Re: More from the Terrorgraph

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

Ross (Goldie) Goldspink <goldicom@powerup.com.au> wrote in message
3860a697@grissom">news:3860a697@grissom...

> How short does a short circuit have to be to activate the track detection?

> Or to put it another way, regardless of profile, how much resistance is
> there between rail and wheel with about ten tonnes (or more) on each
wheel?

I can only comment on the first question, and then only on Victorian
practice.

To quote a piece of paper:

"Train Shunt Resistance"

"The train shunt resistance is the highest value of resistance which, when
applied across the rails at the Feed end of the track section, will cause
the track relay to open its front contacts."

"This value of resistance should be as high as possible consistent with the
stability of the track, typical values being 1 ohm to 2.5 ohms, and should
never be less than .06 ohm"

With a Jointless Track Circuit the minimum value is 0.1 ohms, and with a
High Voltage Track Circuit, it is 0.5 ohms.

These minimum values are theoretically *supposed* to be more than the
resistance of a train.

The question really should be how rusty are the rails?

Problems dropping track circuits are fairly well known (Cowan,
Sprinters...).

--
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)