Isambard Kingdom Brunel
Railways, bridges & atmospherics
Brunel's fortunes took a distinct turn for the better from the time he began work on the Great Western Railway
. Partly, of course, this giant enterprise generated related projects branch lines along the route as well as tunnels, cuttings, stations, bridges and viaducts and as Brunel's reputation as a railway engineer was established, so demand for his work grew apace.
Partly, though, unrelated projects abandoned in earlier years reappeared unexpectedly. In 1835, Brunel's revised designs for Monkwearmouth Dock, Sunderland, were passed by Parliament, the Clifton Bridge
Committee launched a successful bid for funds to restart works and, perhaps most excitingly of all, the Thames Tunnel
Company, which had secured a loan from Government, re-opened the project that had lain dormant for eight years.
As if all this were not enough, Brunel embarked on his groundbreaking designs for steam ships
at around the same time.
Before the Great Western Railway was completed the first train from London through to Bristol ran on 30 June 1841 Brunel had begun work on branch lines and extensions, including (to name the first few) the Cheltenham & Great Western Union Railway, the Bristol & Exeter Railway, the Merthyr & Cardiff Railway and the Bristol & Gloucester Railway. This work could only proliferate with the success of the GWR: the South Devon Railway, the Cornwall Railway and the South Wales Railway are amongst the projects he undertook between 1841 and the end of his career, as well as lines in Italy and India.
Even the less famous of Brunel's railway-associated engineering works are often innovative, elegant or both. To carry tracks through the hilly country of South Devon and Cornwall, he produced graceful designs for a series of standardized timber viaducts, the remains of which can still be seen. At Chepstow, for the first time in history, he used a compressed air cofferdam to sink the piers of his wrought iron bridge for the South Wales railway (these still exist, although the original span was replaced in 1962). The most daring and justifiably well-known of his railway bridges is the Royal Albert Bridge
at Saltash, built to carry the Cornwall Railway over the River Tamar and completed at the very end of Brunel's career.
With each achievement, Brunel sought to surpass what had been done before and often managed to do so. There were exceptions: his designs for locomotives were beyond impractical and he eventually forged a relationship with Daniel Gooch, who produced the engines for his broad gauge tracks. A less definitive failure to broaden the possibilities of rail travel was Brunel's great experiment with the so-called atmospheric system.
Various inventors had attempted to propel trains using compressed air systems, but the system which caught Brunel's attention had been patented by the brothers Jacob and Joseph Samuda in 1839.
The atmospheric system worked roughly as follows. An airtight tube (it was 9 inches in diameter in the Samudas' design) was laid along railway tracks and the air partially removed from it using a stationary steam-powered pump. A piston fitted into one end of the tube would, when released, shoot all the way along it, driven by atmospheric pressure into the partial vacuum. The Salmuda brothers had fitted this piston to the undercarriage of a lightweight vehicle and devised an airtight valve through which the piston could enter the tube. Thus piston and vehicle travelled noiselessly along the entire length of the track. In 1840, they demonstrated their invention along 1¼ miles of uphill track.
Brunel attended and was impressed. It should be remembered that, considering that almost all participants at the time vividly remembered a world without any kind of steam locomotion, this alternative method of propulsion cannot have seemed particularly far-fetched.
In 1843, when he was appointed engineer for the South Devon Railway, Brunel began his advocacy of the atmospheric system in earnest. As on previous occasions, his arguments carried weight with the directors, who agreed to the construction of the first major atmospheric line. The first tranche of the South Devon Railway opened on 30 May 1846, using piston-hauled locomotives.
Although impressive at times, the railway was dogged by problems, with trains frequently overshooting or stopping short of stations as well as failing to run altogether. In1848, Brunel finally abandoned atmospheric propulsion, thwarted by constant difficulties with air leakage along the longitudinal valve and between valve and piston. Starcross pumping station
, in Devon, survives as a reminder of his attempt.