Re: [NSW] Strange rails at Hurstville

["Chris Downs" <cvdowns@ozemail.com.au>]

My understanding was that the running rails used on the City Railway
contained a % manganese to improve their wear qualities, that is a harder
rail.  The down side with this alloy was relatively poor conductivity (for
signalling and return currents?) so electrically bonded standard (used)
rails were laid just inside each running line as conductors to provide the
necessary conductivity.

Some time back in the 80s (or 70s?) the manganese alloy rails were replaced
with standard rails and the extra conductors were removed.

I imagine head hardened rails would be the go now, the same improvement in
wear reduction without the decreased conductivity of the manganese rails.

Does anyone know how manganese alloy rails suited thermit welding?

What rail type is used on the Olympic Park line to produce "sharp" flanges,
or is there a lack of lubrication?

Chris

Graham Fry <fryg@sydpcug.org.au> wrote in message
3954560D.32C3@sydpcug.org.au">news:3954560D.32C3@sydpcug.org.au...
> I am not sure whether this explanation now applies. In the past when the
> city underground was built the additional rails were placed in position
> between the running tracks and electrically bonded to them. Their
> purpose was to reduce the electrical resistance for the return current
> from the train back to the supply substation. It was thought that
> without these extra rail the return current would find alternative
> parallel paths such as pipelines which would lead to rapid corrosion of
> the pipe.
> I don't know whether this theory is still accepted but it might have
> some validity in that these extra rails are where buildings are built
> over rail and without the extra earth return the building's electrical
> system could be affected by the traction system.
>
> Graham Fry