Re: Telegraph: ?30bn 500km/h rail link proposed

No indeed, nothing new.

However, if I were a Government willing to spend a very large sum on a
new north - south rail link, here are a few reasons why Transrapid
doesn't make sense in my opinion:

1. Incompatibility

It is not compatible with the existing railway infrastructure and thus
to serve any major conurbation you have to build new infrastructure as
well, instead of being able to use the existing "classic"
infrastructure to run into existing railheads that already well
connected to their local train and bus services. You don't have the
choice to rereoute trains that already serve major conurbations onto
portions of the high speed route, thus freeing space for other traffic
and accellerating their services.

2. Costs

The Germans have already concluded that the cost:benefit ratio of a
shorter line (Hamburg to Berlin) showed a negative return, i.e. its
costs were always going to exceed its benefits. Apart from the CTRL, no
UK government has ever sanctioned such a large scheme with such a
dubious return.

Only one system has been sold and then on an uncommercial basis to link
Shanghai airport to Shanghai as a technology demonstrator. When asked
if they would like more, E Asia as a whole said something along the
lines of "no thanks, why should we pay a large sum to you when we can
achieve say 80% of the benefits for 40% of the costs using largely our
own resources?"

3. Optimisation of capacity

Because of the constraints outlined in section 1 (above) regarding the
inability to utilise the line part of the time for existing services
(as the French LGVs and German ICE routes do), there would remain a
substantial burden of IC services having to serve population centres
which currently enjoy them, but wouldn't be served by the new
(incompatible) system. Thus the amount of paths or slots available to
be utilised on the old network would not substantially change and thus
space to grow freight services would not be available.

4. Environmental impact and energy usage

Now, as readers of my previous pieces may have noticed, I'm no tree
hugger, but I don't believe this system is as green as the promoters
wish us to think.

The system relies on being elevated along the whole route. Concrete is
very energy intensive to produce and you cannot use large steel
structures on a Maglev system due to induced currents. Also, tunnels
are expensive because they require to be very large to accommodate the
support system (at reduced height) and to ensure that aerodynamic
effects can be controlled. For example, if you don't want the
aerodynamic losses to significantly increase due to the loose piston in
a cylinder effect, the area of the tunnel has to be some 40% bigger at
500km/h than the vehicle passing through it.

Because the vehicle isn't articulated and the speeds at which it can
travel, curvature will have to be carefully controlled with cant to
ensure a decent ride quality. No-one's yet done a tilting MagLev to
enable curvature radius to be tightened that I know of.

MagLev turnouts are possible, but they are horrendously costly. The
ones being considered by TransRapid use a sliding sector plate, like a
traverser hinged at one end and are only suitable for very slow speed
use. So forget a system which branches off to serve another conurbation
along the route, it would slow the system down too much, probably to
the point where a 300km/h conventional line could compete.

So the only practical solution to serve multiple destinations would
require the building of a number of parallel lines, so the land take is
going to be fairly large.

This is all important, but small beer when compared to the energy
hoorors: Let's bear in mind that the general rolling resistance fomula
is a+bv+cv^2, where:

a is the static friction in bearings
b is the rotational inertia of the wheelsets, motors and all other
rotating parts
c is the aerodynamic losses
v is the velocity in metres per second

This has to be modified to cope with the realities of magnetic
levitation, where there is no static friction and where there are no
rotating parts. Hooray the unwise (governments) usually shout at this
point and someone cracks a joke along the lines of "damn it my man,
you've nearly achieved perpetual motion" However, the aerodynamic
losses are the most significant part of the story because they increase
in square proportion to the speed.

An example, at about 160km/h the aerodyanmic losses of an HST represent
over 85% of the power at the rail.

Note my comparison with an HST becasue I have deliberately chosen that
as a comparator and it will be important later.

MagLev has another hidden component to its rolling resistance formula,
that of the power required to lift the body and get it gliding along
that near frictionless surface of magnetic flux. Ideally you want to
raise the load as little as possible becase in an air gap the flux
decreases in proportion to distance. Because this is a system that has
to be built economically and lab grade tolerances can't be replicated
on a large scale and becase your structures may move with the ground
over time, the tolerances for a production scheme have to be somewhat
larger than would have desired them to be, say about 4cm. Thus for a
288 tonne TransRapid vehicle to be levitated would take 113kW without
allowing for losses. As the losses in the air gap would be considerable
as would the switching losses in the converters, allow for 40%
efficciency, thus the lifting energy would be in the order of 250kW

Now, the TransRapid vehicle as conceived is lightweight, short and wide
when compared to a conventional train. Remember that the losses are
mainly aerodynamic at speed, you would want to minimise the drag of
your vehicle wouldn't you? So why is it wide and short, both of which
increase aerodynamic drag? Well, no-one is willing to tell me, but I
have a couple of theories:

a) It has to be wide to ensure that the roll stability of the vehicle
is going to offer a decent ride comfort without the expense of more
lifting power

b) Short, becase articulation for MagLevs hasn't been done yet and if
the vehicle was long it would be heavier (requiring more lifting power)
and would require larger radius curves, increasing the cost of
construction.

Item A makes the frontal area offered by the train larger, making the
area for windage to act on larger, hence increasing aerodynamic drag.

Item B makes the control of vortices in the wake of the vehicle more
difficult becase the air is in non laminar conditions after being
displaced from the front of the vehicle. Ideally you want to make the
tail of a vehicle about 1.5 times longer than the nose (Think V2
rocket, also invented by the Germans) to establish the optimim air flow
over the tail to reduce drag.

But that is difficult to achieve with any bi-directional vehicle Maglev
or Conventional. However, where an HST style train scores is that
whilst the long section of slab sided vehicles does little to actively
return laminar flow conditions to the airflow, it is achieved by
natural decay of the turbulent flow anlong the train length, thus long,
thin trains are more aerodynamic than short fat ones are for a given
frontal area and nose shape.

Let's do some basic maths on a fictional route of 600km. Route A is a
TGV style system, operated by TGV Reseau sets (because I have some data
for them) with a maximum speed of 330km/h.

Route B is the same route, made up of a TransRapid vehcile with a
maximum speed of 500km/h.

Allowing for acelleration and decelleration, the non stop journey time
for Route A is 2 hours 15 minutes. For route B is 1 hour 20 minutes.

The energy required for Route A's train to traverse the section is
20.1MW/hr

The energy required for Route B's train to traverse the section is
36.6MW/hr without allowing for the less aerodynamic form of the
TransRapid vehicle - because the info isn't available to me. It does
include an estimate of the required lifting power.

So even though the TransRapid vehicle only takes a little over half the
time to reach its destination, it takes some 1.8 times the energy of
the best steel wheel on steel rail train to shift roughly the same
numbers of people over the same distance. If the vehicle design does
not significantly evolve, the energy costs per seat start to look poor
when compared to short haul airliners or TGV type trains, all in an age
where energy conservation is supposedly being seriously considered by
governments.

I cannot speak on the issues of noise and construction nuisance, but I
would image the latter to be on a par with open route construction of
an LGV.

5. Summary

TransRapid is a superficially attractive idea if you have no
established high speed ground transport system and want one to provide
point to point connections. It would help if either the land you are
building on is unpopulated or your populated land doesn't mind being
redeveloped (like the "you have no choice" type of governments which
exist around the world) and you don't mind the fact that you are going
to expend 1.8 times the amount of energy transporting folk around at
high speeds than if you have built a decent TGV or ICE style
conventional railway. It is also difficult to extend other than
lengthwise becuase of junction design, so to serve multiple
destinations, requires multiple routes which requires more land.

If you have an established railway and an established population,
TransRapid is not attractive. It's incompatible with your existing
system so can't be used to accellerate particular sectors of traffic
and free up linespace on the conventional network. It also requires you
to build new stations some way from where you live (parkway style)
which are not interconnected with the existing networks and patronage
then suffers (This has happened at SNCF's Haute Picardie and Avignon
stations where patronage has never reached the most pessimistic of
predictions (see Today's Railways magazine of Nov 2005 for the full
story))

For the convenience of competing with the airlines, you actually use up
more energy than for a 737 over the same route and 1.8 times more
energy than a TGV style line which (if correctly designed) allows you
to serve existing transport hubs, accellerate certain sectors, free up
space on your existing network and integrate with it.

Let's face it, if the German Government had its serious reservations on
a route within Germany that was substantially flat (in comparison to
the proposed routes in the UK) and also in comparison to the UK,
sparsely populated AND if a German consortium of German companies
including German Industrial Conglomerates and German Bankers couldn't
flog the system to the Germans, it is my belief that it is inherently
flawed.

Richard

.

Relevant Pages

  • Re: Stupid "free energy" idea
    ... use up in require additional energy to the truck. ... Actually it is impossible to generate more power than you use. ... as by utilizing vehicle traffic on roadways. ... Energy sources useful for the generation of electricity include wind, ...
    (rec.martial-arts)
  • Re: Telegraph: ?30bn 500km/h rail link proposed
    ... > connected to their local train and bus services. ... Germany still hasn't built anything on that route and in many peoples' ... Go to the Transrapid site and read their technical ... > Because the vehicle isn't articulated and the speeds at which it can ...
    (uk.railway)
  • Re: London Underground puzzle
    ... of the train working) he would have waited for another train if the ... In principle, a nice puzzle, but problematic in another way: the route ... Well, which letters are ... Bakerloo to the parallel Jubilee platform at Baker Street. ...
    (rec.puzzles)
  • Re: Getting from Heathrow airport to Bayswater inn hotel by tube.
    ... How can I tell by looking at the train what line this is? ... So I figured I can take a tube. ... http://journeyplanner.tfl.gov.uk suggested this route (I selected ... Earl's Court Underground Station ...
    (uk.transport.london)
  • Re: Mobile S-Rotor!
    ... > When you talk about attaching a wind energy device to a vehicle, ... A perpetual motion machine does work without an energy ... while my device uses the wind created by the moving vehicle as ... If your current estimates of drag ...
    (sci.energy)