Re: Signalling queries

[hayesip@yahoo.com (signal engineer)]

> How long is a typical track circuit anyway? I would guess that it would
> have to be at least as long as the maximum distance between any two
> wheelsets on any piece of rolling stock on Australian railways, so while a
> train is passing over a track circuit, there will always be at least one
> pair of wheels occupying the circuit.....
>
Wow. I'm away from checking this NG because I'm busy helping the
signallers in Wollongong CC operate the new signalling and there's
finally heaps of relevant signalling questions which I've no time to
read or answer. Hey Tom, you'll love my job at the moment. Playing
signaller in the Control Centre. Anyway to answer your question, the
maximum length of a track circuit is dependant on ballast resistance
(normally 1.5 - 3 ohm per km) and impedance bonds. Our FS2500
Jointless Track circuits are capable of 1500m with good ballast. I've
heard Jeumont Scheider Pulse track circuits can go longer. On the
Dapto - Kiama job we ran the FS2500 to 1000m but had problems with one
1000m track (near Bombo) which worked fine until the torrential
downpour on Monday. Then it failed (see another post on the news
story). That was the straw that broke the camels back and they closed
the line again. We had to devise a quick fix before Tuesday which we
did.
 
> > No probs. There are a couple of signal engineers in here that will gladly
>  give U
> > all the information U need.
> > I only can explain the basics :)
> 
> That's okay, I only want the basics! :-) The last time I asked a signalling
> question - "What are catchpoints?" - I got deluged with a veritable tidal
> wave of incomprehensible jargon and technical nit-picking! (That's OK Ian,
> I forgive you now... :-) )...
> 
> Regards
> BT