On Sat, 21 Aug 2010, Neil Williams wrote:

On Fri, 20 Aug 2010 19:46:24 +0100, Tom Anderson
wrote:

The weakness, of course, is the reservoir. If it isn't filled (eg a train
has been parked for ages), or it runs out (eg a train has parked
recently), or it leaks or is vented by mistake, you've lost your ability
to apply the brake. I don't know how this is dealt with - i would guess by
making the reservoir quite large and very reliable (and it is, after all,
just a big tank with a pipe coming out of it)

Part of it is additionally that trains tend to run with more than one
vehicle (not always, I know), and each has its own reservoir. Thus, if
in a 6-car train 2 cars lose their braking system completely, it will
still stop.

True. That doesn't help with the parking-related cases, though, where all
the cars will eventually lose all pressure.

Maybe there's a parking brake for those cases. That wouldn't have been a
lot of use in the case of the runaway grinder, of course.

Exactly. The sort of thing that in nuclear power engineering is called a
scram - a last-ditch, absolutely foolproof, not necessarily recoverable,
way of stopping a runaway.

On the railway that's often handled off the vehicle by a set of catch
points, which are basically points that deliberately derail the train
and send it off into a sand drag or something. Not that useful on
LUL, though.

For engineering work, derailer ramps are often fitted at each end to
catch any runaway and stop it by sending it off the track in the same
sort of way.

Ah, ingenious.

Maybe that's something LUL should look at doing - though if it had
happened here the two engineering staff on the runaway might well not
have survived the experience.

A sobering thought.

tom

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