Marc and Sophia Brunel returned to London after Christmas 1828 and in January 1829 Isambard then set off for a holiday in Normandy and Paris. On the return journey a month later, freezing, jolting, wearisome from Paris to Calais, tossed about across the Channel and by jolted by stage coach to London, Isambard’s high spirits and super-abundant energy never flagged for a moment. He kept up the laughter and high spirits of his two travelling companions all the way.*
*Marc Isambard Brunel. Page 184-5. Paul Clements.
Isambard’s father, Marc, now introduced him to the prospect of designing a bridge across the Clifton gorge in Bristol. A competition for a design had been advertised with a deadline for entries of 19 November 1829. Isambard, and surely Marc also, went down to Clifton to examine the site. The result was four superbly artistic paintings, Isambard was a very talented water colour artist, showing different styles and sites for a suspension bridge across the gorge. These designs were rejected on the advice of the famous road engineer, Thomas Telford, – he objected to the length of the span – who had just erected a much shorter suspension bridge across the river Conway. Telford then produced a design for Clifton – which Isambard quite rightly exposed as ludicrous. In October 1830 the Bridge Committee announced a fresh competition to be judged the following January.
Isambard was elected a Member of the Institution of Civil Engineers in 1829 a year after the Institution was founded and elected a Fellow of the Royal Society on 10 June 1830 in recognition of his work in the Thames Tunnel, his determination to make the Gaz engine work (against all the laws of nature) and his designs for the Clifton Bridge. The latter existed only as very beautiful water colours.
From 7th to 14th January 1831, from 17th to 22nd and from 26th to 31st Isambard was in Manchester and when he was not there he was in Bristol or Tollesbury Essex. During all that time, Marc Brunel worked on the design of the Clifton Bridge: this information I took from Marc Brunel’s diary at the Institution of Civil Engineers. Marc Brunels’ design, signed by his son, for the Clifton bridge, was placed second out of four by the judging Committee but after Isambard explained the design carefully it was accepted.
Marc had always urged his son on to be an Engineer and seems to have doted on him. Marc wrote jubilantly in his diary on 19th March:
Isambard is appointed engineer to the Clifton bridge. The more gratifying that Mr.Telford, Captain Brown and Mr.Tierney Clark were his competitors and that for my own part I have not influenced any of the Bristol people on his behalf.
On 16 March 1831 I.K Brunel was appointed engineer for the Clifton bridge. The ceremony of laying the foundation stone of the Clifton bridge took place on 21 June 1831. Isambard walked alone, at the head of the procession. Work on the bridge went forward very slowly, the huge brick abutment on the west side of the gorge and the twin suspension towers. Then over the week-end of 29-31 October came the Bristol riots – practically an insurrection. The centre of Bristol was set on fire by a mob, the Bishop’s palace burned and the jail opened. Bristol was stunned, and money for the Clifton bridge project slowly ceased to be forthcoming. The project was dead by 1843 with only the Leigh Woods abutment and the towers built.
After the death of I.K Brunel, in September 1859, the civil engineering community – and indeed, the employees of the Great Western Railway and the general public – felt strongly that a memorial was needed for him. The plans of the Clifton bridge were obtained from Brunel’s Duke Street office and examined. It was immediately obvious that the design was hopelessly antiquated. Such advances had been made in technology over the intervening 30 years that would be never have done to have erected a design so old. In particular it had been designed without the benefit of the knowledge developed by Reguis Professor of Civil Engineering and Mechanics, William Rankine.(1820-1872) Rankine, was one of the greatest engineering and mathematical brains produced in Britain in the 19th century. He had devoted his life to the study of physics and engineering and in 1858 published his seminal book ‘Applied Mechanics’ giving the world the benefit of his investigations into – among other things – proper use of wrought iron plate and angle irons to make girders and more especially, on the best way to use lattice work girders to stiffen the intrinsically floppy nature of suspension bridges.
In 1860 a Committee of Brunel’s friends and admirers was formed to raise subscriptions to construct a suspension bridge at Clifton. The excellent idea of building a suspension bridge across the gorge at Clifton, at the site recommended by I.K Brunel, as a memorial to him, was, co-incidentally, also an excellent opportunity to try out Professor Rankine’s suspension bridge principles.
A beautiful cast-iron plaque on the existing Clifton bridge states that it was ‘designed in 1830 by Isambard Kingdom Brunel.’ That is wrong on three counts: the original bridge designs were by Marc Brunel – in 1831 – and those designs were never carried out.
The fault with I.K Brunel’s Clifton design was that it was too flexible. Even in Brunel’s own time, his designs for stiffening the structure of suspension bridges was criticised as unsound and therefore dangerous. On the 16 January 1839 the great naval architect, John Scott-Russell stated ‘Mr. Brunel has proposed a method of preventing oscillation which is expensive and heavy but has not had the desired effect . . . for the whole will perform isochronous oscillation.’ z.
The design devised by Marc Brunel had two tiers of suspension chains. At the pin-joint between each link of the chains, a vertical rod or ‘hanger’ went down to the roadway. The railings on each side of the bridge were merely railings and added no stiffness, vertically or horizontally to the bridge. The under-road stiffening system was a framework of timber tied with wrought iron rods.
The present day Clifton suspension bridge was designed by William Henry Barlow M.I.C.E., C.E., FRS (1812-1902) and Sir John Hawkshaw M.I.C.E., C.E., F.R.S (1811 – 1891) influenced by the most modern research of Professor Rankine’s studies as well as their own great experience. Baker and Hawkshaw added third tier of chains, a 33% increase in strength which then allowed a 33% increase in the number of ‘hangers’ from the chains to the roadway. Immediately the bridge was one third stronger than the Brunels’ design Below the roadway Baker and Hawkshaw used a wrought iron, riveted, latticework, girder to ensure maximum stiffness to the road. and to further stiffen the bridge the hand rail and fence was made an integral part of the structure carrying out the function of a girder above the roadway and riveted to the under-girder. The existing bridge was built to an entirely different design. Looking at thois in a simple, broad, sense: Would any suspension bridge, the most difficult of bridge designs, have been built to a plan 30 years out of date?
- Quoted by Professor Roland A Paxton MBE PhD DEng CEng FICE FRSE in his 2008 lecture to the Construction History Society on ‘John Scott Russell’s anti-vibration proposal for suspension bridge decks’.
The Clifton bridge design is the result of Barlow and Hawkshaw’s brains, influenced of course by the then latest engineering thinking of Professor Rankine’s and owes nothing at all to Marc or I.K Brunel – except that it stands where the Brunels suggested and the brick abutment, which Marc or Isambard designed, was used.
Professor Angus Buchanan’s 2002 book on Isambard Kingdom Brunel, page relates how the Brunel family refused to attend the opening of the Clifton Bridge because they felt their father/husband was not sufficiently recognised – but as it was not his design – he could not have had any recognition.
This family touchiness is reflected in the very delicate wording of the Paper given in 1864 by Barlow with Fowler in the Chair where Barlow (I think these are his exact words) refers to ‘varying and re-arranging’ the Brunel’s design. He didn’t want to offend the Brunel family.