On Jan 25, 9:45 am, Graeme Wall wrote:
In message
" wrote:



On Jan 25, 6:10 am, (Neil Williams)
wrote:
On Thu, 24 Jan 2008 17:03:56 -0800 (PST), Andy
wrote:

See above, this is one of the delights of having a mixed fleet of
incompatible units.

Not on a Sunday, when there are (I think) only 4 diagrams giving a
half-hourly service, and most of them tend to be 4-car. This is
lunacy given the actual demand.

Does anyone know what proportion of the running costs of a train are
power consumption and how that scales with length of train?

Presumably for trains with few stops the power consumption is
approximately constant regardless of the length of the train because
the main loss will be air drag.

Which can be affected by the length of the train, think side winds.

To a first approximation it shouldn't matter because the force will be
perpendicular to the trains movement.

It will have an effect but I'd expect it to be small relative to the
energy required to accelerate and the energy required to push the
train through the air.

If I'm wrong and it is a significant effect then I'd expect that to be
due to turbulence of the air passing under the train and where the
carriages join. But I'd assume that a train reasonably approximates a
long straight bar.

Tim.