FW: Loco Cab Safety

[Peter Donaghy <PeterDo@als.com.au>]

Aus loco discussion mailing list

Paul,

Though it's over sixteen years since I last did physics at Uni, I'll try
to explain the situation as I see it. 

Whilst the passengers in a car are protected by airbags and seatbelts,
they are also protected by the shock-absorbing crumple zones in the
engine and boot sections of the car. Consider a car hitting another car
or a tree: that's approximately one tonne coming to a fairly quick stop;
particularly with crumple zones, the structural integrity of the
passenger cocoon is normally sound. However, at high speeds or when hit
with great force, even this will collapse, and then airbags and
seatbelts will not be of any use.

With a locomotive weighing 120 tonnes, the forces in any collision are
huge - much more than with a car. Additional protection over that
provided in cars includes much heavier and thicker framework, and
upright collision posts in the ends of modern locos, along with
anti-climb strips on some. While this may help in a level crossing
accident, in which the lighter road vehicle bears the brunt of the
collision, it will only provide partial protection when two locos
collide, particularly with heavy wagons behind them. Even thick steel
has its limits for how much force it can bear before bending. Short of
making locos from very thick steel plate, which would throw their axle
loading out to unworkable levels, I don't think much more can be done.
Since there's nothing much larger roaming freely across the landscape
than a loco, additional protection would only be viewed as overkill and
unnecessary, anyway. Seatbelts and airbags would help in a sudden stop,
but sudden stops for a loco generally only happen when something hard or
heavy enough is hit that would severely damage the cab anyway.

Comparison of the forces as a function of masses involved can be gained
from observing pictures of loco-car, loco-heavy truck, and loco-loco
collisions. In each case, resulting damage to the loco is more severe,
but relatively less severe to the hittee, for want of a better (real)
word. A petrolhead analogy is that a Toorak Tractor will always do more
damage to an everyday car than the car will do to the 4WD.

That's my story, anyway, and I'm sticking with it (or should that be
stuck with it?)!!! I hope it makes sense, and helps.

-----Original Message-----
From: Paul Hogan [mailto:pghogan@bigpond.com] 
Sent: Monday, 29 November 1999 11:21 PM
To: Ausloco
Subject: Loco Cab Safety


Aus loco discussion mailing list 
Good Evening,
I posed this question on an aus.rail thread, where no doubt it will get
a suitably rabid response!
In the Ararat collision, the front cabs of the two G class locked
together, meaning the anti-climbing strips did their job, and it was the
respective back cabs of each loco which were demolished by the loaded
wagons behind them.
Whilst the forces involved in a head-on at 50km/h are considerable, the
front cabs appear to be survivable. But it poses a question, what
additional safety protection do the crew have?
Is it fanciful to suggest that seatbelts and airbags, as installed in
motor vehicles would reduce injuries, even in say a head-on level
crossing smash with a large vehicle? No doubt rail administrations would
be uncomfortable with the concept - it is tandamount to admitting that
collisions can happen, when they would prefer us to believe that they
don't.
Any ideas or comments ?
Regards,
Paul






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