams)
wrote:
On Fri, 27 Jun 2008 06:31:22 -0700 (PDT), MIG

wrote:
Also, I wonder if this new speed restriction is due to the wobbling
actually having been unsafe, or was just to stop complaints from
alarmed passengers.

Have the DLR still not worked out how to deal with that issue? I
heard it was due to the use of tram-profile wheels on mainline-profile
rails. If that is the case, can't they just progressively replace or
reprofile the wheelsets?

I heard that but I'm not convinced. You don't get the wobble on pre-
metro systems on the continent nor the manchester metrolink. I'm
pretty sure its a train design fault that no one wants to admit to. A
decent suspension and bogie system should be able to cope with hunting
especially at the pretty low speeds the DLR runs at.

B2003

On Fri, Jun 27, 2008 at 04:11:58PM +0000, Neil Williams wrote:
On Fri, 27 Jun 2008 06:31:22 -0700 (PDT), MIG
wrote:
Also, I wonder if this new speed restriction is due to the wobbling
actually having been unsafe, or was just to stop complaints from
alarmed passengers.
Have the DLR still not worked out how to deal with that issue? I
heard it was due to the use of tram-profile wheels on mainline-profile
rails. If that is the case, can't they just progressively replace or
reprofile the wheelsets?

Given that it doesn't happen elsewhere on the DLR (or not that I've
noticed anyway) then surely if that really is the problem then it's
that section of track that should be replaced, not the wheels.

--
David Cantrell | London Perl Mongers Deputy Chief Heretic

You can't judge a book by its cover, unless you're a religious nutcase

On 30 Jun, 12:34, David Cantrell wrote:
On Fri, Jun 27, 2008 at 04:11:58PM +0000, Neil Williams wrote:
On Fri, 27 Jun 2008 06:31:22 -0700 (PDT), MIG
wrote:
Also, I wonder if this new speed restriction is due to the wobbling
actually having been unsafe, or was just to stop complaints from
alarmed passengers.
Have the DLR still not worked out how to deal with that issue? I
heard it was due to the use of tram-profile wheels on mainline-profile
rails. If that is the case, can't they just progressively replace or
reprofile the wheelsets?

Given that it doesn't happen elsewhere on the DLR (or not that I've
noticed anyway) then surely if that really is the problem then it's
that section of track that should be replaced, not the wheels.

It also happens almost all the way from tower gateway to canary wharf
though when I was on the DLR a month ago I noticed the line speed
seems to have been dropped a bit since last time I was on it. Possibly
to mitigate this issue.

B2003

On 27 Jun, 17:11, (Neil Williams)
wrote:
Have the DLR still not worked out how to deal with that issue? *I
heard it was due to the use of tram-profile wheels on mainline-profile
rails. *If that is the case, can't they just progressively replace or
reprofile the wheelsets?

It's not as simple as that. Wheelsets are a compromise between those
which perform well on straight track and those which perform well on
curves. On mainline railways this balance is easier to strike because
curves are normally not particularly tight. However the DLR has some
extremely sharp curves, for example at West India Quay, hence the need
for suitable wheelsets. Obviously this balance has not yet been
perfected, but it's by no means an easy thing to do.

On Sat, 5 Jul 2008 08:14:43 -0700 (PDT), BRB Class 465
wrote:

It's not as simple as that. Wheelsets are a compromise between those
which perform well on straight track and those which perform well on
curves. On mainline railways this balance is easier to strike because
curves are normally not particularly tight. However the DLR has some
extremely sharp curves, for example at West India Quay, hence the need
for suitable wheelsets. Obviously this balance has not yet been
perfected, but it's by no means an easy thing to do.

Manchester Metrolink appears to manage it without such a ridiculously
poor ride, give or take on the sections of 50-year-old track.

Neil

--
Neil Williams
Put my first name before the at to reply.