Spot-hire

[Dolive22]

Could tunnels be electrified with 750v third rail? And the rest with 25Kv? Designs exist, and are due to be cascaded.

 

[MCR247]

Could tunnels be electrified with 750v third rail? And the rest with 25Kv? Designs exist, and are due to be cascaded.

So outside of each end, the train stops to switch power and continues to then stop to change again? Sounds like more things to go wrong to me

 

[jopsuk]

So outside of each end, the train stops to switch power and continues to then stop to change again? Sounds like more things to go wrong to me

On new stock, could go for the more complex system that Eurostar had fitted that allowed them to change on the move.

 

[ChrisCooper]

There is always the option of raising the pantograph whilst moving. It's done all the time on the Continent, and used to happen regularly in the UK when Eurostars switched from third rail to overhead. It does happen too at least once on HS1, before entering and after leaving the tunnel, to change the pantograph settings between LGV and Tunnel. Tests have been carried out with 91s and Pendolinos involving dropping and raising pantographs on the move. One idea is that in the event of problems with the overhead, trains can coast through an isolated section, but it also does give the possiblity of dealing with the cost of electrifiying tunnels, providing either batteries or auxilliary generators with enough power to get out of the tunnel and back under the wires if stopped, and coasting trains through the tunnels. There would also be the option of providing lower voltage overhead in the tunnels. Remember dual voltage electrification with automatic switchover was developed in the 60s, as early electrification schemes used 6.25kV in areas where clearances were limited (later developments in insulators, and also experiance with 25kV, allowed clearance requirements to be reduced allowing 25kV to become standard). Magnets on the side of the track switched power off and on either side of the neutral sections, as is still done today, with the trains automatically detecting the voltage and switching accordingly. It didn't always work, with a few mercury arc rectifiers blowing up when the equipment stayed in 6.25kV mode when entering a 25kV section, resulting in 4 times the voltage being supplied, but I'm sure with modern electronics it could be a lot more reliable. On the continent trains regularly switch between 25kV, 1500V and 3000V whilst moving.

 

[jopsuk]

91s and 365s (and 317s?) have been dropping and raising on the move quite a lot at weekends recently, with the engineering work at Hitchin.

 

[Pumbaa]

317s no - No stock that had the emergency cord automatically apply brakes was allowed through. 365s were allowed through, but had to stop to raise the Panto. 91s were permitted to coast through, raise Panto on the move and continue on.

 

[sprinterguy]

I agree that making use of a lower voltage would make life a lot easier for the likes of gauge clearances for the OLE, 6.25kV would be a good one.

However I can't see it happening, it does seem a bit of a backward step, to me at least, to start stringing up the wires over the MML and GWML at a lower voltage than the rest of the currently electrified network, when one of the driving forces behind increased electrification is increased interoperability of electric traction over a greater number of routes. Remember part of the reason the Woodhead route was abandoned in the eighties was thanks to it's non standard 1500V DC power supply which was deemed too costly to upgrade to the modern 25kV standard, and the early AC electrics quickly had their 6.25kV equipment removed.

Technology has moved on a lot since then of course, and multi-voltage locos are a much more attractive proposition now than then, such as Eurostar and the class 92s, but I think that we have 25kV and should stick to it, adding another voltage is just an unnecessary complication.

Answering a couple of the other points, I think that a suitably spruced up 150, with their shorter 20m carriages, would be ideal for lightly used branch line routes to replace the Pacers if it was decided that branch lines were to recieve cascaded stock and not new build. Surely a 150 has got to be more efficient for loading and unloading than a Pacer with it's three doors per side arrangement. If a new build was decided upon then I can perfectly see 172 Turbos rambling down the Whitby branch or whatever; more so than the 170s as the 172s have more lightweight bogies, so less trackwear.

I think that the IEP, if and when it gets approval, will be a great opportunity to cascade some good quality stock to lesser routes; 4 and 5 car Voyagers going to Transpennine (if it's not electrified) and the 185s displaced replacing the 158s, which could then take over on regional 150/156 "Sprinter" duties, leaving the 150s to replace the Pacers. Well, that's what would happen if I got my way

And on the subject of spot hire units, I reckon that a few high powered four car 170 Turbos would be about right, and dual voltage 350 Desiros for the electrics.