
APT tilting train: A laughing stock that changed the world - darrhiggs
http://www.bbc.co.uk/news/magazine-35061511
======
hristov
What this article left unsaid was that the project was started before the time
of Margaret Thatcher but ended in production during Margaret Thatcher's
premiership. Margaret Thatcher is well known to oppose the public rails and
all other kinds of public works. It would have been very easy and popular then
to vilify any large public project as a boondoggle.

The result is that the English still use trains (because their large
population requires them) but get to import their trains from France, Italy
and Japan.

~~~
keithpeter
Rail privatisation was a John Major initiative, not Thatcher.

Quote from OP

 _" The Italian firm Fiat bought the patents for the APT's tilting technology
and used it to help develop its Pendolino trains, now manufactured by the
French multinational Alstom."_

Export of technological know-how is something of a UK speciality (ARM chips,
fluidised bed furnaces for efficient combustion of coal &c).

 _" A six-car APT, including a driving trailer and buffet carriage, is in
place at Crewe Heritage Centre. It's clearly visible to passengers passing by
on the adjacent West Coast Main Line where it ran for a few months."_

I go through Crew on a regular basis, and the APT is easily seen from the
track. Along with the rather impressive dents along the side of the coaches
resulting from a failure of the tilting mechanism.

~~~
bbrks
Small world :) I live there and got to go on board the APT with my Grandad
when I was younger, as well as run the model railway at the Heritage Centre
with him.

~~~
keithpeter
Excellent. Now this is really a long shot - do you know of the llama farm (or
farm keeping about a dozen llamas) that is one the way into Crewe from
Stafford? They always surprise me on the way up to Liverpool...

------
alblue
The APT was rushed into service before it was ready and suffered from initial
glitches which ultimately led to bad press killing it off.

On the other hand I use the descendent of the APT (the Virgin Pendelino) to
commute into work and back. The tilting mechanism is really sublime and
incredibly comfortable. It was ahead of its time.

~~~
moron4hire
I'm sorry, I hate to be a pain, but it's a pet peeve of mine. They weren't
"glitches". They were defects.

Glitches are errors that happen outside of the design parameters of the
system. For example, when you touch the antennae on an AM radio and you hear a
pop or buzz from your own electrical field in the radio.

Defects are errors that occur within the design parameters. So a train that
can't handle some snow on the tracks, or a national health insurance
enrollment site that falls over after only a few users show up, those are
defects.

Bugs are a type of insect. Using the word "bug" to describe a defect implies
that the "bug" showed up, an external factor that got in and gummed up the
works or something. But that doesn't happen in software. The defects were
always there.

I think it's important to use the terminology correctly and make a habit of
using it correctly because I think it puts the emphasis on the fact that we
create the defects, and the defects were always there, they didn't just
develop, they just had to be found. That's also why I don't like the term
"software maintenance". When you have to take a site down for several hours
every 3 months for "routine database maintenance", that's a defect in design,
not just "changing the oil".

It was our fault. Calling them "bugs" or "glitches" or "maintenance issues"
diminishes that.

~~~
alblue
The reason "bug" is used is because the first computers were programmed
through hard wiring and mechanical switches, and they were actually insects
that were present. This is from Grace Hopper in 1947:

[http://www.computerhistory.org/tdih/September/9/](http://www.computerhistory.org/tdih/September/9/)

Convention has stuck which is why we have software debuggers, and the word bug
in computer science has come to mean any unintended result, not just the
presence of insect wildlife.

(I myself debugged a floppy drive in '87 which had an earwig stuck behind the
read head backstop resulting in the read head being misaligned to the sectors)

~~~
jcl
Use of "bug" to mean "defect" goes back a lot further than the computer age:

[http://www.etymonline.com/index.php?term=bug&allowed_in_fram...](http://www.etymonline.com/index.php?term=bug&allowed_in_frame=0)

At the time of Grace Hopper, the term was used in engineering contexts to
refer to defects in general, quite unrelated to insects. Per your link, that's
_why_ she wrote "first actual case of a bug being found" \-- it was amusing
and unusual to find a bug (defect) caused by a bug (insect). If this were not
the case, there would be no need to use the words "first" or "actual", or even
note the event.

------
hyperpallium
\tangent another solution is camber or cant, where the outer rail is higher,
banking into the curve, as an aeroplane turns.

A problem is the beginning of a curve. If the straight simply becomes an arc
of a circle, the lateral centrifugal force (see xkcd) goes instantaneously
from 0 to maximum. One might think an Euler spiral, whose rate of turn
increases linearly, would fix this; but now, although the lateral force
increases linearly, the onset of change in force is instantaneous, and is felt
as a jolt by passengers. Apparently it is possible to create turns giving a
smooth ride, but requires sophisticated dynamic models that are presently
beyond me.

I started making a game with very smoothly transitioning banked turns, but
it's a lot more complex than I thought! (Other games use tilting-like
mechanisms, such as suspension, and the natural averaging over the four
contact points of a car, but that's not applicable to what I want to do). If
anyone has some pointers, I'd love to hear them!

P.S. Re trains: Of course, another problem is that banked turns are "static",
the same for all trains regardless of velocity; whereas the "dynamic" tilting
can adjust to current velocity, on-the-fly (in addition to smoothing out
transitions). The rail camber/cant can remain suited to the typical velocity
of non-tilting trains using the same track.

~~~
nightcracker
> the onset of change in force is instantaneous, and is felt as a jolt by
> passengers

An instantaneous change of force (and thus acceleration) create a jolt, I
understand that. But taking the derivative again - 'the onset of change in
force' \- I don't see how that is felt as a jolt.

~~~
hyperpallium
I thought so too; but that's what I read, as what happens when Euler curves
were used in practice (which they were). Unfortunately, I didn't get to the
point of trying it out for myself in my game.

[BTW: Like a bob-sled track, I did find that cross-sections that were sine
waves or quadratic did feel strikingly smooth - those being smooth, with
smooth deviratives, smooth derivatives of derivatives, and so on.]

If you imagine an x-y graph of force over time for a track that went like
(start in a straight, an Euler curve to begin the turn, some time in an
circular arc, and a reverse Euler to straighten it, end in a straight), the
graph would be (level, slope up, level, slope down, level):

    
    
        _
      _/ \_

Apparently, humans are sensitive to the change between levels and linear
slopes. Lines are uncommon in nature [though gravity is constant
acceleration...?]. Perhaps related to inverse kinematics in limb movement?
"Jolt" may be the wrong description.

------
radiowave
To some extent the tilting was a side-show. It was the hydrokinetic brakes
which really allowed the train to travel faster while still meeting the
stopping distances necessary for the conventional signalling used on the line.

~~~
ColinWright
While the brakes are important, the tilting is most definitely not a side-
show. I've been on a train when the tilting is not working, and the lateral
forces are significant. They make it unpleasant to ride, and impossible to
work. Certainly drinking coffee is no joke.

~~~
radiowave
I stand (or preferably, sit) corrected.

------
RickHull
Can't you just camber the track rather than make the trains actively tilt? I
suppose the camber could be problematic at very slow speeds.

~~~
nissehulth
The idea was that it is much cheaper to change the trains than to rebuild
existing tracks.

------
Gibbon1
>In its brief life the APT, with its futuristic sloped front, was vilified as
a waste of money - £47m in total - and mocked by the press.

When I read stuff like this, I want to kick people.

~~~
yellowstoneback
You advocate violence against people who don't agree with your views on public
spending?

~~~
Gibbon1
If I was advocating violence, I would have said so. That said I have a deep
frustration for people with not only a negative can't do attitude. But more
obsessively look for reasons to say I told you so. There are vast numbers of
people like this and it gets worse decade by decade. And these people do vast
damage to society.

And also spending £47m for heavy industry technology project is what I would
call cheap. And except for the rare exceptions where the engineers nail the
design all of these are janky initially. Which of course provides a lot of cud
for the naysayers.

~~~
eru
You'd have to correct the 47m GBP for nominal GPD/capita growth to get a
clearer sense.

Using the data from [http://www.theguardian.com/news/datablog/2009/nov/25/gdp-
uk-...](http://www.theguardian.com/news/datablog/2009/nov/25/gdp-
uk-1948-growth-economy) and picking 1975 nominal GPD (28,742 mGBP) vs 2013
nominal GDP (399,834 mGDP), the 47 mGBP in 1975 become 654 mGBP in 2013.

------
slashink
The Swedish developed train X2, launched 1990 in Sweden as X2000 is still in
service and is using tilting technology to increase speed. It's been running
the most popular commuter line (Stockholm <-> Gothenburg) for 25 years at 200
km/h.
[https://en.m.wikipedia.org/wiki/X_2000](https://en.m.wikipedia.org/wiki/X_2000)

Sadly it's replacements focuses on efficient brakes over tilting.

------
protomyth
Move fast and break stuff doesn't work for infrastructure projects. If you
cannot get good PR on day 1 then delay until you can.

