An Account
of the Construction of the Britannia and Conway Tubular Bridges,
by William Fairbairn
CE (MICE),
Published by John Weal, 59 High Holburn, London,
1849.
Viewed in the library of the Institution of Civil
Engineers, 24 Great George St, Westminster, 30th July 1993
The book gives many details of the testing
of model tubes and the construction of the two bridges. It also contains
a number of letters between Fairbairn and Stephenson. It has several references
to `Evans' as the principal contractor but does not identify him further.
The excerpts below also give some indication of the considerable scale of
the work, its technological inovation and Evans' obvious success in the
venture.
Relevant points:
- The bridge was constructed between 1846 and 1849
- It comprises two tubes (side by side) each 424'
long, 25'6" high, and 15' wide; each weighing 1300 tons.
- The tubes were manufactured on a beach just upstream,
floated into position on pontoons, and jacked 18' into place.
Extracts:
(p.127; letter Fairbairn to Stephenson, Dec 26th
1846:)
"... As respects the makers of the tube, I have
seen them all this week, except Horton, and am now able to report as follows:-
First that Evans states that he will be ready to
commence with the bottom of the tube by the middle of next month. His workshops
and steam engines are nearly completed; and the platform for supporting the
tube, and on which it is to be constructed, is in progress and will be finished
about the 15th of January ..."
(p.131; Stephenson to Fairbairn, undated:)
"... I have received Mr Clarke's report of the
progress made by Evans, which I think is satisfactory, but you must pick
him up about the time he commences riveting as much will depend upon the
system he adopts, and I hope this will have your especial attention and
judgement ..."
(p.137; Fairbairn to Stephenson, 2nd February
1847:)
"ps In consequence of Mr Clarke's arrival, and
hearing that you intend to visit Bangor about the 12th or 13th, I have sent
J McLaren, the person I have appointed as the inspector of the tubes to
Mr Evans at Conway, to arrange all the tools, and start the punching of the
plates and angle iron ...
(p.143; Stephenson to Fairbairn, Nov 31st 1847:)
"... I have sent Clarke down to Conway to arrange
with Evans, for proceeding with the masonry in the upper part of the tubes,
where it is likely to be interfered with by the cast iron girders.
... On my return we must arrange to meet the Board
on the subject of the lifting apparatus. I have no doubt it is right as
to Evans' certificate. "
(p.154:) "... During the progress of the construction
of the tubes for the Britannia Bridge, the machine work was found (according
to the opinion of Mr Mare, the contractor) both expensive and inconvenient
on account of the size and great weight of the plates, and the difficulty
of suspending them over the machine. These drawbacks were not however experienced
by Mr Evans, the contractor for the Conway tubes, who overcame every difficulty
by the introduction of powerful travelling cranes, which enabled him to rivet
the greater part of the bottom and sides of both tubes by the machine."
(p.156; Stephenson to Fairbairn, 23rd August 1847:)
"... I wish in the meantime, you would desire Clarke
to order Evans to put decks to all the pontoons he has built as well as raising
their sides 1 foot"
(p.159; Fairbairn to Stephenson, 24th Dec 1847:)
"... As soon as I hear from you, I will give Mr
Evans orders to prepare the pumps and the two dams, which are all that are
wanted to make experiment" (i.e. testing of the tube)
(p.160:) ... About this time Mr Stephenson expressed
a desire that everything connected with the transport of the tube, particularly
the pontoons which had to float it, should be minutely examined. This was
accordingly done; and the vessels which had been constructed by Mr Evans
the contractor, appeared defective, both as regards workmanship and construction,
considerable alterations were ordered to be made; by the introduction of
strong bulkheads, decks, and tie bars, and by a thorough recaulking, the pontoons
were rendered perfectly secure and fitted for the work they had to perform.
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