Why did BR not electrify Mitre Bridge Junction to Kensington Olympia?

[gg1]

Prompted by posts in the motorail thread, when the decision was taken for Kensington Olympia to become London's motorail hub, why was the 2 miles or so from there to Mitre Bridge Junction not electrified, saving the need for loco changes for such a short distance?

Bear in mind this was in the 60s when BR were happily electrifying short freight only branches off the WCML.

 

[30907]

Prompted by posts in the motorail thread, when the decision was taken for Kensington Olympia to become London's motorail hub, why was the 2 miles or so from there to Mitre Bridge Junction not electrified, saving the need for loco changes for such a short distance?

My guess is that it wouldn't have significantly benefited the major user of the West London Line which was freight.

Bear in mind this was in the 60s when BR were happily electrifying short freight only branches off the WCML.

Garston FLT I know of, which others did you mean?

 

[steamybrian]

I have heard of two different reasons why it was not electrified with 25kv overhead wires (as opposed to 3rd rail dc)
1. It would have meant rebuilding the bridge carrying the LU Line bridge carrying the Hammersmith & City Metropolitan Line which passes over it. (or lowering the track)
2. The overhead electrification would have interfered with the LU 3rd rail electrification current.

 

[Ken H]

I have heard of two different reasons why it was not electrified with 25kv overhead wires (as opposed to 3rd rail dc)
1. It would have meant rebuilding the bridge carrying the LU Line bridge carrying the Hammersmith & City Metropolitan Line which passes over it. (or lowering the track)
2. The overhead electrification would have interfered with the LU 3rd rail electrification current.

I think DC interferes with 25Kv as the DC can cause corrosion due to electrolysis. (Most corrosion is caused by electricity.)

 

[pdeaves]

Garston FLT I know of, which others did you mean?

Runcorn Folly Lane?

 

[gg1]

Garston FLT I know of, which others did you mean?

A few more I'm aware of:

Windsor Street Goods in Brum - wired for around 15 years but I've yet to see photographic evidence of an electric loco ever having used the line
Wolverhampton steel terminal
A stub near Rugby along one of the long closed branches - not sure which one though

I have heard of two different reasons why it was not electrified with 25kv overhead wires (as opposed to 3rd rail dc)
1. It would have meant rebuilding the bridge carrying the LU Line bridge carrying the Hammersmith & City Metropolitan Line which passes over it. (or lowering the track)
2. The overhead electrification would have interfered with the LU 3rd rail electrification current.

Both of those would make sense.

 

[Bevan Price]

I have heard of two different reasons why it was not electrified with 25kv overhead wires (as opposed to 3rd rail dc)
1. It would have meant rebuilding the bridge carrying the LU Line bridge carrying the Hammersmith & City Metropolitan Line which passes over it. (or lowering the track)
2. The overhead electrification would have interfered with the LU 3rd rail electrification current.

Maybe also that - apart from Motorails, and occasional use by diverted WCML services, there was no passenger service from Willesden.

 

[WAO]

I believe that there was a sewer below the track at the present limit of electrification that prevented economic lowering for a difficult bridge. Whether a Cardiff solution could now apply - who knows?

 

[zwk500]

I believe that there was a sewer below the track at the present limit of electrification that prevented economic lowering for a difficult bridge. Whether a Cardiff solution could now apply - who knows?

There was some initial study work done recently for extending OLE to Shepherd's Bush, although I don't know if that ever got on to the technical feasibility & costing work.

 

[Taunton]

Motorail was essentially a summer-only operation, apart from those overnight services tagged on to sleeper trains from the main termini, not Olympia. It would have been unused for half the year or more. It was also an operation using "marginal costing" of existing assets - there was very little actual capital expenditure.

The electric freight branches like Runcorn were an idea of the late-1950s design of the WCML. Motorail came along years later, when concepts had changed.

 

[Ken H]

Motorail was essentially a summer-only operation, apart from those overnight services tagged on to sleeper trains from the main termini, not Olympia. It would have been unused for half the year or more. It was also an operation using "marginal costing" of existing assets - there was very little actual capital expenditure.

The electric freight branches like Runcorn were an idea of the late-1950s design of the WCML. Motorail came along years later, when concepts had changed.

But the cross country services that went onto the Southern also changed traction in the same way. So the extension of the 25Kv into Kenny O would have benefitted those also. But maybe the layout at Kenny O wasn't well laid out for loco changes. Or even permitted.
Also not sure there were that many that did that. 2 or 3 a day perhaps.

 

[Dave W]

A few more I'm aware of:

Windsor Street Goods in Brum - wired for around 15 years but I've yet to see photographic evidence of an electric loco ever having used the line
Wolverhampton steel terminal
A stub near Rugby along one of the long closed branches - not sure which one though

Might Hardendale Quarry fit in to the category, or was that a separate decision later?

 

[Taunton]

But the cross country services that went onto the Southern also changed traction in the same way. So the extension of the 25Kv into Kenny O would have benefitted those also. But maybe the layout at Kenny O wasn't well laid out for loco changes. Or even permitted.
Also not sure there were that many that did that. 2 or 3 a day perhaps.

Motorail was a 1960s-70s concept. Cross-Country via Olympia was a 1980s concept. There wasn't really any significant flow at any one time that justified the cost of electrification, especially given that in Motorail times Willesden always seemed to have a dozen or more class 24/25 hanging round for the short trip from there.

The substantial over-electrification of odd freight spurs was part of the original 1950s plan, later cut back. Someone once calculated that all the wiring of every line in Crewe's Basford Hall yard and surroundings, just not used as all the shunting was (inevitably) done by Class 08s, would have covered most of the Crewe to Kidsgrove line, a much more useful addition.

 

[36270k]

In the 70's parcels trains were usually a class 73 on diesel from Clapham Jn to Mitre Bridge.

 

[A0wen]

I think DC interferes with 25Kv as the DC can cause corrosion due to electrolysis. (Most corrosion is caused by electricity.)

I think the issue is more with 3rd rail where the earthing is done back through the running rails AIUI whereas because LUL run with 4 rails that's less of an issue. @Bald Rick can usually explain it better.

The current limit of the 25kv from Willesden is the A40 Westway bridge - it could be that clearances are a bit short under that ?

 

[alf]

The clearances under the A40 are huge.

The reason regularly suggested on this forum for not extending overhead ac wires South to Shepherds Bush Station, where ac/dc change over would be risk free & time saving, is the electrical interaction with the dc Hammersmith & city bridge.

Not a problem between Euston to Primrose Hill, or Acton on the North London line where dc/overhead changeover has taken place for 30 years.
Or the 4 track WCML with its huge overhead currents where it passes under the Met line bridge near Harrow on the Hill.

Can anyone elaborate on zwk500’s interesting post 9 ?
Did the “it can’t be done” brigade stop it?
Someone should tell them about the Cardiff bridge solution gently suggested at post 8.

 

[zwk500]

The clearances under the A40 are huge.

The reason regularly suggested on this forum for not extending overhead ac wires South to Shepherds Bush Station, where ac/dc change over would be risk free & time saving, is the electrical interaction with the dc Hammersmith & city bridge.

Not a problem between Euston to Primrose Hill, or Acton on the North London line where dc/overhead changeover has taken place for 30 years.

Interfence on dual systems IS a massive problem, hence why it's avoided where possible and minimised where it has to be. The City TL-Farringdon section is, by all accounts, an electrical nightmare.

Or the 4 track WCML with its huge overhead currents where it passes under the Met line bridge near Harrow on the Hill.

I don't think those bridges pose a serious problem

Can anyone elaborate on zwk500’s interesting post 9 ?
Did the “it can’t be done” brigade stop it?

I suspect it went no further than the initial study, because it was shown that the total benefit was 30 seconds to GTR trains and 0 Seconds to Overground and freight. We recommended they considered it anyway because it was an operational benefit from Reliability and passenger service points of view, but it wasn't going to permit any additional traffic without some other larger change (like loop lengthening at Kenny O, or major changes at the Clapham/Latchmere/Longhedge Jns area). I suspect that at the very least, the initial technical design had said it could be done, otherwise the project wouldn't have bothered to ask what the capacity benefits might be.

Someone should tell them about the Cardiff bridge solution gently suggested at post 8.

They're well aware of it, but it doesn't work for every bridge.

 

[Taunton]

Interference on dual systems IS a massive problem, hence why it's avoided where possible and minimised where it has to be. The City TL-Farringdon section is, by all accounts, an electrical nightmare.

Arguably the AC/DC changeover should have been put in the platforms at Kentish Town (just as the GN did at Drayton Park) ...

There are some places where it has worked satisfactorily, and others not, and it does seem down to the understanding of the separate individual designers. Installing AC on the North London line through Highbury apparently impacted the Victoria Line signalling 80 feet below, which had never happened at Euston where it passes beneath the main line platforms.

 

[Gloster]

But the cross country services that went onto the Southern also changed traction in the same way. So the extension of the 25Kv into Kenny O would have benefitted those also. But maybe the layout at Kenny O wasn't well laid out for loco changes. Or even permitted.
Also not sure there were that many that did that. 2 or 3 a day perhaps.

Working from memory, most of the Inter-Regionals going to and from the Southern would have come or gone via Reading. Not that there were ever many of them, so it would have been a lot of expense for little gain. Furthermore, I think the loco continued all the way through to the terminus: electrification would mean diagraming a 33 to take over at Kenny O.

 

[A0wen]

Arguably the AC/DC changeover should have been put in the platforms at Kentish Town (just as the GN did at Drayton Park) ...

But that wouldn't have resolved the problem that the length of dual electrification from Faringdon to City does, which is if the changeover from one system to another failed, the train could run forward to the next station and reversed.

Before the Thameslink upgrade the changeovers were all at Faringdon and it was like Drayton Park which was the only point where both systems coexisted.

 

[Taunton]

But that wouldn't have resolved the problem that the length of dual electrification from Farringdon to City does, which is if the changeover from one system to another failed, the train could run forward to the next station and reversed.

That's a separate question to that which was posed, which was that there were electrical interference issues in Central London.

But Kentish Town is where there are four platforms, so if the changeover fails those behind can be routed round, avoiding the backing-up problem.

I don't know what it is that causes electrical changeover to, still, be so problematical. I recall onetime prominent railway writer Cecil J Allen, back in the early 1960s, doing a footplate ride from Dijon in France to Zurich in Switzerland, changing from French overhead DC to Swiss overhead AC at speed. And it failed ...

 

[zwk500]

I don't know what it is that causes electrical changeover to, still, be so problematical. I recall onetime prominent railway writer Cecil J Allen, back in the early 1960s, doing a footplate ride from Dijon in France to Zurich in Switzerland, changing from French overhead DC to Swiss overhead AC at speed. And it failed ...

It's the impact of failure that does it. Eurostar used to change at speed. Overground still changes on the move. However most traction changes take place on two-track lines where failure of the unit would quickly cause delay to balloon around the network. Hence why most.locations have crossovers to permit easy reversals.

 

[swt_passenger]

The explanation previously given about possible AC wiring as far as Olympia was interference with the NR and LU signalling systems, not with LU traction systems as mentioned in recent posts. The LU problem being expected to be fixed by SSR resignalling, now completed.

the Cross London RUS of 2006 contained this short section, (I haven’t found an online source to link):

Description

Move the AC/DC changeover on the WLL to Shepherds Bush station.

Issue

The AC/DC changeover on the West London Line is currently located close to
North Pole depot. This requires all electric services to stop in section to effect the
changeover, costing around two minutes per train. The opportunity therefore exists
to look at moving the changeover point to the station at Shepherds Bush.

Recommendation

The cost of the alteration would be prohibitive, due to the need for extensive
immunisation of the signalling equipment on the surrounding routes, including the lines
operated by London Underground. However, it is understood that the Hammersmith
& City line is due to be re-signalled in 2013, and this may give the opportunity for the
issue to be revisited.
An alternative solution would be for the changeover to be undertaken on the move, and
it is recommended that this is progressed during the procurement process for any new
electric rolling stock required for the route.

Although that was a proposal to speed up LO services by moving AC/DC changeover only to Shepherds Bush, (a station that didn’t exist in the original electrification period), presumably the signalling immunisation problems were the same through to Olympia, which was also served by LU.

 

[zwk500]

the Cross London RUS of 2006 contained this short section,

Aha! This potentially explains a lot of discussions I had about expected benefits of extending the OLE to Shepherds Bush

 

[Helvellyn]

Might Hardendale Quarry fit in to the category, or was that a separate decision later?

Done as part of the Weaver Junction to Glasgow electrification. It was regularly used by AC traction until the late 1980s (pairs of 86s/87s not being uncommon). It was sectorisation that helped kill this off, with the Metals sub-sector not wanting (or given) its own traction by the early 1990s. After the closure of Ravenscraig the amount of steel traffic on the WCML dropped off. (A lot of the Hardendale traffic was for the steel industry, hence why Motherwell's 37026 was named Shap Fell).

 

[etr221]

Prompted by posts in the motorail thread, when the decision was taken for Kensington Olympia to become London's motorail hub, why was the 2 miles or so from there to Mitre Bridge Junction not electrified, saving the need for loco changes for such a short distance?

Bear in mind this was in the 60s when BR were happily electrifying short freight only branches off the WCML.

My guess is that it wouldn't have significantly benefited the major user of the West London Line which was freight.

Garston FLT I know of, which others did you mean?

One other example was through Camden Road to Maiden Lane FLT (shortlived)

 

[Bald Rick]

I think the issue is more with 3rd rail where the earthing is done back through the running rails AIUI whereas because LUL run with 4 rails that's less of an issue. @Bald Rick can usually explain it better.

Essentially return currents are the issue, and the DC return leaking into the fully earthed AC return. With DC currents being much higher. And the more return current there is (directly related to length of train and frequency of service), the bigger problem it is.

The clearances under the A40 are huge.

Not huge enough, hence the pantograph graveyard adjacent.

or Acton on the North London line where dc/overhead changeover has taken place for 30 years.

it very much is a problem there. I have personally witnessed OLE foundations that have failed due to electrolytic corrosion of the rebar in them. And spent several Sundays pouring concrete to replace them, and the masts, 18 years ago. There is now some clever electrical kit there to reduce the return current issue.

Arguably the AC/DC changeover should have been put in the platforms at Kentish Town (just as the GN did at Drayton Park) ...

absolutely not, as a) that would need another big DC substation somewhere near Kentish Town, b) it would require dual immunisation of all of St Pancras and Kings Cross, and c) the DC returns would be trying to escape all through both layouts, with predictable consequences for any block joints / points insulation in the area.

Changeover st Farringdon / City is unquestionably the correct place.

But Kentish Town is where there are four platforms, so if the changeover fails those behind can be routed round, avoiding the backing-up problem.

except that most trains don’t stop there, and it only has 8 car platforms, and the spare platforms are regularly used for other purposes.

 

[30907]

Working from memory, most of the Inter-Regionals going to and from the Southern would have come or gone via Reading. Not that there were ever many of them, so it would have been a lot of expense for little gain. Furthermore, I think the loco continued all the way through to the terminus: electrification would mean diagraming a 33 to take over at Kenny O.

Depends what era you mean. That's correct for the 1980+ Intercity services, but earlier it was common for the SR to take over trains at Mitre Bridge (post electrification) or Kenny (pre), and the classic WR services ran via Redhill.

But I agree there wasn't much of a case.

 

[Taunton]

Depends what era you mean. That's correct for the 1980+ Intercity services, but earlier it was common for the SR to take over trains at Mitre Bridge (post electrification) or Kenny (pre), and the classic WR services ran via Redhill.

But I agree there wasn't much of a case.

Dick Hardy, railway author, and shedmaster at Stewarts Lane among others, wrote of cross-London services changing over on the embankment above the shed, and inevitably mentions a series of blunders on peak summer days with wrong crews relieving wrong locos etc.

I think it was the 1980s when there were one or two long distance services per day, probably Class 47 hauled throughout, from Brighton or Dover, which stopped at Clapham Junction, Kenny O, etc, and were advertised by quite stylish banners on the rail bridges over main roads at places like Shepherds Bush.

 

[nw1]

Depends what era you mean. That's correct for the 1980+ Intercity services, but earlier it was common for the SR to take over trains at Mitre Bridge (post electrification) or Kenny (pre), and the classic WR services ran via Redhill.

But I agree there wasn't much of a case.

There was also a brief period when many of the Brighton XCs went via the WCML rather than Reading, starting in May 1986. However I don't think it lasted longer than a couple of years.