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Author Topic: Great Western Main Line electrification - ongoing discussion  (Read 149324 times)
stuving
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« Reply #945 on: April 26, 2020, 06:22:35 pm »

So remembering my various equations of motion (v=u+at and all that), I reckon if acceleration is linear then it would take 3,123m to regain 200kph if the time taken is 60 seconds, and the time lost against a steady 200kph would be 3.7 seconds (starting at 175kph).

So call it 2 secs lost to decelerate, 3.9 secs through a 1 mile speed restriction, and 3.7 secs to regain max line speed would give around 10 secs in total.

But of course it's not linear - for the more detailed solution I gave earlier, reacceleration takes 77 s, which splits 34 s to half-way (188 km/s) and then 43 s, and covers 4 km in all. Edging closer to the balancing speed just makes it all take a little longer, so the time loss is 5.8 s. But you're definitely in the same ball-park.
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SandTEngineer
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« Reply #946 on: April 26, 2020, 06:24:31 pm »

Sometimes I really do dispair with this country.  We have a significant main line which is going to be subject to an enforced speed restriction for the next 50 years and beyond.  There is going to be uneccessary brake wear and additional electricity consumption due to braking and accelerating again.

The bridge concerned is not even artchitecturally significant.  Its been refaced and partially infilled so you can't even see the original construction.

I'm all for preserving things of a significant nature, but not in this case.  Its not the only example of that type of Brunel designed bridge.

From English Heritage:

Quote
An example of one of Brunel’s most common standard designs for the original GWR: an overbridge with three semi-elliptical arches, the central one being 30ft wide and the approach arches having smaller spans, carrying a humpbacked roadway.

The bridge was built c.1839-40 on the section of the line from Reading to Steventon which opened on 1 June 1840.

Since construction the bridge has been modified by: substantial refacing in one or more phases in the late-nineteenth or twentieth century; the insertion of tie-rods; the installation in 1963 of concrete bracing in the side arches and the infilling of the lateral pier arches, to strengthen the piers.

Assessment of significance:
A reasonably well preserved example of a standard Brunel bridge type on the original GWR, and therefore a structure dating from the ‘Pioneering Phase’ of railway construction. It has been largely refaced but has otherwise has escaped major alteration and is therefore of medium architectural and historic interest, and no archaeological or artistic interest.
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bradshaw
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« Reply #947 on: April 26, 2020, 06:49:44 pm »

From their local paper

Village wins fight to save Brunel bridge from Network Rail

https://www.heraldseries.co.uk/news/18404498.village-wins-fight-save-brunel-bridge-network-rail/
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Bmblbzzz
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« Reply #948 on: April 26, 2020, 08:03:33 pm »

Putting facts to one side for a minute ( Roll Eyes) and looking at the emotions involved, a good outcome is one which allows everyone to feel they've won, and that seems to be the case here. The bridge hasn't been demolished, OHLE is complete.
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Tuesday had come down through Dundrum and Foster Avenue, brine-fresh from sea-travel, a corn-yellow sun-drench that called forth the bees at an incustomary hour to their bumbling.
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« Reply #949 on: April 26, 2020, 08:29:54 pm »

One other advantage is that in modelling and designing this it may have made it easier for such things in future, perhaps also reducing costs.
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TonyK
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« Reply #950 on: April 26, 2020, 11:15:51 pm »

Well, I for one think this victory is worth marking. Maybe with a salute on the two-tones by all passing trains?

But seriously. From reading back through the thread, it could be a matter of only a few years before this shored-up ruin of a Brunelian masterpiece needs some serious work doing on it again, less if someone in a big lorry clouts the parapet. It will be interesting to see what happens then. Network Rail could be forgiven for saying that they are having nothing to do with it, but don't you dare close our railway. The standard safeguard of closing one lane to traffic will probably lead to calls for a new bridge, and loud questions about why Network Rail didn't do the job as part of the electrification programme.
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« Reply #951 on: April 27, 2020, 07:08:41 am »

Sometimes I really do dispair with this country.  We have a significant main line which is going to be subject to an enforced speed restriction for the next 50 years and beyond.  There is going to be uneccessary brake wear and additional electricity consumption due to braking and accelerating again.

The bridge concerned is not even artchitecturally significant.  Its been refaced and partially infilled so you can't even see the original construction.

I'm all for preserving things of a significant nature, but not in this case.  Its not the only example of that type of Brunel designed bridge.

From English Heritage:

Quote
An example of one of Brunel’s most common standard designs for the original GWR: an overbridge with three semi-elliptical arches, the central one being 30ft wide and the approach arches having smaller spans, carrying a humpbacked roadway.

The bridge was built c.1839-40 on the section of the line from Reading to Steventon which opened on 1 June 1840.

Since construction the bridge has been modified by: substantial refacing in one or more phases in the late-nineteenth or twentieth century; the insertion of tie-rods; the installation in 1963 of concrete bracing in the side arches and the infilling of the lateral pier arches, to strengthen the piers.

Assessment of significance:
A reasonably well preserved example of a standard Brunel bridge type on the original GWR, and therefore a structure dating from the ‘Pioneering Phase’ of railway construction. It has been largely refaced but has otherwise has escaped major alteration and is therefore of medium architectural and historic interest, and no archaeological or artistic interest.

Its called NIMBYisum

The real test will come when a significantly restrictive weight limit has to be enforced, NR will be in no rush to support the Local Authority in its repair, perhaps getting to the stage where its pedestrian only
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Neither a wise man nor a brave man lies down on the tracks of history to wait for the train of the future to run over him.     
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« Reply #952 on: April 27, 2020, 12:26:32 pm »

Knowing a fair bit about this structure, I think it is fair to say that it is not in the best state of repair. I recall driving over it last year that the undulations in the road surfacing were interesting.
It is an Oxfordshire CC maintained asset. They were keen to have a new structure I recall but what really put the spanner in the works was the length of time that the diversion would have been in place was too long for the locals to stomach.
The installation of a single lane traffic light controlled bridge to permit access over the railway was looked at briefly but those proposing this were told by those higher up to cease any further development.
Still, the bridge has been saved. A rather shabby example of a Brunel structure.
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Thatcham Crossing
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« Reply #953 on: April 27, 2020, 12:42:32 pm »

Quote
A rather shabby example of a Brunel structure

Earlier in the year (pre-lockdown) I was passing nearby (on the A34) so thought I'd take the slight detour to have a look at what all the fuss is about.

Whilst I wouldn't claim any kind of architectural knowledge, it really looks quite unremarkable (compared to many other Brunel constructions) and in a bit of a state.

I see talk over on the RailUK Forum that further modelling is being done to look at whether the limit can be raised to 125  Smiley
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IndustryInsider
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« Reply #954 on: April 27, 2020, 12:52:40 pm »

IIRC correctly the extra height needed (for the 125mph running) meant the main reason it would take so long to install a replacement was not replacing the bridge itself, but the works to alter the quite sharp slope up to it from the village. So, if it reaches the point where it needs to be replaced, and it falls to the Council to replace it, then they might be tempted to save money and aggro by just replacing the deck and not increasing the elevation and altering the approaches?

Hopefully further modelling will indeed see the speed increased to 125mph - though it's very noticeable just how quickly the pan raises on westbound trains if you stand at Stocks Lane crossing at 110mph.
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To view my GWML Electrification cab video 'before and after' video comparison, as well as other videos of the new layout at Reading and 'before and after' comparisons of the Cotswold Line Redoubling scheme, see: http://www.dailymotion.com/user/IndustryInsider/
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« Reply #955 on: April 27, 2020, 01:27:08 pm »


The key new announcement  was not the speed 110 mph limit but the withdrawal of the planning appeal. The Listing citation from EH (quoted above) is clearly nonsense and NR's best approach is to apply for "de-Listing" - cheaper and simpler than an Appeal.

The bridge does not seem to have a contact wire gradient problem to the East but only to the West where there are crossings at c400m  (Stocks Lane) and at c600m (the Causeway).

Surely two crossings for a village is excessive and the nearer one to the bridge should be closed. New bridges are expensive.

The bridge is on quite an important local route, being the old A34, offering the only convenient rail crossing between Didcot and Wantage. This should have been appreciated both by NR and the County and an acceptable highways plan for Steventon (now really a suburb of an expanding Didcot) produced.

It's not really NIMBYism, just shoddy, irresponsible government. One for Boris.

OTC
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SandTEngineer
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« Reply #956 on: April 27, 2020, 03:41:46 pm »

Detail of how the modelling was done, here: https://www.railengineer.co.uk/2020/03/06/steventon-bridge-overcoming-the-obstacle/
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TonyK
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« Reply #957 on: April 27, 2020, 06:11:18 pm »


That is extremely intersting, and shows that it wasn't just a question of thinking of a number.
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« Reply #958 on: April 27, 2020, 09:43:07 pm »

The ongoing cost of this ??, the wire runs through the area will require more frequent inspections for ware and are likely to need replacing more often due to ware because of the rapid transitions in wire height.

The knock on effect of this will be more frequent level crossing closures and over night work with machines to carry these inspections and renewals 
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« Reply #959 on: April 27, 2020, 10:44:19 pm »

Surely two crossings for a village is excessive and the nearer one to the bridge should be closed. New bridges are expensive.

Yes and you should read what they said when that was suggested.  That was worse than the bridge. 

The bridge is on quite an important local route, being the old A34, offering the only convenient rail crossing between Didcot and Wantage. This should have been appreciated both by NR and the County and an acceptable highways plan for Steventon (now really a suburb of an expanding Didcot) produced.

Yes it is the old A34 - but  am not sure how relevant that is to its present use.

Yes there are no other rail crossings (other than the two level crossings in Steventon which don't really go anywhere) until Wantage Road/Grove, but there are no other roads there either and I don't think anyone was suggesting a diversion that way.   

On the Didcot side however there is the New A34 bridge (not that useful for local traffic), one at Milton Park and there are several in Didcot.  The diversion through Draycot would be about 6 miles.  There have been more inconvenient diversions. 
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