Re: Beresfield Accident Findings

[chris@transdata.co.nz (Chris Grace)]

Tezza (tezza@atinet.com.au) wrote:

: Eddie Oliver wrote in message <354BB0CF.7CB0@efs.mq.edu.au>...
: >Tezza wrote:
: >> Why would locos be hitting pieces of coal? It's actually carried in the
: >> trucks behind the locos, not alongside the track. And minimal damage
: caused
: >> by emergency braking (I've never seen any), would be far better than a
: >> freight train running into a passenger train.
: >Are you serious?


: >Are you trying to tell us that coal is so nicely confined to the hoppers
: that none ever falls out?


: It's fairly rare, there's more chance of it coming out of the bottom than
: the top. All that'll come off the top is virtually dust, as the coal is
: crushed, not in big lumps. Anything that did fall out would be way below the
: level of a trip. Landslides and rock falls would be a bigger worry on the
: Illawarra and I've never heard of any of them tripping a train.

I'm pretty sure that the trainstops used in NSW are the same ones used on the
London Underground, they are pretty standard Westinghouse gear.

If you look at the history of train protection gear there has been a consistent
move away from using equipment which requires contact with the train. Hence the
GWR ATC equipment in the UK was replaced with AWS (Which was derived from the
Strowger-Hudd system) which was purely inductive rather than requiring contact
with a ramp as the GWR system did.

It has consistently been stated that the trainstops as used on LUL and parts of
NSW railways are not considered usable at high speeds (In this case so far as I
know 'high speed' means over around 35mph). Previous posters have described
tripping when passing speed control trainstops at too high a speed, then
resetting the trip once the train has stopped. If the train was moving too fast
to begin with, it is possible that either the trainstop or the trip would be damaged
by the impact, and this would mean that the rear of the train that had just
tripped would be unprotected. Not only that, but the train which had tripped (and
potentially destroyed its tripcock) would then have to run with it isolated, and
consequently with no protection at all. which defeats the purpose of having it in
the first place.

The other problem is that trainstops are electro-pneumatic. This isn't a problem
in London as the signalling and points are (or were) also electropneumatic and
consequently air supplies were available to operate them. I don't know if the
City Underground in Sydney is all electropneumatic or not, but even if it isn't
we're talking about a pretty restricted geographical area, and in any case
traction current could presumably be used to drive compressors. I
could imagine problems getting compressed air to every signal in
non-electrified or country areas.

And, of course, trainstops are another maintenance problem. I have no idea how
they would fare in the open air in the country - they would obviously be subject
to vandalism, and unlike a signal, this wouldn't be immediately obvious to
drivers, so they'd have to be inspected frequently.

It was often suggested that since the London Underground system worked so well it
should be extended to the whole of British Railways. The arguments listed above
are why this did not happen.
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