On Thu, 19 Aug 2010, Paul Scott wrote:

"Tom Anderson" wrote in message
rth.li...
On Wed, 18 Aug 2010, martin wrote:

Something that I don't think had previously been released:

The crew of the grinding unit, who had no means of re-applying the
brake, jumped off the unit as it passed through Highgate station.

J. Jesus Krispy Kreme Christ on a Borisbike!

'no means of re-applying the brake' is a rather frightening phrase. I
would hope trains were not constructed in such a way that this could
ever be the case, but they are evidently not. Indeed, AIUI, air brakes
work by having a reservoir on each car that drives brake application
when the pressure in the brake pipe drops, but if there is no
compressor in action, as here, then this reservoir will be empty, and
there will be no pressure to apply the brakes even in the absence of
brake pipe pressure. Seems like a bit of a loophole in the fail-safety,
but i'm not sure what else you can do. Presumably a spring does not
supply enough force to apply the brakes!

Why assume it even has a conventional railway air brake system. We're talking
about a large item of yellow plant brought in to the system that is designed
to work independently?

I thought i'd read somewhere that it was a converted tube train, which
would suggest that it might have retained conventional brakes. However, i
now think i imagined that, and that it was this newish Schweerbau machine:

http://www.rtmjobs.com/rail-news/art...on-uk-railway/

Now, the RAIB press report talks about, at first, a train "designed for
re-profiling worn rails", but then about a "grinding unit", whereas this
is a milling machine, which is subtly different. However, the difference
is subtle, so it might get called a grinding machine by mistake, and i
have also seen it asserted that it is a combined grinding and milling
machine, so it might even be correct.

So, we know that the unit involved in the incident was (a) a rail
re-profiler of some sort, (b) operated by Tube Lines, (c) diesel powered,
(d) working on the Northern line, (e) similar-looking to a passenger tube
train, and all of those fit the train described in that article.

Reports earlier that it was an 'engineering train' and pictures of
normal LU battery locos aren't necessarily helping as far as I can see.
It's just as possible that it has never been designed to form part of a
'train' as everyone is assuming...

That is true.

tom

--
i know how they do it i think they just put on a song then the mario thing
plays it i think im not sure though im still looking on it -- darkcat102