I have noticed on sections of the Docklands track part of it moves away
at an angle and is cut off but another section continues it. Is there
any reason why the track is not continious ?

wrote:
I have noticed on sections of the Docklands track part of it moves away
at an angle and is cut off but another section continues it. Is there
any reason why the track is not continious ?

If you mean what I think you do, it's a gap for the track to expand and
contract as it heats and cools.

Neil

Neil Williams wrote:
wrote:
I have noticed on sections of the Docklands track part of it moves away
at an angle and is cut off but another section continues it. Is there
any reason why the track is not continious ?

If you mean what I think you do, it's a gap for the track to expand and
contract as it heats and cools.

Neil

Thanks for the reply. I have not noticed this on Underground or
mainline tracks - so is there a reason this apply to Docklands only ?

wrote:

Thanks for the reply. I have not noticed this on Underground or
mainline tracks - so is there a reason this apply to Docklands only ?

You do get them on the mainline, though not always in the same form.
LUL doesn't need them on most of its tracks as they are mainly jointed
rail, and jointed rail has a gap between each section of rail anyway
(which gives rise to the clickety-clack sound when travelling over it),
so it doesn't need them.

Neil

On 16 Sep 2006 13:29:04 -0700, wrote:


Neil Williams wrote:
wrote:
I have noticed on sections of the Docklands track part of it moves away
at an angle and is cut off but another section continues it. Is there
any reason why the track is not continious ?

If you mean what I think you do, it's a gap for the track to expand and
contract as it heats and cools.

Neil

Thanks for the reply. I have not noticed this on Underground or
mainline tracks - so is there a reason this apply to Docklands only ?

I'm not a track expert but a fair chunk of DLR is on metal viaduct so
you have to have these sorts of measures or else the track base moves
and the track doesn't with interesting results. Such expansion joints
will exist on LU and NR but they are much harder to spot as you can't
get a front seat ride and the stations are not so close to big bits of
infrastructure. Exactly the same applies to big road bridges which move
in the heat.

There may also be something to do with the type of track installation as
well - ballasted vs concrete track bed - but that's getting beyond my
limited knowledge.
--
Paul C


Admits to working for London Underground!

Paul Corfield wrote:
There may also be something to do with the type of track installation as
well - ballasted vs concrete track bed - but that's getting beyond my
limited knowledge.

The latter type is more commonly referred to as "slab track", as that
is what it literally is: a slab of concrete with rails on it.

The actual track feature itself is referred to as an "expansion
switch", and does what it says on the tin: allows the rails to expand
and contract as they heat and cool. They are quite commonly used in
areas with unstressed welded rail (UWR) or long welded rail (LWR) - if
I remember correctly, continuous welded rail (CWR) only uses them in
areas where pointwork is present; the former two generally use them in
various spots when needed.

The ones on the DLR come in two varieties: the normal "slot" variety,
where the rails are cut into a yin/yang-type slot arrangement and
anchored together, and the "slip" variety, where one rail curves
outward to gauge and another is trimmed to butt up against it snugly
like a point blade.

Neil Williams wrote:

wrote:

Thanks for the reply. I have not noticed this on Underground or
mainline tracks - so is there a reason this apply to Docklands only ?

You do get them on the mainline, though not always in the same form.
LUL doesn't need them on most of its tracks as they are mainly jointed
rail, and jointed rail has a gap between each section of rail anyway
(which gives rise to the clickety-clack sound when travelling over it),
so it doesn't need them.

Neil

I'm a bit out of my depth here as I don't really appreciate the
difference between unstressed welded rail (UWR), long welded rail (LWR)
and continuous welded rail (CWR), but it seems to me that where there
has been recent track replacement on the Underground welded rail as
opposed to jointed rail has been used, resulting in a smoother ride and
no-clickety-clack sound.