Re: Axle Counters: wasRe: Independent Review of Rail Safety Arrangements in Australia

["Notagunzel" <notagunzel@bigfoot.com>]

John Duncan McCallum <mccallum@melbpc.org.au> wrote in message
38758EDC.67AD60BC@melbpc.org.au">news:38758EDC.67AD60BC@melbpc.org.au...
> Dave Proctor wrote:

> > Why does it have to be track-circuited? Surely a better (better only
because
> > it is cheaper and therefore stands a better chance of getting up) would
be
> > CTC via axle counters? It works successfully on the cross-country line
from
> > Unanderra to Moss Vale, as well as other places around the country, and
> > would signifigantly reduce the implementation cost.

> A question re axle counters for protecting track sections.
> Assuming that axle counters are used at stations rather than just
> between auto signals,

If you could, track circuits are preferable for short sections around
stations/over points, on account of the high cost of axle counters.  But, if
like one of the Asian resignallings Westinghouse did recently, the track
consists of 100% uninulated steel sleepers, then you have to have axle
counters in the stations.  The CTC between Rockhampton & Townsville AFAIK
uses track circuits at the loops/stations, and Axle counters for the long
sections in between locations.

> how does the system cope with shunting moves? I would assume that the
> axle counter would count each axle passing over it regardless of
direction.

Each Counting point actually has 2 sets of coils, placed at the correct
spacing gives the Evaluator the ability to determine the direction the axle
is passing.  Even if an axle stops directly on top, and then sets back, the
axle counter sorts it all out.  But it does mean, when setting up the Axle
Counters, the Evaluator has to be told (by strapping IIRC) which counting
point(s) count IN on the 'down', and which counting points count OUT on the
'down', and so on.  An Axle Counter section can have more than 2 counting
points, eg if it was placed over a turnout (in which case it would have 3
counting points).

> Therefore, it would get very mixed up if a reverse direction move took
place. Is this the
> case?

Relax - shunting isn't a problem.  If it was, axle counters wouldn't be used
in critical applications.

--
Mr Notagunzel.
Rail Transportation Connoisseur
notagunzel@bigfoot.com
(Regrets to announce there will be no further moves at
http://www.geocities.com/nota_gunzel
until further notice is issued from this office)