Re: [NSW] Cityrail Millennium Train

["Al" <alpout@optusnet.com.au>]

Geoff Lillico <glillic@msn.com.au> wrote in message
JApl6.1603$v5.5993@newsfeeds.bigpond.com">news:JApl6.1603$v5.5993@newsfeeds.bigpond.com...
> Yes there are standards in place.
>
> I would hazard a guess and say that not one correspondant to this thread is
> a structural engineer and nor am I, but unless you have substantiated
> evidence to the contrary, I believe it is unwise to suggest that these new
> trains do NOT comply to the standards set for the Bureau of Rail Safety of
> D.O.T. or those of the Australian Standards Authority.
>

You could be right there, but anyway it's not a structural engineer you're
after, but a mechanical, which I'm starting my final year in on Monday, so
here's my probably totally flawed thoughts about it.  Don't take it as gospel,
but rather as a guide to what the designers are considering.

I also work for a company which makes fire trucks, and has done work for
Goninan on train bodies, bogies etc.  Actually, half the people on the floor
there worked for Goninans when they were making the Tangaras and NRs, but
that's another story.

One thing to consider is that the trains could be built as a monocoque or
unitary construction, similar to a passenger car such as a Commodore or
Falcon.  They do not have a fixed chassis such as a truck, but rather the load
is taken by the panels all over the vehicle.  This could explain why it looks
flimsy, where it could actually have a very strong rigidity (essentially one
big box section).  Advantages to this are light weight and high strength,
which is one reason why most passenger cars are made this way now.  It also
gives better energy absorption in a crash, which is why newer cars are more
survivable than older ones in crashes.

Also, the material used can affect the standards.  Judging by the colour of
the metal in the photos, it's either aluminium or steel sheeting, probably
aluminium, cause it can be made extremely strong but remains lightweight, with
a steel framework as a cheap, but effective backbone.  People, by and large,
aren't all that heavy (2000 people on an 8-car train ~ approx 180 - 200 tonnes
to give a comparison to freight trains), so most of the structural strength is
required for the shock loadings that the trains experience, such as going over
gaps in the track at points, wind blast from passing trains at high speed, and
full throttle-full brake scenarios, such as an uphill into a station.

Finally, the type of accident or load that you consider can make the shape
substantially different to what you expect.  Passenger cars are designed for
accidents coming into the car from the plane of the road (ie front and sides).
What are the kinds of accidents a train can expect?  You could possibly design
the cab as a crumple zone, on the assumption the driver can get out in time
(re Glenbrook).  This also works both ways for front and rear end collisions.
You don't have to worry about T-bones, but rolling is another possibility,
where you don't want the structure to collapse onto people inside it, which is
where a monocoque has another advantage.

Hope that helps,

Al