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Letters 12th March 2009

The main point: £1bn saving by building a more functional Forth crossing

So the Scottish Government is having difficulty in organising the finance for their proposed Forth Replacement Crossing (News last week). Part of the problem is that for the 4km of new road and 2.7km of bridge/viaduct, it has to raise £2.3bn at 2016 prices, i.e. £343M/km. If a structure similar to the 5.1km Second Severn Crossing were built it would cost £137M/km in 2016 prices, assuming 4% compound inflation.

The reason for this difference appears to be due to the proposal being an “iconic” and “world’s first” bridge, crossing both the Rosyth and Grangemouth navigation channels. A functional, cheaper crossing, similar to the Second Severn Crossing, could start at the Dunfermline spur off the M90, thread between Rosyth dockyard and the site of special scientific interest (SSSI) upstream, ending at junction two of the M9.

The total distance from spur to junction, including approach roads, is approximately 5km, so should cost less than the £700M, at 2016 prices, of the Second Severn Crossing. If £300M is allowed for improving both end junctions, £350M for building a third lane each way between Junction 2 on the M9 and the Edinburgh bypass, and £125M for refurbishing the old bridge to carry car and bus traffic only, then nearly £1bn is saved.

Additionally less land is used, no SSSI bisected, no listed buildings demolished, and much improved public transport provided when the new lanes become bus lanes after the old bridge is refurbished.

Ross Carruthers (F) Balcassie, Kirkton of Mailer Road, Craigend, Perth, PH2 0SS  

Bank of Britain should finance infrastructure projects

I opened my NCE last week and thought that I had received the 1 April edition three weeks early when I read your editorial continuing to extol the merits of PFI and humbly thanking the Treasury’s decision to underpin £13bn of stalled PFI infrastructure projects as “providing relatively small amounts of cash to deliver huge amounts of confidence” (Comment last week).

As I read it I listened to the radio news that the government was completing its half share of High Street banks with an investment of £260bn in Lloyd’s Bank to ease the pressure caused by “toxic loans”. Turning to the Severn Barrage article on page 5 of NCE, I realised that level investment in Lloyd’s alone would provide the equivalent to finance, direct from public funds, nine Minehead to Aberthaw barrages (a snip at £29bn).

The political commentators are critical of the government’s decision to invest in Lloyd’s on the grounds that it is now providing huge amounts of cash with no likelihood that it will deliver any amount of confidence or the silver bullet of “quantitative easing”. Surely now is the time to draw a line under PFI as Britain must be, quite properly, the biggest banker in the country and major infrastructure projects (particularly to deliver the green agenda) must be directly financed by the Treasury.

David Morrish 41 Harcourt Way, Stafford ST16 1Qz 

Back on track

With reference to the article “Change Tack for Cheaper Track” (NCE last week), switch and crossing track renewals were frequently carried out in eight hour possessions forty years ago. The track layouts were fabricated off site and brought to the site.

Single leads were installed in eight hours, crossovers in sixteen hours and double junctions in twenty four hours. This technique was used for the remodelling of the track layout at Bristol Temple Meads Station when one hundred plus units of switch and crossing units were installed in an eight week period. The track work was completed to time and the station remained operational the whole time.

Bill Pilkington (M), Wizard View, Mottram St.Andrew, Cheshire. SK10 4QN   


Self-cleaning white horse

Further to articles in NCE on the matter of the Kentish White Horse (NCE 26 February), I suggest that Mark Wallinger uses e-GRC on a steel or reinforced concrete frame. Traditional glass fibre reinforced concrete has been used successfully on very large ‘sculptures’. However, a novel type of GRC with a photocatalytic, selfcleaning surface - the e-GRC - offers an ideal solution! This will ensure that the white horse remains brilliant white for very much longer, and it will even improve the quality of the surrounding air.

Peter JM Bartos (M)

Mother of all Meccano fans

I note that Lego vs Meccano debate has resurfaced (Letters last week). May I in support of Meccano repeat my contribution made 10 years ago? At age 14 I made a warren truss bridge of span 300mm which supported my mother’s 57kg mass without yield or collapse. In the same year I made an analogue computer to solve linear equations in one unknown, provided the coefficients were 1,2 or 3. A later attempt at a machine to handle two unknowns, containing four gearboxes and three differentials, failed through backlash and friction.

Richard Harvey (M) 6 Folkestone Rd, Salisbury, Wilts. SP2 8JP

Building on the engineering legacy of Sir Samuel Brown

I was very interested to read of the discovery during building work for a new rail crossing of the foundations of the suspension bridge that once carried the Middlesborough branch of the Stockton & Darlington Railway across the river Tees (NCE 26 February).

Some readers will be aware that Captain Sir Samuel Brown (1774-1852) was responsible for this unique structure. Brown was a naval officer who had retired from active service in 1812 but who was responsible for introducing iron chain cable as a replacement for hempen cables on ships. Looking for additional markets he designed a chain suspension bridge at his first purpose built chainworks at Millwall in London.

This came to the attention of Thomas Telford and around 1816 Brown joined forces with Telford to submit a joint design for the bridging of the river Mersey at Runcorn but the scheme was abandoned due to lack of financial support. Brown’s main innovation was the design of the suspension chain, consisting of flat eye bar links and pins, which he patented in 1817. He went on to build the first major road suspension bridge in this country, the Union chainbridge across the Tweed in 1820.

Still spanning the river Tweed today, with a deck span of 361 feet (110m) it is the oldest suspension bridge built for road traffic in the world. Brown’s attempt to develop the chainbridge for railway purposes, however, was to be unsuccessful. It proved to be unsuitable for the heavy live loading of steam locomotives which caused oscillations of the deck. It was unable to provide the strength and stiffness required for rail traffic and even loaded wagons had to be spaced apart and pulled across no more than four wagons at a time.

Despite the propping up of the deck, it was replaced by Robert Stephenson in 1842. My understanding is that the bridge used round eye bar links (as opposed to his patented design) which were supplied by Brown’s Newbridge chainworks at Pontypridd, and I was interested to know if any chain links, as part of the backstay anchorages, were found.

Readers may also be interested to know that the bridge is briefly mentioned in my exhibition; Web of Iron - Nature, Art and Engineering, which deals with the role of the engineer and the influence of nature and art in the development of the suspension bridge, focusing on the pioneering work of Thomas Telford and Captain Samuel Brown and where it led (currently on show at the Radnorshire Museum, in association with ICE Wales, at Llandrindod Wells until 4 April).

Stephen K. Jones Stephen.Jones@Wales.GSI. Gov.UK 

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