|
Hi Ian Well here is a cautionary, non-software, tale about rail. My
brother is a mechanical engineer and he did a sandwich course, and the year he
spend in industry as part of it was at British Rail Engineering in Derby. He told me that the Potters Bar rail crash was inevitable once
the railways were split up into parts. Here is why. Hard metal on hard metal is not a good combination; it
eventually results in stress and fracturing. Thus the safe combination is hard
metal and soft metal. As it is easier to replace train wheels than rails, the
rails are made of hard metal and the train and carriage wheels of soft metal.
This was fine, well known, and controlled when one company controlled
everything. Then we had privatisation. Rolling stock was in a different
company to the track. Staff came and went and the knowledge quickly
disappeared. After a few years, the rolling stock company noticed that they
were continually replacing wheels and looked for a solution. Naturally the
solution was to use harder wheels. And this gave us the critical condition of hard wheels and hard
track; train wheels are actually slightly tapered on the flanges in order to
steer themselves round corners, but can also set up slight oscillating motions
on bends, resulting in the flanges repeatedly making contact with the rails and
effectively giving them a hammer blow. The moral of the story is that when you break up a system (track
and rolling stock) into constituent parts and separate companies, each will
optimise its own subsystem, both in engineering and cost/profit terms and
no-one looks after the bigger systems picture. I bet the government that privatised the railways did not do a
risk analysis on the loss of implicit systems knowledge that splitting a system
up would cause. Tony Gore email tony@xxxxxxxxxxxx From: Ian East
[mailto:ian.east@xxxxxxxxxxxxxxxxxxxxxxxxx] Hi Tony Thanks for this. Very worrying, given I drove my
family around Florida recently in a Prius! It's interesting how simple basics can get drowned out.
I suppose it happened to NASA with Challenger. One of the things that attracts me to rail, over road,
(forthcoming book The Cost of the Car) is the engineering heritage.
Safety engineering began with rail, and signalling makes a nice student
exercise in sequential system design, and, more recently, in formal analysis. I worry whether the same art is being applied to car design.
Of course, it is entirely absent in road design, which is
inherently lethal anyway, as the annual carnage shows. And, of course, it is absent in the training of most
'software engineers', as is engineering per se. I too began with µprocessor programming in assembly
language, and believe as much has been lost as gained in the use of 'standard'
HLLs. I have had unending difficulty adapting to universal hacking
– the lack of any real specification, design, or analysis, with software. I'm trying to assemble a series of texts called Electronics,
Systems, and Programming (http://www.openchannelpublishing.com/esp.html) that
combine a more formal approach to software, and would welcome a proposal,
particularly wrt embedded concurrent/reactive systems. (You get £2.50
back a book, instead of 80p at most, and a lower selling price, hence more
sales. And yes, that is realistic, especially with e-books on the rise.) The CPA community is still badly in need of books that
reflect its idea and ideals. The right people are always too busy, I
guess. Best Ian On 31 Mar 2010, at 03:04, Tony Gore wrote:
Hi Ian See this from an engineer who used to work at Ford in around the same era
that I was working in automotive. The key phrase he uses is Although not common over here in the UK because of our penchant
for stick shift (manual gearboxes), most cars in the US have automatic
gearboxes and cruise control. One of the standard signals to cruise control is
the brake signal to disengage it. Tony Gore email tony@xxxxxxxxxxxx Ian East Open Channel Publishing Ltd. (Reg. in England, Company Number 6818450) |