The atmospheric railway can be said to be the first ‘gadgetbahnen’ as it was the first attempt to replace regular railway locomotives with atmospheric trains. On paper, the atmospheric railway was a sure winner but in revenue service a failure. What surprises myself is that this complicated transit mode ever worked at all, as the Dalkey atmospheric railway operated for just over a decade (29 March, 1844 to 12 April, 1854 !
Those who fail to read transportation history are doomed to repeat the same expensive mistakes!
The following is from Exeter Memories.com
The concept behind an atmospheric or vacuum railway was simple. Instead of a conventional steam engine, the railway would have stationary engines at either end. A pipe ran down the middle of the rails, and the lead carriage had a piston head that fitted into this pipe. The engines would generate a vacuum in the pipe by use of suction, and the pressure change would pull the carriages from one end of the line to the other.
Theoretically this should produce a cost saving, as the engines need not move their own weight or carry fuel with them.
The Dalkey Railway
Brunel’s interest was probably peaked by the Dalkey railway in Ireland. A test for atmospheric pressure, the railway only used the pressure uphill with the downhill stretch powered by gravity.
The speeds it was capable of were highlighted in an incident. During a test, the motive carriage (the carriage with the piston) was not coupled to the train by accident. When the train was triggered it made the ascent in 1 minute fifteen seconds, at an average speed of eighty-four miles an hour. The terrified engineering student Frank Ebrington, who was the only passenger, was helped out at the far end unharmed but rather stunned. Mr. Ebrington could be considered, at the time, the fastest man in the world!
The problems with the concept
As Ebrington’s adventure proved, one of the other problems was that those in the train were being driven by people running an engine several miles away, with no idea of local conditions and at that time, no way to let them know of a problem. Also because of trains’ varying weights, the pressure needed would vary, and sometimes trains would stop short of the station or hit the buffers with a bone-rattling impact.
To drive this required huge steam engines. These would have been a fairly standard design, but Brunel was pushing the limits of engineering again, and there were frequent problems.
Creating the South Devon Railway
He persuaded the GWR board that the average life of a locomotive was only ten years, and that the stationary engines would last longer. This must not have sat well with Gooch, whose “North Star” engine worked for almost fifty years and eventually outlived the Broad Gauge rails it ran on. However since installing the pumping engines took longer than expected, Gooch’s engines ended up pulling the first trains on the rails.
Part of the problem was the length of the railway. The pipes for the centre all had to be of an exact diameter, with a slot running down them in exactly the same place. With Victorian methods this precision was not easy to achieve repeatedly over enough components to complete the route. The slots were sealed with overlapping pieces of leather to prevent the loss of pressure but permit the motive piston to pass through. At each joint the pipe rivets were reinforced with caulked yarn to prevent the air entering. Valves were needed at each station, level crossing, pumping station and more.
Water in the pipes from rain of condensation rotted leather and affected the seal. A breakdown in the pumping station prevented any train moving on the line, and the entire system depended on a perfect air-tight seal for miles. A nudged or misaligned valve and the trains came to a halt. In winter the leather seals in the slots froze solid.
By June 1848, the increased cost of coal, and maintenance, incurred a loss for the previous six months, of £2,487. The actual running cost was more than 7 pence per mile higher than a locomotive hauled railway. Brunel discovered that each pumping engine required almost three times the power that he first calculated to exhaust the pipe, primarily due to leakage.
Plans were made to improve the system to prevent failure in the future and reduce running costs. A rubber valve was ordered, and the feasibility of galvanizing the valve was investigated, to prevent corrosion. The cost was estimated at £1,160 per mile of some £25,000 in total.
However, by August, the directors of the railway were becoming impatient with Brunel, and indeed, Brunel was becoming disillusioned with the project. Brunel had submitted a verbal report to the directors on 1 August when he outlined the difficulties so far encountered with the system. He considered that virtually the whole of the valve would need replacing, a job that would take a year, and that the underpowered pumping engines would need a good deal of work to upgrade them. As a consequence, he did not recommend that the atmospheric working be extended beyond Newton Abbot, and recommended that the expense of putting the system right could not be justified, unless Samuda would guarantee the works.
On 29 August, the Board of the South Devon Railway Company decided that atmospheric working would cease on the 9 September. From that date steam locomotives replaced the pumping houses, and the atmospheric equipment sold off. One pumping engine found its way to a lead mine near Ashburton, and some of the pipe was used to drain the marshes of Goodrington for the Dartmouth and Torbay Railway Company. The only reminder of Brunel’s Atmospheric Caper is the engine house at Starcross. Nothing can be found of the pumping houses at Turf and Countess Wear, although the Exeter St David’s pumping house had a water tower added to it before it was removed quite recently.
Brunel was heavily criticized by the board of the South Devon Railway, some of whom had questioned the fees that Brunel had negotiated. Brunel countered this charge by stating that he had reduced the fee for his workmen on the system, had not taken his own £6,000 fee and had lost £20,000 of his own money which had been invested in the venture.
Sources – The South Devon Railway by R H Gregory, Exeter to Newton Abbot by Mitchell and Smith, and the Life of Isambard Kingdom Brunel by I Brunel (son of IKB)