🚀 go-pugleaf

tony sayer wrote:

> In article <d3979d5f.0209101145.1a1d5a7f@posting.google.com>, Richard
> Catlow <RBCatlow@aol.com> writes
> >David Winter asked:
> >
> >> With 3rd rail systems, what is the spacing between substation (ie range of
> >> one substation).
> >>
> >> This will vary with system and load.
> >>
> >> My question is looking at 3 min frequency, 6-car full size single deck
> >> trains, with a 750v nominal supply with either medium (+/- 100v) or wide
> >> tolerance (+/- 200v).
> >>
> >> I know there's some well versed electrical engineering types who lurk
> >> hereabouts - so some indicative figures would be helpful noting that each
> >> situation requires its own assessment.
> >>
> >> Also, what's the range of nominal voltages used with guarded types of side
> >> contact 3rd rail systems (eg Docklands). I know that 1200v DC was used near
> >> Manchester - has any system been implemented with higher DC or AC voltages
> >> in a 3rd rail supply?
> >>
> >Well David, there are many more variables that require assessment to
> >answer your question with certainty, these include:
> >
> >The traction characteristics of the train(s) involved
> >The stopping pattern
> >Geographical and topological data including gradients, curvature,
> >tunnels etc.
>
> <snipped a bit>
>
> Another very interesting bit of reading. Can you explain why the tunnel
> would be significant please?. Is it to do with wind resistance perhaps.
>
> Very surprised that the rail resistance is so low as you quoted, still
> never actually measured a bit.....

I seem to remember that those installed on the Jubilee Line were aluminium (it's
pretty easy to see), which has a greatly reduced resistance - about 30 times lower
than steel I think.  Are these rails solid aluminium alloy, or are they steel with
an aluminium outer layer?

Angus